chemistry paper one

7/29/2019 chemistry paper one

1/12

Name. Index

No..

School Candidates sign.

Date.

233/1

CHEMISTRY

Paper 1

July/August 2010

2 Hours

SIAYA DISTRICT JOINT EVALUATION TEST 2010Kenya Certificate of Secondary Education (K.C.S.E)

233/1

CHEMISTRY

Paper 1

July/August 2010

2 Hours

Instructions to candidates.

1. Write your name and index number in the spaces provided above2. All working must be clearly shown

3. Mathematical tables and electronic calculators may be used.

FOR EXERMINERS USE ONLY.

QUESTION MAXIMUM

SCORE

CANDIDATES

SCORE

1 32 80

This paper consists of 12 printed pages. Candidates should check the question paper to

Ensure that all the pages are printed as indicated and no questions are missing.

Siaya District Academic Commettee Chemistry 233/1 Turn over1


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1. The graph below is a cooling curve of a substance from gaseous state to solid state.

Name:

(a) The process taking place between t0 and t1 (mks)

(b) The energy change that occurs between t3 and t5. ( mk)

2. 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 occur in this method. (1mk)

.



3/12

3. The table below shows PH values for some solutions.

Solutions A B C D

PH values 8 5 1 11

(a) What solution would react vigorously with magnesium metal. Explain. (1mk)

.

(b) Which solution is likely to form a complex ion with zinc oxide? Explain. (1mk)

.

4. Use the chart below to answer the questions that follow:

Identify: (2mks)

Gas P

Solid R.

Solid T..

Liquid S

5. The structure of water molecule can be represented as shown below.

(a) Name the type of bond represented by letters Y and Z. (2mks)

Y..

Z

(b) Relative molecular mass of methane and water are almost similar. However, the boiling point

of water is 1000C while methane is -1610C. Explain (2mks)

.

.


Steam

+


4/12

6. 0.0675 mole of a certain hydrocarbon gas on complete combustion gives 5.94g of

carbon(IV)oxide and 2.43g of water. Calculate its molecular formula. (3mks)

.

7. A mixture of 5.0g of sodium carbonate and sodium hydrogen carbonate was heated until

there was no further change in mass. The loss in mass was 0.31g. Calculate the percentage by

mass of sodium hydrogen carbonate in the mixture.

(). (Assume loss in mass is due to loss of carbon(IV)oxide)

(3mks)

.

8. The table below gives elements represented by letters which are not the actual symbols.

Element U V W X Y Z

Atomic No. 8 12 13 15 17 20

(i) Select an element that can form a divalent anion. (1mk)

(ii) What is the structure of the oxide of W? (1mk)

(iii) Compare the atomic radius of W and X. (1mk)

9. JIK is a common house hold bleach. It contains sodium hypochlorite as the active ingredient.

(a) Write down an equation to show how the active ingredient in JIK bleaches a coloured dye.

(1mk)

(b) Name the process by which JIK bleaches a coloured dye. (1mk)

(c) Suggest why it is better to use JIK as a bleach when washing clothes instead of using

chlorine water. (1mk)

.

10. Why is it advisable to turn a non-luminous flame to a luminous flame while the flame is not in

use? (1mk)

.



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11. When 8.0g of sulphur is completely burnt in oxygen in a calorimeter, the heat evolved raises the

temperature of 500cm3 of water by 350C. Calculate the molar heat of combustion of sulphur.


6/12

15. In an experiment to investigate the effect of burning hydrogen gas, a student set up the apparatus

as shown below:

(a) Identify:

(i) Substance T. ( mk)

(ii) Substance G ( mk)

(b) Write the equation for the reaction of point X (1mk)

16. (a) Using the equations below, distinguish between nuclear fusion and fission.

nHeHH

nKrBaUn

1

0

4

2

2

1

3

1

1

0

94

36

139

56

235

92

1

03

++

+++

(1mk)

.

b) Sketch a graph to show how the mass of a radio active isotope changes with time. (2mks)



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(c) On the graph, show that life of a radio active isotope is constant. (1mk)

17. The set up below was used to study the reaction between ammonia and air in presence of platinum

catalyst.

(a) The platinum wire continues to glow without further heating. Explain (1mk)

.

(b) Brown fumes are observed in the flask. Explain (1mk)

.

(c) Write equations for the reactions representing:

(i) Catalytic oxidation of ammonia (1mk)

(ii) The formation of brown fumes. (1mk)

18. Below is a scheme of some reaction of ethyne.



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(a) (i) State the conditions and reagents required for steps I and II. (1mk)

Step I

Step II

(ii) Give the formula of the products A and D. (1mk)

A

D

(b) Draw and name two isomers of butane. (2mks)

19. When aqueous solution of Iron(II)chloride and potassium thiocyanate are mixed, the equilibrium

below was achieved:

Fe3+(aq) + CNS-(aq) Fe(CNS)

2+(aq)

(brown) (colourless) (blood red)

State and explain the effect of adding a few drops of potasium hydroxide to the equilibrium

mixture. (2mks)

.

.

20. The scheme below represents the manufacture of a cleansing agent M.

(a) Draw the structure of M and state the type of cleansing agent in which M belongs. (2mks)



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(b) State one disadvantage of using M as a cleansing agent. (1mk)

.

21. Use the potential difference values below to answer the questions that follow.

(i) Cr2O2-

7(aq) + 14H+

(aq) + 6e- 2Cr2+(aq) + 7H2O(l) E

0 = +1.33V

Orange Green

(ii) Fe3+(aq) + e- Fe2+(aq) E

0 = +0.76V

Brown Green

Work out the value of 0.2M acidified K2Cr2O7 required to oxidize 20cm3 of 0.3M FeSO4 solution.

(3mks)

.

.

22. Sulphur is a yellow non-metallic element. A molecule of sulphur consists of a puckered

ring of eight atoms covalently bonded.

(a) Draw the structure of a sulphur molecule. (1mk)

(b) What is the structure of sulphur as an element. (1mk)

(c) Explain the diference in structure of sulphur and oxygen yet they are adjacent members in

group VI. (1mk)

.



10/12

23. Chlorine and sodium hydroxide are manufactured by electrolysis of brine in the mercury cathode

cell.

(a) Write an equation for the reaction at the anode. (1mk)

(b) At the anode, Na+ ions are discharged in preference to H+ ions. Explain (1mk)

(c) Sodium metal dissolves in mercury at the cathode to form sodium amalgam. How is solid

sodium hydroxide obtained from sodium amalgam? (1mk)

24. (a) A current of 100 Amps flows through an electrolyte of molten sodium chloride for 15 hours.

Calculate the mass of sodium produced in kg. (2mks)

(1 Faraday = 96500C and Na = 23)

.

.

(b) For the same quantity of electricity as in (a) above, calculate the amount of gaseous product

produced in the cell at 150C and 800mmHg. (2mks)

(Molar gas volume at S.T.P = 22.4gm3)

.

.

25. The solubility of potassium acetate at 200C is 19g/100g of water and at 800 is 25g/100g of water.

What mass of potassium acetate would crystallize out from 78g of a saturated solution when it is

cooled from 800C to 200C? (3mks)

.

.

26. (a) Give two reasons why one would prefer to using Aluminium to copper as overhead electric

cables. (2mks)

.

.



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(b) Study the flow chart below and answer the questions that follow:

(i) Identify substance Q. (1mk)

(ii) Write a chemical equation between Q and Cu2S. (1mk)

27. The diagram below shows a set up which was used by a student to investigate the effect of

electricity on molten Lead(II)iodide.

(a) What observations would be made on the lead iodide during the electrolysis. Explain (2mks)

.

.

(b) Why was it important to carry out the experiment in a fume chamber? (1mk)

.

(c) Write the equations to show the reaction taking place

(i) At the cathode (1mk)

.

(ii) At the anode (1mk)

.


Cu2S + Q Cu(l) + SO2(g)


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28. The apparatus illustrated below were used to prepare and collect carbon(II) oxide in the

laboratory.

(a) State the conditions necessary for the reaction to occur. (1mk)

.

(b) Identify Z and state its role in this reaction. (2mks)

.

(c) Write an equation for the reaction. (1mk)


chemistry paper one

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