Question

(a) What is a salt ? Give the names and formulae of any two salts. Also name the acids and bases from which these salts may be obtained.

(b) What is meant by ‘a family of salts’ ? Explain with examples.

(c) What is meant by ‘hydrated’ and ‘anhydrous’ salts ? Explain with examples.

(d) Write the names, formulae and colours of any two hydrated salts.

(e) What will be the colour of litmus in an aqueous solution of ammonium chloride salt ?

Answer 1

(a) A salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.

Example: Sodium chloride – NaCl; It is obtained from hydrochloric acid and sodium metal.

Ammonium chloride – NH₄Cl; It is obtained from ammonia and hydrochloric acid.

(b) The salts having the same positive ions are said to belong to a family of salts.

Example: Sodium chloride and sodium sulphate belong to the same family of salts called sodium salts.

(c) The salts which contain water of crystallisation are called hydrated salts.

Example: Copper sulphate crystals contain 5 molecules of water of crystallisation.

The salts which have lost their water of crystallisation are called anhydrous salts.

Example: On strong heating, copper sulphate crystals lose all the water of crystallisation and form anhydrous copper sulphate.

(d) Copper sulphate pentahydrate salt – Its chemical formula is CuSO .5H O. It is blue in colour.

Iron sulphate heptahydrate salt – Its chemical formula is FeSO₄ .7H₂O. It is green in colour.

(e) The aqueous solution of ammonium chloride salt turns blue litmus red.