Question

Assertion (A): The aqueous solution of ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}}$ is alkaline in nature.
Reason(R): Acetate ion undergoes anionic hydrolysis
(A) Both A and R true, R is the correct explanation of A.
(B) Both A and R true, R is not the correct explanation of A.
(C) A is true R is false.
(D) A is false, R is true.

Answer 1

To answer this question we know the meaning of hydrolysis. Hydrolysis of an ionic compound is the dissolution of the ions of that ionic compound in water, so the bonds in the compound break, and a new compound forms. To determine whether the hydrolysis is cationic or anionic we have to check the ion undergoing hydrolysis.

Complete step-by-step answer: Sodium acetate ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}}$ is a salt of acetic acid which is formed by the reaction of sodium hydroxide and acetic acid. The formation of sodium acetate salt is shown as follows:
${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\,{\text{ + }}\,{\text{NaOH}}\, \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}\,{\text{Na}}\,{\text{ + }}\,{{\text{H}}_2}{\text{O}}$
Sodium acetate is an ionic compound so, on hydrolysis first, it undergoes ionization. The ionization of sodium acetate is shown as follows:
${\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}} \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{CO}}{{\text{O}}^ - }\,{\text{ + }}\,{\text{N}}{{\text{a}}^ + }$ (${\text{N}}{{\text{a}}^ + }$is spectator cation)
By the ionization sodium ion and acetate ion form. The sodium ion is a spectator ion because it just balances the charge of the acetate ion.
So, acetate ion undergoes dissolution process which is shown as follows:
${\text{C}}{{\text{H}}_{\text{3}}}{\text{CO}}{{\text{O}}^ - }\, + \,{{\text{H}}_2}{\text{O}} \to {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}\,\,{\text{ + }}\,{\text{O}}{{\text{H}}^ - }\,$
By the dissolution of acetate ion, acetic acid, and hydroxide ion forms. As the acetate ion is an anion so, this is anionic hydrolysis. The solution is not neutral but slightly alkaline due to the presence of hydroxide ions in the solution.
So, the assertion (A), the aqueous solution of ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COONa}}$ is alkaline in nature and the reason (R), acetate ion undergoes anionic hydrolysis, both are true.
The solution is alkaline due to hydrolysis of acetate ions so, the reason explains the assertion.
Therefore, option (A), Both A and R true, R is correct explanation of A, is correct.

Note: During hydrolysis two processes take place first ionization (formation of ions) then dissolution (reaction of ions with water). Salts are composed of ions. Anionic hydrolysis gives the alkaline solution. Cationic hydrolysis gives the acidic solution. An aqueous solution is one in which the solvent is liquid water and the solute ions are surrounded by water molecules and incorporated into the network of bonds within the water. Acetic acid is a weak acid. The anion of acetic acid is known as acetate ion.