What are the products obtained in the reaction of white phosphorus with aqueous sodium hydroxide?

I know one will be phosphine ($\ce{PH3}$).

How can we find the oxidation state of phosphorus in the other product?

Thanks for help in advance.

  • 1
    $\begingroup$ We can't. We just know it is hypophosphite; that was not obvious at all, nor could it be easily derived from first principles. $\endgroup$ – Ivan Neretin Feb 8 '17 at 16:53

Actually, there are two reaction involving:

  1. $$\ce{P4 + 3NaOH + 3H2O -> PH3 + 3NaH2PO2}$$

White phosphorus react with sodium hydroxide and water to produce phosphine and sodium hypophosphite . Sodium hydroxide - cold, concentrated solution. This reaction takes place slowly. (Chemiday 1)

The O.S. of phosphorus in sodium hypophosphite is calculated in @Sayantan.G's answer.

  1. $$\ce{P4 + 8NaOH + 4H2O ->[\Delta] 4Na2HPO3 + 6H2}$$

White phosphorus react with sodium hydroxide and water to produce disodium hydrogen phosphite and hydrogen. Sodium hydroxide - concentrated solution. The reaction takes place in a boiling solution.(Chemiday 2)

The O.S. of phosphorus in disodium hydrogen phosphite is:

$$\ce{ +2*1 + 1 + x + 3*(-2) = 0}$$

$$\ce{ x = +3}$$

  • $\begingroup$ Can sodium phosphate form? $\endgroup$ – Mockingbird May 27 '17 at 5:32
  • $\begingroup$ @Mockingbird if we use some phosphorus compound like phosphorus pentoxide, phosphoric acid or phosphorus trihalides and react with sodium hydroxide, sodium phoshate will form. $\endgroup$ – Nilay Ghosh May 27 '17 at 7:12

When Phosphorous reacts with $\ce{NaOH}$, it produces Phosphine and Sodium Hypophosphite. The reaction is as follows:

$$\ce{P4 + 3NaOH + 3H2O -> PH3 + 3NaH2PO2}$$

Oxidation State of Phosphorous in Sodium Hypophosphite is $+1$, as $\ce{Na}$ is $+1$, $\ce{H}$ is $+1$, and $\ce{O}$ is $-2$.


$1+1 \times 2+X-2 \times 2=0$ (As net charge is zero)

Solving for $X$ gives $+1$.

  • $\begingroup$ But the answer in my book was +5 $\endgroup$ – Palash gupta Feb 9 '17 at 2:07
  • 1
    $\begingroup$ I think @Palash ,U should go through Nilay's answer . O.S. Must be +1 or +3 ,I think so😇 $\endgroup$ – Sayantan Ghosh Feb 9 '17 at 13:07

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