KNEC KCSE Chemistry Paper 3 – 2014 Nakuru District Mock

You are provided with

• 10g of solid A which is a mixture of sodium carbonate and sodium chloride. 
• 0.2 M HCl solution B

You are required to

• Determine the concentration of sodium carbonate in the mixture. 
• Percentage of sodium chloride in the mixture.

Procedure
Transfer the entire solid into a 250 Ml volumetric flask. Add about 100cm3 of distilled water.
Shake to dissolve. Top up with more distilled water to make up to the mark. Label this solution
A2. Using a pipette and a pipette filler, transfer 25 cm³ of this solution into a conical flask.
Repeat the procedure two more times to complete table 1

(a) Calculate
(i) The average volume of solution B used ( 1mark)
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(ii) The number of moles of HCl in the average titre (1 mark)
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(b) Write an equation for the reaction ( 1mark)
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(c) calculate the number of
(i) Moles of sodium carbonate in 25cm³ of solution A2 (1 mark)
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(ii) The moles of sodium carbonate in 250 cm³ of solution A2 ( 1 mark)
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(d) Determine the mass of sodium carbonate in solid A (1 mark)
(Na=23, C = 12.0, H=1.0 , O= 16)
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(e) Calculate the percentage of sodium chloride in solid A ( 1 mark)
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You are provided with

• Solution D, 2MHCl
• Solution C 2 M NaOH

You are required to determine the heat of neutralization
Procedure
Wrap a plastic beaker with tissue paper and secure it with a rubber band.
Use a measuring cylinder to transfer 20cm³ of solution C into a plastic beaker.
Take its initial temperature and record it in table 2 below.
Using a clean measuring cylinder, measure 5 cm³ of solution B and add it to solution C. Stir the
mixture immediately with a thermometer and record the highest temperature in table 2
Continue adding 5 cm³ portions of solution every time record the highest temperature attained to
complete the table

Table 2

(4 marks)
Plot a graph of volume of solution D (X-axis) against highest temperature (3 marks)

(a) From the graph:
(i) Determine the volume of solution D that reacts completely with solution C. (1mark)
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(ii) The highest temperature change T ( 1 mark)
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(b) (i) Calculate the amount of heat evolved by the reaction (assume specific heat of capacity =
4.2Jg^-1 K^-1, density of solution = 1 g/cm³) ( 1 mark)
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(a) You are provided with solid E. Carry out the following tests and write your observations and
inferences in the spaces provided.
(i) Place one third of solid E on a metallic spatula and ignite using a Bunsen burner flame.

(ii) Place all the remaining solid in a boiling tube. Add 5cm³ of distilled water. Shake to dissolve
and divide it into 4 portions

(I) to the first portion add three drops of acidified potassium manganate (VII)

(II) To the second add three drops bromine water.

(III) To the third portion add all the sodium hydrogen carbonate provided

(b) You are provided with solid F. Carry out the tests below and record your observations and
inferences in the spaces provided. Place all the solid F in a boiling tube. Add 10cm³ of distilled
water. Divide into four portions.

(i) To the first portion, add aqueous hydroxide drop wise until in excess.

(ii) To the second portion add 5 drops of barium nitrate solution, followed by 3 drops of dilute nitric acid.

(iii) To the third portion add 3 drops of acidified sodium dichromate (VI) solution.