Which of the following oxoacide of phosphorus is a reducing agent and a monobasic acid as well?

Options

A. Orthophosphorous acid `(H_(3)PO_(3))`
B. Orthophosphoric acid `(H_(3)PO_(4))`
C. Hypophosphorous acid `(H_(3)PO_(2))`
D. Cyclotrimetaphosphoric acid, `(HPO_(3))_(3)`

Answer

3

Explanation

The oxoacids which contain `P-H` bond have strong reducing properties. Thus ,hypophosporous acid is a good reducing agent as it contains two `P-H` bonds. For example ,it reduces silver nitrate to metallic silver.
`4AgNO_(3)+2H_(2)O+H_(3)PO_(2)rarr4Ag+4HNO_(3)+H_(3)PO_(4)`
The `P-H` bonds are not ionisable to give `H^(+)` and do not play any role in basicity. Only those `H` atoms which are attached with oxygen in `P-OH` bonds are ionisable and cause bacity .Thus ,hyprophosphorous is monobasic as its structure has only one `P_OH` bond. On the other hand, `H_(3)PO_(3)` and `H_(3)PO_(4)` are dibasic and tribasic,respectively as the structure of `H_(3)PO_(3)` has two `P_OH` bonds and `H_(3)PO_(3)` three.