Chemistry 9701/51 May June 2015 | Cambridge AS Level Past Papers With Mark Scheme

1. Determination of solubility of Mg(HCOO)₂ through titration with KMnO₄; half-equations for HCOO⁻ oxidation and MnO₄⁻ reduction, concentration calculations for saturated solutions, and effects of dilution on titration reliability.
2. Acidification of solutions with H₂SO₄ to maintain reaction conditions for titration; end-point detection through visible color change and its role in accurate volumetric analysis.
3. Impact of temperature on solubility, independent and dependent variables in solubility experiments, and enthalpy implications (∆H) for Mg(HCOO)₂ dissolution.
4. Equilibrium constant (Kc) calculations for H₂ + I₂ ↔ 2HI, using algebraic relationships, experimental data, and graphical interpretation for initial and equilibrium concentrations.
5. Safety considerations in removing air from reaction vessels in equilibrium studies involving H₂ and I₂ due to potential flammability and explosion risks in confined spaces.
6. Effect of changes in flask volume on reaction rates and Kc values, with analysis of pressure and concentration relationships in dynamic equilibrium systems.