Chemistry 9701/51 May June 2021 | Cambridge AS Level Past Papers With Mark Scheme

1. Catalyst comparison for hydrogen peroxide decomposition using oxygen collection, key variables, rate determination methods, reliability measures, and validation of catalyst stability post-reaction.

2. Potassium manganate(VII) solution preparation accuracy, error analysis in mass measurements, modifications to ensure precise mass transfer, and titration endpoint precision methods.

3. Analysis of redox reactions in iron ion titration, weaknesses in measuring procedures, adjustments for experimental accuracy, and concordant titre determination for data reliability.

4. Mass and percentage by mass calculations for Fe²⁺ and Fe³⁺ ions, stoichiometric analysis of MnO₄⁻ with iron species, and enhancements for procedure continuity in titration experiments.

5. Quantitative and qualitative evaluation of titration steps, emphasizing molar ratios, sample preparation, endpoint detection, and systematic error reduction for conclusive analysis.