F.4 Chemistry

[匿名]

2012-02-05 11:37 pm

The following solutions were probided for the preparation of some insoluble salts:

Copper(II) sulphate solution
Lead(II)nitrate solution
Magnesium chloride solution
Sodiumcarbonate solution

a) i) Which TWO of the solutions should be used to prepare copper(II) carbonate?

ii) Write an ionic equation for this reaction.
iii) Describe how the student could preapre a pure, dry sample of copper
(II) carbonate from the two solutions suggested.

b) A student used lead(II) nitrate solution and one other solution from the list to preapare lead(II) sulphate.

i) Suggest the other solution used
ii) Write a chemical equation for the reaction involved
iii) Give ONE observable change of this reaction.

c) Another student planned to preapare magnesium sulphate by mixing magnesium chloride solution and(II) sulphate solution.
i) State ONE reason why the proposed method is inappropriate
ii) Suggest other possible method to prepare magnesium sulphate.

回答 (1)

賣女孩的火柴

2012-02-06 6:36 am

✔ 最佳答案

a)
i)
copper(II) sulphate solution and sodium carbonate solution

ii)
Cu^2+(aq) + CO3^2-(aq) → CuCO3(s)

iii)
Mix equal volumes of copper(II) sulphate solution and sodium carbonatesolution. Filter the reaction mixture. Wash the residue with distilled water and then dry the residue with dryfilter paper. The dry residue obtainedis copper(II) carbonate.

b)
i)
copper(II) sulphate solution

ii)
Pb(NO3)2 + CuSO4(aq) → PbSO4(s) +
or: Pb^2+(aq) + SO4^-2(aq) → PbSO4(s)

iii)
A white precipitate is formed.

c)
i)
Both magnesium sulphate and copper(II) chloride are soluble in water. The mixture contains 4 types of ion :magnesium ions, sulphate ions, copper(II) ions, and chloride ions. It is difficult to isolate magnesium sulphatefrom the mixture.

ii) With stirring and heating if necessary, add copper(II) oxide solid todilute sulphuric acid until copper(II) oxide is in excess, i.e. no morecopper(II) oxide can be dissolved. Filter off the excess copper(II) oxide. Heat the filtrate until a concentrated/saturated solution isobtained. Cool theconcentrated/saturated solution slowly and magnesium sulphate is crystallized. Filter the mixture. The residue is washed with a small amount ofcool ethanol, and the dry with a dry filter paper. The dry residue obtained is the crystals of magnesiumsulphate.

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