Chemistry 9701/21 May June 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Oxidation and reduction in copper-iodide reactions, balancing equations with oxidation numbers, and stoichiometric calculations for hydrated salts using mole ratios.

2. Enthalpy change of formation concepts, Hess's law application for indirect enthalpy determination, and environmental implications of nitrogen oxides in atmospheric reactions.

3. Ammonium nitrate production, bond angles in molecular geometries, and Brønsted-Lowry base definitions linked to ammonia.

4. Organic reaction mechanisms involving nucleophilic substitution (SN1) and addition; identification of intermediates in alkene hydration and stability comparisons.

5. Reactions of acidified manganate(VII) with alkenes; spectral differences in IR for ketones versus alkenes, functional group identification through chemical testing, and reduction of carboxylic acids using lithium aluminum hydride.

6. Structural isomerism in esters, skeletal formulas of organic compounds, and spectral analyses highlighting key functional group absorptions in organic compounds.