A-LevelChemistryChemical energetics9701/12 · Oct/Nov 2016 · Q21 Mark

The diagram shows the pathways of a reaction, with and without a catalyst. [Figure showing energy profile diagram] Which letter represents the overall energy change for the reaction?

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AActivation energy of the first step of the uncatalysed reaction.

BActivation energy of the uncatalysed reaction (from reactants to highest transition state).

COverall enthalpy change of the reaction (from reactants to products).

DActivation energy of the catalysed reaction (from reactants to catalysed transition state).

✓ Correct answer

C: Overall enthalpy change of the reaction (from reactants to products).

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Topic: Chemical energetics, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, Oct/Nov 2016 Paper 1 Variant 2, question 2.

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