Chemistry 9701/42 Oct Nov 2016 | Cambridge AS Level Past Papers With Mark Scheme

1. Transition Elements:
- Definitions of transition elements and calculations involving coordination numbers, oxidation states, and types of bonding in coordination complexes.
- Explanation and drawing of complex structures like [Ni(CN)2(NH3)2] and the stereoisomerism in coordination complexes.

2. Azide Ion and Lattice Energy:
- Decomposition of sodium azide (NaN₃), dot-and-cross diagrams for the azide ion, and the concept of lattice energy.
- Calculating standard enthalpy changes of formation and discussing the difference in lattice energies for different compounds like NaN₃ and RbN₃.

3. Iron Chemistry:
- The electronic configuration of iron and its ions.
- Understanding homogeneous catalysis, including the reaction between peroxodisulfate and iodide ions.
- Studying the reduction of iron(III) oxide and calculating entropy and Gibbs free energy changes.

4. Color of Transition Metal Complexes:
- Explanation of why transition elements often form colored compounds.
- Understanding the use of copper in alloys like brass and determining the copper content through titration.

5. Buffers and pH:
- Working with the phosphate buffer system, writing expressions for the acid dissociation constant (Ka), and calculating buffer concentrations.
- Understanding how buffers resist changes in pH and explaining the behavior of phosphate ions in both acidic and basic conditions.

6. Organic Chemistry:
- Discussing isomerism, optical activity, and reaction mechanisms in compounds like oleocanthal found in olive oil.
- Understanding the processes involved in preparing aromatic compounds and their reactions with reagents like sodium borohydride (NaBH₄).
- Using NMR spectroscopy to identify organic compounds and analyzing spectra to deduce molecular structures.

7. Synthesis and Reactions:
- Synthesis routes for various organic compounds, including ester formation, reactions with LiAlH₄, and hydrolysis with HCl.
- Organic analysis techniques to identify functional groups and study reaction mechanisms.

This paper covers both fundamental principles and application-based questions, requiring knowledge of inorganic chemistry, thermodynamics, organic chemistry, and spectroscopy.