The number of H 2 O molecules participating in hydrogen bonding in CuSO 4 . 5 H 2 O is/are

Only one water molecule, which is outside the coordination sphere, is hydrogen bonded. The other four molecules of water are coordinated with copper cation.

$\left[\mathrm{Cu}{\left({\mathrm{H}}_2\mathrm{O}\right)}_4\right]{\mathrm{SO}}_4.{\mathrm{H}}_2\mathrm{O}$ is the represenation of given compound.