Question

Which of the following salts undergoes anionic hydrolysis
A. $CuS{O_4}$
B. $N{H_4}Cl$
C. $FeC{l_3}$
D. $N{a_2}C{O_3}$

Answer 1

Hint:When an acid-base reaction occurs, results in the formation of salt and water. If the acid and base both are strong, that is strong acid is reacting with a strong base, then a neutral salt will form and the reaction is called a neutralization reaction. But if either of the acid or base is not weak then salt formation will occur but the salt will not be neutral.

Complete answer:
First of all what is salt hydrolysis. It can be defined as a reaction in which cation and anion or both or cation and anion reacts with water to form the solution either acidic or basic or neutral.
If the salt has formed from strong acid and strong base, then a neutral salt will form. For example-Hydrochloric acid and sodium hydroxide.
$HCl + NaOH \to NaCl + {H_2}O$
Here the sodium chloride is neutral salt.
When a strong acid and weak base reacts, an acidic salt will form. For example when hydrochloric acid and ammonium hydroxide will react, it will form ammonium chloride, An acidic salt.
$HCl + N{H_4}OH \to N{H_4}Cl + {H_2}O$
When this ammonium chloride dissolves in water, the chloride ion reacts with the proton of hydrochloric acid and will form an acidic solution. This process is known as cationic hydrolysis. In cationic hydrolysis, the pH of the solution will be below 7.
Now when a strong base and weak acid will react, a basic salt will form. For example sodium hydroxide when reacts with weak acid hydrogen carbonate as
$NaOH + {H_2}C{O_3} \to N{a_2}C{O_3} + {H_2}O$
When sodium carbonate dissolves in water, it will react with hydroxide ion and will form sodium hydroxide and form alkaline solution. This process is known as anionic hydrolysis. In anionic hydrolysis, the pH of the solution will be above 7.
Copper sulphate will form an acidic solution. Similarly ammonium chloride and ferric chloride will also form acidic solutions. The sodium carbonate will only form an alkaline solution and hence would have gone through anionic hydrolysis.

So the correct option is D. $N{a_2}C{O_3}$

Note:
When a salt is given just by adding hydroxide to the cationic part and hydrogen ion to the anionic part of the salt, you can predict if the salt is acidic or basic. Just compare the acid strength of acid formed by adding hydrogen to anionic part with the basic strength of base formed by adding hydroxide ion to the cationic part. If basic strength of base is stronger than the acidic strength of acid formed, the salt will be basic salt and vice versa