A-LevelChemistryAnalytical techniquesMay/June 2017Paper 4 Q710 Marks
Compounds W, X, Y and Z are isomers of each other with the molecular formula C｡H,CIO. All four isomers contain a benzene ring. Only one of the isomers contains a chiral centre. The results of six tests carried out on W, X, Y and Z are shown in the table. observations with each isomer test W X Y Z 1 add cold AgNO3(aq) white ppt. forms immediately none white ppt. forms very slowly none 2 heat with NaOH(aq), white ppt. none white ppt. none then add dilute HNO3 + AgNO3(aq) 3 add NaOH(aq) + I2(aq) none pale yellow ppt. none none 4 warm with Fehling's none none red ppt. none solution 5 add cold, dilute, no change no change no change decolourises acidified KMnO4(aq) 6 add Br2(aq) no change no change no change decolourises and forms white ppt.
📋 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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