The number of hydrogen bonded water molecule(s) associated with ${\text{CuSO}}_4\cdot 5{\text{H}}_2\text{O}$ is:

Shutterstock Explore In blue vitriol (${\text{CuSO}}_4\cdot 5{\text{H}}_2\text{O}$), four water molecules are coordinated to the central ${\text{Cu}}^{2+}$ ion in a square planar arrangement. The fifth water molecule is held by hydrogen bonding between a coordinated water molecule and a sulfate ion. It is not directly coordinated to the metal.