FORM TWO CHEMBA CHEMISTRY MOCK EXAMINATIONS WITH ANSWERS | MTIHANI NA MAJIBU (MARKING SCHEME) YA MTIHANI WA MOCK CHEMISTRY WILAYA YA CHEMBA

THE PRESIDENTS OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

CHEMBA DISTRICT COUNCIL

FORM TWO MOCK EXAMINATION

CHEMISTRY

TIME :2:30HRS Year:2021

Instructions

1. This paper consists of section s A and B with a total of ten (10) questions.

2. Answer all questions in the spaces provided

3. All writing must be in black or blue ink except diagrams which must be in pencil

4. Cellular phones and any unauthorized materials are not allowed in the examination room.

5. Write your number at the top right corner of every page

6. The following atomic masses may be used:H=1,N=14,O=16,C=12 ,S=32,Al=27,Na=23,Ar=40.

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SECTION A (20 Marks)

Answer all questions in this section

1. For each of the items (i-x),choose the correct answer from the among the given alternatives and write its letter in the box provided

i. What is the best way of keeping a clean test tube after use?

A. Keeping it in water

B. Keeping it on a test tube rack

C. Keeping it on a test tube holder

D. Keeping it in a basin for test tubes

ii. Which group and period does the element with 11 electrons belongs?

A. Group I and Period 3

B. Group II and Period 1

C. Group I and Period 1

D. Group II and Period 3

iii. Which of the following is not a component of the First Aid Kit?

A. Goggles

B. Dropper

C. Gloves

D. A pair of scissors

iv. The oxidation state of metallic elements in a compound is always

A. Negative

B. Neutral

C. Positive

D. Zero

v. The net charge inside the nucleus of an atom is contributed by

A. Protons

B. Neutrons

C. Electrons

D. All nucleons

vi. Consider the following reagents ,then state which reagent are involved in the preparation of oxygen gas in the laboratory?

1. H₂O₂ 2. H₂O 3. MnO₄ 4. MnO₂

A. 1 and 2

B. 3 and 4

C. 1 and 3

D. 1 and 4

vii. Which of the following is the correct sequence of the last two step you should follow during the scientific procedure?

A. Hypothesis formulation and conclusion

B. Observation and problem identification

C. Interpretation of data and conclusion

D. Experimentation and conclusion

viii. Which conditions are necessary for iron nail to rust?

A. Oxygen and moisture

B. Carbon and oxygen

C. Oxygen and nitrogen

D. Moisture and nitrogen

ix. Air entering the Bunsen burner barrel can be controlled by

A. Air hole

B. Collar

C. Metal jet

D. Air ring

x. Which process is involved when drying wet clothes ?

A. Liquid to solid

B. Gas to liquid

C. Solid to gas

D. Liquid to gas

2 (a). Match each item in LIST A with correct response in LIST B by writing the letter of the correct response below the corresponding item number provided.

List A

List B

i. A statement of how the results

relate to the hypothesis

ii. A series of the investigations

iii. A statement that identifies an event ,fact, or situation.

iv. A tentative explanation

v. A step in which the researcher explains the results

A. Conclusion

B. Data analysis

C. Data collection

D. Experimentation

E. Hypothesis

F. Observation

G. Problem identification

LIST A	I	Ii	iii	iv	v
LIST B

2 . (b) . i. …………………..are atoms of the same element having the same atomic number but

different mass number.

ii. Which particles are transferred during chemical reaction?..............................................

iii………………………………….. is the substance that alter the rate of chemical reaction.

iv……………………………………..tend to display metallic and non metallic characteristic

v Serum is separated from blood samples by employing a technique called…………………

SECTION B (80 Marks)

Answer all questions in this section.

3 (a). State one use of each of the item (i)-(v) in administering First Aid.

	Item	Use
i	Soap
ii	Gloves
iii	Petroleum jelly
iv	Liniment
v	Cotton wool

(b)Why candles are not suitable for heating in the laboratory? Give two reasons

i)……………………………………………………………………………………………………

ii)………………..…………………………………………………………………………………

(c)state three possible causes of vomiting

i)……………………………………………………………………………………………………

ii……………………………………………………………………………………………………

iii…………………………………………………………………………………………………

4. (a)Sate four modern Dalton’s atomic theory of matter.

i………………………………………………………………………………………………………….

ii…………………………………………………………………………………………………………

iii…………………………………………………………………………………………………………

iv…………………………………………………………………………………………………………

(b)Classify each of the following elements into their respective groups and periods

	Element	Group	Period
I	Magnesium
Ii	Silicon
Iii	Boron
Iv	Hydrogen

5(a) Give two chemical tests of water

i……………………………………………………………………………………………………

ii………………………………………………………………………………………………………

(b) (i) Differentiate water treatment from water purification.

……………………………………………………………………………………………………………

………………………………………………………………………………………………………

…………………………………………………………………………………………………………

……………………………………………………………………………………………………

(ii)Why drinking water should be treated and purified? Give two reasons.

………………………………………………………………………………………………………

(iii)Gemry ‘s mother was always complaining about having stomachache by drinking contaminated water ,which ways would Gemry take to avoid having this problem always? Give three point

……………………………………………………………………………………………………

…………………………………………………………………………………………………

1. The position of the element A,B,C,D,F, and G are shown in part of their periodic table below. The letters are not the usual symbol of the elements.

I VIII

	II III IV V VI VII
			E	F	A
C		D				B	G

Use the letters to answer the following questions

(a)Write electronic configuration arrangement of atom A,B,C,D,E and F

………………………………………………………………………………………………………

……………………………………………………………………………………………………….

(b)State the number of electrons ,protons and neutrons of an atom D,C and G.

………………………………………………………………………………………………………

(c)Which is the most reactive metal?

…………………………………………………………………………………………

2. (a) Write the names and formulae of the two chemicals that can be used in preparation of oxygen gas

i……………………………………………………………………………………………………

ii……………………………………………………………………………………………………

(b)(i)State the appropriate method of collecting oxygen gas based on solubility and density of the

gasin water………………………………………………………………………………………

(ii)How can oxygen gas be tested?..................................................................................................

(c)List four uses of oxygen gas?

i. ……………………………………………………………………………………………………….

ii. ………………………………………………………………………………………………………

iii. ………………………………………………………………………………………………………

iv. …………………………………………………………………………………….............................

3. Briefly explain the five classes of fires based on the nature of the burning material and the extinguisher required. Give one example for each class.

……………………………………………………………………………………………………

…………………………………………………………………………………………………

……………………………………………………………………………………………………

……........................................................................................................................................................

...............................................................................................................................................................

9. a) What is isotopy: ………………………………………………………………………………………

……………………………………………………………………………………………

b) If sample X consist of 99.76% of ¹⁶X, 0.04% of ¹⁷X and 0.20% ¹⁸X.

i) Calculate the relative atomic mass of X

ii) Name the element X?

…………………………………………………………………………………………

10. Briefly explain five characteristics to be considered when looking for a good fuel

………………………………………………………………………………………………………

…………………………………………………………………………………………………….

………………………………………………………………………………………………………

THE PRESIDENT OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

CHEMBA DISTRICT COUNCIL

CHEMISTRY FORM TWO MARKING SCHEME YEAR:2021

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i	ii	iii	iv	V	vi	vii	viii	ix	x
B	A	B	C	A	D	C	A	B	D

(10mark) @01

2. (a)

LIST A	I	Ii	iii	iv	v
LIST B	A	D	G	E	B

(05mark)@01

(b)i)Isotopes

ii)Electrons

iii)Catalyst (05marks)01@

iv)Metalloids

v)Chromatography

SECTION B(80 marks)

3. (a)

	Item	Use
i	Soap	Used to wash hands ,wound and equipment
ii	Gloves	Covering the hands to avoid infecting wounds and prevent direct contact with a victim’s body fluids
iii	Petroleum jelly	Soothing chapped skin
iv	Liniment	Reducing muscle pain
v	Cotton wool	Cleaning and drying wounds

(05maks)01 @

(b)i ) It produce soot (01mark@)=02marks

ii)It does not give more heat

(c)i)Food poisoning

ii)Drinking contaminated water (01mark @)=03 marks

iii)inhaling poisonous fumes or over eating

4. (a)i)An atom is made up of smallest subatomic particles called protons ,neutrons and electrons.

ii) Atoms can be created or destroyed by means of nuclear reactions.

iii)Some element have atoms of more than one kind which differ slight in mass,such element called are isotopes (carbon-12,carbon -13,carbon -14)

iv)Atoms of different elements may combine in many different ratios to form complex compounds (06marks )1.5@

(b)

	Element	Group	Period
i	Magnesium	II	3
ii	Silicon	IV	3
Iii	Boron	III	2
iv	Hydrogen	1	1

(04marks)01@

5. (a)i) By using Cobalt (II) Chloride paper

(ii) By using White anhydrous copper (II) sulphate (01mark @)=02 marks

(b)i) Water treatment is the process of making water usable for domestic ,industrial,medical and other purposes .

WHILE (1.5mark@)=03 marks

Water purification is the removal of contaminants from treated water to produce drinking water that is pure enough for human consumption.

ii)* Help to ensure accurate results from experiments and effective treatment especially

in laboratory and medicals

*Help to ensure the manufactured product are safe for consumption especially in industries

*To kill harmful microorganism that lead disease such as typhoid,cholera(only twopoint)(01mark@)=02 marks

iii)*Boiling

*Use of chemical purifiers such as water guard

*Use of commercial filters (01mark@)=03 marks

6. a)A=2:6

B=2:8:7

C=2:8:1 (05marks) 01 @

D=2:8:3

E=2:4

F=2:5

atoms	Electrons	protons	Neutrons.
D	13	13	14
C	11	11	12
G	18	18	22

(01marks@=03marks)

c) The most reactive Metal is C(01mark)

7. a) i) Hydrogen peroxide (H ₂O₂)(02mark @)=04marks total

ii) Potassium Chlorate (KClO₃)

b)i)Downward displacement of water

ii)Oxygen can be tested by dipping burning splint into a gas jar contain oxygen which relight the burning splint (01mark @ = 02marks)

c)-Used for climbers

-Used for divers

-Used for welding materials (01mark@=04marks)

-Used in breathing and respiration.

TYPE(CLASSES)	BURNING MATERIAL	EXTINFGUISHER
A	Ordinary solid e.g. paper, clothes	-Use water -Any portable extinguisher except CO₂
B	Flammable liquids e.g. petrol ,kerosene	-Fire blanket -Dry powder or carbon dioxide
C	Flammable gases e g propane	-Dry powder -Carbon dioxide
D	Combustible metal e.g. sodium ,magnesium	-Dry powder -Foam extinguisher
E	Electrical equipment	-Dry powder or carbon dioxide

(02marks@=10marks).

9.a).Isotopy is the existence of atom of the same element having the same atomic number but different in its mass numbers. (02 Marks)

b)i) Data given;

% composition of ¹⁶X=99.76% 01 mark

% composition of ¹⁷X = 0.04%

% composition of ¹⁸X =0.20%

Relative atomic mass= % x mass number 01mark

= (99.76/100 x 16) + (0.04/100 x 17) + (0.2 /100 x 18)

= [(99.76x16) + (0.04x17) +( 0.2 x18)] /100 02 marks

= (1596.16 + 0.68 + 3.6)/100

= 1604.04/100

Therefore, the relative atomic mass of X is 16.0404. 02marks

ii. The element X is Oxygen. (02marks)

10.The characteristics of a good fuel;

i. Affordability.

ii. Ease of transportation and storage

iii. Effect on the environment.

iv. High heat content.

v. Low non combustible materials.

vi. Velocity of combustion (ignition point) ( Any Five@02=10marks)

...

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Thursday, April 13, 2023

FORM TWO CHEMBA CHEMISTRY MOCK EXAMINATIONS WITH ANSWERS | MTIHANI NA MAJIBU (MARKING SCHEME) YA MTIHANI WA MOCK CHEMISTRY WILAYA YA CHEMBA

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