DP Chemistry (first assessment 2025)

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Question 22M.1A.HL.TZ1.17

Date	May 2022	Marks available	[Maximum mark: 1]	Reference code	22M.1A.HL.TZ1.17
Level	HL	Paper	1A	Time zone	TZ1
Command term	Predict	Question number	17	Adapted from	N/A

17.

[Maximum mark: 1]

22M.1A.HL.TZ1.17

In which reaction does entropy decrease?

A. NaCl (s) → NaCl (aq)

B. Zn (s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

C. NH₃(g) + HCl (g) → NH₄Cl (s)

D. CuCO₃(s) → CuO (s) + CO₂(g)

[1]

Markscheme

C

Examiners report

Second best answered question in the exam with 85% of candidates identifying the correct answering for reaction in which entropy decreases.

Syllabus sections

Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.1—Entropy, S, is a measure of the dispersal or distribution of matter and/or energy in a system. The more ways the energy can be distributed, the higher the entropy. Under the same conditions, the entropy of a gas is greater than that of a liquid, which in turn is greater than that of a solid. Predict whether a physical or chemical change will result in an increase or decrease in entropy of a system. Calculate standard entropy changes, ΔS⦵, from standard entropy values, S⦵.