a. Would you except the hydrides of `N,O` and `F` to have lower boiling points than the hydrides of their subsequent group members? Give reason.
b. Can phosphorous with outer electronic configuration `3s^(2)3p^(3)` form `PH_(5)`?
c. How many hydrogen-bonded water molecules(s) are associated with `CuSO_(4).5H_(2)O`?

Explanation

The hydrides of N,O and F are `NH_3 , H_2 O and HF` respectively. On the basis of molecular masses of `NH_3` , `H_2O and HF`, their boiling points are expected to be lower than those of the subsequent group members (i.e., `PH_3, H_2 S , HCl`) . However , due to high electronegativity of N,O and F, their hydrides have strong intermolecular hydrogen bonding in their molecules.
As a result of hydrogen bonding, the boling points of `NH_3 , H_2 O and HF` are higher than the hydrides of their subsequent group members, which have almost negligible hydrogen bonding.