Page 36 - Chemistry ICSE Class IX

24 ICSE Chemistry – 9
Ans. The chemical equation,
Al (SO ) + NaOH o Al(OH) 3 + Na SO 4
2
4 3
2
when balanced by the hit-and-trial method gives,
Al (SO ) + 6NaOH o 2Al(OH) p + 3Na SO (CS)
3
4 3
2
4
2
The formation of insoluble product Al(OH) is indicated by an arrow pointing downwards (p).
3
Q.4. Translate the following statements into chemical equations and then balance them:
(a) Chlorine gas burns in hydrogen gas to give hydrogen chloride.
(b) Barium chloride reacts with zinc sulphate to give zinc chloride and a precipitate of barium sulphate.
(c) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(d) Aluminium metal replaces iron from iron oxide Fe O , giving aluminium oxide and iron.
3
2
(e) Hydrogen gas combines with nitrogen to give ammonia.
(f) Phosphorus burns in oxygen to give phosphorus pentoxide.
(g) Sodium metal reacts with water to give sodium hydroxide and hydrogen gas.
(h) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.
Ans. (a) Cl (I) + H (I) o HCl(I) (skeleton equation)
2
2
chlorine hydrogen hydrogen chloride
Cl (I) + H (I) o 2HCl(I) (balanced equation)
2
2
(b) Barium chloride + Zinc sulphate o Barium sulphate + Zinc chloride
BaCl (CS) + ZnSO (CS) o BaSO (U) + ZnCl (CS) (balanced equation)
2
4
2
4
The equation is balanced as such.
(c) Hydrogen sulphide + Air o Water + Sulphur dioxide
H S(I) + O (I) o H O(N) + SO (I) (skeleton equation)
2
2
2
2
(from air)
2H S(I) + 3O (I) o 2H O(N) + 2SO (I) (balanced equation)
2
2
2
2
(d) Aluminium metal + Ferric oxide o Aluminium oxide + Iron
Al(U) + Fe O (U) o Al O (U) + Fe(U) (skeleton equation)
3
3
2
2
This skeleton equation can be balanced by the hit-and-trial method to get,
2Al(U) + Fe O (U) o Al O (U) + 2Fe(U) (balanced equation)
3
2
3
2
(e) Hydrogen gas + Nitrogen gas o Ammonia
H (I) + N (I) o NH (I) (skeleton equation)
3
2
2
The balanced equation is,
3H (I) + N (I) o 2NH (I) (balanced equation)
3
2
2
(f) Phosphorus + Oxygen o Phosphorus pentoxide
P (U) + O (I) o P O (U) (skeleton equation)
4
2
5
2
The balanced equation is,
P (U) + 5O (I) o 2P O (U) (balanced equation)
2
5
2
4
(g) Sodium + Water o Sodium hydroxide + Hydrogen gas
Na(U) + H O(N) o NaOH(CS) + H (I) (skeleton equation)
2
2
The balanced equation is,
2Na(U) + 2H O(N) o 2NaOH(CS) + H (I) (balanced equation)
2
2
(h) Carbon disulphide + Air o Carbon dioxide + Sulphur dioxide
CS (N) + O o CO (I) + SO (I) (skeleton equation)
2
2
2
2
(from air)
The balanced equation is,
CS (N) + 3O (I) o CO (I) + 2SO (I) (balanced equation)
2
2
2
2