Page 229 - Chemistry ICSE Class X

Study of Compounds – Hydrogen Chloride 215
ƒ With metal oxides and hydroxides. Hydrochloric acid reacts with all
basic oxides and hydroxides to give chlorides, e.g.,
CuO + 2HCl o CuCl 2 + H O
2
ZnO(s) + 2HCl(aq) o ZnCl (aq) + H O
2
2
zinc oxide
NaOH(aq) + HCl(aq) o NaCl(aq) + H O
2
ƒ With sulphides. Dilute hydrochloric acid reacts with sulphides giving
hydrogen sulphide gas and the corresponding chloride salt.

Na S(aq) + 2HCl o 2NaCl(aq) + H S(g)
2
2
hydrogen sulphide
FeS(s) + 2HCl(aq) o FeCl (aq) + H S(g)
2
2
hydrogen sulphide
ƒ With sulphites. Dilute hydrochloric acid decomposes sulphites and
bisulphites to give SO gas and chloride salt.
2
Na SO (aq) + 2HCl o 2NaCl(aq) + H O(g) + SO (g)
2
3
2
2
sodium sulphite sulphur dioxide
NaHSO (aq) + HCl o NaCl(aq) + H O + SO (g)
2
2
3
sodium bisulphite
ƒ With thiosulphates. Dilute hydrochloric acid reacts with thiosulphates
to form sulphur dioxide and sulphur.
Na S O (aq) + HCl o 2NaCl(aq) + SO (g) + S(s)
2 2
3
2
sodium thiosulphate sulphur dioxide sulphur ppt.
ƒ With nitrates. Dilute hydrochloric acid does not react with nitrates.
However, HCl forms insoluble chlorides with soluble salts of silver
and lead.
AgNO (aq) + HCl o AgCl(s)p + HNO (aq)
3
3
white ppt.
Pb(NO ) (aq) + 2HCl o PbCl (s)p + 2HNO (aq)
3
2
3 2
lead nitrate white ppt.
+
2+
ƒ Precipitation reaction. With metal ions, such as Ag and Pb , it gives
white precipitate of AgCl and PbCl respectively.
2
AgNO (aq) + HCl(aq) o AgCl(s)p + HNO (aq)
3
3
silver chloride
(CH COO) Pb(aq) + 2HCl(aq) o PbCl (s)p + 2CH COOH(aq)
2
2
3
3
lead acetate white precipitate
ƒ With metals. More electropositive metals react with HCl(aq) to liberate
hydrogen gas. ĐŝĚͲďĂƐĞ ƌĞĂĐƟŽŶ ŝƐ ĐĂůůĞĚ
ŶĞƵƚƌĂůŝnjĂƟŽŶ ƌĞĂĐƟŽŶ͘
Zn(s) + 2HCl(aq) o ZnCl (aq) + H (g)
2
2
Mg(s) + 2HCl(aq) o MgCl (aq) + H (g)
2
2
ƒ With oxidising agents. Strong oxidising agents, such as manganese
dioxide (MnO ), potassium permanganate (KMnO ), etc. oxidise HCl
2
4
to chlorine.
(a) 2KMnO (s) + 16HCl(aq) o 2KCl + 2MnCl + 8H O + 5Cl (g)
4
2
2
2
potassium chlorine
permanganate
'
(b) MnO (s) + 2HCl(aq) o MnCl 2 + H O + [O]
2
2
manganese dioxide
2HCl + [O] o H O + Cl 2
2
'
MnO (s) + 4HCl(aq) o MnCl 2 + 2H O + Cl 2
2
2