The number of water molecules associated with copper sulphate molecule

The number of water molecules associated with copper sulphate molecule to form crystals is

2
4
5
6
This question was previously asked in
UPSC CDS-1 – 2020
Copper sulphate commonly exists as a hydrate with the chemical formula CuSO₄ · 5H₂O. This form is copper(II) sulfate pentahydrate, which is bright blue. The notation ‘· 5H₂O’ indicates that there are 5 water molecules associated with each unit of copper sulphate in the crystal lattice. These water molecules are called water of crystallization.
– Crystalline copper sulphate is a hydrate.
– The formula of common copper sulphate crystals is CuSO₄ · 5H₂O.
– This means 5 water molecules are associated with each CuSO₄ unit.
Anhydrous copper sulphate (CuSO₄), which has no water of crystallization, is white. When water is added to anhydrous copper sulphate, it forms the blue pentahydrate, and this reaction is exothermic. This property makes anhydrous copper sulphate useful as a test for the presence of water.