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NAME:……………………………………………………..INDEX NO:…………………
SIGNATURE………………
233/3
CHEMISTRY
PRACTICAL
Paper 3
JULY 2012
TIME: 2¼ HOURS
THE NAKURU DISTRICT JOINT MOCK EXAMINATION- 2012 Kenya Certificate of Secondary Education
CHEMISTRY
Paper 3
PRACTICAL
2¼ HOURS
Instruction to Candidates
1. Answer ALL questions in the spaces provided in the question paper
2. You are NOT allowed to start working with the apparatus for the first 15 minutes of the 2¼
hours allowed for this paper. This time is to enable you to read the question paper and make sure
you have all the chemicals and apparatus that you may need.
3. Mathematical tables and electronic calculators may be used
4. All working MUST be shown where necessary.
5. Candidates may be penalized for NOT following the instruction given in this paper.
For Examiners use only
Question Max. Score Score
1 12
2 12
3 a)
b)
5
11
Total score 40
This paper consist of 7 printed pages
Candidate should check the question paper to ensure that all the papers are printed
as indicated and no questions are missing.
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1 You are provided with: - Solution A containing 38.6 g per litre of solid A
(solid A is a mixture of sodium chloride and hydrated sodium carbonate) - Solution B which is 0.25M hydrochloric acid - Methyl orange indicator
You are required to determine the percentage of sodium chloride in the mixture.
Procedure
i) Fill your burette with solution B ii) Using a pipette and pipette filler, pipette 25cm3 of solution A into a conical
flask. Add two to three drops of methyl orange indicator.
iii) Titrate and record your results in the table below
Repeat the procedure to obtain consistent results.
I II III
Final burette reading (cm3)
Initial burette reading (cm3)
Volume of B used (cm3)
Find ( 4 marks)
a)(i) Average volume of B used (show values averaged)
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Calculate
ii) The number of moles of B. hydrochloric acid used. (H=1, CL=35.5) (1mark)
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iii) The number of moles of sodium carbonate, Na 2CO3.10H2O in 25.0cm3 of the mixture
(Na =23, C=12, O=16, H=1) (1mark)
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iv) Number of moles of sodium carbonate decahydrate in 1dm3 of the mixture of solution A
(2marks)
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b) Calculate the mass of sodioum carbonate Na 2CO3.10H2O, in the mixture made.
(Na =23, C=12, O=16, H=1) (2marks)
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c) Calculate the percentage by mass of sodium chloride in the mixture solution A (2 marks)
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2 You are provided with:
• Magnesium ribbon, solid L
• 2.0M hydrochloric acid, solution Q
• Stopwatch
You are required to determine the rate of reaction between magnesium and hydrochloric
acid at different concentrations.
Procedure
1 Place 5 test tubes on a test tube rack and label them 1,2,3,4,and 5.ing a 10ml measuring
cylinder measure out the volumes of 2M hydrochloric acid solution Q as shown in the table
and pour them into the corresponding test-tubes. Wash the measuring cylinder and use it to
measure the volumes of water as indicated in the table and pour into the corresponding test-
tubes.
II Transfer all of the solution in test tube I into a clean 50ml beaker. Place one piece of
magnesium ribbon into the beaker and start a stopwatch immediately. Swirl the beaker
continuously ensuring the magnesium is always inside the solution. Note the time taken for
the magnesium ribbon to disappear and record in the table. Wash the beaker each time.
III Repeat the procedure II for each case of the solution in the test tubes 2,3,4 and 5 to
complete the table.
Table 1
Test tube number 1 2 3 4 5
Volume of solution Q(cm3) 10 9 8 7
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Volume of distilled water(cm3) 0 1 2 3 4
Time taken (sec)
Rate of reaction 1
time
(6marks)
(b) Plot a graph of rate of reaction, 1 (y-axis) against volume of solution A (4marks)
time
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ii) Use the graph to determine the time that would be taken for a 1cm length of magnesium ribbon
to disappear if the volume of the acid solution Q used was 7.5cm3
(1mark)
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(iii) In terms of rate of reaction, explain the shape of your graph (1 marks)
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3 You are provided with
Solution W containing calcium ions
Solution X containing sodium ions
Solution Y containing barium ions
Carry out the tests on solutions W,X,Y and Z in order to identify the cations present in solution
Z
Procedure
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Clean one end of the glass rod thoroughly dip the clean end of the glass rod in solution W..
Remove the end and heat it in the non – luminous
part of a Bunsen burner flame. Note the colour of the flame and record it in table 3. Allow the
glass rod to cool for about two minutes. Repeat the procedure with solutions X,Y and Z.
Complete table 3
Table 3
solution Colour of the flame
W
X
Y
Z
(4marks)
(ii) Identify the cation present in solution Z (1mark)
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b) You are provided with solid K. Carry out the tests below and record your observations and
inferences in the spaces provided.
(a) Place one half of solid K in a clean dry test-tube. Heat it gently then strongly.
Observation Inferences
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(2marks) (1mark)
b) Place the other half of solid K in a boiling tube. Add 10cm3 of distilled water and shake well until
all the solid dissolves
(i) To about 1cm3 of the solution add 2M sodium hydroxide drop wise until in excess
Observation inferences
(2marks) (1mark)
ii) Place 1cm3
of the solution in a test tube and add 2 to 3 drops of 2M sulphuric (vi) acid.
Observation inferences
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