KNEC KCSE Chemistry Paper 3 Question Paper / 2016 KCSE KAMDARA JET Examination

You are provided with:
• Solid P
• 2.0M hydrochloric acid, solution Q
• 0.1M sodium hydroxide, solution R
You are required to determine the enthalpy change ∆H, for the reaction between solid P and
one mole of hydrochloric acid.

Procedure I
Transfer 20.0cm3 of 2.0M hydrochloric acid, solution Q in a 100ml.beaker using a burette.
Measure the temperature of the solution after every half-minute and record the values in Table 1.
At exactly 2½ minutes, add all of solid P to the acid carefully. Stir the mixture gently with the
thermometer. Measure the temperature of the mixture after every half-minute and record the
values in Table 1. (Retain the mixture for use in procedure II)

(i) Plot a graph of temperature (y-axis) against time. (3 mks)

(ii) Using the graph, determine the change in temperature ∆T. (1 mk)
(iii) Calculate the heat change for the reaction (Assume that the specific heat capacity of the
mixture is 4.2 Jg^-1K^-1 and the density of the mixture is 1g/cm3). (2 mks)

Procedure II
Rinse the burette thoroughly and fill it with sodium hydroxide. Transfer all the contents of the
100ml. beaker in procedure I into a 250ml. volumetric flask. Add distilled water to make up to
the mark. Label this as solution N. Using a pipette filler, place 25.0cm³ of solution N into a
250ml. conical flask. Add two or three drops of phenolphthalein indicator and titrate against
solution R. Record your results in table 2. Repeat titration two more times and complete Table 2.

Calculate the:
(i) average volume of sodium hydroxide solution R. (1 mk)
(ii) the number of moles of :
I Sodium hydroxide solution R. (1 mk)
II hydrochloric acid in 25cm³ of solution N. (1 mk)

You are provided with solid E. Carry out the following tests and write your observations
and inferences in the spaces provided.
a) Place all of solid E into a boiling tube. Add about 12cm³ of distilled water and shake
thoroughly. Filter the mixture and place the filtrate into another boiling tube. Dry the
residue using pieces of filter paper.
Retain the filtrate for use in 2(b) below.
(i) Transfer half of the dry residue into a dry test tube. Heat the residue strongly and test
any gas produced using a burning wooden splint.

(ii) Place the other half of the residue in a dry test-tube. Add 4cm3 of 2M nitric acid.
Retain the mixture for test (iii) and (iv) below .

(iii) To 2cm3 of solution obtained from a(ii) above, add aqueous ammonia drop by drop
until in excess.

(iv) To 2cm3 of the other solution obtained in a(ii) above, add 2cm3 of potassium iodide
solution

(b) Divide the filtrate obtained in 2(a) above into 5 portions.
(i)To the first portion of the filtrate add aqueous ammonia drop by drop
until in excess.

(ii) To the second portion of the filtrate add 2 drops of sodium sulphate solution.

(iii) To the third portion of the filtrate, add 2 drops of barium nitrate solution followed by
about 2 cm3 of nitric acid solution .

You are provided with solid F. Carry out the tests below and record your observations
and inferences in the spaces provided.
(a)(i) Using a metallic spatula, heat half of solid F in a non-luminous Bunsen burner
flame for some time then remove when it ignites.

(b) Put a half spatula endful of solid F into a boiling tube. Add about 10cm3 of distilled
water and shake vigorously.
Divide the resulting solution into two portions.
(i) To the first portion, dip a piece of universal indicator paper and determine its pH

(ii) To the second portion, add two drops of acidified potassium manganate (VII)
solution and shake vigorously.