DP Chemistry (last assessment 2024)

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Question 22M.2.hl.TZ2.a

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.hl.TZ2.a
Level hl Paper 2 Time zone TZ2
Command term Justify, Outline Question number a Adapted from N/A
a.
[Maximum mark: 2]
22M.2.hl.TZ2.a

Sulfur trioxide is produced from sulfur dioxide.

2SO2 (g) + O2 (g) ⇌ 2SO3 (g)          ΔH = −196 kJ mol−1

Outline, giving a reason, the effect of a catalyst on a reaction.

[2]

Markscheme

increases rate AND lower Ea ✔

provides alternative pathway «with lower Ea»
OR
more/larger fraction of molecules have the «lower» Ea ✔

 

Accept description of how catalyst lowers Ea for M2 (e.g. “reactants adsorb on surface «of catalyst»”, “reactant bonds weaken «when adsorbed»”, “helps favorable orientation of molecules”).

Examiners report

Overall well answered though some answers were directed to explain the specific example rather than the simple and standard definition of the effect of a catalyst.

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