Arrange the following groups of substances in the order of the property indicated against each group:
(i) `NH_(3)PH_(3)AsH_(3)SbH_(3)` increasing order of boiling points
(ii)O,S,Se,To increasing order of electron gain enthalphy with negative sign
(iii) `F_(2),CI_(2),Br_(2),I_(2)` increasing order of bond dissociation enthalphy

Explanation

(i) `PH_(3)lt` As `H_(3)ltNH_(3)ltSnH_(3)ltBiH_(3)` As we more form `PH_(3)` to `BiH_(3)` molecular mass in creases vander waals forces increases and hence B.P but B.P of `NH_(3)` is abnormally higher than those of `PH_(3)` and As`H_(3)` because of intermolecular H Bonding
(ii) `SgtsegtTegtO` Oxygen has lowest due to small size and electron repulsion
(iii) See Q 25 (a) Part set I (D.B)-2010