Chemistry 9701/42 May June 2021 | Cambridge AS Level Past Papers With Mark Scheme

1. Chromium complexes, including electronic configuration, reaction products with reagents like NaOH, H2O2, and NH3, color variations explained by ligand field theory, coordination numbers, and Cr2+ reactions with O2 in acidic conditions.

2. Group 2 and lead nitrates' thermal stability trends, decomposition reactions of nitrates and ethanedioates, quantitative redox analysis, and barium hydroxide dissociation with pH calculations.

3. Electrode potentials for Ru complexes, stereoisomerism in [Ru(en)3]3+, equilibrium constants for AgBr reactions in thiosulfate solutions, and concentration relationships in competing silver-ligand complexes.

4. Thermodynamic calculations including lattice energy, enthalpy of solution, entropy, and Gibbs free energy; feasibility trends with temperature changes; electrolysis reactions involving CaCl2, and entropy-related phenomena.

5. Basicity order of phenylamine, ethylamine, and 4-nitrophenylamine; organic synthesis of dyes and stepwise methylbenzene transformations involving oxidation and electrophilic substitution.

6. Structural isomers of C8H10 analyzed using 13C NMR; multi-step organic synthesis involving alkylation and oxidation of benzene derivatives; and reaction mechanisms for aromatic electrophilic substitution.

7. Reaction kinetics, including order of reaction determination, rate equations, and zero-order reaction half-life analysis; diazonium salt decomposition products, and associated rate constants.

8. Hydrolysis rates of chlorides ranked by reactivity, complete hydrolysis of remifentanil producing three products, and analysis of proton NMR spectrum for structure identification and peak interpretation.