A-LevelChemistryHydrocarbonsOct/Nov 2009Paper 1 Q231 Mark
Sorbic acid is used as a food preservative because it kills fungi and moulds. [Figure 23.1] Sorbic acid will react with • hydrogen in the presence of a nickel catalyst, • bromine in an organic solvent. How many moles of hydrogen and of bromine will be incorporated into one mole of sorbic acid by these reactions? [Figure 23.2]
Amoles of hydrogen: 2, moles of bromine: 2
Bmoles of hydrogen: 2, moles of bromine: 2½
Cmoles of hydrogen: 3, moles of bromine: 2
Dmoles of hydrogen: 3, moles of bromine: 2½
✓ Correct Answer
The correct answer is A: moles of hydrogen: 2, moles of bromine: 2
📋 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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