Question

(c) Name a substance which changes the blue colour of copper sulphate crystals to white.

Answer 1

Copper sulphate generally exists as copper sulphate pentahydrate form $(CuS{O}_4.5H_{2}O)$ which is in blue colour. When it comes in contact with sulphuric acid which is a hygroscopic substance, it absorbs water molecules from copper sulphate pentahydrate.

As all the water molecules get absorbed by sulphuric acid, the white crystals of anhydrous copper sulphate are produced.