DP Chemistry (first assessment 2025)

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Question 21N.1A.HL.TZ0.23

Date	November 2021	Marks available	[Maximum mark: 1]	Reference code	21N.1A.HL.TZ0.23
Level	HL	Paper	1A	Time zone	TZ0
Command term	Determine	Question number	23	Adapted from	N/A

23.

[Maximum mark: 1]

21N.1A.HL.TZ0.23

The graph shows Gibbs free energy of a mixture of N₂O₄(g) and NO₂(g) in different proportions.

N₂O₄(g) $⇌$ 2NO₂(g)

Which point shows the system at equilibrium?

[1]

Markscheme

B

Syllabus sections

Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.4—As a reaction approaches equilibrium, ΔG becomes less negative and finally reaches zero. Perform calculations using the equation ΔG = ΔG⦵ + RT lnQ and its application to a system at equilibrium ΔG⦵ = −RT lnK.