Name: ………………………………………………………………….Adm. No…………………..

END OF TERM ONE 2018 EXAMS

233/1

CHEMISTRY

PAPER 1

THEORY

1. A glass tube was inserted into a flame formed when the air hole of the Bunsen burner was fully open in the diagram below:

a) When a burning splint was brought near point P, a small flame lit at this end of the glass tube. Explain(2mks)

b) Give two reason why the Bunsen burner flame above is preferred for heating than the flame obtained when the air hole is closed. (1mk)

2. a) Using the Brousted – Lowly theory, define:

i) An acid(1mk)

ii) A base(1mk)

b) Given this reaction:

RNH2 + H20 RNH3++ OH-

Identify the acid in the forward reaction(1mk)

3. a) State Graham’s Law of diffusion(1mk)

b)A volume of 50cm3 of oxygen gas diffuse through a porous plug in 80 seconds. How long will it take

150cm3 of sulphur (iv) oxide gas to diffuse through the same plug. (S=32, O=16)(3mks)

4. The chromatogram of two inks and three dyes is drawn below:

a) Name the colours of ink A(1mk)

b) Suggest how separated components can be recovered.(1mk)

c) Suggest two reasons why separations occurs in this method.(1mk)

5. Describe how you would prepare a sample barium sulphate using the following reagents: Dilute sulphuric acid, dilute hydrochloric acid and barium carbonate.(3mks)

6. a) What is a fuel?(1mk)

b)Given that the enthalpy of combustion of methane is 890KJmol1- and that of ethanol is 1368KJmol-1 which

of the two fuels is a better fuel? Explain

Molar masses of methane =16, Ethanol = 46(2mks)

7. An element M has two isotopes 65M and 63M. The relative atomic mass of the naturally occurring is 63.55. Determine the percentage abundance.(3mks)

8. a) Name the straight chain compound having the formula C5H12. Name the homologous series to which it belong.(2mks)

b)Draw and name the structural formulae of the two isomers of these compounds.(2mks)

9. A form one student set-up the following apparatus to investigate the percentage of oxygen in air.

a) Why is sodium hydroxide preferred to water in the above experiment.(1mk)

b) Write an equation to show the percentage of oxygen can be calculated.(1mk)

10.A compound has 28% iron, 24% sulphur and the rest is oxygen. Calculate its chemical formula.(3mks)

Fe= 56, S=32, O=16

11.The diagram below represents the set up used to investigate the reaction between zinc and dilute H2SO4.

Sketch the curve you would obtain if the balance reading is plotted against time(2mks)

12.Using dots and crosses to represent electrons, draw the structures of Hydroxonium H3O+(2mks)

13. In an experiment. chlorine gas was passed into moist hydrogen sulphide gas as shown below.

a) What observation was made in the boiling tube.(1mk)

b) Write an equation for the reaction which took place in the tube.(1mk)

c) What precautions should b e taken in carrying out this experiment? Explain(1mk)

d) Calcium hypochlorite (CaOCl2) is used in water treatment:

i) What is the function of this compound in water treatment.(1mk)

ii) Distilled water is not good for drinking. Explain(1mk)

14.

i) Write an equation for the reaction that takes place in the tube.(1mk)

ii) What property of hydrogen makes this reaction possible?(1mk)

iii) What would you expect to happen, if sodium oxide (Na2O) was used instead of lead (ii) oxide (1mk)

15. Study the flow chart below and answer the questions that follow:

(Solid ) (A brown gas) (Yellow solid when cold)

+

(White precipitate) (Colourless solution)

Dilute Nitric Acid

Excess

Aqueous Ammonia

Give the chemical formula of:

i) Solid P(1mk)

ii) The yellow powder(1mk)

iii) The white precipitate(1mk)

16. Use the bond energies given below to determine whether the reaction given is exothermic or endothermic.(3mks)

C2H4 (g) + H2(g) C2H6(g)

C -C = 346KJmol- -

C-H = 431KJmol- -

C=C = 610KJmol- -

H-H = 435 KJmol- -

17. The table shows the pH values of solutions A,B,C,D and E.

Solution

A

B

C

D

E

pH value

2

14

7

10

5

a) Which solution is likely to be that of sodium hydroxide.(1mk)

b) Select the solutions in which a sample of aluminium oxide is likely to dissolve. Explain(2mks)

c) Flower extracts can be used as acid-base indicators. Give two limitations of such indicator.(2mks)

18. Two sample of hard water C and D were boiled. When tested with drops of soap, sample D formed lather easily while C did not:

a) Name the possible salt that caused hardness in sample D.(1mk)

b) Explain how distillation can remove hardness in sample C(1mk)

c) Give two advantages of hard water.(1mk)

19. a) Draw a diagram showing how ammonia gas is dissolved in water.(2mks)

b) What property of ammonia makes this the method of choice.(1mk)

c) State two uses of ammonia gas.(2mks)

20. Study the table below and answer the questions that follow:

Substance

A

B

C

D

E

F

Melting point (oC)

801

113

119

-39

5

-101

1356

Boiling Point (oC)

1410

445

457

54

-36

2860

Electrical conductivity

Solid

Poor

Poor

Good

Poor

Poor

Poor

Liquid

Good

Poor

Good

Poor

Poor

Poor

a) Identify with reasons the substances that :

i) Have a metallic structure.(2mks)

ii) Have a molecular structure and exist in the liquid state at room temperature and pressure(2mks)

b) Suggest a reason why substance B has two melting points (1mk)

21. Study the flow chart below and answer the questions that follow

(R) (Q) (Sulphur solid)

H2O

a) Identify substance Q(1mk)

b) Write an equation leading to formation of substance R(1mk)

c) State the difference between bleaching action of chlorine gas and sulphur (iv) oxide(2mks)

22. Group (viii) elements are said to be unreactive. Give a reason.(1mk)

23. Burning of fossil fuels has adverse environmental effects. Name one pollutants from the burning of petroleum products.(1mk)

24. Write an equation for the reaction between bromine and water.(1mk)

25. A volume of 10cm3 concentrated hydrochloric acid of density 1.18g/cm3 and purity 36% dissolved in 250cm3 of distilled water. Calculate the molarity of the solution. (H=1, Cl=35.5)(3mks)

26. Metal C does not react with cold water but reacts with steam. D does not react with steam but reacts with dilute acids. B reacts with cold water while A does not react with dilute acids. Arrange the metals in order of reactivity starting with the least reactive.(2mks)

27. Diamond is an allotrope of carbon. Name another element that exhibit allotropy.(1mk)

Page 12 of 12 Form 4 Chemistry End Of Term One Exam 2018