A-LevelChemistryNitrogen and sulfurMay/June 2020Paper 5 Q219 Marks
Nitrogen dioxide can be prepared by strongly heating anhydrous lead nitrate, Pb(NO₃)₂(s). The thermal decomposition occurs according to the equation shown. 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g) The nitrogen dioxide, NO₂, can be separated from the oxygen by cooling the gas mixture produced until the NO₂ condenses and the oxygen does not. [Table] melting point/K boiling point/K nitrogen dioxide 262 294 oxygen 54 90 A student plans to investigate the variation of Kₚ with temperature.
📋 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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