Which of the following oxyacids acts as most reducing agent?

Options

A. `H_3PO_3`
B. `H_PO_4`
C. `H_4P_2O_6`
D. `H_4P_2O_7`

Answer

A

Explanation

H atom directly attached with 'P' atoms is reducing in nature. H atom attached with P atom through oxygen atom is acidic in nature.
`underset(("Orthophosphorus acid"))(O=underset(H_(3)PO_(3))(underset(H)underset(|)overset(OH)overset(|)P-OH)" "underset(("Orthophosphoric acid"))(O=underset(H_(3)PO_(4))(underset(OH)underset(|)overset(OH)overset(|)P-OH)`
`underset(("Hyprophosphoric acid"))(O=underset(H_(4)P_(2)O_(6))(underset(OH)underset(|)overset(OH)overset(|)P-underset(OH)underset(|)overset(OH)overset(|)P=O)" "underset(("Pyrophosphoric acid"))(O=underset(OH)underset(|)overset(OH)overset(|)P-O-underset(OH)underset(|)overset(OH)overset(|)P=O)`
Only orthophosphorus acid `(H_(3)PO_(3))` has H-atom directly attached with 'P' atom, therefore, it is reducing innature.