Chemistry 9701/42 March 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Transition metal chemistry: Iron's properties as a transition element, bonding, and electronic configurations; colour origin in transition element complexes and ligand interactions.
2. Complex ion formation: Equilibrium reactions and shape predictions in Fe and Ni complexes, including monodentate and bidentate ligands, and factors influencing isomerism.
3. Group 2 chemistry: Thermal stability trends in carbonates and solubility of sulfates, with explanations in terms of ionic radius and lattice energy.
4. Electrochemical processes: Electrolysis of Al₂O₃ and the reaction mechanisms involved, including cryolite use and electrolysis calculations.
5. Standard electrode potential and cell diagrams: Measuring standard electrode potentials, constructing half-cell reactions, and predicting spontaneous reactions from cell potentials.
6. Organic reactions and stereochemistry: Mechanisms like reduction, nucleophilic substitution, and ester formation; structural isomerism in amino acids, peptide bond formation, and zwitterion structures.
7. Ligand substitution and stability constants: Stability constants of coordination complexes, ligand types, and their substitution behavior in metal complexes.