Chemistry 9701/33 Oct Nov 2015 | Cambridge AS Level Past Papers With Mark Scheme

1. Determination of x in CuSO₄·xH₂O using iodometric titration with thiosulfate and potassium iodide, including stoichiometric calculations to find moles of Cu²⁺ and the relative molecular mass of hydrated copper(II) sulfate.
2. Purity assessment of hydrated calcium chloride by mass loss on heating; calculation of percentage mass loss, theoretical percentage for pure CaCl₂·2H₂O, and comparison to determine sample purity.
3. Qualitative analysis of FA 5, FA 6, FA 7, and FA 8 through reactions with reagents such as sodium carbonate, copper(II) sulfate, barium chloride, and hydrogen peroxide; identification of cations, anions, and reaction mechanisms.
4. Ionic equations for key reactions including precipitation and decomposition; assessment of reaction completeness through experimental observations and solubility behavior.
5. Use of heating and filtration to separate and identify mixed ions in a solid sample, supported by confirmatory tests for filtrate and residue.
6. Gas testing and identification based on reactions with specific reagents, including the role of indicators and qualitative methods outlined in the Qualitative Analysis Notes.