Page 74 - Chemistry ICSE Class X

62 ICSE Chemistry – 10
ƒ Reaction with carbonates and bicarbonates. Acids decompose
>ĞƐƐ ƌĞĂĐƟǀĞ ĂŶĚ ŶŽďůĞ ŵĞƚĂůƐ͕ ƐƵĐŚ
ĂƐ ĐŽƉƉĞƌ͕ ƐŝůǀĞƌ ĂŶĚ ŐŽůĚ͕ ĚŽ ŶŽƚ carbonates and bicarbonates to give the corresponding salts and
ĚŝƐƉůĂĐĞ ŚLJĚƌŽŐĞŶ ĨƌŽŵ ĂĐŝĚƐ͘ carbon dioxide gas.
For example, sodium carbonate and calcium carbonate react with
dilute hydrochloric acid and sulphuric acid to give the corresponding
salts and carbon dioxide gas.
Na CO (aq) + 2HCl(aq) o 2NaCl(aq) + H O + CO (g)
2
2
2
3
sodium carbonate hydrochloric acid sodium chloride carbon dioxide
CaCO (s) + 2HCl(aq) o CaCl (aq) + H O + CO (g)
2
2
3
2
calcium carbonate hydrochloric acid calcium chloride carbon dioxide
Na CO (aq) + H SO (aq) o Na SO (aq) + H O + CO (g)
3
2
4
2
2
2
4
2
sodium carbonate sulphuric acid sodium sulphate carbon dioxide
CaCO (s) + H SO (aq) o CaSO (s) + H O + CO (g)
3
4
2
2
2
4
calcium carbonate sulphuric acid calcium sulphate carbon dioxide
Fig. 3.1 Carbon dioxide turns NaHCO (aq) + HCl(aq) o NaCl(aq) + H O + CO (g)
3
2
2
limewater milky
sodium bicarbonate hydrochloric acid sodium chloride carbon dioxide
ƒ Reaction with hydroxy bases and alkalis. Acids react with hydroxy
bases such as NH OH and alkalis such as NaOH, to form salt and
4
water. Such reactions are called neutralisation reaction. For example,
sodium hydroxide (NaOH) reacts with hydrochloric acid [HCl(aq)] to
form sodium chloride and water.
NaOH(aq) + HCl(aq) o NaCl(aq) + H O(l)
2
sodium hydroxide hydrochloric acid sodium chloride (salt) water
2NaOH(aq) + H SO (aq) o Na SO (aq) + H O(l)
2
4
2
2
4
sodium hydroxide sulphuric acid sodium sulphate water
(alkali) (acid) (salt)
ƒ Reaction with metal oxides. Acids react with metal oxides (basic
oxides) to give the corresponding salts and water.
CaO(s) + 2HCl(aq) o CaCl (aq) + H O(l)
2

2
calcium oxide (lime) hydrochloric acid calcium chloride water
ZnO(s) + 2HCl(aq) o ZnCl (aq) + H O(l)
2

2
zinc oxide hydrochloric acid zinc chloride water
ZnO(s) + H SO (aq) o ZnSO (aq) + H O(l)
2
4

2

4
zinc oxide sulphuric acid zinc sulphate water
ƒ Reaction with sulphites and bisulphites. Acids react with sulphites
and bisulphites to form the corresponding salt and liberate sulphur
dioxide.
NaHSO (s) + HCl(aq) o NaCl(aq) + H O(l) + SO (g)
2
3
2
sodium bisulphite sodium chloride sulphur dioxide
CaSO (aq) + 2HCl(aq) o CaCl (aq) + H O + SO (g)
3
2
2
2
calcium sulphite calcium chloride sulphur dioxide
ƒ Reaction with sulphides. Acids react with sulphides to liberate
hydrogen sulphide (H S) gas. H S gas has the smell of rotten eggs.
2
2
For example,
FeS(s) + H SO (dil.) o FeSO (aq) + H S(g)
2
2
4
4
iron(II) sulphide iron(II) sulphate hydrogen sulphide
(ferrous sulphate) (smell of rotten eggs)
ƒ Reaction with salts of less volatile acids (viz. chlorides and nitrates).
Chloride and nitrate salts when heated with conc. sulphuric acid give
the corresponding acids — hydrogen chloride and nitric acid.