KNEC KCSE Chemistry Paper 3 Question Paper / 2016 Pre KCSE

You are provided with:
Solution M 0.2M hydrochloric acid,
Solution F containing 15.3g per litre of basic compound G₂X.H₂O.
You are required to determine the relative atomic mass of G.
PRECEDURE:
Place solution M in a burette ,pipette 25cm³ of solution F into a 250cm³ conical flask. Add
two drops of methyl orange indicator and titrate. Record your results in the table below.
Repeat the procedure two more times and complete table I.

(4mks)
ii) What is the average volume of solution M.? (1mk)
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b) Given that one mole of F reacts with 2moles of M. Calculate the;
i) number of moles the basic compound,G₂X, 10H₂O in the volume of solution
F used. (2mks)
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ii) Concentration of solution F in mole per litre. (2mks)
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iii) Relative formula mass of the basic compound, G₂X.₁₀H₂O. (1 ½ mks)
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iv) relative atomic mass of G (Relative formula Mass of X=60 , atomic mass of H=1.0 ,
O=16.0). (1 ½ mks)
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You are provided with:

1. 1.899g of solid P, solid P is adiabatic acid H₂X.
2. 0.5M Solution of the dibasic acid , H₂X , Solution V.
3. Sodium hydroxide, Solution K.

You are required to determine:
a) i) the molar heat of solid P.
ii) the heat of reaction of one mole of the dibasic acid with sodium
hydroxide.
b) Calculate the heat of reaction of solid H₂X with aqueous sodium hydroxide.
PROCEDURE I‍
Place 30cm³ of distilled water into a 100ml beaker. Measure the initial temperature of the
water and record it in the table II below. Add all the solid P at once; stir the mixture carefully
with the thermometer until all the solid dissolves. Measure the final temperature reached and
records it in the table II

a) Determine the change in temperature ∆T1 (1½mks)
…………………………………………………………………………………………………
b) Calculate the:
i) heat change when H₂X dissolves in water, (Assuming the heat capacity
of the solution is 4.2J^-1g^-1 K ^-1 and density is 1g/cm³) (2mks)
ii) number of moles of the acid that were used. (Relative formula mass of
H₂X is 126) (1mk)
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iii) molar heat of solution ∆H1 solution of the acid H2X. (1mk)

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PROCEDURE II.
Place 30cm³ of solution V into a 100cm³ beaker. Measure the initial temperature and record it
in table III below. Measure 30cm³ of sodium hydroxide, solution K.Add all of the 30cm³ of t
of solution K at once to V in the beaker. Stir the mixture with the thermometer. Measure the
final temperature reached and record it in table III.

b) Determine the change in temperature, ∆T₂. ( ½ mk)
…………………………………………………………………………………
c) Determine the:
i) heat change for the reaction (Assume the heat capacity of the solution is
4.2J^-1g^-1K ^-1 and density is 1g/cm³ (2mks)
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………………………………………………………………………….
ii) Number of moles of the acid used (H₂X). (1mk)
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…………………………………………………………………….
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iii) Heat of reaction, H 2 of one mole of the acid H₂X with sodium hydroxide
(1mk)
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d) Given that, ∆H1 is the heat for reaction 

∆ H2 is the heat for the reaction 

Calculate ∆H3 for the reaction (2mks)
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You are provided with solid S. Carry out the tests below and record your observations
and inferences in the spaces provided.
a) Place about one third of solid S in a dry test tube. Heat the solid gently and the
strongly. Test any gases produced with blue and red litmus papers.

b) Dissolve the remaining portion of solid S in 8cm³ of distilled water.
i) Divide the solution into the first portions, to the first portion, add
aqueous sodium hydroxide drop wise until in excess.

ii) To the second portion , add aqueous ammonia dropwise in excess.

iii) To the third portion , add 10cm³ of barium chloride solution.
 iv) To the forth portion , add about 1cm³ of Lead (II) nitrate solution.

v) To the fifth portion, add about 2ml of hydrogen peroxide then about
1cm³ of sodium hydroxide solution.