Question

When we heat the CuSO4, water evaporates but when we add water to it,it again turns blue.if we are adding more water then its chemical should be CuSO4. xH2Owhere x is the no. of water molecules then why it is only called 5H2O?

Answer 1

It is because the water of crystallization actually form chemical bonds with the positive and negative ions of the salts. In CuSO4.5H2O, 4 moles of H2O are in coordinate bonding with Cu²+, while 1 mole of water forms hydrogen bonding with the SO4²- ion.
In simple words, to balance the charges of Cu and SO4, the number of water molecules remains the same.