Question

Account for the following:

NH₃ has higher boiling point than PH₃.

Answer 1

1. NH₃ has a higher boiling point than PH₃ because NH₃ molecules form hydrogen bonds due to the high electronegativity difference between nitrogen and hydrogen.
2. PH₃ molecules do not form hydrogen bonds; their intermolecular forces are only weak van der Waals forces.
3. Hydrogen bonding in NH₃ causes strong molecular association, requiring more energy (higher temperature) to break these forces, thus raising its boiling point.
4. PH₃ has a lower boiling point because only van der Waals forces act, which are weaker than hydrogen bonds in NH₃.