O-LevelChemistryStoichiometry5070/22 · May/June 2015 · Q49 Marks
The flow chart shows some reactions of iron(II) sulfate, FeSO4. [Figure A4.1]
- (a)(i)Iron(II) sulfate is heated strongly. Write the formula of gas B.[1]
- (a)(ii)Calculate the empirical formula of gas C. Name gas C.[3]
- (a)(iii)Two moles of iron(II) sulfate decompose to form one mole of solid A, one mole of gas B and one mole of gas C. Deduce the formula of solid A.[1]
- (b)Write an ionic equation, including state symbols, for the formation of the green precipitate D.[2]
- (c)Suggest the name of reagent X and give the formula for the white precipitate E.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2015). The mark or mark type is shown in brackets.
- [1] (a) (i) B is SO2 (1)
- [3] (ii) Mole ratio line (1)
- Empirical formula SO3 (1)
- Sulfur trioxide/sulfur(VI) oxide (1)
- [1] (iii) Fe2O3 (1)
- [2] (b) Fe2+(aq) + 2OH¯(aq) → Fe(OH)2(s)
- Equation (1)
- State symbols – dependent on correct formulae (1)
- [2] (c) Any soluble barium compound e.g. barium nitrate/barium chloride (1)
- BaSO4 (1)
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