Question

What is meant by 'hydrated' and 'anhydrous' salts? Explain with examples.

Answer 1

Salts that contain water of crystallisation are called ‘hydrated salts’. For example, copper sulphate crystals contain five molecules of water of crystallisation in one formula unit and hence is written as CuSO₄.5H₂O. It is also called copper sulphate pentahydrate.

Salts that have lost their water of crystallisation on heating are called ‘anhydrous salts’. For example, when copper sulphate crystals (CuSO₄.5H₂O), which are blue, are heated strongly, they lose all the water of crystallisation and form anhydrous copper sulphate (CuSO₄), which is white