Chemistry 9701/31 Oct Nov 2019 | Cambridge AS Level Past Papers With Mark Scheme

1. Titration to Determine the Concentration of Hydrochloric Acid: Methods for determining the concentration of HCl by measuring the volume of hydrogen produced from the reaction with magnesium, including calculations of moles of H2 and HCl.
2. Improving Experimental Accuracy: Suggestions for improving accuracy, such as using magnesium ribbon instead of powder and altering magnesium quantities to enhance results, and the effect of using less magnesium.
3. Concentration Determination by Titration: Steps to determine the concentration of HCl in a solution through titration with sodium hydroxide, including the calculations of molar concentration and addressing sources of error.
4. Analysis of Experimental Errors: Identifying potential sources of error, like the escape of gas in gas-volume-based experiments, and explaining how errors in methods can affect concentration calculations.
5. Hydrated Salt Analysis and Identification of Ions: Performing tests to identify cations and anions in hydrated salts, including using reagents like barium nitrate, ammonia, and sodium hydroxide, and calculating the number of water molecules in the hydrated salt.
6. Concentration Calculations and Adjustments: Calculating and adjusting the concentration of HCl based on titration data and ensuring proper volumetric measurements to minimize error.