Question

What is meant by ‘hydrated’ salts? Explain with examples.

Answer 1

The water molecules which form part of the structure of a crystal (of a salt) are called water of crystallisation. Salts that contain water of crystallisation are called hydrated salts.

Copper sulphate crystals contain 5 molecules of water of crystallisation in one formula unit and therefore are written as CuSO₄.5H₂O. It is called copper sulphate pentahydrate (Pentahydrate means five molecules of water).