Question

White phosphorus, when heated with conc. $NaOH$ solution in an inert atmosphere of $CO_2$, forms phosphine and a sodium salt of oxoacid of phosphorus $'X'$. The oxidation state of phosphorus in $'X'$ is

• A. +3
• B. +4
• C. +1
• D. +5

Answer 1

Answer: (C)

White phosphorus, when heated with conc. $NaOH$ solution in an inert atmosphere of $CO _{2}$ forms phosphine and a sodium salt of oxoacid of phosphorus, i.e. $NaH _{2} PO _{2}$.

The reaction is as follows:

$P_4 + 3NaOH + 3H_2O \rightarrow \underset{(X)}{3NaH_2PO_2} + PH_3$

Now, the oxidation of phosphorus in $NaH_2PO_2$ can be calculated as:

$(+1) + 2(+1) + x + 2(-2) = 0$

$\Rightarrow x = +1$

Thus, the oxidation of $P$ in $NaHPO_2$ is $+1$.