Question

\[{\text{PC}}{{\text{l}}_3}\] on hydrolysis, gives fumes of
\[{\text{A ) }}{{\text{H}}_3}{\text{P}}{{\text{O}}_3}{\text{ + HCl }} \\
{\text{B ) }}{{\text{H}}_3}{\text{P}}{{\text{O}}_4}{\text{ + HCl}} \\
{\text{C ) }}{{\text{H}}_3}{\text{P}}{{\text{O}}_2}{\text{ + }}{{\text{H}}_3}{\text{P}}{{\text{O}}_3} \\
{\text{D ) }}{{\text{H}}_3}{\text{P}}{{\text{O}}_3}{\text{ + HCl }} \\\]

Answer 1

Hint: During hydrolysis, one (or more) water molecules react with a given molecule. Hydrogen atoms of water form bonds with more electronegative atoms of given molecules. Hydroxyl groups of water are added to the less electronegative atom of a given molecule.

Complete step by step answer:
\[{\text{PC}}{{\text{l}}_3}\] is phosphorus trichloride. Hydrolysis is the reaction with water. During hydrolysis, the bond between phosphorus and chlorine breaks. Similarly in water, the bond between hydrogen and oxygen breaks. Hydrogen atoms form bonds with chlorine atoms to form hydrogen chloride. There are three chlorine atoms in phosphorus trichloride. Hence, three molecules of hydrogen chloride are obtained when one molecule of phosphorus trichloride undergoes hydrolysis.
Oxygen atom of the hydroxyl group forms a bond with the phosphorus atom.
Three such hydroxyl groups form bonds with phosphorus atoms. The product is phosphorus acid.
Hence, one molecule of phosphorus trichloride reacts with three molecules of water to form three molecules of hydrogen chloride and one molecule of phosphorous acid.
\[{\text{PC}}{{\text{l}}_3}{\text{ + 3}}{{\text{H}}_2}{\text{O }} \to {\text{ }}{{\text{H}}_3}{\text{P}}{{\text{O}}_3}{\text{ + 3 HCl}}\]
Thus, when \[{\text{PC}}{{\text{l}}_3}\] is hydrolysed, it gives fumes of \[{{\text{H}}_3}{\text{P}}{{\text{O}}_3}{\text{ + HCl}}\]

So, the correct answer is “Option D”.

Additional Information: The hydrolysis reaction of phosphorus pentachloride is similar to that of phosphorus trichloride. When phosphorus pentachloride undergoes hydrolysis with water, phosphoric acid and hydrochloric acid are obtained.

Note: In the product, the number of the oxygen atoms is equal to the number of chlorine atoms present in phosphorus trichloride. This is because each chlorine atom of phosphorus trichloride is replaced with one hydroxyl group. Since there are three chlorine atoms in phosphorus trichloride, there are three oxygen atoms in the product.