Chemistry 9701/42 Oct Nov 2018 | Cambridge AS Level Past Papers With Mark Scheme

1. Chromatography: Identifying the compounds responsible for peaks in a gas chromatogram based on their solubility in the stationary phase, calculating the mass percentage of a compound in a mixture, and explaining the principle behind this technique.

2. Electrophilic Substitution in Benzene: Writing equations for reactions involving aluminium chloride as a catalyst and detailing the mechanism for the formation of chlorobenzene. The regeneration of the catalyst is also discussed.

3. Catalysis: Defining homogeneous catalysts and identifying examples, such as Rh in the removal of NO₂ and Fe³⁺ in the reaction between iodide and peroxodisulfate ions.

4. Copper Chemistry: Electronic configuration and orbital splitting in Cu and Cu²⁺, along with questions about the coordination and complex ion formation of copper with bidentate ligands.

5. Cobalt Complexes: Writing equations for the reactions involving cobalt(II) complexes, such as the formation of precipitates and their interaction with different ligands. The catalysis of oxidation by Co²⁺ ions is also addressed.

6. Cis-Trans Isomerism in Complexes: Discussing cis-trans isomerism in platinum complexes and the role of cis-platin as an anti-cancer drug, along with side effects and alternatives like carboplatin.

7. Calcium Nitride and Group 2 Chemistry: Reactions of calcium nitride with water and the trend in the solubility of Group 2 hydroxides are explored. Entropy and lattice energy changes are also part of this section.

8. Nitrite Analysis and Titration: Titration methods to determine the purity of sodium nitrite, including the use of cerium(IV) ions, and the use of manganate(VII) for analyzing nitrite in solution. The reaction enthalpy, Gibbs free energy, and acidity of nitrous acid are also discussed.

9. Buffer Solutions: Explaining the behavior of buffer solutions formed by mixtures of HNO₂ and NaNO₂, along with the acid dissociation constant (Ka) and pH calculations for weak acids.

10. Polymer Chemistry: Synthesis of polyurethanes and drawing polymer structures, including their properties. Additionally, examples of different types of polymers, including synthetic polyamides and conducting polymers, are discussed.

11. Electrophoresis: Analyzing the results of electrophoresis experiments for dipeptides, with questions about the species responsible for specific spots based on pH and amino acid properties.