Question

h3po3 is dibasic acid why?

Answer 1

H3PO3 has replaceable of 2 H atoms. i.e., Even HPO3 is existing and it is also acidic

Answer 2

The P-H bond in H3PO3 is not ionisable and do not play any role in its basicity. Only those atoms which are attached to O in P-OH form are ionisable and are responsible for the basicity. Thus H3PO3 is dibasic as it has two P-OH bond.