DP Chemistry (first assessment 2025)

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Question 20N.1A.SL.TZ0.17

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.1A.SL.TZ0.17
Level	SL	Paper	1A	Time zone	TZ0
Command term	Identify	Question number	17	Adapted from	N/A

17.

[Maximum mark: 1]

20N.1A.SL.TZ0.17

Which arrow shows the activation energy of the uncatalysed forward reaction for this equilibrium?

$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g)$ $∆ H = - 196 kJ {mol}^{- 1}$

[1]

Markscheme

C

Examiners report

Identifying the activation energy of an uncatalyzed reaction from an energy profile diagram was the best answered question in the exam.

Syllabus sections

Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.5—Catalysts increase the rate of reaction by providing an alternative reaction pathway with lower Ea. Sketch and explain energy profiles with and without catalysts for endothermic and exothermic reactions. Construct Maxwell–Boltzmann energy distribution curves to explain the effect of different values for Ea on the probability of successful collisions.