Question

Assertion :In $P_4$, the valency and oxidation number of phosphorous are same. Reason: In the reaction between phosphorous and sodium hydroxide, phosphorous acts as both oxidising and reducing agent.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is D Both Assertion and Reason are incorrect

The oxidation number of phosphorus in $P_4$ is zero. However, the valency of phosphorus in $P_4$ is three because each $P$ atom is attached to three other $P$ atoms.
In the reaction between phosphorus and $N$, the oxidation state of phosphorus changes for $0$ to $+3$ and $+1$. The oxidation state of other atoms remains same. Thus, phosphorus undergoes disproportion reaction.
$P_4+3NaOH+3H_{2}O\to 3Na{H}_{2}P{O}_2+P{H}_3$.