Chemistry - QA Exercise 1. You are provided with a sample mixture that contains iron(III) ions, aluminium ions, barium ions, silver ions and potassium ions. Work out a scheme to separate them in the mixture and outline the procedure for the separation. The following reagents are provided for separation: sulphuric acid, sodium hydroxide solution, ammonia solution, hydrochloric acid 2. Look at the following flow chart: (a) (i) (ii) (b) (i) (ii) Identify compound A. State the colour of compound A. Identify solution B. Write a balanced equation for the reaction between compound A and dilute sulphuric acid. (c) (i) Identify metal C, solution D and solid E. (ii) Name the reaction between solution B and metal C. (d) Identify precipitate F. ANS 1. The ions can be separated according to the following procedure: 1. Add excess hydrochloric acid to the mixture. Only Ag+ ions will form a precipitate. [1] 2. Filter the solution to obtain Fe3+ ions, Al3+ ions, Ba2+ ions and K+ ions in the filtrate. [1] The insoluble silver chloride is obtained as residue. 3. Add excess sulphuric acid to the filtrate. Only Ba2+ ions will form a precipitate. [1] 4. Filter the solution to obtain Fe3+ ions, Al3+ ions and K+ ions in the filtrate. [1] The insoluble barium sulphate is obtained as residue. 5. Add excess ammonia solution to the filtrate. [1] Fe3+ ions and Al3+ ions will form a precipitate. [1] 6. Filter the solution to obtain K+ ions in the filtrate. [1] Iron(III) hydroxide and aluminium hydroxide precipitates are obtained as residues. 7. Add excess sodium hydroxide solution to the residues. Only aluminium hydroxide will redissolve to form a colourless solution. [1] 8. Filter the mixture to obtain aluminium complex in the filtrate. [1] Iron(III) hydroxide precipitate is obtained as residue. 2.(a) (i) Copper(II) hydroxide [1] (ii) Pale blue precipitate [1] (b) (i) Copper(II) sulphate solution [1] (ii) Cu(OH)2(s) + H2SO4(aq) → CuSO4(aq) + 2H2O(l) [1] (c) (i) Metal C is iron. [1] Solution D is iron(II) sulphate solution. [1] Solid E is copper. [1] (ii) Displacement reaction [1] (d) Iron(II) hydroxide [1]
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