Question

Which of the following salt has a blue colour and why?
CuSO₄.5H₂O    or    CuSO₄

Answer 1

CuSO₄.H₂O has a blue colour.
The blue colour is due to the presence of water molecules in the structure. The colour of a salt crystal is usually given by the water of crystallisation. But anhydrous salts (without the water molecules) lose their colour and shape and become white. Thus, CuSO₄, which does not have water molecules, appears white.