(a) Given reasons for the following :
(i) Bond enthalpy of `F_2` is lower than that of `Cl_2`.
(ii) `PH_3` has lower boiling point than `NH_3`.
(b) Draw the structures of the following molecules :
(i) `BrF_3` (ii) `(HPO_3)_3`
(iii) `XeF_4`

Explanation

(a) (1) See Q. 23, (iii), Set-I, Delhi Board, 2009.
(ii) `PH_3` has lower boiling point than `NH_3" because "NH_3` molecule possess intermolecular hydrogen bondings which binds them strongly whereas `PH_3` has weaker Vander Waal' s forces. Thus, `PH_3` has lower boing point than `NH_3`.
(b) (1) and (iii) See Q. 12, (i), (ii), Set-II, Delhi Board, 2010.
(ii) See Q. 29, b (i), Set-I, Outside Delhi, 2011.