A-LevelChemistryReaction kineticsMay/June 2023Paper 3 Q117 Marks
The thiosulfate ion, S2O3²⁻, decomposes when an acid is added. S2O3²⁻(aq) + 2H⁺(aq) → S(s) + SO2(aq) + H2O(l) The rate of this reaction can be investigated by measuring how long it takes the solution to produce enough sulfur so that it cannot be seen through. You will investigate how the concentration of the thiosulfate ion affects the rate of the reaction. Note: A small amount of sulfur dioxide gas may be formed in the experiment. It is very important that you avoid inhaling any fumes. As soon as each experiment is complete, empty the reaction mixture into the quenching bath and rinse the beaker thoroughly. FA 1 is 0.100 moldm⁻³ sodium thiosulfate, Na2S2O3. FA 2 is 2.00 moldm⁻³ hydrochloric acid, HCl.
📋 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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