A-LevelChemistryChemical energeticsOct/Nov 2016Paper 1 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?

Q: What topic does this question test?

This question tests Chemical energetics in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

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

The correct answer is C: Overall enthalpy change of the reaction (from reactants to products).

📋 Examiner Report & Trap Analysis

Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...

🎯 Mark Scheme Breakdown

Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.

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About This A-Level Chemistry Question

Topic

This multiple-choice question tests Chemical energetics in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Chemistry Oct/Nov 2016 examination, Paper 1 Variant 2.

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