A-LevelChemistryStates of matterOct/Nov 2025Paper 1 Q81 Mark
A pure sample of a gas has a density of 2.62g dm⁻³ at 101000 Pa and 25°C. The gas behaves ideally under these conditions. Which expression gives the Mr of the gas?
A101000 × 0.001 / 2.62 x 8.31×25
B101000 × 0.001 / 2.62 x 8.31×298
C2.62 x 8.31×25 / 101000 × 0.001
D2.62 x 8.31×298 / 101000 × 0.001
✓ Correct Answer
The correct answer is D: 2.62 x 8.31×298 / 101000 × 0.001
📋 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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