Chemistry 9701/31 Oct Nov 2010 | Cambridge AS Level Past Papers With Mark Scheme

1. Titration of Hydrochloric Acid: The experiment involves determining the concentration of hydrochloric acid by titrating it with sodium thiosulfate. Potassium iodate and potassium iodide are used to release iodine, which is titrated with the thiosulfate. Results are recorded and analyzed for consistency.
2. Calculation of Sodium Thiosulfate Concentration: The concentration of sodium thiosulfate is calculated using its known mass concentration and the volume used in titration. Moles of iodine reacted with thiosulfate are also determined.
3. Moles of Iodine and HCl: From the titration data, the moles of iodine produced and the amount of hydrochloric acid required to produce this iodine are calculated. The concentration of HCl in FA 1 is then determined.
4. Error Calculation: The error in burette readings and pipette measurements is assessed, with percentage errors calculated for the titration volume and the pipetted volume of FA 1.
5. Copper(II) Carbonate Decomposition: The experiment involves heating copper(II) carbonate and measuring the loss in mass. Theoretical mass loss and deviations from expected values are explained based on the decomposition reaction.
6. Identification of Metal Ions: Various aqueous solutions containing metal ions (Al³⁺, Mg²⁺, Pb²⁺, Zn²⁺) are tested with sodium hydroxide, ammonia, and potassium iodide for identification through precipitation and color change.
7. Copper(II) Ion Reactions: Tests with zinc powder, hydrochloric acid, and water are used to observe copper(II) ion reactions, including displacement and solubility changes.