DP Chemistry (last assessment 2024)

Question 19M.2.sl.TZ1.b(iii)

Date	May 2019	Marks available	[Maximum mark: 2]	Reference code	19M.2.sl.TZ1.b(iii)
Level	sl	Paper	2	Time zone	TZ1
Command term	Explain	Question number	b(iii)	Adapted from	N/A

b(iii).

[Maximum mark: 2]

19M.2.sl.TZ1.b(iii)

This question is about peroxides.

Hydrogen peroxide decomposes to water and oxygen when a catalyst such as potassium iodide, KI, is added.

2H₂O₂ (aq) $\xrightarrow{{{\text{KI (aq)}}}}$ O₂ (g) + 2H₂O (l)

Apart from a greater frequency of collisions, explain, by annotating your graphs in (b)(ii), why an increased temperature causes the rate of reaction to increase.

[2]

Markscheme

E_a marked on graph [✔]

explanation in terms of more “particles” with E ≥ E_a
OR
greater area under curve to the right of E_a in T₂ [✔]

Examiners report

Explaining why temperature increase caused an increase in reaction rate was generally incorrectly answered with most students failing to mention “activation energy” in their answer or failing to annotate the graph.

Syllabus sections

Core

Core » Topic 6: Chemical kinetics » 6.1 Collision theory and rates of reaction

Core » Topic 6: Chemical kinetics

Question 19M.2.sl.TZ1.b(iii)

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