Chemistry - QA Exercise

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]