A-LevelChemistryStates of matterOct/Nov 2020Paper 5 Q217 Marks
A student uses the apparatus shown to calculate the relative molecular mass, Mr, of a gaseous alkane. The experiment took place at 298K and 101kPa. [Apparatus diagram] The alkane is flammable. The student opens the tap and allows a small amount of the alkane gas into the measuring cylinder, displacing water. The gas in the measuring cylinder is allowed to reach room temperature and the volume recorded. This process is repeated and the measurements of mass of gas cylinder and total volume of gas collected are recorded in the table.
📋 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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