Question

Ammonia is a stronger base than phosphine.why?

Answer 1

Ammonia(NH3) is a stronger base than phosphine(PH3) because the electron density on the nitrogen atom is higher than that on Phosphate atom due to smaller size of nitrogen atom.Therefore, lone electron pair on nitrogen atom is more easily available.
Bond disassociation energy of P-H bond is smaller than N-H bond due to relatively larzer size of P atom. This makes PH3 a better reducing agent than NH3