Chemistry 9701/21 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, calculating the minimum masses of BaCO3 and CuO needed, and ensuring the highest yield of YBa2Cu3O7 after cooling the product.
2. Titration for Cu3+ Ion Quantification: Describing the titration procedure to determine the proportion of Cu3+ ions in YBa2Cu3O7, explaining the roles of reagents like sodium citrate and NH3.
3. Electrochemical Considerations in Titration: Using electrochemical data to explain why citrate complexation and neutralization are necessary for the accurate determination of Cu3+ ions.
4. Sodium Citrate Solution Preparation: Calculating the mass of hydrated sodium citrate needed to prepare a 1.0 mol/dm³ citrate ion solution and explaining the preparation procedure.
5. Titration Method Improvements: Identifying issues in the titration method and suggesting improvements for accuracy, such as refining the endpoint determination.
6. Polymer Viscosity and Mean Molecular Mass: Analyzing viscosity data for poly(phenylethene) solutions, calculating the mean molecular mass, and understanding the effect of intermolecular forces on polymer behavior.
7. Capillary Viscometer Rinsing and Data Processing: Explaining the purpose of rinsing the capillary viscometer with water and propanone, and processing experimental data to calculate the mean molecular mass of poly(phenylethene).
8. Effect of Temperature on Viscosity: Predicting how the time taken for a 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 discussing how the value of 'a' varies with different solvent-solute interactions.
10. Electrophilic Substitution and Reactions of Butamben: Analyzing the base behavior and reactions of butamben, including its treatment with different reagents, and interpreting its proton NMR spectrum.
11. Mass Spectrometry of Butamben: Identifying fragments in the mass spectrum of butamben, including m/e values for specific fragments.