Page 94 - Chemistry ICSE Class X
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80 ICSE Chemistry – 10
'
ZnCl (s) + H SO (l) o ZnSO (aq) + 2HCl(g)
2
4
4
2
zinc chloride conc. zinc sulphate hydrogen chloride
sulphuric acid
Decomposition of nitrates with conc. sulphuric acid
', < 200°C
KNO (s) + H SO o KHSO 4 + HNO (g)
3
4
2
3
potassium conc. sulphuric potassium hydrogen vapour of
nitrate acid sulphate (acid salt) nitric acid
Decomposition of sulphites and bisulphites with dilute acids
Na SO (aq) + 2HCl(aq) o 2NaCl(aq) + H O(l) + SO (g)
2
2
2
3
sodium sulphite hydrochloric acid sodium chloride sulphur
(normal salt) dioxide
ZnSO 3 + H SO (dil.) o ZnSO (aq) + H O(l) + SO (g)
4
2
2
4
2
zinc sulphite sulphuric acid zinc sulphate sulphur
dioxide
By neutralisation reaction
Salts can be prepared by the reaction of bases (both soluble and insoluble),
such as metal oxides, metal hydroxides or metal carbonates, with an acid.
Salts are named after the name of the parent acid.
By a reaction between an acid and a base. When an acid is completely
neutralised by a base, salt is formed.
HCl(aq) + NaOH(aq) o NaCl(aq) + H O(l)
2
hydrochloric acid sodium hydroxide sodium chloride water
H CO (aq) + 2NaOH(aq) o Na CO (aq) + H O(l)
3
2
2
2
3
carbonic acid sodium hydroxide sodium carbonate water
By the reaction of a metal hydroxide with an acid. A metal hydroxide
on reacting with an acid gives the corresponding salt.
Zn(OH) (s) + H SO (aq) o ZnSO (aq) + 2H O(l)
2
4
4
2
2
zinc hydroxide sulphuric acid zinc sulphate water
2Al(OH) (s) + 3H SO (aq) o Al (SO ) (aq) + 6H O(l)
2
2
4
2
3
4 3
aluminium hydroxide sulphuric acid aluminium sulphate water
By the reaction of a metal oxide with an acid. When a metallic oxide
react with an acid, a salt is formed.
ZnO(s) + H SO (dil.) o ZnSO (aq) + H O(l)
4
2
2
4
zinc oxide sulphuric acid zinc sulphate water
CaO(s) + 2HCl(dil.) o CaCl (aq) + H O(l)
2
2
calcium oxide hydrochloric acid calcium chloride water
General Methods of Preparation of Insoluble Salts
Following general methods can be used for preparing insoluble salts:
By direct combination (or by synthesis)
Sulphides of iron and lead are insoluble in water. These can be prepared by
direct combination of the elements.
'
Pb(s) + S(s) o PbS(s)
lead sulphur lead sulphide
'
Fe(s) + S(s) o FeS(s)
iron sulphur iron sulphide
By precipitation reaction (or by double decomposition method)
Insoluble salts can be prepared by its precipitation from appropriate
solutions.
