Chemistry 9701/05 May June 2003 | Cambridge AS Level Past Papers With Mark Scheme

1. Determination of Sodium Thiosulphate Concentration: Using a titration method involving chromate ions and iodide ions, the concentration of sodium thiosulphate (Na2S2O3.5H2O) was determined, along with the moles of iodine produced and the reduction of CrO4²⁻ to Cr³⁺ during the reaction.
2. Calculation of Moles and Concentrations: Through careful titration, the moles of sodium thiosulphate, iodine, and chromate ions were calculated, followed by the determination of the concentration of thiosulphate in the diluted solution.
3. Stoichiometric Calculations: Using the equations and titration results, the number of moles of iodine and chromate ions involved in the reaction were determined, confirming the reduction of CrO4²⁻ to Cr³⁺.
4. Copper Carbonate Analysis: A practical experiment was planned to determine the percentage of copper carbonate in malachite, including reaction equations, gas volume measurements, and processing of results to calculate the percentage of copper carbonate in the sample.
5. Experimental Design and Data Recording: The procedure for determining copper carbonate content was outlined, including the equipment and methods for tabulating results and processing data to find the percentage of copper carbonate.