A-LevelChemistryChemical energeticsOct/Nov 2010Paper 1 Q41 Mark
Methanol may be prepared by the reaction between carbon monoxide and hydrogen. CO(g) + 2H₂(g) → CH₃OH(g) The relevant average bond energies are given below. E(C=O) 1077 kJ mol⁻¹ E(C-O) 360 kJ mol⁻¹ E(C-H) 410 kJ mol⁻¹ E(H-H) 436 kJ mol⁻¹ E(O-H) 460 kJ mol⁻¹ What is the enthalpy change of this reaction?
A-537 kJ mol⁻¹
B-101 kJ mol⁻¹
C+101 kJ mol⁻¹
D+537 kJ mol⁻¹
✓ Correct Answer
The correct answer is B: -101 kJ mol⁻¹
📋 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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