DP Chemistry (first assessment 2025)

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Question 21N.1A.SL.TZ0.19

Date	November 2021	Marks available	[Maximum mark: 1]	Reference code	21N.1A.SL.TZ0.19
Level	SL	Paper	1A	Time zone	TZ0
Command term	Deduce	Question number	19	Adapted from	N/A

19.

[Maximum mark: 1]

21N.1A.SL.TZ0.19

The equilibrium 2H₂ (g) + N₂(g) $⇌$ N₂H₄(g) has an equilibrium constant, K, at 150 °C.

What is the equilibrium constant at 150 °C, for the reverse reaction?

N₂H₄(g) $⇌$ 2H₂ (g) + N₂(g)

A. K

B. K⁻¹

C. −K

D. 2K

[1]

Markscheme

B

Syllabus sections

Reactivity 2. How much, how fast and how far? » Reactivity 2.3—How far? The extent of chemical change » Reactivity 2.3.3—The magnitude of the equilibrium constant indicates the extent of a reaction at equilibrium and is temperature dependent. Determine the relationships between K values for reactions that are the reverse of each other at the same temperature.