Question

Phosphorus on reaction with NaOH produces ${ PH }_{ 3 }$ and $Na{ H }_{ 2 }{ PO }_{ 2 }$, this reaction is an example of
a.) Oxidation
b.) Reduction
c.) Disproportionation
d.) Displacement

Answer 1

You should know that sometimes it is also called dismutation. It is basically a redox reaction in which one compound of intermediate oxidation state converts into two compounds by undergoing oxidation as well as reduction. Now try to figure out the answer by yourself.

Complete step by step answer:
To solve this, let us discuss the types of reactions given to us in the options.
Firstly we have oxidation and reduction. Oxidation is the loss of electrons and thus forms a positive species or if the starting reactant is neutral, it forms a neutral species. Reduction is the opposite of oxidation as it is the gain of electrons.

Then we have disproportionation.
Disproportionation reaction is a redox reaction where the oxidation and reduction both take place from the same element/species and form two or more different products.
In simpler words, we can explain it as a reaction where the same element is both reduced and oxidised at the same time.

And lastly we have displacement.
It is a reaction where the atom or the set of atoms is completely displaced by another atom. Basically, the more reactive metal pushes its ions to the less reactive metal.

In the question it is given to us that phosphorus reacts with sodium hydroxide. We can write the reaction as- ${{P}_{4}}+3NaOH\to P{{H}_{3}}+3Na{{H}_{2}}P{{O}_{2}}$

Here, we can see that phosphorus has an oxidation state of zero. When it reacts with sodium hydroxide, it forms $P{{H}_{3}}$ where oxidation state of phosphorous is -3 and $Na{{H}_{2}}P{{O}_{2}}$ where oxidation state of phosphorous is +1.
Here, phosphorus undergoes both oxidation and reduction thus it is a disproportionation reaction.
Therefore, the correct answer is Disproportionation Reaction.
So, the correct answer is “Option C”.

Note: Every disproportionation reaction is a redox reaction but every redox reaction is not a disproportionation reaction. Thus, disproportionation is a special case of a redox reaction. Certain compounds undergo disproportionation in order to gain higher stability which results from oxidation or reduction. Also we should remember that gain of electron is reduction and loss of electron is oxidation.