# 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. Feb 8, 2017 at 16:53

Phosphorus reacts with sodium hydroxide to give phosphine and alkali hypophosphite:

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

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

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

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

Mechanism: The water that is involved is actually moisture that is accounting for the hydrolysis of phosphorus. The reactions can be dissected into three semi-reactions:

$$\ce{3P + 3H2O -> 3OPH + 3H}$$
$$\ce{P +3H -> PH3}$$
$$\ce{30PH + 3H2O -> 3H3PO2}$$

The phosphine so obtained usually inflames spontaneously on coming into contact with the air; each bubble as it escapes forms a vortex ring of smoke. This is due to presence of some amount of $$\ce{(PH2)_x}$$, the simplest of them being the dimer, $$\ce{P2H4}$$.

• Can sodium phosphate form? May 27, 2017 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. May 27, 2017 at 7:12
• You used Chemiday. That is a well-regarded and reliable source, as surely as my running a sub-3 hour marathon (when I tried one it was closer to seven). Can you review and identify primary references? Jul 26, 2021 at 11:12

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 $$+1$$.