Chemistry 9701/51 Oct Nov 2019 | Cambridge AS Level Past Papers With Mark Scheme

1. Synthesis of Yttrium Barium Copper Oxide (YBa2Cu3O7): Designing an experiment for synthesizing YBa2Cu3O7, including the minimum masses of BaCO3 and CuO needed, and the post-synthesis steps for ensuring the highest yield.
2. Titration for Cu3+ Ion Quantification: Describing the titration steps to quantify Cu3+ ions in YBa2Cu3O7 and explaining the necessity of each reagent, including sodium citrate and NH3.
3. Electrochemical Considerations in Titration: Using electrochemical data to explain the necessity of neutralization and citrate complexation in the reduction of Cu3+ ions.
4. Sodium Citrate Solution Preparation: Calculating the mass of hydrated sodium citrate needed to prepare a specific concentration of citrate ions and describing the procedure for accurate solution preparation.
5. Titration Method Improvements: Identifying issues in the titration method and suggesting improvements to enhance accuracy, such as refining the endpoint determination.
6. Polymer Viscosity and Mean Molecular Mass: Analyzing the viscosity data for poly(phenylethene) solutions, calculating the mean molecular mass, and predicting how intermolecular forces affect the value of 'a' in the polymer's solution.
7. Capillary Viscometer Rinsing and Data Processing: Suggesting the rationale for rinsing the capillary viscometer and processing experimental data, including plotting graphs and calculating the mean molecular mass of poly(phenylethene).
8. Effect of Temperature on Viscosity: Predicting how the time taken for the solution to pass through the viscometer is affected by changes in temperature and suggesting methods for controlling the measurement temperature.
9. Polymerization and Structural Analysis: Calculating the number of repeat units (x) in poly(phenylethene) and explaining how the value of 'a' varies with different solvent-solute interactions.