A-LevelChemistryAnalytical techniquesMay/June 2023Paper 5 Q27 Marks
Paper chromatography can be used to separate the individual amino acids formed when tripeptides are hydrolysed. One molecule of a tripeptide produces three amino acid molecules when hydrolysed. A student is asked to identify the amino acids formed from the hydrolysis of three different tripeptides, A, B and C, using paper chromatography. [Figure 2.1] shows the results of the student's chromatography experiment. [Figure 2.1] The individual amino acids can be identified from their R_f values. R_f = distance travelled by the amino acid spot / distance travelled by the solvent front
📋 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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