A-LevelChemistryChemical energeticsMay/June 2010Paper 1 Q41 Mark
Some bond energy values are listed below. bond bond energy/kJ mol⁻¹ C-H 410 C-Cl 340 Cl-Cl 244 Br-Br 193 These bond energy values relate to the following four reactions. P Br2 → 2Br Q 2Cl → Cl2 R CH3 + Cl → CH3Cl S CH4 → CH3 + H What is the order of enthalpy changes of these reactions from most negative to most positive?
AP→Q→R→S
BQ→R→S → P
CR→Q→P→S
DS P→Q→R
✓ Correct Answer
The correct answer is C: R→Q→P→S
📋 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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