For H3PO3 and H3PO4 the correct choice is A H3PO3 is dibasic

For H3PO3 and H3PO4 the correct choice is:
(A) H3PO3 is dibasic and reducing (B) H3PO3 is dibasic and non−reducing
(C) H3PO4 is tribasic and reducing (D) H3PO3 is tribasic and non−reducing

Solution

(A)
The structure of H3PO3 is as follows: There are only two –OH groups and hence
dibasic. The oxidation number of P in this acid is +3. Whereas P may have +5
oxidation state also. Therefore, H3PO3 can be oxidised which means H3PO3 is a
reducing agent.