Chemistry 9701/33 March 2020 | Cambridge AS Level Past Papers With Mark Scheme

1. Hydrogen Peroxide Titration: Experimental procedure to determine the "volume strength" of hydrogen peroxide by titration with acidified potassium manganate(VII), including steps for dilution, titration, and calculation of the concentration of H2O2.

2. Titration Calculations: Calculating the number of moles of potassium manganate(VII), hydrogen peroxide concentration, and the volume strength of the hydrogen peroxide solution using the reaction equation and titration results.

3. Error Calculation: Demonstrating how to calculate the accuracy of a pipette and comparing it to a burette, using the maximum error in the reading of a 25.0 cm³ pipette.

4. Enthalpy Change Experiment: Method to measure the enthalpy change for the catalytic decomposition of hydrogen peroxide using manganese(IV) oxide (MnO2), including temperature measurements and energy calculations.

5. Accuracy Discussion: Analysis of whether the same mass of manganese(IV) oxide should be used in all experiments and whether the student’s suggestion regarding temperature rise with varying hydrogen peroxide volumes is correct.

6. Qualitative Analysis: Testing the presence of cations and anions in given solutions (FA 6, FA 7, and FA 8), including observations during reactions with sodium hydroxide, potassium manganate(VII), and silver nitrate, and identification of the ions present.

7. Experimental Observations: Collecting detailed observations of color changes, precipitate formation, and gas production during qualitative tests, including further tests to confirm identities of unknown ions.

8. Half-Equation for Oxidation: Writing a half-equation for the oxidation reaction taking place during one of the qualitative tests and identifying the ions involved.