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233/3
CHEMISTRY
PAPER 3
(PRACTICAL)
JULY /AUGUST 2015
TIME: 2 ¼ HOURS
BUTERE EAST JOINT EVALUATION EXAM – 2015
Kenya Certificate of Secondary Education (K.C.S.E)
Chemistry
Paper 3
(PRACTICAL)
Time: 2 ¼ Hours
INSTRUCTIONS TO CANDIDATES
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Write your name, indexnumber,Sign and date.
Answer all the Questions in the spaces provided.
You are not allowed to start working with the apparatus for the first 15 minutes of the 2 ¼ 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 you need.
All working must be clearly shown where necessary.
Mathematical tables and electronic calculators may be used.
This paper consists of 4 printed pages.
Candidates should check to ascertain that all pages are printed as indicated and that no Questions are
missing.
For Examiner’s Use Only
Question
Maximum Score
1
21
2
12
3
07
Total
40
Candidate’s Score
This paper consists of 4 printed pages.
Candidates should check the question paper to ascertain that all pages are printed as indicated.
And that no questions are missing.
©Butere East Joint Exam 2015
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Chemistry 233/3
1.
You are provided with:
•
Dilute hydrochloric acid solution A
•
0.1M sodium hydroxide solution B
•
10g of a mixture of sodium hydrogen carbonate and sodium chloride per litre, solution C.
You are required to determine:
Molarity of solution A.
Percentage purity by mass of sodium hydrogen carbonate
Procedure 1
• Fill the burette with solution A. Pipette 25cm3 of 0.1M sodium hydroxide solution B into a clean
conical flask and add 2 drops of methyl orange indicator and titrate with solution A until a
permanent pink colour occurs. Fill in the table below. Repeat the titration two more times and
complete the table 1 below.
Table I
TITRE
(4mks)
1
2
3
Final burette reading (cm3)
Initial burette reading (cm3)
Volume of solution A used (cm3)
a) Calculate the average volume of solution A used.
(2mks)
b) Calculate the number of moles of hydrochloric acid solution A that reacted with 25 cm3 of sodium
hydroxide solution B.
(2mks)
c) Calculate the concentration of solution A in moles.
(3mks)
PROCEDURE II
Pipette 25cm3 of solution of C into a conical flask. Titrate with solution A using 2 drops of methyl
orange indicator.
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Chemistry 233/3
Record your results in table II below.
Table II
(4mks)
TITRE
1
2
3
Final burette reading (cm3)
Initial burette reading (cm3)
Volume of solution A used (cm3)
d) Calculate the average volume of solution A used.
(2mks)
e) Write anionic equation for the reaction taking place between solution A and mixture C.(lmk)
f)Calculate:
i) Molarity of sodium hydrogen carbonate in moles per litre.
(2mks)
ii) Mass of sodium hydrogen carbonate in the mixture in grammes per litre.
(lmk)
iii) Mass of the sodium chloride in the mixture.
(lmk)
iv) The percentage purity of the sodium hydrogen carbonate.
2.
(2mks)
You are provided with solid K in a test tube.
You are required to determine the freezing point of solid K.
PROCDURE
Using a test tube holder, immerse the test tube containing solid K into the hot water bath ensure that
half the test tube is immersed). Continue heating the water until the solid melts. Insert a thermometer
into the liquid being formed in the test tube and note the temperature when the entire solid has just
melted. Record the temperature in table Ill. Remove the test tube from the water and immediately
start a stop watch/clock and record the temperatures of the contents of the test tube after every half-
©Butere East Joint Exam 2015
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Chemistry 233/3
minute and complete the table Ill below. Dip the thermometer into the hot bath to clean it then wipe
it with a tissue paper.
TableIII
Time (min)
(4mks)
0
½
1
1½
2
2½
3
3½
Temp (0C)
a) On the grid provided plot a graph of time (horizontal axis) against temperature (vertical axis)
(4mks)
b) From the graph determine the freezing point of solid K.
3.
(l mk)
You are provided with solutions X, Y and Z. Add 3 drops of aqueous ammonia to each solution and
writeyour observations and inferences in the spaces provided.
Solution
Observations
Inference
X
1mk
©Butere East Joint Exam 2015
1 mk
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Chemistry 233/3
Y
1mk
2mks
1mk
1mk
Z
©Butere East Joint Exam 2015
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Chemistry 233/3