Chemistry · Oct / Nov 2022 · Paper 62 · Question 2
0620
As printed in the paper
The question as text
A student investigated the temperature change when two different aqueous solutions of sodium hydroxide, solution G and solution H, reacted with dilute hydrochloric acid. Two experiments were done.
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Show the answer and mark scheme
2(a)[5]
M1 all eight temperatures recorded for Experiment 1 correct (21.0, 24.0, 26.5, 28.0, 29.0, 28.5, 28.0, 27.5)
M2 all eight temperatures recorded for Experiment 2 correct (22.0, 25.0, 27.5, 28.0, 27.5, 27.0, 26.5, 26.0)
M3 all 7 temperature changes in Experiment 1 calculated correctly (3.0, 5.5, 7.0, 8.0, 7.5, 7.0, 6.5)
M4 all 7 temperature changes in Experiment 2 calculated correctly (3.0, 5.5, 6.0, 5.5, 5.0, 4.5, 4.0)
M5 all temperature changes recorded to one decimal place
2(b)[5]
M1 y-axis scale in linear with scale of 2 cm = 2 °C
M2 all points for Experiment 1 plotted correctly. (0,0) not required
M3 all points for Experiment 2 plotted correctly. (0,0) not required
M4 two acceptable smooth curves drawn which are both extended to (0,0)
M5 lines labelled or key
2(c)[2]
M1 correct working shown on graph for 13 cm3 of acid to Experiment 1 line
M2 correct reading from their working shown on graph
2(d)[1]
excess / too much (hydrochloric) acid
or
reaction over / stopped / finished / all NaOH / G / H has been used up
2(e)[2]
M1 solution G is more concentrated (than solution H)
M2 as maximum temperature change higher in Experiment 1
OR
M2 (maximum temperature change) needs more (hydrochloric acid) in Experiment 1
2(f)[2]
M1 temperature (changes) higher
M2 as less heat lost / polystyrene is a (better) insulator
2(g)[2]
advantage: (burette is) (more) accurate / precise
disadvantage: slow / takes more time (to add) / can overshoot required volume
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