Chemical formula of copper sulphate pentahydrate \(\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_4\right] \mathrm{SO}_4 \cdot \mathrm{H}_2 \mathrm{O}\).
Copper sulphate pentahydrate contains \(5 \mathrm{H}_2 \mathrm{O}\) that is 5 water of crystallisation. The 5 molecules of water present in the crystal framework of the molecule where four water molecules are coordinated to \(\mathrm{Cu}^{2+}\) while one is hydrogen bonded with \(\mathrm{SO}_4^{2-}\).
The copper (II) is bound to four water molecules in a square planar geometry and two oxygen atoms from two sulphate ions (one \(\mathrm{H}_2 \mathrm{O}\) is \(\mathrm{H}\) bonded here).
Hence, correct formula is \(\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_4\right] \mathrm{SO}_4 \cdot \mathrm{H}_2 \mathrm{O}\).
