A-LevelChemistryAnalytical techniquesMay/June 2018Paper 3 Q211 Marks
In this question you will determine the identity of the halogen in compound W. Compound W is the halogenoethanoic acid CH2XCO₂H, where X is a halogen. 4g of W were heated with 250 cm³ of 0.400 moldm-³ aqueous sodium hydroxide. Some of the sodium hydroxide reacted with compound W. The solution that remained after this reaction is FA 3. By titrating FA 3 with hydrochloric acid, you will determine how much of the sodium hydroxide remained after reaction with W. You will then calculate how much sodium hydroxide had reacted and use this to determine the identity of X in CH2XCO2H. FA 3 is aqueous sodium hydroxide after reaction with W. FA 4 is 0.100 mol dm³ hydrochloric acid, HCl. bromophenol blue indicator
📋 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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