Test for Topics Chemistry Form 4

TOPIC : 1 NON-METALS

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CHEMISTRY EXAMINATION FORM THREE

TOPICAL EXAMINATIONS.

NON-METALS

NAME………………………………………..CLASS…………………………………

INSTRUCTIONS:-

This paper consists of sections A, B and C

Answer all questions

All answers must be written in the spaces provided

All writings should be in blue/black inks except for drawings that should be in pencils

The method of collecting hydrogen chloride gas in a class experiment is known as:

Downward displacement of water

Downward displacement of air

Upward displacement of air

Fountain

Condensation

Which action should be taken immediately after concentrated sulphuric acid is spilled on the skin?

It should be rinsed off with large quantities of running water.

It should be neutralized with solid CaCO3.

It should be neutralized with concentrated NaOH.

The affected area should be wrapped tightly and shown to medical health provider.

It should be neutralized with concentrated KOH.

The only metal which does not react with dilute hydrochloric acid is:-

Magnesium

Aluminium

Copper

Zinc

Sodium

Which among the following equations correctly shows the reaction between chlorine gas and water?

C l2(g) + H20(1) → CI2(g)

B 2C12(g) + 2H20(1) → 4C1-1(aq) + 02(g) + 2H2(s)

Cl2(g) + H20(1) →HCl + HOCI(aq)

2Cl2(g) + 2H20(I) →2H0C1 +H2(g)

2C12(g) + 3H200) → C12 (.0 + 2H30+

(v) Which of the following pair of gas can be prepared in the laboratory an: collected over water?

Oxygen and Ammonia

Hydrogen and Hydrochloric acid

Hydrogen and Oxygen

Oxygen and Hydrogen chloride

Hydrogen and Ammonia

(vi) Two substances are allotropes of carbon if they:

A. both reduce heated iron (III) oxide to iron

B. have different crystalline structure

D. have equal masses

C. have equal shape

E. have the same arrangement of atoms

vii) Which of the following sets of elements is arranged in order of increasing electro negativity?

A. Chlorine, fluorine, nitrogen, oxygen, carbon

B. Fluorine, chlorine, oxygen, nitrogen, carbon

Carbon, nitrogen, oxygen, chlorine, fluorine

Nitrogen, oxygen, carbon, fluorine, chlorine

Fluorine, nitrogen, oxygen, chlorine, carbon

viii) The gas formed when dilute nitric acid reacts with magnesium metal is;

Nitrogen

Hydrogen

Oxygen

Nitrogen dioxide

ix) Which of the following is true about carbon?

Carbon dioxide is very acidic

Solid carbon d

2. Match the items in list A with the responses in list B by writing the letter of the correct response beside the item number.

List A

List B

Oxygen

Sulphur dioxide

Ammonia

Hydrogen chloride

Carbon monoxide

Nitrogen

Hydrogen

Chlorine

Nitrogen dioxide

Carbon dioxide

Green-yellow gas which rapidly bleaches damp litmus paper.

Heats with cracking sound.

It rekindles a glowing splint of wood.

Colourless gas, extremely poisonous since it combines with haemoglobin in red blood cells.

Brown-ring test.

Produces a white precipitate of silver chloride in a drop of a solution of silver nitrate.

It is the only alkaline gas.

Substitution reaction.

Explodes with air when a flame is applied.

Sweet-aroma smell

It is a brown gas.

It has very irritating smell and decolorizes potassium manganate (VII) solution with no precipitates left.

It turns lime water milky.

Colourless, odourless, non-poisonous gas commonly used as a refrigerant.

Characteristic yellow flame.

Good solvent for fats and grease, non poisonous.

Blackens lead (II) ethanoate paper.

Turns brown on exposure to air.

Freezes at 0°C and boils at 100°C.

Rotten-egg smell.

3.(a) With the help of chemical equation, what will be observed when ammonia reacts with:

Hydrogen chloride?

Copper (II) oxide?

(b) It is not advisable to sleep inside a house which is not well ventilated with a burning wooden charcoal. Give a reason for that and write the chemical equation to represent your answer.

4 .(a) The chemical properties of concentrated sulphuric acid can be grouped into oxidizing property and dehydrating property. In which property should sulphuric acid be grouped when it reacts with copper metal? Give reason and write the equation of the reaction.

(b)The preparation of chlorine gas can be represented by the following equation:

Mn02 + 4HCI→ MnCl2 + 2H20 + Cl2.

Calculate the number of moles of HCI which are needed to react with 20g of Mn02 and list two main chemical properties of chlorine gas.

5. (a) (i) What is the name given to the different forms of the element which exists in the same physical state?

(ii) Carbon exists in two different forms of the same physical state and one of those carbon forms is represented by structure X below. Give the name of the carbon form with structure X.

Name the second form of carbon.

State one property and one use which depends on the property you have stated for each form of carbon.

Carbon can be used to convert copper II oxide to copper as shown in the equation.

C(S) + 2CuO(s) → 2Cucs) +CO2(g)

What is the function of carbon in this equation?

Calculate the mass of CuO which can react with 12g of carbon in the equation given in 5 (b) (i) above.

What is the effect of carbon monoxide in the blood?

7.(a) Identify the substances by using the following information:

A solid is yellow when hot and white when cold.

When water is added to a white powder heat is evolved and the white powder changes to blue crystals.

An aqueous solution of a greenish crystalline sulphate forms a pale-green precipitate with sodium hydroxide solution which turns to brown on standing and when exposed to air.

A colourless gas turns a yellow acidified potassium dichromate paper to green.

A colourless gas becomes brown on exposure to air.

(b) With the help of chemical equations explain what happens to the following compounds of ammonia when heated in separate test tubes:

A mixture of ammonia chloride and sodium hydroxide solution

Ammonium chloride crystals

Ammonium nitrate crystals

Ammonium sulphate crystals

Ammonium nitrite crystals

8. The Diagram below shows the preparation of chlorine gas in a laboratory fume-chamber. Study the diagram and answer the questions that follow.

(a) What do letters A, 8, C, D and E represent?

Why is the gas prepared in the fume-chamber?

Can the gas be collected over water? Why?

What will happen to a damp blue litmus paper if it is introduced into a gas jar full of chlorine gas?

What will happen if a gas jar of hydrogen sulphide is inverted over a gas jar of chlorine such that the two gases get mixed? Write a balanced equation for the reaction which will take place between hydrogen sulphide gas and chlorine gas.

(b) (i) List down two uses of chlorine gas.

(ii) Give a balanced chemical equation for the method of preparation of chlorine used in this question.

9. (a) Write ionic equations for the following:

Laboratory preparation of ammonia gas.

Precipitation of barium sulphate from barium chloride and sodium sulphate and silver chloride from a soluble chloride.

Neutralization of a strong acid and a strong alkali.

(b) Consider the following elements of group seven in the order in which they appear in their group in the Periodic Table. F, C, Br, and I.

Which element is the most electronegative?

Name the least electronegative element.

Which element has the largest atom?

Write the electronic configuration of the chlorine atom.

11. Which method is used in the laboratory gas preparation of:

Ammonia?

Chlorine?

Hydrogen?

Give reasons for your answers.

yellow flowers are introduced into a gas containing chlorine gas?

a burning splint is introduced into a gas jar containing hydrogen gas?

a glass rod which was dipped in concentrated hydrochloric acid is introduced into a gas jar containing ammonia gas?

sulphur dioxide gas is bubbled through a yellow acidified potassium dichromate solution?

12. The preparation of ammonia in the laboratory is done by heating a mixture of ammonium chloride and sodium hydroxide.

(a) (i) Write a balanced chemical equation for the above reaction.

(ii) Using balanced chemical equations, state how ammonia reacts with hydrogen chloride gas and heated copper (II) oxide.

(b) (1) State two uses of ammonia.

(ii) Name the catalyst used in the preparation of ammonia.

Aqueous ammonia is added to iron (III) chloride, little by little, until in excess.

Sodium nitrate is strongly heated.

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TOPIC : 1 NON - METALS AND THEIR COMPOUNDS

P CLASS="western" ALIGN=CENTER STYLE="margin-bottom: 0.11in; line-height: 150%"> CHAPTER 0NE.

NON- METALS AND THEIR COMPOUNDS.

KEY TERM AND CONCEPTS.

Non-metal- this is an element that reacts by gaining an electron

Oxidizing property- this isa tendency of a non-metal to gain electron

Displacement reaction- this is a reaction which a more reactive element displaces a less reactive element from a compound.

Bleaching property- this is ability of a substance to remove color from another substance either by oxidation or by reduction.

Frasch process- this is a process in which sulphur is mined from its deposits.

Allotropy- this is the existence of an element in two or more different physical forms at the same physical state.

Oleum- this is a compound that is formed when sulphuric acid is dissolved in sulphur trioxide.

Dehydrating property- this is the ability of conc. Sulphuric acid remove water and element that make water from other compounds.

Drying agent property- this is the tendency of a substance called a drying agent to remove water from another substance.

Fountain experiment- is an experiment designed to illustrate the solubility of ammonia in water.

Delocalized electrons- these are electrons which are not used in bonding and are free to carry charges.

Meaning of non- metals- are elements which form negative ions by gaining electrons. They react by gaining electrons and the number of electrons an non-metals gains is called its valency.

For example;

Cl + e → Cl-

Chlorine is thus said to be monovalent. All non- metals form negative ions and are called electronegative elements. Thus electronegativity is the ability of an element to form negative ions.

General properties of non- metals.

Oxidizing properties- all non metals are oxidizing agents because they can accept electrons.

The strength of oxidation differs from one non- metal to another depending on the number of electrons gained.

The oxidation property vary as follows

F>Cl>Br>I>O>S>P>N>C

So fluorine is the strongest oxidizing agent, hence it is said to be the most electronegative element.

Displacement of non-metal by another non- metal from a compound.

Depending on oxidizing power, non- metals can displace each other from their solutions. Chlorine displaces both bromine and iodine from their compounds, while bromine can displace iodine from its compound.

hlorine + hydrogen bromide hydrogen bromide + bromine gas.

Cl2(g) + HBr → HCl + Br2

With sodium bromide, bromine gas is liberated from the solution as follows

chlorine + sodium bromide → sodium chloride + bromine

Cl2 + 2NaBr → 2NaCl + Br2

Chlorine reacts with potassium iodide to get potassium chloride and iodine

Cl2 + 2KBr → Br2 + 2KCl

In the same way bromine displaces iodine ions from potassium iodide and iodine is formed.

When chlorine is bubbled through potassium iodide, the clear solution turns dark brown and a dark solid is deposited.

Chlorine.

Chlorine is a very reactive gas and hence it does not occur freely in nature. It is found combined with other elements e.g sodium forming sodium chloride.

Preparation of chlorine gas in the laboratory.

Figure 1.1 preparations of chlorine

It is prepared by action of concentrated hydrochloric on an oxidizing agent. The oxidizing agent provides the oxygen atoms needed to oxidize the acid. The potassium permanganate is placed in the flask and arranged as shown above.

When the acid comes into contact with the permanganate, effervescence occurs and a greenish – yellow gas is given off. The hydrogen chloride produced together with chlorine dissolves in water. The chlorine gas is passed through concentrated sulphuric acid in order to be dried out. It is collected by downward delivery because it is denser than air.

Eqn- hydrochloric acid + potassium permanganate→potassium chloride + managanese chloride + water + chlorine.

16HCl(aq) + 2KMnO 4(s) →2KCL (aq) +2MnCl 2(aq) + 8H2O(l) + 5Cl2(g).

Chemical properties of chlorine gas.

Action on metals.

It reacts with all metals to form metallic chloride.

Examples include;

Alluminium + chlorine → Aluminium chloride

2AI(s) + 3Cl 2(g) →2AlC 3(aq)

Sodium + chlorine → sodium chloride

Na (s) + Cl 2(g) → NaCl(s)

Bleaching Action.

Chlorine bleaches damp litmus paper and wet flowers. This shows that chlorine is a bleaching agent. The gas first reacts with water to form a mixture of hydrochloric acid and chloric I Acid- hypochlorous acid.

Chlorine + Water → hydrochloric acid + hypochlorous Acid

Cl2(g) + H20(l) → HCL(aq) + HOCl(aq)

Chloric I acid is unstable and hence decomposes to form hydrochloric acid and an oxygen atom.

HOCl(aq) →HCl(aq) + ( dye + [o] ) –colorless.

The colured flowers are decolourised after some time.

Hydrogen chloride can exist in gaseous form i.e hydrogen chloride gas and hydrochloric acid.

Chlorine as an oxidizing agent.

Chlorine reacts by accepting electrons,

Cl2(g) + 2e(aq) → 2Cl-(aq)

With hydrogen sulphide

Cl2 oxidizes hydrogen sulphide to Sulphur at room temperature while itself is reduced to chloride ion

Hydrogen chloride + chlorine→ hydrogen chloride + Sulphur

H2S(g) +Cl2(g) → 2HCl(aq) + S(s)

With Sulphur (iv) oxide

Chlorine oxidises Sulphur IV oxide to sulphuric (VI) Acid.

SO2(g) + 2H2O(l) + Cl 2(g) → H2SO4(aq) + 2HCL(aq)

When Sulphur IV Oxide is passed into water, sulphorous acid is formed. This acid is converted into sulphuric acid when chlorine is blown over it.

With iron (II) chloride.

Iron (II) chloride is oxidized into iron (III) Chloride

2FeCl 2(s) + Cl2(g) → 2FeCl 3(s)

Uses of chlorine.

It is used as;

Bleaching agent

Germicide and weed killer

Manufacture of hydrogen chloride gas

Manufacture of plastics

In water treatment

For treatment of sewage,

As a disinfectant

Test for chlorine gas.

It is greenish –yellow in color gas which rapidly bleaches a damp litmus paper.

Hydrogen Chloride Gas.

Preparation

This gas is prepared by reacting concentrated sulphuric acid with sodium chloride in a round bottomed flask. Sodium chloride is also called a rock salt. The apparatus for the preparations are shown below;

Figure 1.2 preparation of hydrogen chloride.

Eqn. sodium chloride + Sulphuric Acid → sodium hydrogen sulphate + Hydrogen Chloride

NaCl (s) + H2SO4(aq) → NaHSO4(aq) + HCl(aq).

The gas is dried by passing over concentrated Sulphuric acid

Physical properties of the gas.

It is colourless

It is denser than air

It is very soluble in water

Chemical properties of hydrogen chloride gas

It is an acidic gas, thus turns litmus paper red,

It does not support combustion

When exposed in air it forms white fumes

It is higly soluble in water

Reacts with ammonium to form white fumes of ammonium chloride.

HCl (g) + NH 3(g) → NH4Cl(s)- white fumes.

The diagram below shows how the gas can be dissolved in water due to its solubility.

It reacts with metals to from hydrogen gas and forming hydrogen chloride.

Hydrochloric acid.

When hydrogen chloride gas is dissolved in water, hydrochloric acid is formed. In the industry, this acid can be manufactured by reacting hydrogen gas and chlorine gas. Hydrogen is obtained from cracking of alkanes, while chlorine is obtained from the down cell. The two gases are reacted at very high temperature as shown in the equation below.

H2(g) + Cl2(g) → 2HCl(g).

To avoid explosion a small amount of hydrogen is allowed to burn in a jet. The product is dissolved in water to form hydrochloric acid which is 35% pure.

Uses of HCl acid.

Removing rust from iron

Chlorination of water

Sewage treatment

Manufacture of silver chloride used in photographic films.

SUMMARY ON CHLORINE.

Chlorine is found in group seven of the periodic table and is called an halogen

It is a very reactive element

Can be prepared in lab using HCL and a catalyst

The gas is acidic. Greenish yellow, has a chocking smell and very poisonous

In industry, chlorine is manufactured in large scale by reacting hydrogen and chlorine

Hydrogen chloride, a compound of chlorine is manufactured by reacting conc. HCl and sodium chloride mixed with conc. Sulphuric acid.

The solution of hydrogen chloride in water is called hydrochloric acid.

Chlorine has a wide applications in the industry.

CHLORINE QUESTIONS

I.Explain how chlorine water can be formed.

Ii. Which Acid of HCL/HOCL is a bleaching agent

Write an equation to show bleaching action of hypochloilsa acid.

Explain using equation how the presence of chloride ions can be identified in

Solid

Solution

Study the diagram below and answer the questions that follow

The apparatus above are used to prepare chlorine

State substance

What is the use of conc. Sulphuric acid?

State the use of p.

Write equation for reaction occurring at the flask.

How can you show that test tube used for collection of chlorine is full?

Name the method of collection

Give two uses of chlorine

State 2 compounds of chlorine that pollute the environment.

Write equation for reaction between

Chlorine and Magnesium

Chlorine and phosphorous

Chlorine and copper

Chlorine and hydrogen Sulphate

Explain what happens when a stream of chlorine gas is passed over

Hydrogen sulphuric gas

Iron II solution.

Write equation for the reaction.

Explain how chlorine water can be formed.

Ii. Which Acid of HCL/HOCL is a bleaching agent

Write an equation to show bleaching action of hypochlorous acid.

Explain using equation how the presence of chloride ions can be identified in

Solid

Solution

Write equation for reaction between

Chlorine and Magnesium

Chlorine and phosphorous

Chlorine and copper

Chlorine and hydrogen sulphate

a)Explain what happens when a stream of chlorine gas is passed over

Hydrogen sulphuric gas

Iron II solution.

b) Write equation for the reaction.

Ammonium sulphate is fertilizer produced by passing ammonia gas into concentrated sulphuric acid. Write down an equation for the reaction.

SAMPLE NECTA QNS.

2004.

6. Figure 1 below represents the laboratory preparation of hydrogen chloride gas.

(a) Name the parts labelled A, B, C and D.

(b) (i) Do you think the gas can be collected over water? Give reasons for your answer.

Explain the test for the gas.

What is the function of C?

Name the method used to collect the gas.

Write a balanced chemical equation for the reaction taking place during the preparation of hydrogen chloride gas.

(i) Ammonia gas and hydrogen chloride.

(ii) Hydrogen chloride gas and water.

The reaction between hot concentrated sodium hydroxide and chloride gas produces sodium chlorate (V), Sodium chloride and water.

Write down an equation for the reaction.

Give one use of sodium chlorate (V).

The following experiments were carried out chloride water contained in two test tubes.

A blue flower petal were carried out on chlorine in two test tubes.

The second test tube was corked and exposed to sunlight. After a few days, it was found to contain a gas that rekindles a glowing splint. Write down an equation for this reaction.

NITROGEN AND ITS COMPOUNDS.

Nitrogen is a non metal in group V of the periodic table. It is a gas at room temperature and relative unreactive.

Occurrence.

Nitrogen occurs in free state in the atmosphere. It accounts for 78% of the atmosphere. It is also occur in combined form of chile salt petre (NaNO3), as a mineral deposit in chile. It also occurs in minute quantities in compoinds like ammonium sulphate and sodium nitrate. Nitrogen is an important constituent of living matter.

Obtaining nitrogen from the atmosphere.

Nitrogen occurs in free state in the atmosphere, and can be separated by removing all other constituents. The apparatus below shows how it can be separated.

The water is used to drive off air. It passes, through conc. Sodium, hydroxide which absorbs carbon IV oxide. Its then passes over, heated copper metal. The oxygen is removed. The remaining air is nitrogen which of course is not pure because of traces of rare gases.

2NaOH(aq) + CO 2(g) →Na2CO 3(aq) + H2O(l)

Absorption of oxygen

2Cu(s) + O2(g) → 2CUO(s)

The presence of noble gas make atmospheric nitrogen denser than pure gas.

Nitrogen can also be prepared in the laboratory by heating ammonium nitrate

NH4NO3 + NH4Cl→ NaCl + NH4NO2

Properties of Nitrogen.

It is colourless, odourless, and insoluble in water

It tests negative for all common test for gases

It reacts with nitrogen under special conditions.

It can react with burning magnesium to form magnesium nitride

3Mg(s) + N2(g) → MgN3(s)

When magnesium nitride is reacted with water, ammonia gas is formed.

Mg3N2 + H2O(l) → 3Mg(OH)2+ 2NH3(g).

Uses of nitrogen.

In manufacture of ammonia by haber process

Makes atmospheric oxygen inert

Is a source of fertilizer especially when fixed by bacteria

Used as refrigerant in semen preservation

Used in light bulb to prevent the oxidation of filament

Ammonia

It is a compound of hydrogen and nitrogen. It has a pair of electrons thus making it highly soluble.

It is a gas with a pungent smell.

Preparation of ammonia gas.

It is prepared by reacting ammonium gas with an alkali.

Figure 1.3 preparation of ammonia

Ca(OH)2(aq) + NH4Cl (s) → CaCl2(s) + 2 H2O(l) + 2NH3(g)

The ammonia is dried by use of calcium oxide. Ammonia reacts with many common drying agent like sulphuric acid and calcium chloride

2NH 3(g) + H2SO4(l) → (NH4)2SO4(s)

Ammonia is less denser than air and is collected by upward delivery.

Physical properties of ammonia gas.

Is colorless gas.

It is less dense than air

Has a chocking pungent smell

Highly soluble in water

Chemical properties of ammonia gas.

It is an alkaline gas, thus turns moist litmus paper blue

Reacts with hydrogen chloride to form white fumes of ammonium chloride- this is the chemical test for ammonia gas.

Ammonia gas is highly soluble in water as shown by the fountain experiment.

NH 3(g) + H2O(l) → NH+ + OH-

The fountain experiment.

This is an experiment that is used to show how soluble in water ammonia gas is. A hard round bottomed flask is fitted with two tubes each with clips as shown below. It is then immersed in a water bath half full with water.

Figure 1.4 The fountain experiment

A little litmus solution is added to the water in trough. One of the taps is opened and a drop of water enters into the flask. This dissolves a great volume of the gas, that a partial vacuum is created. When the other tap is opened, water is forced up the flask until it is full of water, the solution turns blue because ammonia is basic.

Reactions of ammonia with acids.

Ammonia being an alkali reacts with acids to form a salt and water only. This is neutralization reaction.

NH 3(g) + H2SO4(aq) → (NH4)2SO4

Combustion of ammonia

In excess of oxygen, it forms water and nitrogen gas.

NH 3(g) + 3O2(g) → 2N2(g) + 6 H2O(g)

In presence of a catalyst, such as hot platinum wire, ammonia reacts to form nitrogen II oxide and water. The NO is oxidized to brown nitrogen dioxide.

Reaction with copper oxide.

Ammonia reduces copper II oxide to form brown copper metal, nitrogen gas and water.

CuO(s) + NH 3(g) → Cu(s) + N2(g) + H2O.

THE HABER PROCESS.

This is an industrial manufacture of ammonia gas. It is based on direct combination of nitrogen gas and hydrogen gas. The hydrogen comes from cracking of alkanes, while the nitrogen is obtained by separation of nitrogen gas from air through fractional distillation.

N2(g) + 3 H 2(g) → 2NH3g + ∆-ve

The reaction takes place in the following condtions;

High pressure of about 200-500atm

Low temperature of about 450Oc

Use of iron catalyst

The process.

A mixer of nitrogen and hydrogen gas is passed through a purifier to remove impurities which may poison the catalyst. The mixer is then passed through a compressor at a pressure of 500atm. The two gases combine as follows; N2(g) + 3 H2(g) → 2NH3g) + ∆-ve

The hot mixer is passed through heat exchanger where it is cooled. It is then passed through a catalytic chamber where the uncombined gases are combined. The ammonia condenses and is collected as a liquid. This process has no dangerous by- products as the uncombined gases are recycled.

Figure 1.5 The haber process

Uses of Ammonia gas.

Ammonia solution is used in laundry work. It removes temporary hardness of water.

Dissolves acids in under cloths thus help to remove stains

Used in the manufacture of nitric acid

Used as a refrigerant in big warehouses

Manufacture of hydrazine which is used as a rocket fuel

Used in softening of water.

SUMMARY.

Nitrogen is a colourless gas that is unreactive

It occupies 78% of the atmosphere

It can be obtained from the air by isolation

Ammonia can be manufactured by combining hydrogen and nitrogen under special conditions.

Ammonia is alkaline and highly soluble in water

Nitrogen gas has many uses in the industry including in refrigerations.

Nitrogen is a colorless gas, very unreactive it is in group seven accounting for 78% of atmosphere.

Can be obtained from air by isolation

Can also be prepared by decomposition of ammonia nitrate.

Main oxide of nitrogen are

Nitrogen I oxide

Nitrogen II oxide

Nitrogen III oxide

Nitrogen I oxide has sweet sickly smell and support burning

Nitrogen (IV) Oxide is reddish brown gas

Ammonia can be manufactured by combining nitrogen and hydrogen under special conditions. i.e

Pressure of 200 – 500 tm

Temperature of 4500C

Iron Catalyst

Ammonia is used to make fertilizers and nitric acid

Ammonia is alkaline and a highly soluble in water it is the most soluble gas in water

Nitric acid is manufactured by catalystic oxidation of ammonia

Nitric acid is a fuming gas, which attacks and comments most things except glass.

Nitrates are affected by heat depending on reactivity of the metal.

All nitrate are sources in water

Nitrate can be identified by brown ring test.

END OF TOPIC QUESTIONS.

i. Explain how a sample of nitrogen can be isolated from air

ii. Ammonia is manufactured by water process. Name the best conduct for this process, and state 2 uses of ammonia

Explain how nitrogen can be prepared in laboratory

Explain the observation made.

Brown former are observed when NO is exposed to air

Nitric acid is stored in dark brown bottles

Nitric acid is often yellow.

Given NH4(SO4)2 and NH4NO3 Which one would you say is the best fertilizer? Show your working

Calculate the volume of oxygen produced when 20g KNO3 is is decomposed. Molar gas vol at composed. Molar gas vol at stp = 22.4 liter

Using equation show and name reagent used to make

Nitrogen

nitrogen oxide

Nitrogen dioxide gases in laboratory

When a small burning Magnesium ribon was lowered into jar nitrogen dioxide, a white powder was product and brown colour disappeared. Suggest explain for the observation

b . The equation below is for manufacture of ammonium by Haber process

N2 (g) + 3H2 (g) 2NH3 ∆H = -Ve

In term of reacting volume what is the best pressure for the reaction above.

Does it require high or the low temperature?

State how the oxidation of ammonia gas by burning in oxygen differs from it catalytic uses platinum as the catalyst.

The set up below shows the preparation of nitrogen gas. Study it and answer questions that follows.

State the purpose of sodium hydroxide

Write down an equation that shows the reaction taking place in the round bottomed flask

With the aid of an equation, explain what takes place in the combustion tubes.

The nitrogen obtained using this is not pure. Explain why this is so

During the haber process of the manufacture of ammonia, hydrogen and nitrogen rreact according to the equation show below.

N2 + 3H2 → 2NH2(g) (H = -92Kj)

Name the catalyst used in above process.

Calculate how much energy would be envolved it 10g of hydrogen is used (H = 1.0).

SAMPLE NECTA QUESTIONS.

3. (a) Write ionic equations for the following:

Laboratory preparation of ammonia gas.

Precipitation of barium sulphate from barium chloride and sodium sulphate and silver chloride from a soluble chloride.

Neutralization of a strong acid and a strong alkali.

2007.

QN5 © (c) What will happen when:

yellow flowers are introduced into a gas containing chlorine gas?

a burning splint is introduced into a gas jar containing hydrogen gas?

a glass rod which was dipped in concentrated hydrochloric acid is introduced into a gas jar containing ammonia gas?

sulphur dioxide gas is bubbled through a yellow acidified potassium dichromate solution?

2009.

QN. 11.The preparation of ammonia in the laboratory is done by heating a mixture of ammonium chloride and sodium hydroxide.

(a) (i) Write a balanced chemical equation for the above reaction.

(ii) Using balanced chemical equations, state how ammonia reacts with hydrogen chloride gas and heated copper (II) oxide.

(b) (1) State two uses of ammonia.

(ii) Name the catalyst used in the preparation of ammonia.

Aqueous ammonia is added to iron (III) chloride, little by little, until in excess.

Sodium nitrate is strongly heated.

QNS. 8. (a) Ammonia gas can be prepared by heating an ammonium salt with an alkali.

Name the most common pair of reagents suitable for this reaction.

Write the equation for the reaction.

(b) Ammonia is very soluble in water and less dense than air. How does each of the properties determine the way in which ammonia is collected in a gas jar?

A solution of chlorine in water is acidic.

Yellow phosphorus is stored under water.

SULPHUR AND ITS COMPOUNDS.

OCCURRENCE.

Sulphur occurs in form of mineral compounds such as

Pyrite- Fes

Gypsum – CaSO4-2H2O

Mirabilite- Na2SO4.10H2O.

Sulphur is also a constituent of plant and animal protein. Elemental Sulphur is not toxic to humans but it has fungicidal effects.

Pure Sulphur is fragile, crystallined, yellow in color, with several allotropic modifications. These allotropes include, rhombic, monoclinic, plastic, and prismatic.

Sulphur occur in rings called Sulphur 8 rings.

Extraction of Sulphur.

Sulphur is obtained from underground by a process called frasch process. The Sulphur is found about 200m underground. Three concentric rings are erected downward to the molten Sulphur. Super heated water at 170oC, IS passed through outer pipe, where it melts the hot Sulphur. Hot air is passed at 16atm, through middle pipe and helps in making the Sulphur molten. Because of the pressure of the build inside; molten Sulphur is passed through middle ring (pipe) and is collected in a reservoir.

Diagram.

Figure 1.6 Frasch process

Allotropes of Sulphur.

Sulphur exists in two main allotropes,

Rhombic and monoclinic

Other allotropes includes plastic and amorphous Sulphur.

Rhombic Sulphur.

Also called alpha Sulphur or octahedral Sulphur due to the shape of its crystals. It is formed when Sulphur is dissolved in warm methyl benzene. The shape of rhombic Sulphur is as shown below.

Figure 1.7 Rhombic sulphur

rhombic Sulphur is stable below 96oc.

Monoclinic Sulphur.

It is also called prismatic Sulphur or beta Sulphur. It is formed when Sulphur is heated slowly on evaporating dish until it melts. Monoclinic Sulphur is stable above 960C.

Figure 1.8 monoclinic sulphur

Plastic Sulphur.

Formed when molten Sulphur is gradually poured in a beaker of cold water. At room temperature plastic Sulphur gradually changes into rhombic Sulphur.

The temperature of 960C, above which monoclic Sulphur is formed and below which rhombic sulphur is formed is called transition temperature.

Figure 1.9 Transition between the two allotropes

Effects of heat on Sulphur.

At 119oC, SULPHUR melts to give a yellow liquid whose viscousity decreases until 1550C. This is because of breaking S-S rings.

On further heating, viscosity increases, upto 159oc due to opening of S8 rings

Above 200Oc, viscosity with the liquid eventually acquiring a more reddish hue at high temperature. This is caused by thermal breaking of Sulphur chains

The liquid boils at 444oc to form a reddish brown vapour.

Properties of Sulphur.

Combustion

Burns in plenty of air to from Sulphur dioxide, in air enriched with oxygen, it burns to form Sulphur trioxide.

S (s) + 02(g) →SO2(g)

2S(s) + O2(g) → 2S03(g)

Reaction with metal.

Sulphur reacts with iron and copper to form sulphides.

Fe(s) + S(s) → FeS(s)

Fe(s) + Cu(s) → Cu2S(s)

Both iron sulphide and copper sulphide are black in color.

Reaction with non metal

With cabon, Sulphur combines to from carbon disulphide which is very poisonous.

Cs + S s CS2 g

Reactions with acids.

With nitric acid, sulphuric acid is formed and the nitric acid is reduced to brown nitrogen IV Oxide.

S(s) + 6HNO3(aq) → H2SO4 + NO2 + 2H2O

Concentrated sulphuric acid oxidizes Sulphur into Sulphur dioxide and water.

H2SO4(l) + S (s) → 3S02(g) + 2 H2O(l).

Hydrochloric acid does not behave the same way because it is not an oxiziding agent.

Uses of Sulphur.

As a fungicide in dusting of vines

Manufacture of sulphuric acid in contact process

Vulcanization or hardening of rubber

Making bleaching agents in the paper industry

Manufacture of fire works, dyes and Sulphur compounds.

The contact process.

This is the industrial manufacture of sulphuric acid. The process involves four stages which are;

Preparation of Sulphur IV Oxide

Purification of Sulphur IV oxide

Conversion of Sulphur IV Oxide into Suphur VI Oxide.

Conversion of Sulphur (VI) Oxide into sulphuric VI acid.

Preparation of Sulphur IV Oxide

Formed by burning Sulphur in air or burning Sulphur ores in air.

S(s) + O 2(g) → SO2(g)

2Fe S(s) + O 2(g) → SO2 (g)

Other sulphides such as zinc, copper, can be used instead of iron.

Purification of Sulphur (IV) Oxide

The mixture of Sulphur(IV) Oxide and excess air are purified to remove dust particles which may poison the catalyst.

Conversion of Sulphur dioxide into Sulphur trioxide.

This requires a pressure of 2-3atm, temperature of 400-500Oc and a vanadium (V) Catalyst.

This reaction takes place in a catalytic chamber.

2S02(g) + O2(g) 2S03(g) heat= -94KJ/mol

Conversion of Sulphur (VI) Oxide into sulphuric (VI) Acid.

The Sulphur VI oxide is passed over absorption tower where it reacts with concentrated sulphuric VI Acid to form oleum,

Sulphur(VI) Oxide + Sulphuric (VI) acid→ Oleum

SO 3(g) + H2SO4(l) → 2 H2S20 7(l)

The oleum formed is then diluted with water to give concentrated sulphuric acid. This occurs in dilution chamber

Oleum + water → Sulphuric (VI) Acid

H2S2O 7(l) + H2O(l) → H2SO4(l)

DIAGRAM FOR CONTACT PROCESS.

Figure 1.10. The contact process

Chemical properties of concentrated sulphuric acid.

Dehydrating property

This is the ability of the acid to remove elements of water, that is hydrogen and oxygen from a compound.

When conc. Sulphuric acid is added to sugar in a bench, the acids removes oxygen and hydrogen leaving a black mass of carbon.

C12H22011(s)

12C + 11H20

Crystals of blue copper II Sulphate turns white when Conc-sulphuric acid is added.

CUSO4.5H2O(s)

CuSO 4(s) + 5H20(l)

Drying agent

The acid is hygroscopic, it absorbs water from the atmosphere and it becomes diluted. When left in open, the volume of the sulphuric acid is found to have increased.

Oxidizing power of Conc Sulphuric acid.

It oxidizes zinc and copper to form their salts. Sulphur dioxide gas is also liberated.

Cu(s) + H2SO4(l) → CuSO4(aq) + 2H2O(l) + SO2(g)

Zn(s) + H2SO4(l) →ZnSO4(aq) + 2H2O(l) + SO2(g)

The acid oxidizes non-metals to their 0xides

C(s) + H2S04(l) → CO2(g) + S0 2(g) + H20(l)

S(s) + H2S04(l) → S02(g) +2 H20(l)

Dilute Sulphuric acid.

Reaction with metals

It reacts with metals above hydrogen liberating hydrogen gas. For very reactive metal, the reaction is very dangerous and should not be tried.

The reactivity decreases as one moves down the reactivity series.

Eg. Mg (s) + H2S04(aq) → MgSO4(ag) + H2(g)

Reaction with carbonate and hydrogen carbonate.

The product of this reaction is carbon dioxide salt and water. The presence of carbon dioxide can be confirmed by use of lime water where it turns into white precipitate.

The reaction between calcium and lead with sulphuric acid stops after a certain period of timw due to formation of insoluble salts.

Na2CO3(s) + H2SO4(aq) →Na2SO4(aq) + CO2(g) + H20(l)

ZnCO3(s) + H2SO4(aq) →ZnSO4(aq) + CO2(g) + H20(l)

CuCO 3(s) + H2SO4(aq) →CuSO4(aq) + CO2(g) + H20(l)

Reaction with hydroxides of metals.

It produces salts and water with hydroxides and metal oxides, this is called neutralization.

Copper oxide reacts with dilute sulphuric acid to form a blue solution of copper II Sulphate.

CuO(s) + H2SO4(aq) →CuSO4(aq) + H20(l)

With copper hydroxide,

Cu(OH)2(s) + H2SO4(aq) →CuSO4 + H2O

USES OF SULPHURIC ACID

Sulphuric acid is used in the following ways.

Manufacture of fertilizers

Making synthetic fibres

In refining petroleum

Petro chemicals and dye stuffs

Pigments of paints

In metallurgy sulphuric acid is used in extraction of metals

In car batteries and accumulators

As drying agents for gases

In pickling; cleaning of metal surfaces

In the manufacture of soaps and detergents.

Sulphur (IV) Oxide.

This gas is prepared in the laboratory by reacting conc. H2SO4 acid and copper metal. The gas is dried over conc. Sulhuric acid and collected by down ward delivery. It has irritating smell and is colorless.

Figure 1.11 Preparation of sulphur dioxide

Properties of Sulphur IV Oxide.

Physical properties.

It is a colorless gas with an irritating smell.

It turns damp litmus paper blue and then bleaches it.

It is denser than air

It is readly soluble in water forming sulphorous acid.

Chemical properties.

The gas neutralizes alkalis such as sodium hydroxide forming sodium hydrogen sulphite and water.

NaOH(aq) + SO2(g) → NaHSO3(aq),

When the alkali is in excess, a sulphite is formed

2NaOH(aq) + SO2(g) →Na2SO3(aq) + H2O(l)

Reducing property.

Sulphur dioxide reduces dichromate ions into chromium (III) Ions. This is the test for Sulphur dioxide

CrO72- (aq) + 3SO2(g) + 2H+(aq) →2Cr3+(aq) +3SO42- + H2O(l)

SO2 reduces acidified purple manganite (VII) ions, MnO4 to Colorless manganese (II) ion, (Mn2+). SO2 Itself being oxidized to sulphuric (VI) acid.

2MnO-4(aq)+5S02(g) +2H2O(l) →2Mn2+ (aq)+5SO2- +4H+(aq).

Bleaching property.

Sulphurous acid bleaches by reduction, in which it supplies oxygen to the dye.

SO2(g) + H20(l) →H2SO3(aq)

H2SO3(aq) + ( dye +O) → H2SO4(aq) + dye- colorless

Oxidizing property.

Sulphur dioxide oxidizes hydrogen sulphide into Sulphur and water.

SO2 + 2H2S(g) →3S(s) + 2H2O (l)

A yellow deposit of Sulphur is formed.

It oxidizes magnesium into magnesium oxide and is itself reduced into Sulphur.

Mg(s) + SO2(g) →2MgO(s) + S(s)

Uses of sulphur IV Oxide.

For fumigation to kill insect pest because the gas is poisonous

For leaching straws, sponges, paper and silk

Preservation of fruit juices and other food stuffs

Used as intermediate compound in manufacture of sulphuric acid in contact process

Effects of sulphuric acid

Accumulation of sulphuric acid in the atmosphere can lead to;

Formation of acid rain which affects animals and plants

Irritation of throat and eyes due to exposure, if inhaled, it can cause infection of respiratory system

Acid rain interferes with the PH of soil thus affecting plant growth.

SUMMARY

Sulphur is a non metal in group (IV) of periodic table it is found in Lousiana and Texas in USA in free from and also in force from and also in performance genes eq at , france are hydrogen sulphide

Sulphur is extracted by frasch process

Sulphur occur in two allotropic forms rhombic with octahedral shape and stable above 960C and monoclinic sulphur which is stable above 960C it is prismatic.

Sulphur is yellow in colour and has a variety of use in manufacture of sulphuric acid, fungicides, bleaching agents etc.

When heated Sulphur, behaves very intresting changing in viscousing till it boils at 4440C.

Hydrogen sulphide Is a strong reducing agent

Sulphur has two oxide, Sulphur dioxide and Trioxide. Sulphur dioxide is prepared by reactions of Conc. Sulphuric acid on copper.

Conc.sulphuric acid is an oxidizing agent dehydrating agent and hydroscope

The acid can displace more volatile acid from their salts

Sulphur (IV) oxide has pollution effect on the environment.

END OF TOPIC QUESTIONS

Name two sources of sulphur

Explain how frasch process works in extracting sulphur

Name two allotropes of Sulphur

Briefly explain what happens when Sulphur is heated till foils. Draw a graph showing the changes of discoursing as temperature increase.

Jane is given two solutions, suspected to be Sulphite and Sulphates. Describes how she can differentiate the two

Explain why

During contact process Sulphur Trioxide is dissolved in sulphuric acid and not water

A temperature of 4500C is used in contact process although the process require low temperature?

You should not add water to acid sulphuric acid.

The reaction between sulphurdioxiede and nitric acid is as follows

SO2(g) + 2HNO3(g) → H2SO4(g) + 2NO2(g)

Identify

Reducing agent

Oxidizing agent

Between SO2 and HNO3 Which is strong reducing agent.

The diagram below illustrates the extraction of sulphur in the Frasch process.

Name the pipe through which heated water is pumped.

The equation below shows how sulphur (IV) oxide is converted to sulphur (VI) oxide.

2SO2(g) + O2(g) → 2SO3(g) (∆H = -196Kj)

Name one catalyst used for this reaction

State and explain the effect on the yield of sulphur (VI) oxide when:

The temperature is increased

The volume of oxygen used in increased.

Explain what happen when,

Acidified potassium dichromate (vi) is reacted with sulphuric (iv) oxide wite equation for reaction.

Concentrated sulphuric acid is poted in sugar on bench

Stating from sulphur, describe how you can prepare

Plastic sulphur

Sulphur dioxide

Hydrogen sulphide

Complete this equations

H2S(g) + O2 → ?

H2S(g) + O2→?

Describe an experiment which can be used to show that Sulphuric acid is hygroscopic

Explain why paper turn brown after being exposed to sunlight for long time.

b. how do bleaching agent of chlorine and Sulphur dioxide differ?

c. which is the best bleaching agent.

11. Explain two ways which can be used to show a gas is Sulphur (IV) Oxide

When a sample of concentrated sulphuric acid is left in an open beaker in the laboratory for two days, its volume is found to have increased.

State the property of the concentrated acid that is shown by this observation

State one use of concentrated sulphuric acid that depends on the property in a above

Using an equation explain how sulphur (IV) oxide bleaches substances.

Name the catalyst preferred in the contact process of manufacturing sulphuric acid and explain why it is preferred.

SAMPLE NECTA QUESTIONS.

2015

(a) Briefly explain what will happen when:

concentrated sulphuric acid is exposed to the atmosphere.

iron (II) sulphate is exposed to air for a long time.

a bottle containing AgNO3 is left open.

(b) Give three applications of the process of neutralization in daily life.

CARBON

Carbon exists mostly in free state as graphite and diamond. It exists in a number of forms such as wood charcoal, animal charcoal, coke and soot or lamb black. It occurs in many substances eg, carbon dioxide, carbonate, shells, and in all organic matter.

Allotropes of carbon.

Allotropy is the existence of an element in more than one form in the same physical state.

Allotropes- are different forms of an element with different physical properties but the same chemical properties.

Allotropes of carbon.

Diamond

Graphite

Amorphous

Diamond and graphite are crystallized forms while amorphous is non-crystallized form.

Diamond

Diamond is the hardest substance known on earth. In diamond, each carbon is joined by covalent bond to four other carbon atoms. This forms a tetrahedral structure. The forces that bond the atoms are equally strong in all directions in diamond. Compared to graphite, diamond is more denser because its atoms are closely packed. Diamond has no free electrons and hence it is an insulator meaning it does not conduct electricity.

Figure 1.12. Diamond structure

Physical properties of diamond.

Has high melting and boiling point due to strong covalent bonds.

It is a bad conductor of heat and electricity

It is colourless, transparent and sparkling

Uses of diamond.

Because of high refractive index, it is used as a gemstone or valuable stone

For cutting glass, drilling of rocks, and for abrasive purposes because of its hardness

Used to make jewellery, such as rings, because of its shiny and attractive appearance

Graphite.

In graphite, only three out of four electrons in carbon are used in bonding. One electron is thus left to move free. For this reason, graphite is able to conduct electricity

The arrangement of atoms in graphite forms hexagonal rings of six carbon atoms. The hexagonal layers are joined by weak covalent bonds-allowing them to slide over each other.

Figure 1.13. Graphite structure

Physical properties of graphite.

Due to delocalized electrons, it is a good conductor of electricity

It is soft and slippery because of weak van der waal forces

Has high melting and boiling point because of presence of strong electrovalent bonds.

Uses Of Graphite.

It is mixed with clay to make lead pencils.

Used as an electrode in electrolytic cell because it is very innert

Used as a lubricant because of its greasy and slippery property

Amorphous carbon.

Is a non crystallined form of carbon. The arrangement of atoms are disorderly. This allotrope does not occur naturally but exists in various forms.

Charcoal

Coke

Lampblack

Charcoal.

Charcoal exists in three main forms, animal charcoal, suagar charcoal and wood charcoal.

Animal charcoal

Formed when bones are heated in limited supply of air. It is used to whiten crude sugar by removing the brown impurities.

Sugar charcoal

It is formed by destructive distillation of sugarcane. Also formed when conc. Sulphuric acid dehydrates sugar. This charcoal is used to absorb gases in chemical processes.

Wood charcoal

Formed by destructive distillation of wood. It is used as gas masks because it absorbs poisonous gases

Coke.

Is formed when coal is heated in absence of air.

Uses of coke.

Used as a fuel in furnaces, boilers and ovens

It is used as a reducing agent in the extraction of metals

Used as a source of gaseous fuel

Lamb black.

They are formed when petroleum, kerosene, turpentine, and natural gas and other hydro-carbons are burnt in limited supply of air.

Uses of lamb black.

Making Indian ink, black shoe polish, carbon paper, and printers ink.

In making rubber tyres, which makes the rubber strong.

Reducing properties of carbon.

Carbon is a reducing agent.

It reduces the oxides of metals to their respective metals and carbon dioxide

Lead (II) Oxide + Carbon→ lead + carbon dioxide

Copper(II) Oxide + Carbon→copper + Carbon IV Oxide.

Carbon also reduces hot nitric V acid to nitrogen (IV) oxide (NO2), and hot suphuric acid to Sulphur IV acid respectively.

Carbon + Sulphuric Acid→carbon dioxide + Sulphur dioxide + water

Carbon + nitric acid→carbon dioxide + nitrogen IV Oxide + Water

Carbon (IV) Oxide.

Occurrence.

It occurs in the atmosphere where it occupies 0.03%. it is also a constituent of bodies of plants and animals.

Preparations.

It is prepared by reacting dilute hydrochloric acid with marble chips- calcium carbonate.

Figure 1.13. Preparation of carbon dioxide

The dilute hydrochloric acid reacts with the carbonate forming effervescence with evolution of carbon dioxide.

Calcium carbonate + hydrochloric acid → calcium chloride + carbon (V) Oxide

CaCO3(s) + 2HCl(aq) →CaCl2 (aq) + C02(g) + H20 (l)

Physical properties of carbon dioxide.

It is colourless, odourless gas with a faint acid taste

It is soluble in water forming carbonic acid

It is heavier, than air.

Chemical properties.

The gas does not support combustion

Dissolves in water forming weak carbonic acid

It reacts with alkalis to form carbonates

Carbon dioxide can react with burning magnesium. When burning magnesium is introduced in a gas jar fully of carbon dioxide, it continues to burn oxidizing the magnesium into magnesium oxide while itself is reduced to carbon. The heat produced by burning magnesium decomposes carbon IV Oxide to carbon and oxygen.

The oxygen reacts with magnesium.

Uses of carbon (IV) Oxide

Used as fire extinguisher because it does not support combustion

Use to make fizzy drinks

Used as a refrigerant

Used in baking bread and coke.

In fruit preservation, by creating an atmosphere in which there is less oxygen and more carbon dioxide.

Test for carbon dioxide

This gas is tested by passing through lime water in which the lime water changes into white precipitate.

The formation of white precipitate is due to the presence of solid calcium carbonate

Ca(OH)2aq + CO2(g) →CaCO3(s) + H2O (l)

When excess carbon dioxide is passed, the solution turns into colourless due to formation of soluble calcium hydrogen carbonate.

NON METALS AND THEIR COMPOUNDS

Non metals react by gaining electrons; they are electronegative.

Electro negativity is the tendency of a non metal to gain electrons.

Non metals displace each other in their aqueous compounds.

Chlorine bleaches only in the presence of water.

Chlorine reacts by gaining electrons. it is an oxidizing agent.

Chlorine gas is a poisonous. It is prepared in a fume cupboard.

Hydrogen gas is poisonous. It is prepared by the action of concentrated sulphuric (IV) acid on rock salt.

Hydrogen chloride gas turns wet blue litmus paper red; it has acid properties in solution form.

Hydrogen chloride gas forms white fumes of ammonia chloride with ammonia gas. This is the test for hydrogen chloride gas

Sulphur is extracted from natural deposits by the frasch process.

The main allotropes of sulphur are rhombic, monoclic and plastic sulphur.

Sulphur exhibits both oxidizing and reducing properties.

Sulphuric (VI)Acid is manufactured by the contact process.

Concentrated sulphuric acid (VI) acid is adehyrating agent. It can remove water or elements of water from compounds.

Sulphur (IV) oxide causesbleaching by reaction.

Sulphur (IV) oxide reacts as an oxidizing agent with some reagents during which it reduces to sulphur.

Sulphur (IV) oxide is used as an intermediate in the manufacture of sulphuric (IV) acid.

Nitrogen gas can be prepared in the laboratory by isolution from air.

Nitrogen is inert at room temperature due to the strong triple convalent bonds between its atoms.

Nitrogen is a major raw material in the manufacture of ammonia gas.

Ammonia is prepared in the laboratory by heating an ammonia salt with a base.

Ammonia is highly soluble in water and exhibits alkaline properties in solution form,

Ammonia forms white fumes of ammonium chloride when reacted with hydrogen gas. This is the test for ammonia.

Carbonate (IV) oxide can be prepared in the laboratory by the action of dilute acids on suitable carbonate.

Carbonate (IV) oxide forms a white precipitate with calcium hydroxide or barium hydroxide. This is the test for the carbon (IV) Oxide.

Allotropy is the existence of an element in more than on form but in the same physical state.

NON METALS AND THEIR COMPOUNDS

Define allotropy.

Name two crystalline allow tropes of carbon.

Damp blue and red litmus paper loses their color when put in a jar of chlorine. By use of equations explain.

State one major industrial use of hydrogen chloride gas.

State the differences between rhombic and monoclicsulphur.

Explain what is observed when concentrated sulphuric (IV) Acid is added to :

Sugar

Hydrated copper (II) sulphate

By the use of relevant chemical equations explain how acid rain is formed.

State and explain any two uses of nitrogen.

Describe the chemical test for ammonia.

TOPICAL EXAMINATIONS

CHEMISTRY FORM FOUR

NON-METALS

SECTION A 20 MARKS.

The method of collecting hydrogen chloride gas in a class experiment is known as:

Downward displacement of water

Downward displacement of air

Upward displacement of air

Fountain

Condensation

Which action should be taken immediately after concentrated sulphuric acid is spilled on the skin?

It should be rinsed off with large quantities of running water.

It should be neutralized with solid CaCO3.

It should be neutralized with concentrated NaOH.

The affected area should be wrapped tightly and shown to medical health provider.

It should be neutralized with concentrated KOH.

The only metal which does not react with dilute hydrochloric acid is:-

Magnesium

Aluminium

Copper

Zinc

Sodium

Which among the following equations correctly shows the reaction between chlorine gas and water?

C l2(g) + H20(1) → CI2(g)

B 2C12(g) + 2H20(1) → 4C1-1(aq) + 02(g) + 2H2(s)

Cl2(g) + H20(1) →HCl + HOCI(aq)

2Cl2(g) + 2H20(I) →2H0C1 +H2(g)

2C12(g) + 3H200) → C12 (.0 + 2H30+

(v) Which of the following pair of gas can be prepared in the laboratory an: collected over water?

Oxygen and Ammonia

Hydrogen and Hydrochloric acid

Hydrogen and Oxygen

Oxygen and Hydrogen chloride

Hydrogen and Ammonia

(vi) Two substances are allotropes of carbon if they:

A. both reduce heated iron (III) oxide to iron

B. have different crystalline structure

D. have equal masses

C. have equal shape

E. have the same arrangement of atoms

vii) Which of the following sets of elements is arranged in order of increasing electro negativity?

A. Chlorine, fluorine, nitrogen, oxygen, carbon

B. Fluorine, chlorine, oxygen, nitrogen, carbon

Carbon, nitrogen, oxygen, chlorine, fluorine

Nitrogen, oxygen, carbon, fluorine, chlorine

Fluorine, nitrogen, oxygen, chlorine, carbon

viii) The gas formed when dilute nitric acid reacts with magnesium metal is;

Nitrogen

Hydrogen

Oxygen

Nitrogen dioxide

ix) which of the following is true about carbon?

Carbon dioxide is very acidic

Solid carbon d

2. Match the items in list A with the responses in list B by writing the letter of the correct response beside the item number.

List A

List B

Oxygen

Sulphur dioxide

Ammonia

Hydrogen chloride

Carbon monoxide

Nitrogen

Hydrogen

Chlorine

Nitrogen dioxide

Carbon dioxide

Green-yellow gas which rapidly bleaches damp litmus paper.

Heats with cracking sound.

It rekindles a glowing splint of wood.

Colourless gas, extremely poisonous since it combines with haemoglobin in red blood cells.

Brown-ring test.

Produces a white precipitate of silver chloride in a drop of a solution of silver nitrate.

It is the only alkaline gas.

Substitution reaction.

Explodes with air when a flame is applied.

Sweet-aroma smell

It is a brown gas.

It has very irritating smell and decolorizes potassium manganate (VII) solution with no precipitates left.

It turns lime water milky.

Colourless, odourless, non-poisonous gas commonly used as a refrigerant.

0. Characteristic yellow flame.

Good solvent for fats and grease, non poisonous.

Blackens lead (II) ethanoate paper.

Turns brown on exposure to air.

Freezes at 0°C and boils at 100°C.

Rotten-egg smell.

3.(a) With the help of chemical equation, what will be observed when ammonia reacts with:

Hydrogen chloride?

Copper (II) oxide?

(b) It is not advisable to sleep inside a house which is not well ventilated with a burning wooden charcoal. Give a reason for that and write the chemical equation to represent your answer.

(b)The preparation of chlorine gas can be represented by the following equation:

Mn02 + 4HCI→ MnCl2 + 2H20 + Cl2.

Calculate the number of moles of HCI which are needed to react with 20g of Mn02 and list two main chemical properties of chlorine gas.

5. (a) (i) What is the name given to the different forms of the element which exists in the same physical state?

(ii) Carbon exists in two different forms of the same physical state and one of those carbon forms is represented by structure X below. Give the name of the carbon form with structure X.

Name the second form of carbon.

State one property and one use which depends on the property you have stated for each form of carbon.

Carbon can be used to convert copper II oxide to copper as shown in the equation.

C(S) + 2CuO(s) → 2Cucs) +CO2(g)

What is the function of carbon in this equation?

Calculate the mass of CuO which can react with 12g of carbon in the equation given in 5 (b) (i) above.

What is the effect of carbon monoxide in the blood?

7.(a) Identify the substances by using the following information:

A solid is yellow when hot and white when cold.

When water is added to a white powder heat is evolved and the white powder changes to blue crystals.

An aqueous solution of a greenish crystalline sulphate forms a pale-green precipitate with sodium hydroxide solution which turns to brown on standing and when exposed to air.

A colourless gas turns a yellow acidified potassium dichromate paper to green.

A colourless gas becomes brown on exposure to air.

(b) With the help of chemical equations explain what happens to the following compounds of ammonia when heated in separate test tubes:

A mixture of ammonia chloride and sodium hydroxide solution

Ammonium chloride crystals

Ammonium nitrate crystals

Ammonium sulphate crystals

Ammonium nitrite crystals

8. The Diagram below shows the preparation of chlorine gas in a laboratory fume-chamber. Study the diagram and answer the questions that follow.

(a) What do letters A, 8, C, D and E represent?

Why is the gas prepared in the fume-chamber?

Can the gas be collected over water? Why?

What will happen to a damp blue litmus paper if it is introduced into a gas jar full of chlorine gas?

(b) (i) List down two uses of chlorine gas.

(ii) Give a balanced chemical equation for the method of preparation of chlorine used in this question.

9. (a) Write ionic equations for the following:

Laboratory preparation of ammonia gas.

Precipitation of barium sulphate from barium chloride and sodium sulphate and silver chloride from a soluble chloride.

Neutralization of a strong acid and a strong alkali.

(b) Consider the following elements of group seven in the order in which they appear in their group in the Periodic Table. F, C, Br, and I.

Which element is the most electronegative?

Name the least electronegative element.

Which element has the largest atom?

Write the electronic configuration of the chlorine atom.

11. Which method is used in the laboratory gas preparation of:

Ammonia?

Chlorine?

Hydrogen?

Give reasons for your answers.

yellow flowers are introduced into a gas containing chlorine gas?

a burning splint is introduced into a gas jar containing hydrogen gas?

a glass rod which was dipped in concentrated hydrochloric acid is introduced into a gas jar containing ammonia gas?

sulphur dioxide gas is bubbled through a yellow acidified potassium dichromate solution?

12. The preparation of ammonia in the laboratory is done by heating a mixture of ammonium chloride and sodium hydroxide.

(a) (i) Write a balanced chemical equation for the above reaction.

(ii) Using balanced chemical equations, state how ammonia reacts with hydrogen chloride gas and heated copper (II) oxide.

(b) (1) State two uses of ammonia.

(ii) Name the catalyst used in the preparation of ammonia.

Aqueous ammonia is added to iron (III) chloride, little by little, until in excess.

Sodium nitrate is strongly heated.

TOPIC : 2 ORGANIC CHEMISTRY

School Base-Online

CHEMISTRY EXAMINATION FORM FOUR

TOPICAL EXAMINATIONS.

ORGANIC CHEMISTRY

NAME………………………………………..CLASS…………………………………TIME: 21/2HRS

INSTRUCTIONS:-

This paper consists of sections A, B and C

Answer all questions

All answers must be written in the spaces provided

All writings should be in blue/black inks except for drawings that should be in pencils

SECTION A 20 MARKS.

MULTIPLE CHOICE QUESTIONS.

The empirical formula of a certain compound is CH3. Its molar mass is 30g. What will be its molecular formular?

A. CH 4 B. C7 H 4 C. C3 H 6

D. C2H8 E. C4H12

ii) C2H4C1 can be represented in different structures which are called:

Homologous series

Isomers

Structural formular

Identical structures

Condensed structures

(iii) When an alcohol reacts with a carboxylic acid they form an organic compound called:

A. an alkyne B. an ester

C. a haloalkane D. an alkene

E. an alkane

(vi) The compound CH3CH2CI is named as:

carbon dichloride

methyl chloride

ethyl chloride

propyl chloride

(v) A gas burned in air forms carbon dioxide and water only. From this experiment the gas is likely to be:

Hydrogen

Carbon dioxide

Ethane

Nitrogen

Ozone

(vi) The correct chemical equation for the combustion of ethanol is:

CH,CH2OH +1/202 →CH3CH0+ H20

CH3CH2OH + 302 → C02 +3H20

CH,CH2OH + 02 → CH,COOH + H2O

CH,CH2OH + 202 → 2C0 + 3H20

CH3CH2OH + 202 → HCO + CO2 + H2O + H2

When ethane (c2H6 ) burns in air with a bright smoky flame, the product(s) formed will be:

carbon dioxide gas

carbon dioxide gas and water

water

water and oxygen gas

oxygen gas

(viii) Which group of organic compounds is prepared by the dehydration of the corresponding alcohol?

Alkynes

Alkenes

Alkanes

Esters

Carboxylic acids

(ix) Alkynes are organic compounds whose homologous series has a general molecular formula of:

CnH2n

CH(2n+2)

CnH(2n-2)

CnH(2n+1)

CnH(n+2)

(x) An organic compound of structural formula R-COOH belongs to the homologous series of:

alkenes

esters

alcohols

alkanes

acids

MATCHINGITEMS QUESTIONS

LIST A

LIST B

Have the same general formula

Break down of large alkane into smaller alkane.

Same molecular formular but different structural formula

Reaction that mostly occurs in alkanes

Has double bond or triple bond

Self addition of alkanes to form a larger molecule

Sweet smelling substance

Process by which alcohol is formed in laboratory

The product formed when ethene is hydrated using phosphorus catalyst

Substance that increases the cleaning ability of water.

Soap

Detergent

Esterification

Ester

Substitution reaction

Chain reaction

Elimination reaction

Hydrolysis

Polymerization

Saturated hydrocarbon

Unsaturated hydrocarbon

Polymer

Homologous series

Isomers

Isomerism

Cracking

Fractional distillation

Fermentation

Alcohol

Carboxylic acid

SECTION B.

3. Consider a four carbon hydrocarbon (C4Hn), where n is an integer. Give the name of homologous series, molecular formula and structural formula for different isomers of the compound formed by each homologous. In each case indicate the causes of isomerism.

4. a) (i) Define isomerism.

(ii) Write down the molecular structure and IUPAC names of the isomers whose molecular formula is C4H10.

b) Name the homologous series of organic compounds which are represented by the molecular formulae:

CnH(2n+2)

CnH2n

CnH(2n+2)O(In each case n =1,2,3...)

(c) Complete the following equations of chemical reactions and give the IUPAC names of each organic compound which appears in each equation:

CH4 + 02→

C2H4, + Cl2→

CaC2 + 2H2O →?

5. (a) Chemical analysis shows that the empirical formula of a compound is CH2O and its relative molar mass is 60.

Calculate its molecular formula.

Name the compound formed and write its open structural formula.

(b) Write balanced chemical equations of the reaction between the compound named in 8(a) (ii) above and:

Sodium metal

Ethanol

Sodium hydroxide

State the common names of the chemical reactions represented by the equations in 8(b) (ii) and 8(b) (iii) above.

(a) Define the following terms:

Homologous series

Isomerism

(b) Write down the expanded structural formulae of the following compounds:

Chloroethane

2-methylbutane

Ethanol

2, 2-Dimethylpropane

(i) CH2 = CH, + 02 →? (ii) CaC2+2H20 →?

(iii) CH4 +C12

? (iv) C2 H50H + 02 →?

(a) Define the following:

A homologous series

Hydrocarbons

Isomerism

Write the structural formulae of all possible isomers of hydrocarbons whose molecular formula is C4H10 and give their IUPAC names.

You are provided with the following compounds:

H H H H H H

H─C─C─H B. H─ C═C─H C. H─C─C─OH

H H H H

H ─C≡C─H

Give the systematic IUPAC names of the compounds A, B, C and D.

How can you distinguish compound A from D?

8. (a) Classify the following compounds as alkanes, alkanes and alkynes C7H12 ,C4H10 ,C5H5„ C3H4 ,C2H4 and C6H12

(b) Complete and balance the following chemical equations:

CH ═ CH + 02 →

CH,CH2OH + Na →

CH3C00H+ KOH →

CH2 ═CH2 + CI2

9. (a) Which homologous series of organic compounds can be represented by the following general formula?

(i) C6H2n +2 (ii) CnH2n (iii) CnH2+1OH

Give the name of the first compound in each series.

(i) Describe a reaction by which a named compound of series in (a) (ii) can be converted to a compound of series in (a) (i).

(ii) How can a compound of series (a) (iii) be converted to a compound of series in (a) (ii)?

10. (a) (i) State three characteristics of a homologous series.

Draw the displayed/open structure formula of 2, 2-dichlorohexar:-:

Giving two reasons, explain why 2, 2-dichloro-3-methylbutane has structural isomer of 2,2-dichloropentane.

11. The following are the general structural formulae of certain organic compounds: R-OH, R-COOH, and RCOOR.

(a) Name the:

Homologous series represented by

R - OH, R - COOH and R - COOR and RCOOR.

Functional groups represented by R-OH and R-COOH.

(b)Write down the chemical equation of the reactions between the following:

Ethanol and sodium metal.

Propanol warmed with excess acidified potassium permanganate.

Propanol and acetic acid warmed together in the presence of concentrated sulphuric acid.

12. (a) Write the formula for the following compounds:

(i) But-2-ene

(ii) Pent-2-yne

(iii) 1, 2 dichloroethane

(iv) 2, 4 dimethylhexane

(b) Briefly explain what will be observed when silver nitrate solution is added to aqueous solution of sodium chloride.

School Base-Online Page 8

TOPIC : 2 INTRODUCTION TO ORGANIC CHEMISTRY

CHAPTER 2

INTRODUCTION TO ORGANIC CHEMISTRY

KEY TERMS AND CONCEPTS.

Organic chemistry - is the study of carbon which forms long linked chains, excluding oxides, carbonates, hydrogen carbonates, carbides and sulphides.

Hydrocarbon- this is a compound made up of carbon and hydrogen only

Saturated hydrocarbon- this is a hydrocarbon which is made up of single carbon-carbon bond.

Unsaturated hydrocarbon- these are hydrocarbon which have either double bond or triple bond.

Homologous series-these are organic compounds which have same general formula, have similar preparation techniques and differ from each other by a CH2 group.

Cracking- this is breaking down of a large hydrocarbon into small molecules of hydrocarbons by use of heat of catalyst.

Fractional distillation- this is an industrial technique that is used in separation of crude oil in the industry.

Molecular formula- shows the number of carbon atoms and hydrogen atoms in a molecule without showing how they are bonded.

Isomerism- this is the existence of hydrocarbon in such a way that it has same molecular formula but different structural formula.

Substitution reaction- this is at type of reaction in which an activated atom is displaces hydrogen atom in alkane in presence of sunlight.

Hydrogenation – this is the addition of hydrogen into an hydrocarbon such as alkene

Addition reaction- is a type of reaction which occurs in hydrocarbon which are unsaturated in which an atom of a molecule is added into the compound.

Esterification- this is the reaction between an alcohol and carboxylic acid to form a sweet tasting substance called ester.

Saponification – this is the process of making soap

Detergent – this is any type of cleansing material that is capable of removing dirty.

Meaning - organic chemistry is a branch of chemistry which deals mainly with the study of structures, properties and composition of carbon containing compounds. Organic compounds are compounds with carbon-carbon and carbon-hydrogen bonds.

Compounds of carbon such as carbon dioxide, carbonates, hydrogen carbonates are not studied under organic chemistry.

The branch of chemistry that deals the compounds of hydrogen and oxygen only is called hydrocarbon.

Significance of organic chemistry

All living matter is made up of organic compounds, hence the importance in studying it.

Many house hold products can be made by use of organic chemistry, from food, drugs, and fuels, cleaning detergents, plastics and synthetic fibers.

Knowledge in organic chemistry is very important in courses such as medicine, pharmacology, chemical engineering, dentistry and biochemistry.

The unique property of carbon

Carbon has catenation ability which is the ability to form long chains with other elements

Carbon atoms can form double, triple or single bonds among themselves

Carbon uses all its four electrons in forming a bond

Origin of organic compounds

Organic compounds as the name suggests come from living matter. Living organisms which lived many years ago underwent chemical changes to produce the organic compounds we have today. The main source of these compounds is the crude oil, which was formed due to chemical processes which take place on dead organism buried under ground by volcanic rocks. Natural gas is also a source of organic compounds.

Fractional distillation of crude Oil

This is one way in which several types of hydrocarbons can be obtained from crude oil. During this process long carbon chains of hydrocarbons are broken into shorter chains of hydrocarbons, this process is called cracking or pyrolysis.

The crude oil is first heated up in a furnace and molecules with smaller molecular mass boil first and enter into fractionating column as gases. The gaseous hydrocarbons, condenses on the upper part because the fractionating column is hot at the bottom and cooler at the top. Molecules with larger molecular masses have high boiling point, hence turn into liquid near the bottom.

Smaller hydrocarbons are used as fuels while chained hydrocarbons are used as lubricating oil, as tarmac on roads, and fuel in ships and boilers.

The table below shows some of the uses of the hydrocarbons

No. of carbon atoms	Boiling point	Fraction	% yield	uses
1-5	-	Gases	2	Lab gas, domestic gas
5-12	0-65	Petrol	5	Fuel in petrol engines
8-12	65-170	Paraffin	9	Jet fuel, aero plane, domestic use
15-18	250-340	Light diesel	17	Fuel for heavy vehicle ships
18-25	-	Diesel oil	-	Fuel for heavy vehicles
20-70	-	Lubricating oil	-	Used for smooth running of Engines
>70		bitumen	-	Road tarmacking

Table 2.1

All this process is carried out in oil refinery. This industrial process has many environmental effects. This is because some of the gases produced are very poisonous like carbon monoxide, and Sulphur dioxide. When they diffuse into the atmosphere they can cause acidic rain and contribute greatly to global warming.

Hydrocarbons

These are compounds made of only carbon and hydrogen. There are three families of hydrocarbons, these are;

Alkanes

Alkenes

Alkynes.

The above families can be classified into two categories;

Saturated hydrocarbon

Unsaturated hydrocarbon

Saturated hydrocarbons

Are hydrocarbons whose carbon atoms are bonded to the maximum number of hydrogen atoms possible. They have a single bond between carbon atoms.

Unsaturated hydrocarbons

These are hydrocarbons whose carbon atoms do not have the maximum number of hydrogen atoms bonded to them. They have multiple bonds, double or triple.

Homologous series

A homologous series is a group of organic compound with the following features;

They differ from the each other by CH2- group

They have similar chemical and physical properties

They can be prepared using similar methods

They have a general formula

All the three families if hydrocarbons form a homologous series.

Occurrence

All the hydrocarbons occur in crude oil in various proportions. Smaller alkanes can be obtained from long carbon chain alkanes by a process called cracking.

Cracking can take two form; thermal cracking and catalytic cracking.

In thermal cracking, heat is used to break long chains of hydrocarbons into smaller chains, while in catalytic cracking; a catalyst is used to aid in breaking down of a larger hydrocarbon into smaller hydro-carbon.

Thermal cracking

C8H18 → CH3CH3 +CH2=CH2 +CH3 CH=CH2 + H2(g)

When Decane is cracked, heptanes and propene are obtained as follows

Catalytic cracking

Platinum of nickel catalyst can be used;

2CH3CH2CH3 → CH4+CH2=CH2+CH3=CH2+H2(g)

Isomerism

This is the occurrence of a hydrocarbon in such a way that it has the same molecular formula but different structural formula.

Organic compounds with the same molecular formula but different structural formulas are called isomers

Types of formulas

Molecular formula.

It shows the total number of atoms in a compound without indicating how bonding has occurred. Example is C3H6.

Structural formula.

This formula shows how and where each hydrogen is joined in the carbon atoms.

Table 2.2

Condensed formula.

Condensed structural formula does not show how each hydrogen is bonded to the carbon.

Table 2.3

Alkanes

Are hydrocarbons whose carbon atoms contain a maximum number of hydrogen atoms bonded to them. They are usually found in natural gas, petroleum and diesel

Characteristics

The general formula of alkane is CnH2n+2, where n= number of carbon atoms

Ends with the prefix –ane

Next alkane formula differs by a –CH2 group

All are saturated.

Structures of alkanes

Table 2.4

Nomenclature of alkanes

The following guidelines are used in naming of alkanes

The parent name of alkane is identified by the longest continues carbon chain. The prefix in the carbon chain indicates the number of carbons in the molecule.

No. of carbon atoms	Prefix	Name
1	Meth-	Methane
2	Eth-	Ethane
3	Prop-	Propane
4	But-	Butane
5	Pent-	Pentane
6	Hex-	Hexane
7	Hept-	Heptane
8	Oct-	Octane
9	Non-	Nonane
10	Dec-	Decane

Table 2.5

The parent name of all alkanes must end with ane-

The parent chain is the longest continuous carbon chain

The braches that can be attached to parent chain include the following;

Alkyl group

Are alkanes that lack hydrogen they include, methyl – CH3-, Ethyl-CH3CH2-, Propyl- CH3CH2CH2- and butyl- CH3CH2CH2CH2-

Halide groups - these are atoms of halogen family, they include, chlorine, fluorine, iodine, bromine.

They are named as chloro, floro, iodo and bromo, respectively when they appear as branches.

Number the carbon atoms in such a way that the branch gets the smallest numerical value.

The number of the branch should be separated by a hyphen- eg, 2-methyl,3-chloro

If there are halide in a branch, they should be named first in alphabetical order followed by the alkyl group

For more than one identical branch, use the prefixes, di, tri, tetra, depending on the number of branches which are identical.

Example 1

Name the following compound.

H3CH2CH2CH2CHCH3

CH3

The longest chain has six carbon atoms, hence parent name is hexane

The branch is at carbon, number 5.

The branch is methyl.

The name becomes – 2-methyl hexane.

Example 2.

Name the compound below;

CH3 Cl

H3- C- CH- C- CH3

CH3 CH3 Cl

The longest chain is 5 carbon atoms

3- methyl branches at carbon number 2and 3

2- chloro groups at carbon number 4

The compound is named as;

4,4-dichloro2,2,3-trimethylpentane

Laboratory preparation of alkanes.

Figure 2.1 preparation of methane

Alkanes can be prepared by heating any sodium alkanoate with soda lime.

Soda lime is a mixture of sodium hydroxide and calcium hydroxide.

The reaction yields sodium carbonate and alkane. The alkane formed corresponds the number of carbon atoms making the alkyl group of the alkanoate salt used.

Equations.

Sodium alkanoate + sodium hydroxide →sodium carbonate + alkane

CnH2n+1COONa + NaOH → Na2CO3 + CnH2n+2

For example;

Sodium ethanoate + sodium hydroxide → sodium carbonate + ethane

CH3COONa(s) + NaOH → Na2CO3(s) + CH3CH3

Sodium Propanoate + sodium hydroxide → sodium carbonate + propane

CH3CH2COONa(s) + NaOH → Na2CO3(s) + CH3CH2CH3

Physical properties of alkanes

Solubility

They are insoluble in water but soluble in organic solvents

Melting and boiling points

They generally have low melting and boiling point. However, the melting and boiling point increases as the number of carbon atoms increases.

Density

Density increases with the increase in number of carbon atoms. The more the carbon atoms the heavier the compound.

They become more viscous and less flammable down the series.

Chemical properties of alkanes

They burn in sufficient air to form carbon dioxide and water. In limited supply of air, carbon monoxide is formed.

Eg.

2C4H10 (g) +13 02(g) →8CO2(g) + 10 H20 (l)

Higher alkanes burn in air to produce soot and carbon II Oxide gas.

Substitution reaction.

Alkanes do not react with halogens in dark. But will react very vigorously in presence of U.V light to form halo alkane. The role of sunlight is to break the molecules into radicals.

The reaction occurs in two steps,

Propagation step, where the radical is generated and termination stage where the radicals combine.

In this reaction hydrogen is being replaced by a halogen. The reaction can occur in series forming a chain of reactions.

The chlorination of methane occurs as follows;

The role of sunlight is to break the Cl2 molecule into radicals

Cl2 → Cl. + Cl.

The activated chlorine radicals replace hydrogen atoms.

Q. Show the reaction between bromine and ethane in presence of U.V light.

Alkane does not undergo other forms of reactions because they are saturated.

Uses of alkanes

Butane is used in cooking, lighting and in laboratories.

Heavy alkanes are used as lubricants and tarmac

Used in manufacture of other chemicals such as chloroform.

ALKENES

Are saturated hydrocarbons with one or more carbon-carbon double bond

Characteristics

they have the general formular, CnH2n

the name ends with –ane

the simplest alkane is ethane

they differ by a –CH2 group

all are saturated because of double bonds.

Table 2.6

Nomenclature of alkenes

The parent name is formed from the carbons making the longest continuous carbon chain.

The prefixes below are used to identify the atoms.

No. of carbon atoms	prefix	Name.
2	Eth-	Ethene
3	Prop-	Propene
4	But-	Butane
5	Pent-	Pentene
6	Hex-	Hexane
7	Hept-	Heptane
8	Oct-	Octane
9	Non-	Nonene
10	Dec-	Decene

Table 2.7

The carbon atoms are numbered in such a way that the carbons containing double bond are given the lowest numerical value possible. The number of carbon is placed prefix and suffix of the parent name.

CH2=CH – CH3 Prop-1-ene.

For branched alkenes the longest continuous carbon- carbon chain containing the double bond makes the parent of the alkene. When naming the branch, always indicate the number of carbon to which it is attached. During the numbering, ensure that the carbon containing the double bond gets the lowest number possible.

Use di, tri, tetra if same branch occur for more than one time.

When naming the halides should be given priority

The parent name should be written last.

Example 1

Name the compound below;

CH3 Cl

CH3- C = C - C - CH3

Br Cl

The longest carbon chain is 5 carbon atoms.

Methyl branch at carbon number 2

Bromo- group at carbon at 3

2 chloro- groups at carbon number 4

The name thus becomes,

3-bromo-4,4-dichloro-2-methylpente-2-ene.

Laboratory preparations of alkenes

They can be prepared by dehydration of alcohol using concentrated sulphuric acid or heating them in presence of aluminium oxide.

Figure 2.2

Alkanol → alkene + water

C2H5OH(aq) → C2H4 (g) + H2O (l)

Physical properties of alkenes.

Insoluble in water but soluble in other polar solvents

The melting and boiling point increases with increase in molecular weight

Ethane is a colourless and odourless gas at room temperature

Chemical properties of alkenes

Because of the presence of double bond, alkanes are very reactive.

Combustion.

They burn with a lot of soot because of high percentage of carbon in the compound. They form water and carbon dioxide. In limited air, carbon monoxide is formed;

Plenty of air;

CH2CH2 +3O2 → 2CO2 + 2H2O(g) ∆ H –VE

In limited air;

CH2CH2 +2O2 → 2CO + 2H2O(g) ∆ H –VE

Additional reaction.

Because ethene has a double bond, it is capable of accommodating more atoms by opening the double bond.

Where X - Y is hydrogen.

Types of addition reaction

Halogenation

1,2 dibromoethene

Addition of hydrogen halide.

Ethane reacts rapidly with hydrogen halide to form iodo-ethane.

Hydrogenation.

This is the addition of hydrogen. The process requires a catalyst and a temperature of 2000c. The catalyst used is nickel.

Polymerization.

Alkenes can undergo self-addition to form polymer. The double bond opens then a molecule of ethane is added, several molecules, called monomers, and are joined to form large molecules called polymers.

Reaction with potassium permanganate;

Ethane reacts rapidly with acidified potassium permanganate VIII solution and the solution is decolourized being reduced into Manganate III Salt. Ethan-1, 2-diol is formed.

The purple colour of manganite VII is decolourized.

Reaction with sulphuric acid.

Ethene reacts with conc. H2SO4 to form ethyl hydrogen sulphate which when hydrolysed with water to form ethanol.

The decolourization of potassium manganite VII, bromine gas and potassium dichromate VIII saves as a test for alkenes and unsaturation in general.

Uses of alkenes

In the manufacture of polymers like nylons

Manufacture of polychloroethene or polyvinyl chloride

Ethane is used in ripening of fruits

Manufacture of ethanol by hydrolysis

Manufacture of glycol which is used as a coolant.

Alkynes

They are hydrocarbons with triple carbon-carbon bond. They have a general formula CnH2n-2, where n= 2,3,4,5. Like alkene, they are unsaturated.

The first five members include the following

Nomenclature of alkynes.

The name of alkyne is formed by replacing the ane in alkane with yne. The IUPAC naming is the same as that of alkane.

Consider the longest carbon chain with a triple bond.

Number the carbon atoms such that the triple bond gets the lowest value

Identify the branch and the carbon it is attached to.

Insert the carbon with triple bond numerical value between yne of alkyne

In case of more than one branch, use tri, di or tetra as appropriate.

Laboratory preparation of ethyne

It is prepared by the reaction of calcium carbide with water. The gas is insoluble in water hence collected over water. Cold water is used for the reaction.

The reaction equation is;

CaC2 + 2H2O→ C2H2 + Ca(OH)2.

PROPERTIES OF ETHYNE.

Colorless

Insoluble in water

Has sweet smell

Highly explosive since it is endothermic.

Reactions of alkyne.

Like alkenes, alkyne undergoes the following reactions.

Combustion- where water and carbon dioxide is formed

Hydrogenation

Halogenations

Reaction with water

Test for alkynes.

Like ethene, alkynes decolourises bromine, potassium manganate VII and potassium dichromate VII.

Bromine changes from orange to colourles

Potassium permanganate changes from purple to colourless

Potassium dichromate changes from orange to green

Uses of alkynes.

Ethyne-acetylene is used as a flame which gives very high temperature.

Manufacture of adhesives and plastic

Manufacture of synthetic fibre and nylon

Manufacture of chemical solvents

ALCOHOLSAND CARBOXLIC ACID.

Alcohols are also called alkanols. This group of organic compound have a general formula of CnH2n+10H. They thus form homologous series.

The first member of the series is CH3OH, = Methanol

Alcohols have functional group OH, Where most chemical reactions takes place

Alcohol can be formed by replacing the H Ion in water with an alkyl group

Ethanol

Ethanol is an alcohol with a molecular formula C2H6O.

The structural and condensed formulae of ethanol are shown in figure below

CH3CH2OH

Ethanol can be produced by fermentation ( aerobic oxidation) of starch , glucose or sugar solutions with yeast.

The starch is maintained at a temperature of 600cand malt is added to the mixture

The enzyme diastase in starch catalyzes the hydrolysis of sugar to maltose

For example:

C12 H22 O11 + H2 O → 4CHOH + 4C2 O2

Sucrose (Sugar) + water → ethanol + carbon dioxide

Warm conditions are needed for fermentation to take place.

The temperature is maintained at 300c where yeast is added to provide enzyme maltase to which catalysesthehydrplysis of maltose to glucose.

C12H22O11 + H2O →2CH6H12O6(aq).

Enzyme zymase als ocatalyses the decomposition of glucose to ethanol and carbon dioxide.

C6H12O6(aq) → 2C2H5OH + CO2(g)

Ethanol obtained is not pure but can be made more pure by distillation to obtain 95% absolute alcohol/ethanol

Other methods of preparing alchols.

Hydrolysis of ethanol

When ethane is bubbled in concentrated sulphuric acid,hydrolysis takes place and ethanol is formed. The reaction takes place stepwise as follows;

First, there is formation of ethyl hydrogensulphate

CH2=CH2 + H2SO4 → CH3CHOSO2OH

Water is added to the product and warmed to form ethanol

CH3CHOSO2OH + H2O → CH3CH2OH + H2SO4

Hydration.

This is done by use of a catalyst. In this case, ethane is hydrated using phosphorous acidas a catalysts in present of water.

C2H4 (g) + H2O(g) ↔ CH3CH2OH

Physical properties of ethanol

It is colorless liquid with a pleasant smell

It is soluble in water

Melting point and boiling point increase down the group

NB. The melting and boiling points of corresponding alkanes is lower than that of alcohol because of hydrogen bonding.

ALCOHOLS

Alcohols are a homologous series of organic compounds with general formula Cn H2n+1

The table below gives information about the first five members of the series.

You will notice that the names of the alcohols come from the corresponding alkanes

ISOMERIC OF ALCOHOLS

Just as it was possible to have alkanes, alkenes and alkynes with the same molecular but different structural formulae, it is possible also with alcohols providing they have more than two carbon atoms.

The structural formulae of alcohols with four carbon atoms

In the case of 2- methlypropan -1- ol and 2- methylpropan 2-ol , the names are based on the alkaline with three carbon atoms, propane. The side group , methyl (CH3 -) is added as a prefix.

Naming of alcohols

There is a naming system for organic compounds. You select the longest carbon chain and use it as the basis for the name. So a compound with three number indicates which carbon atoms the –OH group is joined to.

REACTIONS OF ETHANOL WITH OXYGEN

Vinegar can be made by allowing ethanol solution to oxidize in air. The sour taste is the taste of ethanoic acid formed when ethanol is oxidized.

CH3CH2OH + O2(g) → CH3 COOH(I) + H2 O

Ethanol + Oxygen

ethanoic acid + water

The oxidation can be carried out in the laboratory by heating ethanol with acidified potassium dichromate (VI) Solution.

Reaction of ethanol with sodium

If a small piece of sodium is added to ethanol added to ethanol, slight effervescene is seen and colorless gas is produced. This gas burns with a squeaky pop (hydrogen).

2CH3CH2 OH (I) + 2Na(s)

2CH3CH2O- Na+ (s) + H(g)

Ethanol + sodium sodium

ethoxide + hydrogen

This reaction can provide a convenient way of disposing of small amounts of sodium left over experiments.

Reaction with ethanoic and concentrated sulphuric acid

If ethanol is heated with ethanoic acid and one drop concencentrated sulphuric acid as catalyst a sweet smelling ester is produced

CH3 COOH (I) + C2H5OH(I)

CH3 COOC2 H5 (I) +H2O

Ethanoic acid + ethanol

ester + water

Dehydration of ethanol.

This is the removal of water molecules from water to form ethane. The conditions required are

Temperature of 1800C

Concentrated sulphuric acid as a dehydrating agent.

CH3CH2OH conc sulphuric acid →CH2CH2 + H20(l)

Uses of alcohols

Alcohols are used as fuels, solvents and as materials for producing other organic compounds.

Biothenol, produced by fermentation of green plants, is now widely used by as an alternative to petrol and diesel.

Petrol and diesel come from crude oil which is a finite resource, but ethanol from fermentation from sugar or starch is not finite.

However, using ethanol as a fuel may reduce the amount of vegetable material for use as food.

Ethanol drinks and its problems.

Distillation of these solutions can produce sprits , such as whisky and gin that can contain 40% ethanol.

Methanol is highly poisonous and must never be drunk instead of ethanol.

Small quantities of ethanol consumed may help people overcome inhibitions and even give them confidence, but problems come if large quantities of ethanol are drunk often.

Even relatively small quantities of ethanol can slow reaction times and impair judgments. This would make driving a car, for example, unwise if not unlawful.

Ethanol drunk regulary can be addictive and lead to all sorts of problems.

There is considerable medical evidence that drinking alcohol damages the liver and kidneys and can be a cause in the development of certain cancers.

CARBOXYLIC ACIDS

The names of various organic acids and their sources are given.

Organic acid are sometimes formed when oxidation of organic chemicals take place.

When milk sour, lactose (sugar ) convert lactic acid and when ethanol sours ethanoic acid is formed.

Carboxylic acids are homologous series of organic compounds with general formula of CnH2n+1CHOOH.

Again these names are based on the names of alkenes. So the carboxylic acid containing one carbon atom is methanoic acid. Carboxylic acids are found in many natural products, such fruit, milk,

Properties of carboxylic acids

Solutions of ethanoic acids carry out similar reactions to other acids, react with bases and alkalis to form a salt and water, react with carbonates to form carbon dioxide and with a fairly reactive metal to produce hydrogen.

Carboxylic acids will also react with alcohols, in the presence of concentrated sulphuric acid to produce an ester.

SOAP MAKING

The word detergent means cleaning agent. Until about 50 years ago this meant soap.

Soap has the disadvantage of not lathering well within hard water. Today manufactures also produce soap less detergents.

These lather equally well with hard or soft water.

Soaps are made from natural fats and oils, e.g. lard, animal fat, castor oil, palm oil.

They are boiled with sodium hydroxide solution.

Fat or oil + sodium hydroxide → soap + glycerol

Soap is precipitated out of the mixture by adding salt solution.

Apart from problems with using hard water, soap less detergents have become more popular becomes soaps can only be made from natural fats and oils and these are becoming more expensive.

Soap less detergents can be made from some of the residues from fractional distillation of crude oil that might otherwise be wasted.

Soaps and detergent clean in a similar way. Both contain molecules that resemble tadpoles and have a head that likes being in water and the tail likes being in oil and grease.

SUMMARY

Ethanol can be produced by fermentation (aerobic oxidation) of starch, glucose and sugar solutions with yeast in warm conditions.

Alcohols are homologous series of organic compounds with general formula CnH2+n OH.

The naming of alcohols and carboxylic acids comes from the name of the corresponding alkaline.

Alcohols such as ethanol react with oxygen, sodium and ethanoic acid (in the presence of concentrated sulphuric acid)

Alcohols are used as fuels, as solvents and as materials for producing other organic compounds.

Carboxylic acids are homologous series of organic compounds with general formula Cn H2n +1 + COOH.

Carboxylic acids have similar properties to other acids when in solution.

Soaps are made when natural fats and oils. e. lard, animals fat, castor oil , plm oil are boiled with hydroxide solution.

TOPIC SUMMARY

Organic chemistry is the study of organic compounds.

Members of homologue series have similar chemical properties.

Hydro carbons are categorized into saturated and unsaturated hydrocarbons.

Fractional distillation of crude oil provides short chain organic compounds that are useful.

Pyrolysis is the breaking down of the long carbon chains into smaller or shorter carbon molecules.

Alcohols are organic compound with the OH – group.

Alcohol are weak acidic and eliminate hydrogen gas with the reactive metals.

A homologous series is a group of organic compounds (homologues) with the same general formula.

The three homologous of hydrocarbons are alkane, alkanes and alkynes.

Alkanes do not decolorize bromine water or acidified potassium manganese (VII) solution. This is because they are saturated.

The melting and boiling points of the hydrocarbons increase with their molecular size.

Hydrocarbons are soluble in organic solvents but not in water.

Alcohols are classified as drugs. They are harmful to human health.

Carboxylic acids react with alcohols in the presence of concentrated sulphuric (VI) acid to produce esters.

Detergents are cleaning agents which are used to improve the cleaning properties of water.

Soaps are generally made from the reaction of an ester and strong alkali. This process is called saponification.

Soapless detergents are made from petroleum products.

Soapy detergents are biodegradable while soap less detergents is non biodegrable.

A polymer is a long – chain macro molecules( monomers)

Polymerization is the process by which small units (monomers) of the same or different kind join to form a large unit polymer.

END OF TOPIC QUESTIONS.

But – 2- ene undergoes hydrogen according to the equation given below

CH3CH ═ CHCH3(g) → CH3CH2CH2CH3(g)

Name the product formed when but -2- ene reacts with hydrogen gas.

State one industrial use of hydrogenation.

Write the structure of the following compounds:

But -2- yne

2,2- dimethylpropane

What is meant by isomerism

Draw and name two isomers of butane

Compound W reacted with chlorine to form compound X only. The structural

Formula of X is shown below:

CH3 – CH – CH – CH3

Give the structural formula and name of compound W.

Name compound x.

In petrol chemical industries, long chain alkanes are broken down in to simple substances in a progress called cracking.

Why is cracking necessary?

State the two conditions required in cracking.

Draw the structure of 1-chloro -2, 2 – dimethylpropane.

In a reaction, an alcohol K was converted to hex -1-ene. Name reagent and condition necessary for the reaction to occur.

A) Give the IUPAC systematic names of compounds Q and R

Q: CH3CHCLCHLCH2CH3

R: CH3CHCLCHCLCH3

b. The organic compounds Q and R in above, are formed when one mole of hydrocarbon N reacts with two moles of hydrocarbon N reacts with two moles of hydration chloride gas what is

Structural formula of N?

The IUPAC systematic name of N?

Distinguish between the isotopes and isomers.

Give the open structures of

3-chlorohex – 1- yne

CH3OH

Write an equation for the reaction that takes place between ethene and concentrated sulphuric (VI) acid

Petroleum (crude oil) is a mixture of several compounds which are separated in Dares Saalam refinery by means of apparatus as shown below.

What is the name of the apparatus above?

What is the name of the process which is used in separation of crude oil?

What physical property of compounds in the mixture does the separation depend on?

Use the letter A to G to describe where the following could be formed:

The fraction that represents gaseous.

The fraction that represents liquids with the lowest boiling points.

State the use produced produced at G and C

Draw apparatus for the separation of the product produced at D and water.

The tables below gives information about the major constitutes of crude oil/ study it and answers the questions that follow.

constituent	Boiling point 0C
Gases Petrol Kerosene Diesel Lubricating oil bitumen	Below 40 40 – 175 175 – 250 250 – 350 350 – 400 Above 400

(iv) Which of the constituent crude with has molecules with the highest number of carbon atoms? Explain.

(v) Name the process you would use to separate a mixture of petrol and diesel and explain how the separation takes place.

(vi) Explain why the constituents of crude oil do not have sharp boiling points.

A. Name the gas that is the likely to be a constituent of crude oil and write its formula.

b. What condition could cause a poisonous gas to be formed when kerosene in burnt? Explain.

c. Give one use of bitumen.

Give the systematic names of the following compounds:

CH2 ═ C – CH3

│

CH3 CH2CH2C ═

State the observations made when butan – 1- ol reacts with.

Acidified potassium dichromate solution

Potassium metal

Give the names of the following:

CH3CH2CH3

CH3CCCH3

Ethene is used in making polymerization . Name the type of polymer that is formed when ethene is polymerized.

Write all the isomers of but -2- ene and give their IUPAC names.

A hydrocarbon compound Z decolorizes bromine liquid in the presence of light but does not decolourise acidified potassium manganate (VII). Name and draw the structural formula of the eighth member of this homologous series.

What is meant by isomerism?

Draw and name two isomers of butyne.

A students mixed equal volume of ethanol and butanoic acid. He added a few drops of concentrated sulphuric acid (VI) acid and warmed the mixtre.

Name and write the formula of the main products

Name..................

Formula.............

Which homologous series does the product named in above belong?

Explain the environmental effects of burning plastic in air as a disposal method.

Write chemical equations to represent the effect of heat on ammonium carbonate.

Sodium octadecanoate has a CH3(CH2)6 COO- Na+, which is used as soap. Explain why a lot of soap is needed when washing with hard water

Ethanol and pentane are miscible liquids. Explain how water carbon be used to separate a mixture of ethanol and pentane.

Give the IUPAC name of the following compound CH3COOCH2CH3

Write an equation to show products formed for the complete combustion of CH2═ CH2.

Give the IUPAC name of following organic compounds:

CH3 – CH – CH2 – CH3

│

CH3- CH- CH2 – CH2 – CH3

│

C2H5

CH3COOCH2CH2CH3

The structure below represents a cleansing agent.

State the type of cleansing agent represented above.

State one advantage and one disadvantage of using the above cleansing agent.

What is meant by the term esterification?

Draw the structural formulae of two compounds that may be reacted to form ethylpropanoate.

Draw the structure of pentatonic acid

Draw the structure of pentatonic acid.

Draw the structure and give the name of the organic compound formed when ethanol reacts with pentanoic acid in thepresence of concentrated sulphuric (VI) acid.

Substance A and B are represented by the formulae ROH and RCOOH respectively.

Name the common product produced by booth.

State the observation made when each of the sample A and B are reacted with sodium hydrogen carbonate.

In the presence of ultraviolent light, ethane gas undergoes a substitution reaction with chlorine.

State what is meant by substitution reaction.

Give the structural formula and name of the organic product formed when equal volomes of ethane gas and chlorine gas react.

Name the compounds P,R, S and T whose formulae are shown below.

S= CH3CH2CH2OH

P= CH3CH2CH2CH3

R= CH3CH2CH2COOH

T= CH3CH=CHCH3

Describe an experiment you would carry out distinguish T from p

CO2

tudy the flow chart below and use it to answer the questions that follows

CH2=CH2

urn in O2

eagent P Process 1

Ethyl ethanoate

CH3CH2OH

Reagent Q KmO4/H/processn4

Process3

Nam the compounds labeled A and B on the flow chart.

Draw the structural formula for the compound C.

Name the process labeled 1,2,3 and 4.

Identify the reagents labeled P and Q.

State the condition required in the formation of substance B.

TOPICAL EXAMINATIONS

CHEMISTRY FORM FOUR

ORGANIC CHEMISTRY.

SECTION A 20 MARKS.

MULTIPLE CHOICE QUESTIONS.

The empirical formula of a certain compound is CH3. Its molar mass is 30g. What will be its molecular formular?

A. CH 4 B. C7 H 4 C. C3 H 6

D. C2H8 E. C4H12

ii) C2H4C1 can be represented in different structures which are called:

Homologous series

Isomers

Structural formular

Identical structures

Condensed structures

(iii) When an alcohol reacts with a carboxylic acid they form an organic compound called:

A. an alkyne B. an ester

C. a haloalkane D. an alkene

E. an alkane

(vi) The compound CH3CH2CI is named as:

carbon dichloride

methyl chloride

ethyl chloride

propyl chloride

(v) A gas burned in air forms carbon dioxide and water only. From this experiment the gas is likely to be:

Hydrogen

Carbon dioxide

Ethane

Nitrogen

Ozone

(vi) The correct chemical equation for the combustion of ethanol is:

CH,CH2OH +1/202 →CH3CH0+ H20

CH3CH2OH + 302 → C02 +3H20

CH,CH2OH + 02 → CH,COOH + H2O

CH,CH2OH + 202 → 2C0 + 3H20

CH3CH2OH + 202 → HCO + CO2 + H2O + H2

When ethane (c2H6 ) burns in air with a bright smoky flame, the product(s) formed will be:

carbon dioxide gas

carbon dioxide gas and water

water

water and oxygen gas

oxygen gas

(viii) Which group of organic compounds is prepared by the dehydration of the corresponding alcohol?

Alkynes

Alkenes

Alkanes

Esters

Carboxylic acids

(ix) Alkynes are organic compounds whose homologous series has a general molecular formula of:

CnH2n

CH(2n+2)

CnH(2n-2)

CnH(2n+1)

CnH(n+2)

(x) An organic compound of structural formula R-COOH belongs to the homologous series of:

alkenes

esters

alcohols

alkanes

acids

MATCHINGITEMS QUESTIONS

LIST A

LIST B

Have the same general formula

Break down of large alkane into smaller alkane.

Same molecular formular but different structural formula

Reaction that mostly occurs in alkanes

Has double bond or triple bond

Self addition of alkanes to form a larger molecule

Sweet smelling substance

Process by which alcohol is formed in laboratory

The product formed when ethene is hydrated using phosphorus catalyst

Substance that increases the cleaning ability of water.

Soap

Detergent

Esterification

Ester

Substitution reaction

Chain reaction

Elimination reaction

Hydrolysis

Polymerization

Saturated hydrocarbon

Unsaturated hydrocarbon

Polymer

Homologous series

Isomers

Isomerism

Cracking

Fractional distillation

Fermentation

Alcohol

Carboxylic acid

SECTION B.

4. a) (i) Define isomerism.

(ii) Write down the molecular structure and IUPAC names of the isomers whose molecular formula is C4H10.

b) Name the homologous series of organic compounds which are represented by the molecular formulae:

CnH(2n+2)

CnH2n

CnH(2n+2)O(In each case n =1,2,3...)

(c) Complete the following equations of chemical reactions and give the IUPAC names of each organic compound which appears in each equation:

CH4 + 02→

C2H4, + Cl2→

CaC2 + 2H2O →?

5. (a) Chemical analysis shows that the empirical formula of a compound is CH2O and its relative molar mass is 60.

Calculate its molecular formula.

Name the compound formed and write its open structural formula.

(b) Write balanced chemical equations of the reaction between the compound named in 8(a) (ii) above and:

Sodium metal

Ethanol

Sodium hydroxide

State the common names of the chemical reactions represented by the equations in 8(b) (ii) and 8(b) (iii) above.

(a) Define the following terms:

Homologous series

Isomerism

(b) Write down the expanded structural formulae of the following compounds:

Chloroethane

2-methylbutane

Ethanol

2, 2-Dimethylpropane

(i) CH2 = CH, + 02 →? (ii) CaC2+2H20 →?

(iii) CH4 +C12

? (iv) C2 H50H + 02 →?

(a) Define the following:

A homologous series

Hydrocarbons

Isomerism

Write the structural formulae of all possible isomers of hydrocarbons whose molecular formula is C4H10 and give their IUPAC names.

You are provided with the following compounds:

H H H H H H

H─C─C─H B. H─ C═C─H C. H─C─C─OH

H H H H

H ─C≡C─H

Give the systematic IUPAC names of the compounds A, B, C and D.

How can you distinguish compound A from D?

8. (a) Classify the following compounds as alkanes, alkanes and alkynes C7H12 ,C4H10 ,C5H5„ C3H4 ,C2H4 and C6H12

(b) Complete and balance the following chemical equations:

CH ═ CH + 02 →

CH,CH2OH + Na →

CH3C00H+ KOH →

CH2 ═CH2 + CI2

9. (a) Which homologous series of organic compounds can be represented by the following general formula?

(i) C6H2n +2 (ii) CnH2n (iii) CnH2+1OH

Give the name of the first compound in each series.

(i) Describe a reaction by which a named compound of series in (a) (ii) can be converted to a compound of series in (a) (i).

(ii) How can a compound of series (a) (iii) be converted to a compound of series in (a) (ii)?

10. (a) (i) State three characteristics of a homologous series.

Draw the displayed/open structure formula of 2, 2-dichlorohexar:-:

Giving two reasons, explain why 2, 2-dichloro-3-methylbutane has structural isomer of 2,2-dichloropentane.

11. The following are the general structural formulae of certain organic compounds: R-OH, R-COOH, and RCOOR.

(a) Name the:

Homologous series represented by

R - OH, R - COOH and R - COOR and RCOOR.

Functional groups represented by R-OH and R-COOH.

(b)Write down the chemical equation of the reactions between the following:

Ethanol and sodium metal.

Propanol warmed with excess acidified potassium permanganate.

Propanol and acetic acid warmed together in the presence of concentrated sulphuric acid.

12. (a) Write the formula for the following compounds:

(i) But-2-ene

(ii) Pent-2-yne

(iii) 1, 2 dichloroethane

(iv) 2, 4 dimethylhexane

(b) Briefly explain what will be observed when silver nitrate solution is added to aqueous solution of sodium chloride.

SAMPLE NECTA QUESTIONS.

NECTA 2004.

8. (a) Chemical analysis shows that the empirical formula of a compound is CH2O and its relative molar mass is 60.

Calculate its molecular formula.

Name the compound formed and write its open structural formula.

(b) Write balanced chemical equations of the reaction between the compound named in 8(a) (ii) above and:

Sodium metal

Ethanol

Sodium hydroxide

State the common names of the chemical reactions represented by the equations in 8(b) (ii) and 8(b) (iii) above.

2005 QN8.

(a) Define the following terms:

Homologous series

Isomerism

(b) Write down the expanded structural formulae of the following compounds:

Chloroethane

2-methylbutane

Ethanol

2, 2-Dimethylpropane

(i) CH2 = CH, + 02 →? (ii) CaC2+2H20 →?

(iii) CH4 +C12

? (iv) C2 H50H + 02 →?

2006.

QN 8

8. (a) Define the following:

A homologous series

Hydrocarbons

Isomerism

Write the structural formulae of all possible isomers of hydrocarbons whose molecular formula is C4H10 and give their IUPAC names.

You are provided with the following compounds:

H H H H H H

H─C─C─H B. H─ C═C─H C. H─C─C─OH

H H H H

H ─C≡C─H

Give the systematic IUPAC names of the compounds A, B, C and D.

How can you distinguish compound A from D?

2007.

QNS. 8. (a) Classify the following compounds as alkanes, alkanes and alkynes C7H12 ,C4H10 ,C5H5„ C3H4 ,C2H4 and C6H12

(b) Complete and balance the following chemical equations:

CH ═ CH + 02 →

CH,CH2OH + Na →

CH3C00H+ KOH →

CH2 ═CH2 + CI2

2010.

QNS. 6 (a) Which homologous series of organic compounds can be represented by the following general formula?

(i) C6H2n +2 (ii) CnH2n (iii) CnH2+1OH

Give the name of the first compound in each series.

(i) Describe a reaction by which a named compound of series in (a) (ii) can be converted to a compound of series in (a) (i).

(ii) How can a compound of series (a) (iii) be converted to a compound of series in (a) (ii)?

2011.

QN. 4.(a) Organic chemistry deals with carbon element and its compounds. Name one carbon hydrogen compound and write the equation for its combustion.

(b)Write all the structural isomers of alcohols whose molecular formula is C4H90H and give their IUPAC names.

2013.

QNS6. (a) (i) State three characteristics of a homologous series.

Draw the displayed/open structure formula of 2, 2-dichlorohexar:-:

Giving two reasons, explain why 2, 2-dichloro-3-methylbutane has structural isomer of 2,2-dichloropentane.

(b) Carbon monoxide and hydrogen are used in the manufacture at methanol and the equilibrium is established according to the following equation:

CO (g) +2H 2 (g) → CH3 OH(g) ∆H= -80kj.moll

Give two features of the reaction at equilibrium

Explain why an increase in temperature causes a decrease a equilibrium yield of methanol.

2013.

QNS.7(a)Briefly explain how aluminium is obtained from its oxide.

(b)Write down the chemical equation of the reactions between the following:

Ethanol and sodium metal.

Propanol warmed with excess acidified potassium permanganate.

Propanol and acetic acid warmed together in the presence of concentrated sulphuric acid.

2013.

QNS 8. The following are the general structural formulae of certain organic compounds: R-OH, R-COOH, and RCOOR.

(a) Name the:

Homologous series represented by

R - OH, R - COOH and R - COOR and RCOOR.

Functional groups represented by R-OH and R-COOH.

TOPIC : 3 POLLUTION

School Base-Onlone

CHEMISTRY EXAMINATION FORM FOUR

TOPICAL EXAMINATIONS.

POLLUTION

NAME………………………………………..CLASS……………………………………TIME: 21/2HRS

INSTRUCTIONS:-

This paper consists of sections A, and B

Answer all questions

All answers must be written in the spaces provided

All writings should be in blue/black inks except for drawings that should be in pencils

SECTION A 20 MARKS.

The problem of acid rains is now a reality in industrialized countries. The gases which escape from industries into the atmosphere and cause acid rains include:

nitrogen, carbon dioxide and chlorine

chlorine, nitrogen monoxide and ammonia

chlorine, carbon dioxide and sulphur dioxide

nitrogen dioxide, carbon dioxide and sulphur dioxide

chlorine, nitrogen and nitrogen monoxide

Which of the following actions would result into an increase in the temperature of the earth?

Increase of distance from the sun

Removal of water vapour from the atmosphere

Increase of cloud cover

Removal of noble gases from the atmosphere

Increase of the carbon dioxide content of the atmosphere.

which of the following is not a type of pollution?

Aerial pollution

Marinepollution

Water pollution

Terrestrial pollution

which of the following is not a typeof land pollution?

Nuclear waste

Homegarbage

Fertilizers

Solid chemicalwastes

v) which of the following ispoint source of water pollution?

A. Fertilizer from the farm

B. Oil spills

C.Liquid industrial effluent

D. Release of sewage waste into water bodies

vi) excessive growth of water plants and algae is called?

Point pollution

Leaching

Eutrophication

Dead zones

vii) the majorcomponent of photochemical smog is;

Ozone

Particulate matter

Carbon monoxide

Nitrogen dioxide

viii) which of the following chemical does not contribute to global warming?

CH4

CO2

N2O

IX) The zone of the atmospherewhich contains the ozone layer is called?

Mesosphere

Stratosphere

Higher atmosphere

Troposphere

x) the compound of sulphur that causes acidic rain is;

A. Sulphur dioxide

B. Sulphur trioxide

C. Hydrogen Sulphide

D. Sulphuric acid

2. Matching items Questions.

LIST A

LIST B

Chemical reaction of sunlightwith oxides of nitrogen and volatile organic matter in the atmosphere

Sources of pollution that release wastes directly into water body

Areas with low oxygen concentration due to eutrophication leading limited growth.

Gases which contribute to global warming

Increase of the earths temperature

A layer of oxygen molecules that prevents harmful ultra-violet rays

The process by which emission of radiations warms the planet earth.

Protection and preservation of natural environment.

Disintergration of ozone layer due to green house gases

Nuclear plants

Solid waste

Liquid waste

Nuclear waste

Sewage

Ozone layer depletion

Ozone layer prolifecation

Point pollution

Non-point pollution

Greenhouse gases

Global warming gases

Smog

Fog

Eutrophication

Dead zones

Global warming

Greenhouse

Environmental conservation

Ozone layer

SECTION B.

3. (a) Define the following terms:

(i) Pollution

(ii) Pollutant

List down the three main types of pollution.

(i) Define "green house effect".

(ii) Why does the increase of the concentration of carbon dioxide gas in the atmosphere result into increase of the earths surface temperature?

(iii) What is the function of ozone layer at the top of earths atmosphere?

(iv) List down any two gases produced by industries that destroy the ozone layer.

4. (a) (i) Define the term pollution.

(ii) List down the three (3) main types of pollution.

(ii) What is the importance of ozone layer in the earths atmosphere?

Explain the effect of destroying the ozone layer.

5. (a) (i) Define the term terrestrial pollution.

(ii) Mention three (3) materials that contribute to terrestrial pollution.

(iii) Mention three (3) gases which cause acid rains.

(b) Explain the effect of the following to the environment:

Acid rain

Artificial fertilizer

Plastic containers

(a) (i) Define the term fertilizer.

(ii) What are the three (3) effects of excessive nitrogen to plants?

(b)(i) State four (4) methods of application of fertilizers.

What are the four (4) advantages of using manures in the farms?

Calculate the percentage composition of nitrogen in ammonium sulphate fertilizer (NH4 )2 SO4 .

(a) (i) What does the term terrestrial pollution mean?

Mention three (3) causes of terrestrial pollution.

Explain four (4) methods of preventing terrestrial pollution.

(b) What is the effect of ultraviolet radiations on living organisms?

(ii) What control measures should be taken to prevent the destruction of ozone layer?

8. (a) Mention three (3) natural resources that should be protected from pollution.

(b) Name two (2) pollutants in each of the following:

Land

Water

Air

(ii) Give three (3) examples of gases which cause greenhouse effect.

9.Describe five causes and effects of soil pollution.

10. a) what is ozone layer?

b) name four ozone layer depleting substances

c) suggest two things that should be done to prevent ozone layer from depletion

11. Eutrophication is the excessive growth of aquatic plants and algae in water bodies

b) Give two causes of eutrophication

b) Explain three effects of eutrophication

c) Explain four ways in which mining contribute to water pollution.

School Base-Online Page 6

TOPIC : 3 POLLUTION

P CLASS="western" ALIGN=CENTER STYLE="margin-right: 0.3in; margin-top: 0.08in; margin-bottom: 0.11in; line-height: 150%"> CHAPTER 4

ENERGY AND FUELS.

KEY TERMS AND TERMINOLOGIES.

Energy- this is the capacity or ability to do work

Principle of conservation of energy- this states that energy cannot be created or destroyed but can be transformed from one form to another.

Kinetic energy- this is energy in motion.

Potential energy- this is energy of a body at rest.

Thermochemistry- this is the study of energy changes

Enthalpy- this is the energy content of substance

Exothermic reaction- this is the type of reaction that give off heat energy to the environment.

Endothermic reaction- this is a type of reaction that absorbs heat from the surrounding.

Fuel- is any combustible material/ substance which on burning in air gives a large amount of heat that can be used economically for domestic and industrial purposes.

Velocity of combustion- this is the rate at which a fuel burns

Ignition point- this is the temperature at which a fuel must be heated before it starts burning.

Pyrometric burning effects- this is the highest temperature that can be reached by a burning fuel.

Producer gas- this is a mixture of carbon monoxide and nitrogen

Water gas – this is a mixture of carbon monoxide and hydrogen, with a small amount of carbon dioxide.

Energy value of fuel- is the total amount of heat liberated by the complete combustion of unit mass of the fuel in air.

Renewable energy source- are sources of energy that are continuosly being replaced within a short period of time.

Non renewable energy sources- these are energy sources that cannot be replenished within short periods of time.

Global warming- this is continuous raising of earth’s temperature due to accumulation of green house gases.

Green house gases- these are gases that destroy ozone layer leading to penetration of harmful rays into earth’s surface.

Nuclear energy- this is a type of energy that is derived from changes which occurs in the nucleus of an atom.

Nuclear fission- this is the splitting of the nucleus of the atom causing energy to be released.

Nuclear fusion- the nuclei of atoms come together or get fused. This leads to generation of large amount of heat.

Energy is the capacity or ability of a body or system to do work. The SI unit for energy is the joule M.

Energy exists in two major forms, namely potential and kinetic energy.

Potential energy is the energy in matter due to its position or state. Examples of potential energy include chemical energy, elastic energy nuclear energy and gravitational energy.

Kinetic energy is the energy possessed by a body due to motion. The motion could be of waves, electrons, atoms, molecules or the object itself. A Body in motion is in movement. Examples of kinetic energy include electric energy, radiation energy, thermal energy and sound energy.

Mechanical energy is the sum of kinetic energy and potential energy.

Conservation of Energy.

The principle of conservation of energy states:

“Energy can neither be created nor destroyed, it only be changed from one form to another”.

Appliances only convert energy to different forms but they do not create it. The efficiency of any appliance is always less than 100%. For example, an electric Iron box converts electric energy to light and heat energy. The total energy input is always equal to the total energy output, irrespective of the form of energy.

Transformation of energy

This is a process of changing energy from one form another is referred to as transformation of energy. The following of how energy is transformed from one form to another.

Changing mechanical energy to electrical energy

A hydroelectric power plant converts mechanical energy into electrical energy. The figure below sows te structure of wind mill power.

Figure 4.1 hydroelectric power.

Electrical energy can also be generated from the wind. This is done using a windmill.

The wind possesses kinetic energy which can rotate the blades of a windmill.

If the windmill is used to rotate a dynamo, electrical energy is produced. The combination of a windmill and a dynamo converts mechanical energy from the wind to electrical energy.

2. Changing electrical energy to heat energy

Appliances that produce heat when connected to a source of electricity include the electric cooker, electric iron, electric heater and the electric bulb.

These devices make use of a high resistance wire. When an electric current passes through this wire, the electrical energy is converted to heat energy.

Figure 4.2 An electric cooker.

Change of electrical energy to mechanical energy

When a source of electric current is connected to an electric motor, a rotational motion is produced in the motor. In this way, electrical energy is converted to mechanical energy.

Change of electrical energy to mechanical energy

When a source of electric current is connected to an electric motor, a rotational motion is produced in the motor. In this way, electrical energy is converted to mechanical energy.

In solar cookers, a shiny parabolic metal surface is used to focus sun rays to produce heat. Solar energy is therefore, converted to heat energy.

Figure 4.3 An electric motor

4. Change of electrical energy to sound energy

In an electric bell, electrical energy is converted to sound energy. The figure below shows a simple electric bell.

Figure 4.4 electric bell

Energy changes in chemical reactions

Energy is never static, in many chemical reactions, energy is converted to heat energy and sometimes to light energy and many other forms.

However, not all chemical changes are accompanied by production of heat. Some -chemical changes absorb heat.

The study of energy changes that accompany chemical reactions is called thermochemistry.

Molecules have kinetic energy due to the rational and rotational motion of the particles that makes them. In addition to the kinetic energy, molecules also have potential energy due to their position and composition.

The potential energy stored in molecular bonds that exist within molecules (intramolecular) and also between

different molecules (intermolecular).

The sum of all kinetic and potential energies of a substance is known as heat content or enthalpy (H). The units of H are joule (J) or kilojoule (kJ).

Chemical reactions involve the rearrangement of atoms and molecules. The rearrangement is achieved by breaking bonds in reactant molecules and forming new bonds in product molecules.

Energy is required to break bonds whereas energy is given out when new bonds are formed. The difference between the energy released and the one absorbed in a chemical reaction is the energy change for the reaction. This is usually referred to as enthalpy change.

Enthalpy change in chemical reactions

The enthalpy change in a chemical reaction is the energy gained or lost during a chemical reaction when molar quantities are reacting. It is represented by the symbol ∆H (read as delta H). The units for ∆H are kilojoules per mole (kJ mol-).

The enthalpy change in a chemical reaction is the difference between the heat content of the reactants and that of the products, that is, AH =- heat content of the products (Hp) minus heat content of the reactants (HR):

AH = Hp - HR

The value of AH is usually shown at the end of a chemical equation.

A + B → C + D ∆ = XKj/mol

where x is the value for ∆H.

Chemical equations which show enthalpy change in a reaction are referred to as thermochemical equations.

Enthalpy change is directly proportional to the amounts of substances taking part in the reaction. This means that the enthalpy change will double if the amount (number of moles) of the reactants is doubled.

Exothermic and endothermic reactions

Chemical reactions are classified as either exothermic or endothermic, in terms of the energy changes that take place.

Consider a chemical reaction in which molecules A and B react to form molecules C and D.

A+B → C+D

(reactants) (products)

If the sum of the heat content of molecules A and B is more than the sum of the heat content of molecules C and D, the excess energy is released to the surroundings.

Such a reaction is referred to as an exothermic reaction.

An exothermic reaction is a reaction in which energy is lost from the reaction mixture. The delta H of exothermic reaction is given a negative sign, showing that energy is lost into the surrounding.

For an exothermic reaction, HR is greater than Hp, and therefore the value of ∆H is negative. This shows that energy has been lost from the reaction mixture.

Examples of exothermic reactions are:

combustion reactions.

mixing of water and strong acids such as concentrated sulphuric acid.

If the heat content of molecules C and D (products) is greater than the heat contents of molecules A and B (reactants) the extra energy required is absorbed from the surroundings. Such a reaction is an endothermic reaction.

An endothermic reaction is a reaction in which the energy content of the products is more than that of the reactants.

For an endothermic reaction, Hp is greater HR and therefore the value of ∆H is positive. This shows that heat has been gained in the reaction mixture.

Examples of endothermic reactions are:

dissolving ammonium chloride in water

mixing water and potassium chloride

photosynthesis.

Reversible reactions are both endothermic and exothermic. If the forward reaction is exothermal then the reverse reaction is endothermic.

The magnitude of AH for the two processes is the same. Only the signs differ (negative for the exothermal reaction and positive for the endothermic reaction).

Consider the reaction between sulphur dioxide and oxygen gases in the manufacture of sulphuric acid.

2S02(g) + 02(g) = 2S03(g) AH = -196 kJ mol-

From the thermochemical equation, the forward reaction is exothermic. Therefore, the reverse reaction is endothermic with the same value AH, but different in sign. That is:

2S03(g)

2S02(g) + 02(g) AH = +196 kJ

Energy level diagrams

The energy changes in a chemical reaction are shown graphically using a type graph called an energy level diagram. T vertical (y-) axis of an energy level diagram represents the energy while the horizontal (x-) axis represents the path of the reaction a it progresses from the reactants to form the products.

In an exothermic reaction, the reactants are a higher energy level than the products. The difference between the two energy levels is to energy released to the surroundings in the reaction. This is shown as a vertical drop in an energy level diagram.

In an endothermic reaction, the reactants have lower energy content than the products. The difference between the two energy levels is the energy gained from the surrounding region. This energy is represented as a vertical rise in an energy level diagram.

Many cold packs used for relieving pain make use of the reaction of ammonium nitrate with water. Such packs come in a plastic bag made of tough white plastic.

The bag contains ammonium nitrate crystals and a smaller bag filled with water. The smaller bag is made of a thin weak plastic that is easy to break.

To use the cold pack, one tears the inner bag. This releases the water, which dissolves the ammonium nitrate in an endothermic reaction.

The extra heat needed for the reaction is absorbed from the surrounding area.

Fuels

A fuel is any combustible substance which on burning in air gives a large amount of heat that can be used economically for domestic and industrial purposes.

Classification of fuels

Fuels can be classified into two main categories, according to their occurence and their physical state.

Classification according to their physical state.

Fuels can be of three types;

Solid fuels,for examples firewood, charcoal, coal coke,

Liquid fuel- example includes kerosene, petrol, diesel, biodiesel

Gaseous fuels- this include liquid petroleum gas, coal gas, water, and hydrogen.

Classification according to occurrence.

Natural or primary fuels,- they occur in nature and includes wod, coal, peat, petroleum, and natural gas.

Artificial or secondary fuels- these are fuels either manufactured from the industry or derived from primary fuels. They include coke, kerosene, petrol, coal gas and producer.

Characteristics of a good fuel.

The choice of the fuel to be used depends on various characteristics. The following are the characteristics of fuel to consider when deciding what fuel to use.

Energy

Velocity of combustion

Ignition point

Non-combustible

Poisonous

Pyrometric burning effect

Availability

Affordability

Energy value. A good fuel should have a high energy value. The energy value of a fuel is determined by the amount of energy produced per unit mass of the fuel. This is called the heat value of the fuel.

Velocity of combustion. This refers to the rate at which a fuel burns. A good fuel should burn with a moderate velocity for a continuous supply of heat.

Ignition point. This is the temperature to which the fuel must be heated before it starts burning. A good fuel should have an average ignition point. A low ignition point is risky due to fire hazards while high ignition point makes it difficult to start a fire with the fuel. Fuels with high ignition points are safe to transport and store.

Non-combustible material content. A good fuel should have a low content of noncombustible material. The non-combustible material is left in form of ash once the fuel burns. A high content of non-combustible material lowers the heat value of the fuel.

Poisonous products of combustion. A good fuel should not give offpoisonous gases during combustion. The fuel should also give off very little or no smoke.

Pyrometric burning effect. This is the highest temperature that can be reached by the burning fuel. A good fuel should have a high pyrometric effect. Gaseous fuels have the highest pyrometric effect.

Availability. A good fuel should be readily available in large quantities.

Affordability. A good fuel should be affordable to most people.

Ease of transportation and storage. A good fuel should be easy and safe to transport and store.

Effect on the environment. A good fuel should not have harmful effects on the environment during its production and its use. Fossil fuels, which produce carbon dioxide on burning, are a major contributor to global warming.

Coal

Coal is the most important solid fuel. It is a fossil fuel formed by the anaerobic decomposition of long dead. Mt energy found in coal is solar energy stored in tat plants. This energy remains in the compounds after the decay process.

Composition of coal

The four major components of coal are

moist

volatile matter,

ash and

fixed carbon (coke Volatile matter is the material that is driven when coal is heated to about 950°C in the absence of air. It consists of gases and low-boiling point organic compounds that condense into oils when cooled, and tar.

Ash is the non-combustible residue material after coal is burnt. Coke is the material left the volatile matter are driven off

Types of coal

There are different types of coal that vary composition and properties. The most import-types of coal are -peat, lignite, bituminous (soft) and anthracite (hard) coal.

Destructive distillation of coal

Destructive distillation is a process through w organic fuels such as wood, coal and oil shale decomposed by heating them in the absence of (oxygen) to obtain useful products such as co charcoal, oils and gases.

The main aim of destructive distillation of coal to get rid of the volatile matter.

Coal that contain large amount of volatile matter burns with smoky flame and has a low energy value.

Destructive distillation takes place in the absence of oxygen (in an airtight oven) and prevents coal from burning.

The remaining material, is pure carbon. This is the most widely used coal product. It is mainly used in metal-extraction furnaces.

Some of the gases produced du the distillation process can be refined to form ammonia, coal tar and light oil.

Destructive distillation of coal is generally carried out in two types of kilns. These are the beehive kiln and the Otto Hoffman kiln.

Bee Hive kiln

This is the earliest and the cheapest process of mining coal.

The kiln is a dome-shaped structure de up of bricks.

It has two openings, one at the Top for charging (adding) the coal and the other on side to discharge (remove) coke. A side door is o used for supplying air to ignite the coal.

A uniform layer of coal is spread over the hearth se) through the charging door. Air is supplied through the side door to ignite the coal. The volatile matter escapes and burns inside the side door.

Otto Hoffman kiln

In this kiln, the by-product of distillation process are also recovered

By products includes ammonia, coal, benzol oil and tar

It has narrow silica chambers separated by spaces for burning gas, with a charging at the top, gas outlet and doors

Coal is heated to drive away liquid or gaseous components in materials, a process called dry distillations

Coke formed is quenched using water spray- also called wet quenching

The coke is about 75% by mass coal

Charcoal

Charcoal is made by the dry distillation of wood.

The dry distillation of wood is done at a temperature of between 4 000 and 4 500°C in an earth pit kiln or earth mound kiln.

In the earth pit kiln, the wood is heaped in a hemispherical pile in a central pit. It is then covered with earth and sod, leaving only a few small air holes near the bottom.

The wood is lit at the centre and allowed to burn until the whole pile is on fire. A smoldering combustion takes place, utilizing the oxygen and hydrogen components of the wood fibre.

The products of this combustion are water, carbon dioxide and volatile organic compounds which escape into the atmosphere.

The holes for allowing air in are then closed. The pit is kept covered until the fire goes off and the charcoal cools. All the volatile matter is driven out in this process.

The residue consists of carbon and the inorganic components of the wood. The yield of charcoal is only 20% by weight and 75% by volume, of the wood.

Gaseous Fuels.

There are two important gaseous fuels, the producer gas and water gas

Producer gas.

A mixture of carbon monoxide and nitrogen

Formed by burning carbonaceous fuel in limited supply of air

Production

Producer gas is manufactured in a producer furnace, which consists of a large air-tight cylindrical vessel made of mild steel.

The vessel is lined on the inside with fire bricks: At the bottom, there is a pipe for blowing in air and an opening for removing ash.

Coal is added through a hopper at the top and producer gas comes out through an exit near the top.

When air, mixed with a little steam, is passed through the inlet, the carbon (from coal) combines with oxygen (from air) in the lower part of the furnace to form carbon dioxide:

C(s) + 02(g)→CO2(g) AH = -406 kJ

The carbon dioxide formed rises up through the red-hot coal and gets reduced to carbon monoxide during its passage:

CO2(g) + C(s)→2C0(g) = +163 kJ

The nitrogen gas in the air is not affected at all during the process. Thus, a mixture of carbon monoxide and nitrogen, with traces of carbon dioxide and some organic compounds, comes out through the exit at the upper end of the furnace.

Since more heat (406 kJ mo1-1) is produced in the lower part than is absorbed in the upper part (163 kJ mot-), some excess heat is obtained in the long run. This heat keeps the coal hot.

Uses of producer gas.

Used as fuel in open hearth kilns/ furnaces

Provide a reducing atmosphere in certain metal- extraction operations

Water gas

Water gas is a mixture of carbon monoxide and hydrogen, with a small amount of carbon dioxide.

Production

It is produced in a water gas generator by action of steam on a bed of coke at 1000c

C(s) + H20(l) → CO2(g) + 2H2(g) ∆H =80Kj/mol

Due to the fact the reaction is endothermic, coke coals down in a few minutes leading to reversal of the reaction to form carbon dioxide and hydrogen instead of water gas.

C(s) + H20(g) → CO2(g) + 2H2O(g) ∆H = 80kJmol-

To avoid above reaction, the current of steam is alternated with blast of air, where the following reactions takes place;

C(s) + O2(g) → CO2(g) ∆= - 80kjmol

2C(s) + O2(g) → 2CO(g) ∆ =- 247kjmol

This exothermic reaction raises the temperature of the coke, as the temperature reaches 1000, the entry of air is stopped and steam is passed again. This alternation is repeated from time to time leading to maximum yield of water gas. The water gas is produced during steam blow.

Properties

Water gas burns with a non-luminous flame and hence it is also called blue water

It has an energy value of about 13 6281C

It burns with a high temperature flair about 1200°C.

Alternative sources of energy

There are two types of energy sources; renewable and non-renewable sources

Renewable sources of energy-

These are the sources of energy which are continuously being replaced within very period of time. Examples are solar energy and wind energy

Non-renewable energy sources

Non-renewable sources of energy are sources that cannot be replenished within short periods of time. They include fossil fuels such as oil, natural gas and coal, and nuclear energy.

Most of the energy being used in the world today comes from non-renewable sources of energy, mainly fossil fuels. These fuels are being used faster than they are being replaced.

Since they take millions of years to form, they could get exhausted in the near future. World leaders, are putting efforts to control the use of non-renewable sources of energy.

Fossil fuels and global warming

When fossil fuels, such as oil and coal, are burnt in air, they emit huge amounts of carbon dioxide and other harmful gases, such as sulphur dioxide. These gases have a harmful effect on the environment.

Carbon dioxide traps the heat from the sun in the lower atmosphere causing the earths average temperatures to rise. This is referred to as global warming. Global warming has many negative effects, such as the following:

Rising sea level due to the melting of the ice at the poles.

Change in amounts and patterns of rainfall.

Increase in frequency of extreme weather events such as floods, drought, and heat waves.

Increase in types and numbers of disease-causing organisms.

Solar energy

Solar energy refers to energy that is obtained from sunlight. It is important to note that the origin of all types of energy is the sun. Solar energy is the main sources of energy on earth, because plants makes food using it and all other organisms depend on it directly or indirectly

Solar energy cannot be exhausted. As long as the sun exists, there will always be solar energy reaching the earth. This type of energy is clean since it does not release harmful gases into the atmosphere.

Biomass

Biomass refers to the organic matter in living plant material. This type of energy is made up of organic compounds that are produced in growing plants.

Biomass is actually solar energy stored in organic matter. As trees and plants grow, they use solar energy to make food (carbohydrates) through the process of photosynthesis.

Carbohydrates are the organic compounds that make up biomass. When plants die, process of decay releases the energy stored in carbohydrates.

Biomass is a renewable energy source because growth of new plants and trees replenishes supply.

Biomass can be used directly as fuel or indirectly to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol bagasse (a by-product of sugar cane process can be used in internal combustion of engines boilers.

The main advantages of biofuels is that they carbon neutral thus they contribute very to global warming unlike fossil fuels.

It has been noted that since biofuels are produced f various sources such as straw, timber, man rice husks, sugar cane, flaxseed and palm oil, supply is almost limitless. Other biodegradable outputs from industry, agriculture, household and forestry can also be used.

NB: Biomass is definitely going to be the fuel for future.

Biogas.

Comes from decomposing biological wastes. mostly comes from animal waste.

Waste matter is put in a chamber and allowed to decompose producing a biogas

Biogas mainly consists of methane gas

When methane has been extracted from biogas, the remaining material is used as fertilizer.

Geothermal energy

Is energy obtained by tapping the heat of earth’s crust

The temperature of the earth is very high and can sometimes escape to the surface

In some areas, these energy is close to the surface, such places includes, Iceland, New Zealand and rift Valley in Kenya.

Geothermal power plants are used to generate electricity in such areas

Wind energy

Wind is moving air. Wind energy is usually harnessed using windmills.

The wind turns the blades of the windmills, which in turn run turbines and produce energy.

Areas where winds are very strong and constant, such as offshore and high altitude sites, are preferred locations for tapping

Wind power is a renewable source of energy which does not release harmful gases such as carbon dioxide and methane into the atmosphere.

Wind strength near the earths surface varies and thus it cannot guarantee continuous power supply unless combined with other sources of energy.

Many countries are turning to this source of energy because of its clean nature.

The disadvantage of this form of energy is that it requires large idle land with the right topography to set up.

Water power

Water possesses energy in the form of kinetic energy due to motion or thermal energy resulting from temperature differences. This energy can be harnessed and put into use.

Water source of energy can take different forms;

Hydroelectric power plants produce electric energy

Flow of tides produces tidal stream energy

Movement of waves can produce wave energy

Temperature changes between the warm surface of water and cooler deeper waters can be used to produce ocean thermal energy.

Nuclear Energy.

Nuclear energy is derived from changes that occur in the structure of the nuclei of atoms. These changes are called nuclear reactions.

Some nuclear energy is produced naturally. For example, the sun and other stars make heat and light energy through nuclear reactions.

Nuclear energy is also produced in man-made industrial plants called nuclear reactors. The energy produced from the reactors is used to generate electricity.

The nuclear energy used in nuclear reactors is produced in two main ways namely, through fission and fusion reactions.

Nuclear fission

In nuclear fission, the nuclei of atoms are split causing heat energy to be released.

Uranium is the main element used in fission reactors to produce heat energy.

The heat energy produced is used to generate steam to turn turbines. The turning turbines are used to produce electricity.

Nuclear fusion

In nuclear fusion, the nuclei of atoms are join together, or fused. This happens only under high temperatures. The sun and all other stars create heat and light through nuclear fusion.

Nuclear energy is increasingly becoming pop especially in the production of electricity. Nuclear power plants need less fuel than plants which fossil fuels.

One tonne of uranium produces mi energy than several million tonnes of coal several million barrels of oil.

The main disadvantage of nuclear energy is emission of radiation. Nuclear radiations ca deformation of body cells which can make people sick or even kill them.

END OF TOPIC QUESTIONS.

Which of the following substances is an outcome of renewable source of energy?

Coal

Petroleum

Biogas

Natural gas

Which of the following statements is true about water gas:-

Is poisonous gas

Contains hydrogen

Is the same as biogas

Contain carbon dioxide and hydrogen

Contain hydrogen and Nitrogen

Which one of the following chemical process will produce producer gas

(s) + H2O(g) CO(g) + H2(g)

O2(g) + 4N2(g) + C(s) 2CO(g) + 4N2(g)

O2(g) + H2(g) + O2(g) H2O(g) + CO2(g)

CO(g) + O2(g) 2 CO2(g)

Which of the following statement is true about water gas?

It is poisonous

Contain hydrogen

Is the same as biogas

Contains hydrogen and nitrogen

Contains carbon monoxide and hydrogen

Which of the following is a common component in both producer gas and water gas?

Hydrogen B. Carbon monoxide C. Steam D. Nitrogen

Which of the following statements is true about water gas;

Contains hydrogen and nitrogen

Is the same as biogas

It is poisonous

Contains carbons monoxide and hydrogen

Which one of the following is not a characteristics of a good fuel

Readily available

Has low energy value

Should be afforded

Easy to transport

The source of energy which, when used can be put into use again is known as;

Fuel B. Solar energy C. Water gas D. Renewable energy

TOPICAL EXAMINATION

CHEMISTRY FORMIII

FUEL AND ENERGY

MULTIPLE CHOICE QUESTIONS.

Which one of the following energy transformation can produce H.E.P?

Electrical energy changes to heat energy

Electrical energy changes to mechanical energy

Mechanical energy changes to Electrical energy

Mechanical energy changes to chemical energy

One of the following is not correct about coke being a better fuel than coal as it;

Does not produce carbon dioxide gas

Does not produce poisonous gas

Has a higher heat content [ ]

Is clean and smokeless

___________is the characteristic of good fuels:-

Firewood

Easily available ( )

Melting

Ability to burn houses into ashes.

What is kindling temperature

A kind temperature

Temperature out of a burning material

The highest temperature obtained from a burning substance

The lowest temperature at which a combustible material can catch fire.

Which of the following is a renewable source of energy?

Coal

Petroleum

Biogas

Natural gas

Which of the following is not a primary source of energy?

Wood

Kerosene

Crude oil

Natural

Which of the following is not a characteristic of a good fuel?

Readily available

Should have low energy value

Should be affordable

Easy to transport

In production of hydroelectric power, which of the following is the best energy transformation?

Electric energy to heat energy

Electrical energy to mechanical energy

Mechanical energy to electrical energy

Chemical energy to electrical energy

Which of the following has a chemical energy?

Natural gas

Biomass

Coal

Solar energy

Which of the following is not an advantage of biogas?

It is cheaper source of energy

Pollutes the environment

It is renewable source of energy

Creates employment among the youth

Matching items questions

LIST A

LIST B

Combustible material that gives large amount of heat.

Fuel that does not pollute the environment

Fuels that occur in nature

Fuel that is derived from primary fuel

Temperature at which fuel must be heated before it starts burning

Highest temperature that can be reached by a burning fuel

The rate at which a fuel burns

Capacity to do work

Fuel formed from remains of plants and animal materials.

Renewable source of energy from waste

Pyrogalic burning effect

Kindling point

Clean fuel

Polluting fuel

Primary fuel

Natural fuel

Secondary fuel

Velocity of combustion

Energy

Power

Biomass

Biogas

Wind

Non-combustible materials

Electricity can be used to perform work also for heating purpose. Explain how it can happen and use four (4) practical examples in each case.

(a) What is fuel? ………………………………………………………………………………………………

(b) Mention three categories of fuel and give two examples for each category.

(i) ………………………………………..

examples …………………………………. and ………………………………….

(ii) …………………………………………

examples ………………………………… and …………………………………

(iii) ……………………………………………

examples …………………………………. and ………………………………….

source of fuel. Give two points of advice to the society on how to use less

charcoal and firewood efficiently.

(a) Write P for primary and S for secondary in the following fuels.

Wood……………. Petrol…………… Coal gas……………………….

(b) Which gaseous fuels are a result of the following processes?

(i) Destructive distillation of coal…………………………………….

(ii) Destructive distillation of wood…………………………..........

(iii)Air reacts with red hot coke at 10000C……………………..

(a) Write the chemical symbol for each of the following elements.

Argon_________(ii)Lead________(iii)Silver__________(iv)Manganese____ (v) Barium______________(vi)Xenon_____________.

(b) Write the chemical formulae of the following compounds:-

Potassium sulphate

Copper (II) carbonate

Aluminium oxide

Magnesium hydroxide

Explain the major ways of obtaining artificial fuels from natural fuels in all the three states of matter.

By the help of a well labeled diagram explain how one can conduct an experiment on destructive distillation of coal.

(a) What is fuel

(b)Give two example of each of following categories of fuels

i) Solid fuel

Liquid fuel

iii) Gaseous fuel

( c) State any two qualities of good fuel

(a) Define the following terms

Green house effect

Global warming

Acidic rains

Pollution

(b)Give any four examples of green house gases

(a) Define the following terms:

Fuel ………………………………………………

Calorific value of a fuel ………………………………

Energy value of a fuel ………………………………………………………

(b) Give two examples of each of the following:

(i) Solid fuel ………………………………….., ……………………………..

(ii) Liquid fuel…………………………………..,……………………………...

(iii) Gaseous fuel ……………………………….., …………………………….

(i) ………………………………………………………………………………

(ii) ………………………………………………………………………………

(iii) ……………………………………………………………………………..

(iv) ……………………………………………………………………………..

SAMPLE NECTA QNS.

2005.

6. (a) Define the term fuel.

(b) State two (2) examples in each of the following types of fuel:

Liquid

Solid

Gaseous

List down three (3) advantages of liquid fuel over solid fuels.

State five (5) characteristics of a good fuel.

TOPIC : 4 SOIL CHEMISTRY

School Base-Online

CHEMISTRY EXAMINATION FORM THREE

TOPICAL EXAMINATIONS.

SOIL CHEMISTRY.

NAME………………………………………..CLASS…………………………………………….TIME: 21/2HRS

INSTRUCTIONS:-

This paper consists of sections A, B and C

Answer all questions

All answers must be written in the spaces provided

All writings should be in blue/black inks except for drawings that should be in pencils

SECTION A 20 MARKS.

Addition of sulphate of ammonia to the soil corrects the deficiency of:

oxygen and nitrogen

nitrogen and hydrogen

nitrogen and sulphur

sulphur and oxygen

sulphur and hydrogen

a straight fertilizer contains

Two primary micronutrients

Only one primary macronutrient

One primary macronutrient and one micronutrient

Two macronutrients

Which of the following best describes a manure?

Organic substances of animal and plants origin

Are plants wastes

A mixture of different fertilizers

Products of parent rock disintegration

Which of the following compounds can be suitable for liming?

Calcium oxide and hydroxide

Magnesium oxide and sodium hydroxide

Calcium oxide and sodium hydroxide

Magnesium hydroxide and sodium oxide

Which of the following explain weathering?

Breakdown of soil particles to facilitate erosion

Break down of parent rock to facilitate erosion

Break down of organic matter in the process of soil formation

Break down of synthetic fertilizer to facilitate to enhance absorption

Which of the following is not a cause of loss of soil nutrients?

Liming

Leaching

Soil capping

Soil erosion

The following are factors affecting soil PH except One, which one?

Parent rock

Fertilizers

Human activity

Rainfall

Non of the above

Which of the following is not a straight fertilizer?

Ammonium fertilizers

Phosphate fertilizer

Potassic fertilizer

Nitrogenous fertilizer

Which of the following does not facilitate chemical weathering?

Hydrolysis

Dissolution

Oxidation

Soil reaction

The process by which soluble nutrients are washed into the lower layers of the soil and beyond the roots is called

Soil reaction

Soil erosion

Leaching

Leachate

2. Matching items questions.

LIST A

LIST B

Scattering of fertilizers on the shamba

Fertilizer is put on the planting hole

Putting fertilizer on the side of growing plant.

Application of fertilizer by spraying on leaves

Application of dissolved fertilizer on the roots through drips

Acidic or alkalinity of the soil

Any inorganic material added to the soil to change its PH

Addition of calcium in various forms in order to increase the soil PH

Ability of soil to provide nutrients in proper quantities and in balanced way for plants growth.

The capacity of the soil in its normal environment to support plant growth

Soil acidity

Soil reaction

Soil fertility

Soil erosion

Soil productivity

Broadcasting

Banding

Liming

Drip application

Placement method

Side dressing application

Foliar spraying

Pouring

Fertilizer ratio

3. (a) Give the meaning of the following terms:

Soil pH

Liming

Macronutrient

(i) Define soil erosion.

(ii) List down four main causes of soil erosion.

A) List down four advantages of organic manure over artificial fertilizers.

(i) What is meant by the term "nitrogen fixation"?

(ii) State two major processes by which the atmospheric nitrogen is converted to usable form in the soil.

(a) What do you understand by each of the following?

Soil reaction

Liming

b) (i) Differentiate active acidity from potential acidity. (ii) What is a fertile soil?

(iii) State four (4) factors that affect soil fertility.

What is manure?

Name four (4) types of organic manure.

(a) What do you understand by the following terms?

Soil erosion

Leaching

Soil fertility

Soil pH

The weight of fresh soil collected from a farmers field was 24g. It was oven-dried at 106°C for 22 hours, cooled in a desiccator and weighed. The oven-dry weight was 19.5g. What was the percentage of moisture in the soil sample?

c) Explain why a good farmer is advised to include leguminous plants in crop rotation.

7. a) Group the following plant nutrients into macro-nutrients and micro-nutrients: S, Zn, Mo, N, Cl, P, Co, K and Ca.

b) Give one function of each of the following essential plant nutrients:

(i) N (ii) P (iii) Zn

c) A certain soil requires 40kg of nitrogen per litre in order to fulfill the plant requirement of nitrogen. Calculate in kg the quantity of ammonium sulphate {(NH4 )2 SO4} fertilizer required to meet the demand.

8. (a) Define the following terms:

Soil

Soil profile

Micronutrients

Explain why a fertile soil is not necessarily productive.

Soil erosion is one of the problems facing many farming areas in Tanzania leading to poor harvest. As a chemist give four advices to the farmers to overcome soil erosion.

9. (a) Briefly explain each of the following:

(i) Soil pH (ii) Basic soil (iii) Terracing

(b) The weight of a fresh soil sample from a school farm was 55gm. The sample was dried in an oven at 200°C, cooled in desiccators and re-weighed. The weight of the sample, after cooling to constant weight was 46gm. What was the percentage of water in the soil sample?

(ii) Why do we classify nitrogen as a macronutrient in regard to plants nutrients?

10. (a) (i) What are the natural causes of soil acidity?

(ii) What cations prevail in acidic soils?

(b) (i) On treatment with calcium hydroxide the soil pH was raised from E to 7. What can you say about the properties of calcium hydroxide-

What effects can the alkalinity of a soil have on the availability c: nutrients?

Is it sensible to add lime to a field which has received an application of ammonium sulphate fertilizer? Explain.

(c) With reference to pH, solubility and any other factors, list the ma]:: properties of the following fertilizers used in our country:

Ammonium sulphate

Super phosphate

Urea

(d)Give the meaning of the following terms:

Soil structure

Acidic soil

Liming

Addition of inorganic fertilization in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four points.

School Base-Online Page 6

TOPIC : 4 SOIL CHEMISTRY

CHAPTER 4

SOIL CHEMISTRY

KEY TERMS AND CONCEPTS.

Soil chemistry- is the study of various chemical nutrients present in the soil and their influence on the properties of the soil such as alkalinity and acidity.

Weathering- this is a physical and chemical breakdown of the rock material near the earth’s surface.

Exfoliation- occurs in hot deserts where day temperatures rise over 400c and night temperature falls below 100c.

Chemical weathering- this is the breakdown of rocks by chemical altering of constituent mineral.

Dissolution- occurs when entire mineral dissolves in water.

Hydrolysis- a chemical weathering process whereby hydroxyl ions and hydrogen ions replace other ions in minerals.

Biological weathering- use of biological agents in breakdown of soil into small particles.

Macro-nutrients- are minerals nutrients which are required in very large quantities.

Micro-nutrients- are minerals which are required in very small quantities.

Soil- erosion- this is the removal of top soil from one place to another by agents of soil such as animals, moving water and gravity.

Leaching- is the process through which soluble plant nutrients are washed into lower layers of the soil and beyond the root zone.

Mulching-is the covering of bare soil with a layer of organic matter such as straw, grasses, leaves and rice husks.

Minimum tillage- this is the practice of keeping operations on land such as ploughing at minimal level.

Straight fertilizer- is a fertilizer that contains only one of the primary macronutrients

Compound fertilizer- this is a fertilizer that contains twoor more of the primary micro-nutrients

Fertilizer analysis- this refers to the percentage of each of the primary macronutrient.

Fertilizer ratio- this refers to the simple ratio of the nutrients relative to each other.

Soil reaction- this refers to acidity or alkalinity of the soil

Soil pH- This refers to the concentration of hydrogen ions(H+) in the soil.

Amendment- this is any inorganic material added to the soil to change the PH of the soil.

Liming- is the application of calcium in various forms to the soil in order to increase the PH of the soil.

Soil fertility- this is the ability of the soil to provide nutrients in proper quantities and in balanced way for plants growth of plant.

Soil productivity- is the capacity of the soil in its normal environment to support plant growth.

Introduction

Soil is the upper most layer of the earth’s crust. It is a non living substance. Soil contains micro-organisms, air, humus and water. It holds roots and enables plants to grow.

Soil formation

Soil is formed from the parent rock through a process called weathering. During weathering, rocks are continually broken into small particles by air, and water and other factors. The process takes place over many years. The soil is formed through three main types;

Physical weathering

Chemical weathering

Biological weathering

Physical weathering

It is also called mechanical weathering. Large particles are broken down into small particles. These factors include;

Water

Moving ice

Wind and temperature.

Movement of these agents carries rock particles making them to disintergrate. Heat of the sun makes the rocks to expand during the day and contract during the night leading to breaking of rocks.

Chemical weathering

It involves the change of chemical composition of rocks due to chemical reactions in the rocks which leads to rocks breaking down. Chemicals from plant roots and microbes also cause the breaking of rocks.

Factors which influence chemical weathering include; water, oxygen, and carbon dioxide.

Figure 4.1 Chemical weathering

Biological weathering

This is the process of soil formation by the action of living organisms on the rocks. The biological agents of weathering are;

Plants and animals

Microorganism, such as fungi and bacteria.

Figure 4.2 Biological weathering

Moving animals exert pressure on rocks making them to break into small particles. As plant roots penetrate through the soil, they break the ground and rocks into tiny particles. Animals such as moles, ants, and earth worms burrow in the soil causing disintegration of large soil particles.

Soil reaction

Soil reaction is an indication of acidity or alkalinity of soil and is measured in PH units.

Soil PH

This refers to alkalinity and acidity of a given soil solution. It is the degree of acidity and alkalinity of soil solution. The PH of soil depends on the concentration of hydrogen ions and hydroxyl ions. If the concentration of hydrogen ions is high, the soil is said to be acidic. But if the concentration of hydroxyl ions is high, the soil is said to be alkaline.

Causes of soil acidity;

Soil acidity can be caused by the following factors;

Presence of humus

Water logging

Presence of soluble salts

Rain water

Cultivation

Application of fertilizer

Biological activities of the soil

Presence of sulphates

Removal of bases

Presence of humus

Humus contains iron and aluminum ions which form complexes that undergo hydrolysis increasing hydrogen ions hence increase soil acidity.

Soil forming from acid rocks.

Rocks like granite contain mineral elements that combine with water forming acidic solution. These lowers soil PH.

Presence of soluble salts

Soluble salts, resulting from fertilizers, mineralization of dead matter and weathering of minerals may undergo dissociations process leading to increase of soil acidity.

Water logging

Excess water on poorly drained soils causes hydrolysis of alluminium and iron salts leading to accumulation of hydrogen ions in the soil. This increases soil acidity.

Rain water

Carbon (IV) Oxide in the atmosphere can dissolve in rain water to form carbonic acid. The acid ionizes in the soil water hence reducing soil PH due to accumulation of hydrogen ions.

CO2(g) + H2O(l)→ H2CO3(aq)

Cultivation

Farming activities such as monocropping lead to deficiency of others depending on the crops grown. This influences soil acidity.

Application of fertilizers

The use of acidic fertilizers, such as urea, decreases soil Ph hence raising its acidity.

The following biological activities influence soil acidity

Aerobic oxidation of organic matter.

Aerobic respiration produces carbon dioxide which makes soil acidic

Anaerobic decomposition of organic matter

In absence of oxygen anaerobic respiration of organic matter occurs, leading to the formation of acids, such as lactic acid. These cause soil acidity.

Nitrification- during this process, aerobic bacteria uses oxygen to convert ammonia into nitrate and hydrogen ions. The hydrogen ions dissolve in soil water hence increasing soil acidity

Removal of bases- basic nutrients tend to leach down deeper into the soil layers as water percolates from top soil layers to deeper soil layers. This process leaves the top soils with substances that contain replaceable hydrogen ions which rise.

Presence of sulphates- sulphate soils contains iron sulphide minerals. The soil have the potential to form sulphuric acid which ionizes hence causing.

Measuring of soil PH

Soil PH meter can be used to determine soil the PH. Some indicators and dyes can be used to measure the PH of the soil. When measuring soil PH it is necessary to collect the sample from various places because soils PH differ.

Universal indicator is a mixture of dyes found in acidic and base indicators.

Effects of acid soil on crops

It leads to the development of certain nutritional diseases among crops

It favors the growth of certain weeds

Makes certain nutrients less available to plants.

Management of soil Ph

Soil Ph can be maintained by a process called liming. Liming is a process is a process of adding lime to the soil in order to reduce soil acidity. Lime can be found in the following forms;

Oxide

Carbonates

Hydroxides

Examples of liming materials includes

Calcium carbonate

Calcium oxide

Calcium hydroxide

Other substances that can be used to modify soil PH are potassium hydroxide and magnesium carbonate.

Essential elements in plants growth

There are 17 elements required for plant growth. These are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, iron, Sulphur, boron, manganese, zinc, chlorine, cobalt and molybdenum.

Essential mineral elements are divided into two categories;

Macro- elements

Micro-element

Macro-elements. Are elements required in large quantities. Examples are nitrogen, phosphorus, potassium, calcium and Sulphur.

Micro-elements- are elements required in small amounts or trace amounts. Examples, copper, iron, zinc, magnesium and manganese.

Functions of primary macronutrients in plant growth

Nitrogen

It is absorbed in form of ammonium and nitrate ions. It plays the following functions in plants.

Required in the formation of protein

Help in rapid vegetative growth

Nitrogen deficiency

The following are signs of nitrogen deficiency

Leaves fail to reach the expected size, lower leaves begin to yellow.

Weaker stems and small leaves

Flowers that are smaller than size

Excessive nitrogen weakens stems, leaves, and reduces sugar content and makes plant easily attached by pests and diseases.

Phosphorus.

Functions;

Energy transformation in form of ATP and ADP

Formation of co-enzymes

Promotion of lateral and fibrous roots

Seed formation

Improving resistance of plants to disease

Signs of phosphorous deficiency

Dark than normal leaves, bluish green color of the foliage

Pre-mature aging of leaves

Purple pigment appear on the leaves

Potassium

Performs the following functions in a plant

Takes part in formation of sugar and starch in leaves

Maintains cell turgidity and permeability of cell membrane

Help in translocation of carbohydrate

Signs of potassium deficiency in the soil

Brown scorching and curling of the leaves

Purple spots may appear on leave side

Plant growth, root and seed development is reduced

Plant is prone to frost damage and diseases

Sulphur.

Enzyme formation and promotion of root growth and nodule formation

Plant culture

This is a collection of techniques used to maintain or grow plant cells, tissues or organs under sterile conditions on a nutrient culture solution of known composition.

Advantages of plant culture propagation

Production of exact type of plant which give rise to particular good flower or fruits

To quickly produce mature plants

Production of multiple plants in absence of seeds

Regeneration of whole plant from plant cells that has been genetically modified.

Production of crops in sterile containers which makes it easier to move them without contaminating with diseases and pests

Production of plants from seeds which has very low chances of germination

To clean particular plants of viral and other infections and to quickly multiply these plants as cleaned stock for horticulture and agriculture

The ability of a plant cell to regenerate to a whole organism is called totipotency. Plants without cell walls (protoplasts), pieces of leaves, stem or roots can often be used to generate new plants on culture media given the required nutrients and plant hormones.

Techniques

The stating material is undertaken to surface sterilization in chemicals like alcohol, and sodium or calcium hypochlorite. These plants are called, explants.

Explants are placed on the surface of a solid culture media, but are also sometimes placed in a liquid media particularly when cell suspension cultures are required.

Solid and liquid media are generally composed of inorganic salts with a few organic nutrients, vitamins, and plant hormones. Solid media are prepared from liquid media with the addition of a gelling agent usually a purified agar.

The composition of media particularly the plant hormones and the nitrogen sources nitrates versus ammonium salts or amino acids has profound effects on the morphology of the tissues that grow from the initial explants.

As culture grows, pieces are usually sliced off and transferred to a new medium (sub cultured) to allow for growth or alter the morphology of the culture.

As shoots emerge from the culture, they may be sliced off and rooted with auxins to produce plantlets. When mature, plantlets can be transferred for further growth in the green house as normal plants.

Applications of tissue culture

To conserve rare or endangered plant species

Production of identical sterile species

Screen cells rather than plants for advantageous characteristics

To cross-pollinate distantly related species and then prepare tissue culture for resulting embryo which would otherwise normally die.

Certain techniques such as meristem tissue culture can be used to produce clean plant materials from stock

To rapidly study the molecular basis for physiological, biochemical and reproductive mechanisms in plants.

Commercial production of plants used for potting by florists

Control measures for retaining soil fertility

Use of natural manure.

Poultry and cattle manure have macro nutrients such potassium, nitrogen and phosphorous which maintains soil fertility

Use of fertilizers

Fertilizers contain various mineral elements and therefore assist in increasing soil fertility

Use of green manure

This involves growing of leguminous crops and then plugging them into the soil in order to improve soil fertility.

Application of suitable farming methods

Suitable farming methods like intercropping, cultivating along the slopes and mulching help in conserving the soil moisture.

Use of fallows

Leaving a piece of land uncultivated for one season and cultivating it the following season allows it to regain fertility.

Control of soil erosion

Soil erosion is responsible for carrying away of nutrients. It involves the removal of the top fertile soils by agents such as wind, water and human activities. Soil erosion can be controlled by doing the following;

Planting of cover crops

Keep the right number of animals that can be supported by certain piece of land.

Practicing afforestation and reforestation

Practice contour farming across the slopes

Constructing terraces across the slopes

Mulching.

Manure

Is an organic substance that is added to the soil so as to increase nutrients. There are three types of manure,

Animal manure

Green manure

Animal manure

This manure comes from animals such as goats, cows, sheep, horse, chicken and farm yard manure.

Green manure

Also called plant manure, this involves growing certain type of crops for express purpose of adding fertility to the soil. They incorporate nutrients and organic matter in the soil. Luminous plants such as clover are used to fix nitrogen into the soil.

Compost manure

Includes decomposed remnants of organic materials. Organic materials that make up compost manure include plant remains and animal cow dung.

How to make pit compost manure

Dig a pit for a waste with dimensions of 1m by 1m by 1.5m. Dump organic waste here.

Add cow dung mixed with water when it attains a thickness of one inch

Repeat the activity until the pit is filled.

Cover the pit with soil when it is full

Preparation of heap compost manure

Clear a corner of your backyard by the fence for your compost pile

Construct or place your compost pit if you choose to confine in your pile.

Add browns- I.e fallen leaves, twigs, wood matter, saw dust, wood chip and other materials containing carbon such as shredded cardboard and paper. Also add greens- that is grass clippings, green garden waste, vegetable waste, egg shells and fruits.

Add animals manure from the compost heap if available

Moisten the heap periodically with water to give room for micro-organisms to decompose them.

Turn the heap with a shovel after every 2-3 weeks in order to speed the decomposition

The compost manure will be ready after 1-4 months

Advantages of manure

Add humus to the soil hence improve soil structure

Cheap to prepare and apply

Add organic matter to the soil

Promote microbial activities by providing habitat to the micro-organism

They prevent loss of nutrients by leaching

They improve soil structure and drainage.

Disadvantage of natural manure

Not easy to store and transport

Can cause soil acidity

Nutrient content is not guaranteed because composition is variable

It can promote weed growth

Its nutrients are present in unavailable form.

Fertilizers

Are organic compounds manufactured in the industries and added to the soil in order to increase soil fertility.

Types of fertilizer

-nitrogeneous fertilizer

Phosphatic fertilizer

Potash fertilizer

Nitrogenous fertilizers.

They mainly supply nitrogen into the soil. Examples include;

Ammonium sulphate

Ammonium nitrate

Ammonium hydroxide

Urea.

Phosphoric fertilizers.

They supply phosphorous in the soil. The examples include;

Super phosphate fertilizer

Calcium phosphate

Ammonium phosphate

Potash fertilizer

They supply potassium into the soil. Examples include the following;

Potassium nitrate

Potassium sulphate

Potassium chloride

Fertilizer grade and analysis

A fertilizer grade is an expression referring to the legal guarantee of the available plant nutrients expressed as a percentage by weight in a given fertilizer. Fertilizer manufacturers are required to follow certain rules when labelling fertilizers in order to make them easily understood by farmers. These are;

Three numbers separated by dash on their labels, 5-10-5. This means the fertilizer contains three main elements that are nitrogen, phosphorus and potassium in that order in terms of percentage. The rest of the fertilizer is other nutrients and filler.

The first number gives the percentage of nitrogen. 5% nitrogen in the bag by weight.

The second number gives phosphorus. It gives the concentration of phosphorus in the fertilizer. It is important in plant rooting and flower formation.

The third number states the concentration of potassium. Potassium contributes to overall health and vigor of the plant. 5% of the fertilizer given is potassium.

Fertilizers are generally classified as

Complete fertilizer- are fertilizers that contain all the three main nutrients.

Straight fertilizers- these are fertilizers that contain one of the three main nutrients

Compound fertilizers are fertilizers that contain at least two out of three major nutrients.

Other ingredients- any additional ingredient will be listed on the side label.

Methods of fertilizer applications

Broadcasting- this is the uniform distribution of fertilizer over the soil

Banding- applying fertilizer in stripes or bands along the rows of plants

Topdressing- it involves applying dissolved fertilizer onto the plants

Side-dressing- this is the application of fertilizer in pockets in the soil close to plants roots

Advantages of artificial fertilizers

They contain nutrients in guaranteed proportions and available in all forms

They are less bulky, hence easy to store and transport.

Some fertilizers discourage the growth of weeds.

Disadvantage of artificial fertilizers

They do not improve soil structure and drainage

They have fixed composition and do not add other nutrients into the soil

They are difficult to apply on the fields as compared to natural manures due to calculations involved.

They discourage microbial activities due to their fixed compostions.

Soil fertility and productivity

Soil fertility

Soil fertility refers to the ability of the soil to grow and support plant life. Fertile soil contains the sufficient nutrients needed for plant growth and is often composed of a large number of micro-organism such as fungi, bacteria, earthworms, protozoa and nematodes. A fertile soil is rich in trace elements such as copper, cobalt, iron, zinc, manganese, Sulphur and magnesium. Nutrients such as potassium, phosphorus, and nitrogen must be abundant in the soil for it to be said to be fertile.

Soil productivity

Is the ability of the soil to provide water and nutrients to allow deep rooting of agricultural plants. The main measure of soil productivity is usually crop yield per millimeter of available water.

Factors that determine soil fertility and productivity

Soil PH- A fertile soil posses a PH range of 6.0-6.8. This is optimum PH range for most crops although some plants prefer acidic or alkaline conditions.

Soil structure- the overall arrangement of soil particles, creating good drainage and making soil fertile

Fertile soil contain organic matter that improves soil structure

Presence of sufficient minerals- trace elements in the soil make the soil fertile and productive

Presence of micro-nutrients for plants growth

Large amount of top soil and range of micro-organisms that support plant growth.

Factors which lead to loss of soil fertility

Plant nutrients from the soil can be lost due to the following;

Water logging

Soil erosion

Leaching

Poor farming methods

Burning of vegetation

Water logging

Water logged soil have little air spaces. This limits the activity of micro-orgasm and also makes the plant not to have enough air on the roots

Soil erosion

Soil erosion is the removal of top fertile soil by wind water or animals from one place to another.

Leaching

This is the process whereby dissolved nutrients in the soil are drained down to deeper soil layer. Plant roots cannot therefore reach them. Heavy rains and excessive irrigation causes leaching.

Poor farming practice

Poor farming methods such as mono-cropping can lead to loss of certain nutrients in the soil. When you plant only one type of crop, the plant nutrients are exhausted.

Burning of vegetation to clear the land

Burning kills most of the micro-organisms in the soil. These are very important in aiding in decomposition of organic matter to produce nutrients.

TOPIC SUMMARY

Soil is formed from the parent rock through the process of weathering.

There are three main types of weathering namely:

Physical weathering

Chemical weathering

Biological weathering

Natural manure provides a habitat to microbial organisms and humus. However they contain nutrients in unavailable forms.

Inorganic fertilizers contain nutrients in guaranteed proportions and available forms but do not improve soil structure and microbial activities.

Knowledge about fertilizer grades enables a farmer to know the available nutrients in the fertilizer.

Weathering is the process by which rocks are continually broken down into smaller particles and changed in form due to exposure to air, water and other factors.

Liming is the process of adding lime to the soil to support plant life.

Soil productivity is the ability of the soil to provide water and nutrients.

Soil texture is the relative proportion of the various sizes of the sizes of the mineral particles.

Soil PH is the acidity or alkanity of the soil solution.

Soil PH determines the crops that can be grown in a field hence the need for its measurement.

Essential plant nutrients can be categorized into:

Macro – elements. These include nitrogen , phosphurs and potassium.

Micro – elements. These include manganese, zinc, iron and copper.

Soil fertility can be retained by practicing suitable farming, use of manure, crop rotation and preventive measures against soil erosi

SOIL CHEMISTRY

Define the term soil.

State the three types of weathering.

Explain how each of the following factors causes weathering:

Moving

Wind

Temperature

Define the term soil Ph.

State the factors that influence soil Ph

What is liming

State any three liming materials.

Describe an experiment to measure the Ph of a given soil sample.

Differentiate between soil fertility and soil prodactivity.

Explain various factors which determine soil fertility and productivity.

Explain how each of the following factors lead to loss of soil fertility.

Leaching

Soil erosion

Clearing land by burning

Define the term weathering.

Explain how chemical weathering occurs.

How does soil PH influence soil fertility?

What causes soil acidity?

State the importance of applying agriculture lime to the soil.

Leguminous plants are said to be green manure. Explain.

Explain the various roles played by potassium element in the soil

Explain factors which determine soil fertility and productivity.

Discuss the advantages of growing plant nutrients medium.

TOPICAL EXAMINATIONS

CHEMISTRY FORM FOUR

SOIL CHEMISTRY

SECTION A 20 MARKS.

Addition of sulphate of ammonia to the soil corrects the deficiency of:

oxygen and nitrogen

nitrogen and hydrogen

nitrogen and sulphur

sulphur and oxygen

sulphur and hydrogen

a straight fertilizer contains

Two primary micronutrients

Only one primary macronutrient

One primary macronutrient and one micronutrient

Two macronutrients

Which of the following best describes a manure?

Organic substances of animal and plants origin

Are plants wastes

A mixture of different fertilizers

Products of parent rock disintegration

Which of the following compounds can be suitable for liming?

Calcium oxide and hydroxide

Magnesium oxide and sodium hydroxide

Calcium oxide and sodium hydroxide

Magnesium hydroxide and sodium oxide

Which of the following explain weathering?

Breakdown of soil particles to facilitate erosion

Break down of parent rock to facilitate erosion

Break down of organic matter in the process of soil formation

Break down of synthetic fertilizer to facilitate to enhance absorption

Which of the following is not a cause of loss of soil nutrients?

Liming

Leaching

Soil capping

Soil erosion

The following are factors affecting soil PH except One, which one?

Parent rock

Fertilizers

Human activity

Rainfall

Non of the above

Which of the following is not a straight fertilizer?

Ammonium fertilizers

Phosphate fertilizer

Potassic fertilizer

Nitrogenous fertilizer

Which of the following does not facilitate chemical weathering?

Hydrolysis

Dissolution

Oxidation

Soil reaction

The process by which soluble nutrients are washed into the lower layers of the soil and beyond the roots is called

Soil reaction

Soil erosion

Leaching

Leachate

2. Matching items questions.

LIST A

LIST B

Scattering of fertilizers on the shamba

Fertilizer is put on the planting hole

Putting fertilizer on the side of growing plant.

Application of fertilizer by spraying on leaves

Application of dissolved fertilizer on the roots through drips

Acidic or alkalinity of the soil

Any inorganic material added to the soil to change its PH

Addition of calcium in various forms in order to increase the soil PH

Ability of soil to provide nutrients in proper quantities and in balanced way for plants growth.

The capacity of the soil in its normal environment to support plant growth

Soil acidity

Soil reaction

Soil fertility

Soil erosion

Soil productivity

Broadcasting

Banding

Liming

Drip application

Placement method

Side dressing application

Foliar spraying

Pouring

Fertilizer ratio

3. (a) Give the meaning of the following terms:

Soil pH

Liming

Macronutrient

(i) Define soil erosion.

(ii) List down four main causes of soil erosion.

A) List down four advantages of organic manure over artificial fertilizers.

(i) What is meant by the term "nitrogen fixation"?

(ii) State two major processes by which the atmospheric nitrogen is converted to usable form in the soil.

(a) What do you understand by each of the following?

Soil reaction

Liming

b) (i) Differentiate active acidity from potential acidity. (ii) What is a fertile soil?

(iii) State four (4) factors that affect soil fertility.

What is manure?

Name four (4) types of organic manure.

(a) What do you understand by the following terms?

Soil erosion

Leaching

Soil fertility

Soil pH

c) Explain why a good farmer is advised to include leguminous plants in crop rotation.

7. a) Group the following plant nutrients into macro-nutrients and micro-nutrients: S, Zn, Mo, N, Cl, P, Co, K and Ca.

b) Give one function of each of the following essential plant nutrients:

(i) N (ii) P (iii) Zn

8. (a) Define the following terms:

Soil

Soil profile

Micronutrients

Explain why a fertile soil is not necessarily productive.

Soil erosion is one of the problems facing many farming areas in Tanzania leading to poor harvest. As a chemist give four advices to the farmers to overcome soil erosion.

9. (a) Briefly explain each of the following:

(i) Soil pH (ii) Basic soil (iii) Terracing

(ii) Why do we classify nitrogen as a macronutrient in regard to plants nutrients?

10. (a) (i) What are the natural causes of soil acidity?

(ii) What cations prevail in acidic soils?

(b) (i) On treatment with calcium hydroxide the soil pH was raised from E to 7. What can you say about the properties of calcium hydroxide-

What effects can the alkalinity of a soil have on the availability c: nutrients?

Is it sensible to add lime to a field which has received an application of ammonium sulphate fertilizer? Explain.

(c) With reference to pH, solubility and any other factors, list the ma]:: properties of the following fertilizers used in our country:

Ammonium sulphate

Super phosphate

Urea

(d)Give the meaning of the following terms:

Soil structure

Acidic soil

Liming

Addition of inorganic fertilization in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four points.

SAMPLE NECTA Q. 2004

9. (a) What do you understand by each of the following?

Soil reaction

Liming

b) (i) Differentiate active acidity from potential acidity. (ii) What is a fertile soil?

(iii) State four (4) factors that affect soil fertility.

What is manure?

Name four (4) types of organic manure.

2005QN

10. (a) What do you understand by the following terms?

Soil erosion

Leaching

Soil fertility

Soil pH

[vi] Explain why a good farmer is advised to include leguminous plants in crop rotation.

2006. QN6

a) Group the following plant nutrients into macro-nutrients and micro-nutrients: S, Zn, Mo, N, Cl, P, Co, K and Ca.

b) Give one function of each of the following essential plant nutrients:

(i) N (ii) P (iii) Zn

2007

QN. (a) (i) Define the term fertilizer.

(ii) What are the three (3) effects of excessive nitrogen to plants?

(b)(i) State four (4) methods of application of fertilizers.

What are the four (4) advantages of using manures in the farms?

Calculate the percentage composition of nitrogen in ammonium sulphate fertilizer (NH4 )2 so4 .

2008.

QN. 10. (a) Define the following terms:

Soil

Soil profile

Micronutrients

Explain why a fertile soil is not necessarily productive.

Soil erosion is one of the problems facing many farming areas in Tanzania leading to poor harvest. As a chemist give four advices to the farmers to overcome soil erosion.

2009.

QN. 10.(a) Briefly explain each of the following:

(i) Soil pH (ii) Basic soil (iii) Terracing

(ii) Why do we classify nitrogen as a macronutrient in regard to plants nutrients?

2010.

QNS. 9. (a) (i) What are the natural causes of soil acidity? (ii) What cations prevail in acidic soils?

(b) (i) On treatment with calcium hydroxide the soil pH was raised from E to 7. What can you say about the properties of calcium hydroxide-

What effects can the alkalinity of a soil have on the availability c: nutrients?

Is it sensible to add lime to a field which has received an application of ammonium sulphate fertilizer? Explain.

(c) With reference to pH, solubility and any other factors, list the ma]:: properties of the following fertilizers used in our country:

Ammonium sulphate

Super phosphate

Urea

2015.

QNS.11 Addition of inorganic fertilization in the farm is not as important as addition of organic manure. Discuss the correctness of this statement in four points.

School Base -Online

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