Question

NH3 has higher boiling point than PH3. Why?

Answer 1

Hey mate!!!

The boiling point of NH3 is higher than that of PH3 due to hydrogen bonding in the former. Unlike NH3, PH3 molecules are not associated through hydrogen bonding in liquid state. That is why the boiling point of NH3 is higher than PH3. 

HOPE IT HELPS.

Answer 2

Although PH3 is a larger molecule with greater dispersion forces than ammonia, NH3 has very polar N-H bonds leading to strong hydrogen bonding. This the dominant intermolecular force and results in a greater attraction between NH3 molecules than there is between PH3 molecules.

also melting point is inversly proportion to polarisation and directly proportion to lattice energy