🌊PAPER 51-Qns

 

THE PRESIDENT’S OFFICE

REGIONAL ADMINISTRATION AND LOCAL GOVERNMENT

O-STUDY LIBRARY

FORM THREE ANNUAL EXAMS, NOVEMBER 2021

CHEMISTRY

Time: 3 Hours

INSTRUCTIONS:

1. This paper consists of sections A,B and C

2. Answer all questions in Section A and B and only one questions in Section C

3. The following constants may be used

• Atomic masses H=1, O=16, C= 12, Ca =40, Na=23, Cl = 35.5, K=39

• G.M.V = 22.4dm³

SECTION A (15 MARKS)

Answer all questions in this section

1. For each of the items (i) to (x) choose the most correct answer from the given alternatives and write its letter in the answer sheet provided

i)Sodium chloride Salts, when exposed in air, turns into a solution. It is described as:-

1. Hygroscopic salt

2. Effervescent salt

3. Deliquescent salt

4. Hydroscopic salt

ii)Wood charcoals are obtained in a process called

1. Fractional distillation

2. Normal distillation

3. Destructive distillation

4. Restrictive distillation

iii)The valence of an element with atomic number 10 is

1. 2

2. 3

3. 1

4. 0

iv)When a certain liquid is mixed with CUSO4(s)Crystals change from white to blue. The liquid is possible to be …..

1. Water

2. Ethanol

3. Kerosene

4. Petrol

v)The loss in mass when 100g of marble is heated to constant mass is

1. 220g

2. 88g

3. 22.4g

4. 22400g

vi)Which equation shows reduction of an iron compound

1. 4Fe +302 →2Fe2 O3

2. Fe + 2HCl → Fecl2 +H2

3. 4Fe +O2 →2Fe2O3

4. Fe2O3 +3CO → 2Fe +3CO2

vii)What is the oxidation number of the phosphorus atom in the H3PO4

1. +5

2. O

3. +2

4. +1

viii)During volumetric analysis the solution added to the burette is referred to as the:-

1. Acid and Base

2. Analyze

3. Secondary solution

4. Titrant

ix)Fire caused by combustible Metal is

1. Class A fire

2. Class B fire

3. Class C fire

4. Class D fire

x)Which is the hottest part of a non-luminous flame?

1. The outer zone

2. The tip of the outer zone

3. The tip of the middle zone

4. The outer and inner zone

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

2. Match the following items from Column A with corresponding responses from Column B by writing the letter beside the item number in your answer sheet.

LIST A	LIST B
Alcohol and water Cooking oil and water Iodine and sand Sulphur and Iron filings Oil from seeds	Layer Separation Chromatography Magnetization Filtration Solvent extraction Decantation Sublimation Fractional distillation Hand picking

LIST A	i	ii	iii	iv	v
LIST B

SECTION B: (70 MARKS)

Answer all question in this section, each question carries (7 marks)

3. (a) The non – luminous flame is used in different areas. Give three (03) such areas and explain why a flame is preferred for those uses

(b) With one examples categorize laboratory apparatus according to their uses (4 category only)

4. (a) Element K and L have atomic number 19 and 17 respectively, according to the periodic table

1. Write the electronic configuration of K and L

2. Which is non- metal between K and L

3. Write the chemical formula when K combines with L

(b)Give the appropriate extinguisher for the following classes of fire

1. Class A

2. Class B

3. Class E

4. Class F

5. (a) There is a campaign to stop the use of charcoal as a domestic fuel. Give three points to support the Campaign

b) Assume the equation for dissociation of Calcium Carbonate in a closed system is

CaCO₃(s)⟺CaO(s) + CO₂ (g) ΔH =+175.5KJMol^-1

What will be the effect on the proportion of Calcium carbonate in the equilibrium mixture if:-

1. Temperature is increased

2. Pressure is increased

3. Carbon dioxide is removed from the system

4. Helium gas is introduced into the system

6. (a) Provide a suitable indicator to be used in the following titrations

1. Ethanoic acid with ammonia solution

2. Sulphuric acid and Sodium hydrogen Carbonate

3. Sodium hydroxide and ethanoic acid

(b) You are provided with the following solutions in bottles labeled A, B, C and D attached with PH values 5.4, 7.3, 13 and 7 respectively. Which bottle contain

1. Detergent soap

2. Water

3. Lemon juice

4. Blood

7. (a)Write the balanced ionic equation from the following statements

1. Neutralization of potassium hydroxide solution with Sulphuric acid solution

2. The reaction of zinc powder with dilute hydrochloric acid

(b) Write four characteristics of a good chemical equation

8. (a) Define Mole

(b) What volume of oxygen at S.T.P will be produced if 20g of potassium chloride (v) are thermally decomposed?

9. (a) Differentiate between the following

1. An isotope and isotopy

2. An ion and an atom

(b) Sir Dalton has been so influential in chemistry by his useful contribution in explaining issues related to atoms. Using five points elaborate the main concerns of his contribution about atomic theory.

10.(a) Name the following compounds according to IUPAC system

1. (NH4)2CO3

2. N205

3. SF6

(b) A compound is analyzed and found to contain 68.54% Carbon 863% Hydrogen and the rest is Oxygen. Calculate

1. Its empirical formula

2. Its molecular formula if its vapor density is 52

11.(a) Explain the effect of adding the following substances to Hard water

1. Lime water

2. Washing soda

(b) Formation of lime scale in the pipes is both advantageous and disadvantageous. Verify this statement by giving one point in each

12.(A)You are provided with the following reactions

1. 2H2O2 →2H2O +Y2

2. Zn +H2SO4 →Y +H2(g)

1. Identify the gas x and compound Y

2. Mention any three uses of gas x

(B) Explain the property of hydrogen gas that make it suitable for

1. Production of oxy-hydrogen flame

2. Filling weather balloon

3. Manufacture of Ammonia

SECTION C (15 MARKS)

Answer only one (1) question from this section

13.(a) Define the following

1. Standard Solution

2. Molar solution

3. Indicator

(b) A form three students conducted titration which involved solution NaXCO₃ and Nitric acid

solution if 25cm³ of solution NaXCO₃ required exactly 12.5cm³ of 0.2M of Nitric acid for complete neutralization. Calculate:

1. The Molarity and molar mass of Na_xCO₃ if its concentration in g/dm3 is 8.4

2. The atomic mass of element x given that NaxCO₃ reacted with HNO₃ in a 1:1 mole ratio

3. Suggest the name of element X

4. Give the name of anion XCO₃

5. Assign the correct charge of anion XCO₃

14.(a).Define the following terms

1. Electrolysis

2. Electrolyte

3. Electrode

4. Electrolytic cell

(b) State Faraday second law of electrolysis

(c)Mention three (3) factors for selective discharge of ions during electrolysis

(d)Briefly explain three (3) application of electrolysis

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