DP Chemistry (first assessment 2025)

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Question 19N.1A.HL.TZ0.17

Date	November 2019	Marks available	[Maximum mark: 1]	Reference code	19N.1A.HL.TZ0.17
Level	HL	Paper	1A	Time zone	TZ0
Command term	Determine	Question number	17	Adapted from	N/A

17.

[Maximum mark: 1]

19N.1A.HL.TZ0.17

Which reaction has the greatest increase in entropy of the system?

A. HCl (g) + NH₃ (g) → NH₄Cl (s)

B. (NH₄)₂Cr₂O₇ (s) → Cr₂O₃ (s) + N₂ (g) + 4H₂O (g)

C. CaCO₃ (s) → CaO (s) + CO₂ (g)

D. I₂ (g) → I₂ (s)

[1]

Markscheme

B

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⦵.