A-LevelChemistryReaction kineticsMay/June 2023Paper 1 Q151 Mark
The equations for two reactions are shown. reaction X 2NOBr ⇌ 2NO + Br₂ reaction Y 2NOCl → 2NO + Cl₂ The two reactions have similar reaction mechanisms. The initial rate of reaction X is greater than that of reaction Y when measured under identical conditions of temperature, pressure and reactant concentration. Which statements explain this difference? 1 The activation energy for reaction X is less than that of reaction Y. 2 The Br–Br bond is weaker than the Cl–Cl bond. 3 A higher frequency of collisions between molecules of NOBr occur than between molecules of NOCl.
A1 and 2
B2 and 3
C1 only
D3 only
✓ Correct Answer
The correct answer is C: 1 only
📋 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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