Question

Why is phosphorous acid stronger than phosphoric.. Phosphoric has more oh groups so shouldn't it stabilize the negetive O-

and why is ammonia a stronger base than phosphine and others in the group.. N has more Electronegetivity so shouldn't it have less tendency to donate the lone pair

Answer 1

Phosphorous acid has the higher acidity corresponding to a lower p value and is thus more acidic than phosphoric acid. ... Hydrogen doesn't pull as much on electrons as Oxygens do and hence that part of the molecule becomes more positive causing a stronger dipole moment than that in phosphoric acid

Ammonia is a stronger base than phosphinebecause in ammonia the central atom Nitrogen is smaller hence electron density is concentrated with in smaller range and easily available. Whereas in the case of phosphine the size of phosphorous is large electron cloud is distributed in large area & not easily available