Question

Which salt will give a basic solution on hydrolysis?
A.KCN
B.KCl
C.\[\;N{H_4}Cl\]
D.\[C{H_3}COON{H_4}\]

Answer 1

Hint: A salt is an ionic compound that is formed when an acid and a base neutralize each other. The salts of weak acids and strong bases on hydrolysis give a basic solution.

Complete answer:
It may seem that salt solutions would always be neutral, they can frequently be either acidic or basic and the salt that is made up of a strong base and a weak acid will be basic in nature.
HCl is a strong acid, HCN and \[C{H_3}COOH\;\] are weak acids, NaOH is a strong base and \[\;N{H_4}Cl\] is a weak base.
Ammonium chloride (NH4​Cl) is a salt of a weak base and a strong acid. Its solution will be acidic in nature. It is formed when the strong acid hydrochloric acid (HCl) is neutralized by the weak base \[N{H_3}\]. Ammonium chloride is soluble in water. The chloride ion produced is incapable of hydrolyzing because it is the conjugate base of the strong acid HCl. In other words, the \[Cl{\;^ - }\] ion cannot accept a proton from water to form HCl and \[OH{\;^ - }\], as the fluoride ion did in the previous section. However, the ammonium ion is capable of reacting slightly with water, donating a proton and so acting as an acid.
KCl is a salt of a strong acid and strong base. Its solution will be neutral.
Hence, KCN will give a basic solution on hydrolysis.
\[KCN \to {K^ + } + C{N^ - }\]
\[C{N^ - } + {H_2}O \to HCN + O{H^ - }\]

Therefore, the correct answer is option (A).

Note: Salt hydrolysis is a reaction in which one of the ions from a salt reacts with water, forming either an acidic or basic solution. Based on how strong the ion acts as an acid or base, it will produce varying pH levels. When salts and water react, there are many possibilities due to the varying structures of salts. A salt can be made of either a weak acid and strong base, strong acid and weak base, a strong acid and strong base, or a weak acid and weak base.