A-LevelChemistryAnalytical techniquesOct/Nov 2018Paper 4 Q114 Marks
An aldehyde, an alkane and a carboxylic acid, all of similar volatility, are mixed together. The mixture is then analysed in a gas chromatograph. The gas chromatogram produced is shown. [Figure showing gas chromatogram with peaks X, Y, Z] The separation of the compounds depends on their relative solubilities in the stationary phase. The stationary phase is a liquid alcohol.
📋 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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