Question

Which of the following acid reduce AgNO₃ into Ag.

(1) H₃PO₂

(2) H₃PO₄

(3) H₄P₂O₇

(4) (HPO₃)_n

Answer 1

Correct option is (1) H₃PO₂

The acids which contain P-H bond have strong reducing properties. Thus, hypophosphorous acid is a good reducing agent as it contains two P-H bonds and reduces, for example, AgNO₃ to metallic silver

H₃PO₂ + 4AgNO₃ + 2H₂O → H₃PO₄ + 4Ag + 4HNO₂