# Reaction of white phosphorus with aqueous sodium hydroxide

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?

• We can't. We just know it is hypophosphite; that was not obvious at all, nor could it be easily derived from first principles. – 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:

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

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

• Can sodium phosphate form? – Mockingbird May 27 '17 at 5:32
• @Mockingbird if we use some phosphorus compound like phosphorus pentoxide, phosphoric acid or phosphorus trihalides and react with sodium hydroxide, sodium phoshate will form. – 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 $$-2$$.

Solution:

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

Solving for $$X$$ gives $$+1$$.

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