Chemistry 9701/23 Oct Nov 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Ionization energy trends in Group 2 elements: explanation of decreases down the group, and higher second ionization energy of beryllium due to increased nuclear attraction after first electron removal.

2. Phosphorus, sulfur, and chlorine oxides: reaction equations, acidity trends, environmental impact of sulfur oxides, and thermodynamic calculations for reaction enthalpy changes in reducing SO₂ emissions using limestone.

3. Synthesis and properties of lithium aluminum hydride (LiAlH₄): structural bonding in Al₂Cl₆ and AlCl₃, decomposition reactions, and metallic bonding description in lithium-aluminum alloys.

4. Organic synthesis of 2-hydroxybutanoic acid: mechanistic steps involving LiAlH₄, NaBH₄, and cyanohydrin formation from aldehydes, with IR spectral analysis to confirm functional groups.

5. Halogen volatility trends, thermal stability of hydrogen halides, and intermolecular force comparisons between HF and HI based on electronegativity and hydrogen bonding.

6. Iodoalkanes and their reactions: synthesis of CH₃I, reaction mechanisms of halogenoalkanes with nucleophiles, elimination reactions forming alkenes, and oxidative cleavage using KMnO₄.

7. Reactivity trends in halogens and organic halides, including electrophilic addition to ethene, nucleophilic substitution, elimination mechanisms, and identification of reaction products in oxidative cleavage of alkenes.