Question

In the reaction, $P+NaOH\to P{H}_3+Na{H}_{2}P{O}_2$:

• A. $P$ is oxidised only
• B. $P$ is reduced only
• C. $Na$ is reduced
• D. $P$ is reduced as well as oxidised

Answer 1

The correct option is D $P$ is reduced as well as oxidised

The oxidation number of elemental phosphorus is $0$. The oxidation number of phosphorus in phosphine is $-3$. Thus, phosphorus is reduced.
The oxidation number of phosphorus in $Na{H}_{2}P{O}_2$ is $+1$. Thus, phosphorus is oxidized as its oxidation number changes form $0$ to $+1$. This is an example of disproportionation reaction.