Is H3PO3 a dibasic acid or a tribasic acid ?
H3PO3 has three hydrogen atoms and looking at the structure it is clear that in H3PO3 only two hydrogen atoms are joined through the oxygen atoms and are ionisable. The third hydrogen atom is linked to P-atom directly and is not ionisable. The H-atom joined to the P- atom is reducing in nature and is not ionisable as a proton and therefore H3PO3 acts as a dibasic acid.
