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Q.
Which one has the lowest boiling point?
AIPMTAIPMT 1989The p-Block Elements - Part2
Solution:
In the hydrides of group number five, the boiling
points changes as
$_{238.5K}^{ \, \, NH_3 \, \, \, >} \, _{185.5 K}^{ \, \, PH_3} \, _{\, \, \, \, 254.6 K}^{ < \, \, AsH_3} \, _{ \, \, \, \, 254.6 K}^{< \, \, SbH_3} \, _{ \, \, \, \, \, \, 290 K}^{< \, \, \, BiH_3}$
$\therefore \, $ Generally mass increases then boiling point increases.
The higher boiling point of $NH_3$ is due to excessive
hydrogen bonding, so $PH_3$ have lowest boiling point
among hydrides of group number 15, i.e. nitrogen
family.