Arrange the following in the increasing order of the properties stated against them.
(a) (i)`NH_(3)` , (ii)`PH_(3)`, (iii)`AsH_(3)` , (iv)`SbH_(3)`-boiling point.
(b)(i)`Bi^(3+)` ,(ii)`Sb^(3+)` , (iii)`As^(3+)`-stability of `+3` oxidation state.
( c)(i)`NH_(3)`, (ii)`PH_(3)` , (iii)`AsH_(3)` , (iv)`SbH_(3)` , (v)`BiH_(3)`-reducing character.

Explanation

(a)`PH_(3) lt AsH_(3) lt NH_(3) lt SbH_(3)`-boiling point.
`NH_(3)` has higher boiling point due to `H-`bonding.In rest of the hydrides the boiling point increases down the group with increasing atomic number on account of the increasing magnitude of van der Waal's attraction.
van der Wall attraction `prop` molecular weight.
(b)`Bi^(3+) lt Sb^(3+) lt As^(3+)`-stability of `+3` oxidation state decreases down the group due to inert pair effect.
( c)`NH_(3) lt PH_(3) lt AsH_(3) lt SbH_(3) lt BiH_(3)`-reducing character increses down the group as bond dissociation energy decreases.