Question

Which of the following salt undergoes hydrolysis?

• A. $N{a}_{2}S{O}_4$
• B. $N{H}_{4}Cl$
• C. $NaCl$
• D. $CaC{l}_2$

Answer 1

Answer: (B)

Only the salts of strong acid and weak base or weak acid and strong base undergo hydrolysis to produce acidic or alkaline solutions.
(i) $N{a}_{2}S{O}_4$ : Salt of strong acid $H_{2}S{O}_4$ and strong base $NaOH$ .
(ii) $NaCl$: Salt of strong acid $HCl$ and strong base $NaOH$ .
(iii) $CaC{l}_2$ : Salt of strong acid $HCl$ and strong base $Ca{(OH)}_2$ .
$\because$ $N{a}_{2}S{O}_4,NaCl$ and $CaC{l}_2$ are salts of strong acid and strong base.
$\therefore$ They do not undergo hydrolysis.
(iv) $N{H}_{4}Cl$ : Salt of weak base $N{H}_{4}OH$ and strong acid $HCl$ .
$\therefore$ $N{H}_{4}Cl$ hydrolyses as follows:
$N{H}_{4}Cl+H_{2}O\to N{H}_{2}OH+HCl$
The resulting solution is acidic because $HCl$ is strong acid.