Page 13 - 1202 Question Bank Chemistry Form 5 KSSM

PAPER 2

Section A

Answer all questions.

3
1. Diagram 1 shows the apparatus set-up for an experiment to determine the heat of precipitation. 25 cm
−3
3
−3
of 2.0 mol dm lead(II) nitrate solution is added to 25 cm of 2.0 mol dm sodium sulphate solution in a
polystyrene cups wrapped with hand towels.
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Polystyrene cups wrapped with hand towels

3
−3
+ 25 cm of 2.0 mol dm
3
−3
25 cm of 2.0 mol dm
lead(II) nitrate solution sodium sulphate solution
Diagram 1
(a) What is meant by heat of precipitation from this reaction? [1 mark]

(b) What is the colour of the precipitate formed? [1 mark]

(c) Table 1 shows the results of the experiment. HOTS Analysing

Description Temperature (°C)

Initial temperature of lead(II) nitrate solution 29.0
Initial temperature of sodium sulphate solution 30.0
Highest temperature of the mixture 41.5

Table 1
(i) Mark (3) in the box provided to show which process has the higher heat in the reaction. [1 mark]

Heat absorbed to break the bonds in the reactants.
Heat released during the formation of bonds in the products.

(ii) Calculate the heat energy change in the reaction.
−1
−3
−1
[Specific heat capacity of solution, c = 4.2 J g °C ; density of solution = 1 g cm ] [2 marks]

(iii) Calculate the heat of precipitation for the reaction. [2 marks]

62 Question 1:
SOS TIP (c) Heat energy is absorbed to break existing bonds during reaction.
Heat energy is released when new bonds are formed during reaction.