Question

The $ {\text{PC}}{{\text{l}}_{\text{3}}} $ reacts with water, then forms acid of phosphorus, what is the basicity of acid of phosphorus?

Answer 1

Hint: To answer this question, you must recall the basic definition of an acid. According to the Arrhenius concept of acids and bases, an acid is a substance that in its aqueous solution dissociates to form a hydronium ion. The number of protons it can donate is known as its basicity.

Complete step by step solution:
We know that acids are those chemical species which dissociate in water to form hydrogen ions or hydronium ions and a conjugate base. An acid can be classified into three main categories on the basis of the hydronium ions released per molecule of the acid. These three types are monobasic acids, dibasic acids and tribasic acids.
The word basic in monobasic, dibasic and tribasic represents the amount of basic particles one molecule of the acid can neutralize. In a similar fashion, we can classify bases as monoacidic, diacidic and triacidic bases.
When phosphorus trichloride is reacted with water, it forms orthophosphoric acid. The chemical formula of this acid formed is $ {{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{3}}} $ and the reaction through which it is formed is given as
 $ {\text{PC}}{{\text{l}}_{\text{3}}} + 3{{\text{H}}_2}{\text{O}} \to {{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{3}}} + {\text{3HCl}} $
 $ {{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{3}}} $ can extract two hydrogen ions per molecule in its aqueous solution and is thus a dibasic acid.

Note:
Monobasic acids are the acids which in their aqueous solution produces one hydronium ion per molecule of the acid. Example- hydrochloric acid
Dibasic acids are the acids which in their aqueous solution produce two hydronium ions per molecule of the acid. Example- Sulphuric acid
Tribasic acids are those acids are those acids which in their aqueous solution give three hydronium ions per molecule of the acid. Example- ortho phosphoric acid