Chemistry 9701/43 May June 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Reactions of cobalt(II) complexes with hydroxide and ammonia, ionic equations for ligand exchange, equilibrium shifts with chloride ions, and stereoisomerism in coordination complexes.

2. Solubility and thermal decomposition trends in Group 2 hydroxides; temperature predictions for thermal stability variations in magnesium and strontium hydroxides.

3. Redox half-equations in photosynthesis, electrode potential calculations for oxygen reduction, and identification of positive electrodes in electrochemical cells.

4. Basicity comparison of aromatic and aliphatic amines, synthetic routes to primary amines, and reaction mechanisms for bromination and nucleophilic substitution.

5. Electrophilic substitution in benzene, mechanisms of bromination, relative reactivity of phenols and benzene, and structural isomer analysis using carbocations and NMR spectroscopy.

6. Relative acidities of substituted carboxylic acids, equilibrium constant predictions for acid-base reactions, dissociation steps in polyprotic acids, and reagent-based tests for functional group identification.

7. Solubility product expressions for sparingly soluble salts, carbonate and silver ion concentration calculations, electrode potential measurements, and thermodynamic feasibility analysis of dissolution reactions.

8. Buffer solution concepts, ammonium ion dissociation equilibrium, and pH calculations for mixed acid-base systems using ammonium-ammonia buffers.

9. Catalyst cycles for MnO₂ in hydrogen peroxide decomposition, reaction order and rate constant relationships, and mechanistic pathways for iodide and peroxide reactions.

10. Oxidation states of transition metals, variable oxidation behavior in d-block elements, and enzyme-substrate interaction models for catalytic activity.