Chemistry 9701/31 Oct Nov 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Determination of the hydration number (x) in hydrated sodium thiosulfate using iodine titration; mass and molar calculations for stoichiometric accuracy.

2. Error analysis in titration measurements, percentage error derivation, and influence of anhydrous salt substitution on titre outcomes.

3. Rate of reaction analysis for acidified thiosulfate decomposition; relationship between thiosulfate concentration and reaction rate, additional experimental designs for reliability.

4. Identification of cations and anions in qualitative analysis using silver nitrate, ammonia, sodium thiosulfate, and barium chloride; ionic equations for observed precipitates.

5. Detailed observations and explanations of reactions involving sodium sulfite or sulfate, distinguishing anions using chemical tests.

6. Safety measures for sulfur dioxide release, including proper quenching protocols and ventilation, highlighting practical considerations for reaction monitoring.