TIME: 3:00 HOURS                                                                                           AUGUST 2023


1. This paper consists of sections A, B and C with the total of Eleven (11) questions. 2. Answer all questions in section A, B and two question from section C. 3. Cellular phones and any unauthorized materials are not allowed in the examination room.

4. Write your examination number on every page of your answer booklet(s) 5. The following constants may be used

Atomic masses= H = 1, O=16, S=32, Cl=35.5, Na=23, C=12, Ag=108. Avogadro’s constant:6.02x1023

GMV at s.t.p =22.4dm3

1 faraday=96,500C

1litre=1dm3 =1000cm3

SECTION A (16 marks)

Answer all questions

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

i. Loose or floppy clothing is not allowed in the laboratory. Why?

A. Movement has to be fast
B. It will get wet when water splashes
C. It may catch fire or cause one to fall
D. It causes poor ventilation in the body
E. It prevents experiment from being conducted well

ii. What mass of sulphuric acid (H2SO4) is found in 400 cm3of its 0.1M aqueous solution?

A. 2.67g
B. 9.8g
C. 4.89g
D. 3.92g
E. 8.69g

iii. One of the isotopes of an element X has atomic number Z and a mass number A. what is the number of neutrons contained in the nucleus of the element? 

A. Z - A
B. A
C. A + Z
D. Z
E. A – Z

iv. What is the proper set of apparatii would you use to measure various substances in the laboratory?

A. Stopwatch, beaker, burette and pipette
B. Beaker, pipette, stopwatch and electrical balance
C. Electrical balance, pipette, stopwatch and thermometer
D. Thistle funnel, pipette, burette and measuring cylinder
E. Beaker, measuring cylinder, thermometer and pipette

v. When methane undergoes substitution reaction with excess chlorine, what is the final product?

A. Chloromethane
B. Dichloromethane
C. Trichloromethane
D. Tetrachloromethane
E. Chloroethane

vi. Aluminum does not react with water and does not corrode much in air. Why? A. It is below hydrogen in reactivity series

B. It forms a stable carbonate which prevent reactions
C. The metal is covered with protective coating of an oxide
D. It is very stable
E. Does not react with water

vii. Which of the following compound does not belong to the alkene homologous series?

A. C2H4 
B. C3H6 
C. C4H8
D. C8H16 
E. C5H12

viii. Substance X liberates chlorine gas from acidified potassium chloride. What is the behavior described by X

A. Catalysis 
B. An oxidation 
C. Reduction
D. Decolourization 
E. Colorization

ix. When a burning fuel produces blue colour it means there is A. Adequate supply of oxygen with production of soot. B. Inadequate supply of oxygen without production of soot. C. Inadequate supply of oxygen with production of soot. D. Adequate supply of oxygen with production of more heat E. Inadequate supply of oxygen with production of more heat

x. What is the number of molecules in 16.8dm3of chlorine at S.T.P? 

A. 4.52X1023
B. 6.02X1023
C. 7.5X1023
D. 3.14X1023
E. 9.03X1023

2. Match the items in list A with the correct response in list B writing the letter of the  correct response beside the item number in the answer sheet provided. 



I. A black solid element which burns with reddish glow  giving off colourless gas which is slightly acidic. 

II. Silvery white metal which burns with golden yellow  flame giving an oxide which is basic in nature. 

III. A yellow element in colour which burns with blue  flame giving colourless gas which is strongly acidic  in nature. 

IV. A shinning white strip metal which burns with  dazzling white flame giving an oxide which is  

slightly basic in nature. 

V. A silvery white metal which burns with brick red  flame giving off oxide which is white solid. 

 vi. A reactive metal which does not react very well with  oxygen in air

A. Calcium 

B. Nitrogen 

C. Aluminium 

D. Iron 

E. Carbon 

F. Sodium 

G. Copper 

H. Beryllium 

I. Argon 

J. Magnesium 

K. Sulphur 

L. Phosphorus 

M. Chlorine 

N. Zinc 

O. Fluorine 

P. Lead

SECTION B (54 Marks)

3. a) Consider the following elements:

16 O8 , 19F9 , 20Ne10 , 23Na11 and 24Mg 12. Atoms and ions of this elements can be Iso electronic (have the same number of electrons)

i. Write down their symbols when their Iso -electronic

ii. Write down their common electronic arrangement in their ions and atoms. b) Although Sulphur dioxide is an oxide, it can be further oxidized

i. Write an equation and conditions for further oxidation of Sulphur dioxide ii. Write down an equation showing how the product can be used industrially to obtain a desired material to be produced.

iii. Give the name for this industrial process

iv. Write down two uses of the product formed by the industrial process named in (iii) above.

4. Mwaisa guided students of form four to study carefully an experiment carried out in order to distinguish various substances formed during an experiment. The procedures were as follows

a) Measure about 120 cm3of water and pour it in a beaker

b) Add a spatulafully of common salts and stir to allow all salts to dissolve. c) Continue to add more salts to the solution, stirring until no more salts can dissolve.

d) Place the solution on tripod stand and heat gently, as you continue stirring. e) Stop heating when salts dissolves.

f) Place the beaker in a trough of cold water and allow cooling for 3 to 5 minutes. Note the result observed.


i. What type of solution was obtained when a spatulaful of table salt were dissolved in 120 cm3of water at room temperature? Give reason

ii. What type of solution was obtained when no more salts dissolved in cold water at room temperature? Give reason

iii. What is the name of the final solution obtained after cooling in trough of cold water? Give reason

iv. Explain the two (2) applications of the concept studied above.

5. a) Give three application of separation of mixture to daily life.

b) 20.0cm3 of sodium hydroxide containing 8.0gdm-3 was required for complete neutralization of 0.18g of dibasic acid. Calculate the relative molecular mass of the acid.

6. a) State Faraday’s laws of electrolysis

b) Dilute Silver nitrates solution was decomposed by the passage of electric current through it. What mass of Silver and what volume of Oxygen (measured at (s.t.p) would be liberated in electrolysis by 9650 Coulombs of electricity?

7. Sulphuric acid act as dehydrating agent, oxidizing agent as well as an acid. Decide by a very brief answer how it behaving in each of the following cases.

i. It evolves hydrogen gas when reacting with magnesium.

ii. It is used to dry hydrogen chloride gas.

iii. It reacts with sodium hydroxide to form salt and water.

iv. It releases Sulphur dioxide gas when reacting with copper.

v. It turns sugar black

vi. It turns copper sulphate white

vii. It produces carbon dioxide when added to the carbonate.

8. a) What do you understand by the following terms

i. Mole concept

ii. Molar volume of gas

b) Consider the equation below for dissociation of sulphuric acid

H2SO4 (aq) 2H+(aq) + SO42-(aq)

From the equation how many ions are there in 9.8g of sulphuric acid?

Answer any two questions from this section

9. (a) Describe the extraction of sodium from its ore and write all the reaction equation (b) State four uses of sodium metal

10. A local industrialist came to your school to search information on the following concepts

i. Land pollution

ii. Eutrophication

- Explain to her, what these concepts means

- What are the causes, effects and precautions she is supposed to take to avoid their effects?

11. In certain chemical plant that deals with the production of hydrogen gas, a certain chemist passes an electric current in series through copper (II) sulphate and sulphuric acid solutions. In both electrolytes, inert electrodes were used. If 8400 cm3 of hydrogen gas at S.T.P were produced for several hours, what volume of oxygen gas would also be produced? What mass of copper was produced?

Post a Comment