🌊PAPER 42-Qns

 

O-STUDY LIBRARY

CHEMISTRY FORM THREE

ANNUAL EXAMINATION NOVEMBER 2023

TIME: 2 HOURS

INSTRUCTIONS:

1. This Paper Consists of Sections A,B and C

2. Answer all questions in section A and B and only one(1) question from section C

3. Cellular phone and any unauthorized material are not allowed in examination room

4. Write your Examination Number on every page of your answer sheet(s).

5. The following constant may be useful

• Atomic masses H=1, C=12, N=14,O=16,Na=23,Mg=24,S=32,Cu=64.

• Avogadro’s number = 6.02 x 10²³

• G.M.V at S.T.P = 22.4dm³

• 1Faraday = 96500 coulombs

• 1 litre = 1dm³= 1000cm³

SECTION A. (20 MARKS)

1. For each item (i)-(x) choose the correct answer among the given alternatives and write the letter beside the item number in the booklet provided.

(i) Which of the following is the agricultural product made by the application of chemistry?

1. Yeast

2. Drug

3. Clothes

4. Pesticide

5. Cement

(ii) When methane undergo substitution reaction with excess chlorine .what is the end product

1. Chloromethane

2. Dichloromethane

3. Dichloromethane

4. Monochloromethane

5. Tetrachloromethane

(iii) An element X is found in period 4; group II of the periodic table .if the element X Undergo the reaction X→X₂+2e- ; the electronic configuration of X ion formed will be

1. 2: 8:6

2. 2:6

3. 2:8:4

4. 2:8:8:2

5. 2:8:8

(iv) A current of 0.2A was passed through an electrolyte for 16 minutes and 40 seconds .What is the quantity of electricity produced in coulombs?

1. 2000C

2. 1000C

3. 200C

4. 0.2C

5. 7686C

(v) Which carbonate is the most stable to heat?

1. Calcium carbonate

2. Copper II carbonate

3. Copper II carbonate

4. Lead II carbonate

5. Zinc Carbonate

6. Iron carbonate

(vi) Skin injury that cause a change in the color of skin

1. Bruises

2. Bum

3. Scalds

4. Shock

5. Suffocation

(vii) A good fuel is the one which has.

1. High speed of continuous energy supply

2. High energy value supplied

3. Low carbon dioxide production

4. High carbon dioxide production

5. High content of non-combustible materials

(viii) The region of the atmosphere which contains the ozone layer is called

1. Mesosphere

2. Stratosphere

3. Atmosphere

4. Troposphere

5. Metamosphere

(ix) Aluminum is said to be amphoteric oxide because

1. It acts as an acid and also It acts as a base

2. It acts as a neutral compound

3. It acts as strong reducing agent

4. It acts as a basic compound

(x) The main impurities in Nitrogen gas prepared in the laboratory are:-

1. Water vapour

2. Oxygen

3. Carbon Dioxide

4. Dust particles

5. Noble gases

Qns	i	ii	iii	iv	v	vi	vii	viii	ix	x
Ans

2. Match the item in LIST A with a correct response in LIST B by writing the letter of the response below the corresponding item in the table given.

LIST A	LIST B
A gas that forms explosive mixture with air and water A gas that forms a reddish brown fumes when comes in contact with air A gas that turns lime water milky A colorless gas that bleaches moist coloured flower Only basic gas	Nitrogen monoxide gas Carbon-dioxide gas Carbon Monoxide gas, thione gas Chlorine gas Sulphur dioxide gas Ammonia gas Nitrogen gas Oxygen gas Hydrogen gas Hydrogen sulphide gas

LIST A	i	ii	iii	iv	v
LIST B

SECTION B. (70 MARKs)

Answer All questions in this section

3. (a) A stone is said to be a good example of matter. Give two reasons to support this fact.

b. Outline two significance of chemical symbols of an element.

c. Explain by giving reasons why:

1. Laboratory door open outwards

2. Laboratory floor is rough and never polished

3. Fume chamber is important in chemistry laboratory

4. (a) Identify the substances by using the following information.

1. A solid is yellow when hot and white when cold

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

3. When water is added to a white powder, the white powder changes to blue crystals

b. With the aid of an equation in each case, explain what will be observed when

1. Chlorine gas is bubbled through a solution of iron II chloride

2. Hydrogen Chloride gas is passed through a jar containing ammonia gas.

3. A piece of sodium metal is dipped into a beaker of water containing some red litmus paper

4. Carbon dioxide is blown into a test tube filled with lime water.

5. (a) outline three reasons to explain why Carbon Dioxide is used to extinguish fire.

(b) A sample of mass 28.6g of hydrated sodium carbonate ( Na₂CO₃.10H₂O)

was heated such that; its water was entirely absorbed by 32g of anhydrous copper II sulphate to form a blue compound of hydrated( CuSO4.XH2O) .find the value of X in the copper sulphate.

6.(a)A student aimed to prepare a gas X by reacting a moderate reactive metal with a dilute acid .Use this information to answer the following question

1. What is the name of the gas X

2. What is the test of the gas X

3. With reasons; state the appropriate method of collecting gas X

4. Write the balanced chemical equation for the reaction.

(b) State four properties that make Aluminium useful in overhead cables

7. (a) Calculate the molarity of 5% by weight of a solution of sodium hydroxide

(b) What is the simplest chemical formula of a compound formed when 36g of Magnesium combines with 14g of Nitrogen?

8.(a) During electrolysis of an aqueous solution of salt of metal M , a current of 2.0A was passed for 32 minutes and 10 seconds .The mass of metal M deposited was 2.24g.

1. On which electrode was the metal deposited

2. Calculate the amount of charge needed to deposit 1 mole of metal M

3. Calculate the charge carried on the ion

4. Write an ionic equation to show how the ion of metal M are discharged at the electrode (R.A.M of metal M is 112)

(b)During electrolysis of brine, sodium is deposited at the cathode and chlorine gas is released at the anode .If 2.0g of sodium are collected at the cathode,find the volume of chlorine released at S.T.P.

9. (a) State the le-chatelier’s principle

(b)State what will happen in the process of equilibrium involving the equation

2SO2(g) + O2(g) ⥫⥬ 2SO3(g) ∆H = -94.4KJMol -1.

If;

1. Temperature is lowered

2. Pressure is increased

3. The concentration of SO 3 is removed from the system.

(c)Briefly write one application of le- chatelier’s principle.

9. (a) States any three main physical properties of water and show the usefulness of each property

(b)During large – scale treatment of water, what two chemicals are added at various stages?.Explain their use.

10. (a) i. Extraction of metal is said to be a reduction process. Explain

ii. Why is sodium collected upwards in the down cell?

(b) Describe the use of each of the following during extraction of sodium

1. Calcium chloride

2. Steel gauze

(c) Name the ores commonly used in the extraction of iron metal

11. (a)State the modern periodic law

(b)Study the periodic table below then answer the questions that follow

Write the formula of compounds formed when element

1. U and W combine together

2. Q and W combine together

Draw and write electronic configuration of Y.

12. (a)Catherine is planning to make a fire to cook ugali for her family. What are the necessary conditions which must be present so that she can make a fire successfully for cooking ugali for her family?

(b)Give a reason for each of the followings

1. Water is universal solvent

2. Some metals like zinc do not get rusty.

3. Chlorine gas is collected by downward delivery

4. Carbon dioxide turns lime water into milky color.

SECTION C (15 MARKS)

Answer only one (1) question.

13. (a)Give good reason (s) for the following. (Answer according to the question demand).

1. Natural gas is so popular in heating and cooking in homes. (2 points)

2. Nuclear energy is not a sustainable source of energy. (2 points)

3. Coal and petroleum are non-renewable sources. (1 point)

(b) State the main raw materials and processes involved in the manufacture of each of the following products.

1. Wood charcoal

2. Coke

3. Lamp black

4. Animal charcoal

14. (a) 25cm³ of 0.1MHCl were neutralized by 23cm³ of Na2CO3 solution.Calculate the concentration of the alkali in grams per litre.

(b)Suggest a suitable indicator of each of the following titrations

1. Hydrochloric acid against ammonia solution

2. Sulphuric acid against sodium hydroxide solution

3. Ethanedioic acid against potassium hydroxide solution.

 

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