Question

In the reaction, ${{P}_{4}}+NaOH\to P{{H}_{3}}+Na{{H}_{2}}P{{O}_{2}}$ mole ratio of $Na{{H}_{2}}P{{O}_{2}}$ and $P{{H}_{3}}$ is:

Answer 1

Hint: Start this question by writing the complete equation and balance it. Also, keep in mind the oxidation states and atomic numbers while solving it.

Complete step by step answer:
The reaction given above is an example of disproportionation reaction. It is because ${{P}_{4}}$acts both as an oxidant and reductant.
White phosphorus reacts with a cold and concentrated solution of sodium hydroxide and water to produce phosphine and sodium hypophosphite. This reaction takes place slowly.
We can balance the given equation as –
${{P}_{4}}+3NaOH+3{{H}_{2}}O\to P{{H}_{3}}+3Na{{H}_{2}}P{{O}_{2}}$
From the reaction we can see that there are 3 moles of $Na{{H}_{2}}P{{O}_{2}}$ (sodium hypophosphite) and 1 mole of $P{{H}_{3}}$.
Therefore, the answer is – the mole ratio of $Na{{H}_{2}}P{{O}_{2}}$ and $P{{H}_{3}}$in the given reaction is 3.

Additional information:
Reactants –
White phosphorus - ${{P}_{4}}$
White phosphorus or simply tetraphosphorus (${{P}_{4}}$) exists as molecules which is made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability.
Sodium hydroxide - $NaOH$
Water - ${{H}_{2}}O$

Products –
Phosphine - $P{{H}_{3}}$
It is a colorless, flammable, toxic gas and is classified as a pnictogen hydride. Phosphine burns and produces a dense white cloud of phosphoric acid.
Sodium hypophosphite - $Na{{H}_{2}}P{{O}_{2}}$
Sodium hypophosphite is also known as sodium phosphinate. It is the sodium salt of hypophosphorous acid. It is a solid at room temperature and appears as odorless white crystals.

Note: The given reaction is a disproportionation reaction. It is also known as redox reaction in which a compound of intermediate oxidation state converts to two different compounds, one of higher and one of lower oxidation states, and hence oxidation and reduction takes place simultaneously.