Zinc metal reacts with aqueous copper(II) sulfate.
Zn(s) + CuSO₄(aq) → Cu(s) + ZnSO₄(aq)
The enthalpy change of this reaction, ΔΗ, can be determined by adding excess zinc powder to a measured volume of 0.500 mol dm⁻³ aqueous copper(II) sulfate.
The temperature of 25.0 cm³ of 0.500 mol dm⁻³ aqueous copper(II) sulfate is recorded for three minutes. At four minutes 3 g, an excess, of zinc powder is added and the mixture is continuously stirred. The temperature is recorded at times shown in the table.
time/min | 0 | 1 | 2 | 3 | 4½ | 5 | 5½ | 6 | 6½ | 7 | 8 | 9 | 10
temperature /°C | 18 | 19.5 | 19.5 | 19.5 | 32.5 | 38 | 36 | 34 | 33 | 32.5 | 31.5 | 31 | 31

Q: What topic does this question test?

This question tests Chemical energetics in A-Level Chemistry (syllabus code 9701). It is worth 10 marks.

Q: Which exam paper is this question from?

This question appeared in the Cambridge A-Level Chemistry Feb/Mar 2021 examination, Paper 5 Variant 2 (9701_m21_qp_52.pdf).

Question

Zinc metal reacts with aqueous copper(II) sulfate.
Zn(s) + CuSO₄(aq) → Cu(s) + ZnSO₄(aq)
The enthalpy change of this reaction, ΔΗ, can be determined by adding excess zinc powder to a measured volume of 0.500 mol dm⁻³ aqueous copper(II) sulfate.
The temperature of 25.0 cm³ of 0.500 mol dm⁻³ aqueous copper(II) sulfate is recorded for three minutes. At four minutes 3 g, an excess, of zinc powder is added and the mixture is continuously stirred. The temperature is recorded at times shown in the table.
time/min | 0 | 1 | 2 | 3 | 4½ | 5 | 5½ | 6 | 6½ | 7 | 8 | 9 | 10
temperature /°C | 18 | 19.5 | 19.5 | 19.5 | 32.5 | 38 | 36 | 34 | 33 | 32.5 | 31.5 | 31 | 31

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