White phosphorus, when heated with conc. NaOH solution in an inert atmosphere of CO 2 , forms phosphine and…

White phosphorus reacts with conc. $\mathrm{NaOH}$ to form phosphine and sodium hypophosphite.

${\mathrm{P}}_4 + 3\mathrm{NaOH} +{\mathrm{H}}_2\mathrm{O} \to {\mathrm{PH}}_3 + {\mathrm{NaH}}_2{\mathrm{PO}}_2$

The oxidation state of phosphorus will be :

 $$\begin{gathered} +1+2+\mathrm{X}-4=0 \\ \mathrm{X} =+1 \end{gathered}$$