Which of the following salt solutions turns red litmus blue?
Which of the following salt solutions turns red litmus blue?
$\mathrm{NH}_4 \mathrm{CN}$
$\mathrm{NH}_4 \mathrm{Cl}$
$\mathrm{NH}_4 \mathrm{NO}_3$
$\mathrm{NaNO}_3$
Solution
The pH of a solution depends on the hydrolysis of a salt. Except $\mathrm{NH}_4 \mathrm{CN}$, all the other salts are products of strong acids HCl or $\mathrm{HNO}_3$. Hence, $\mathrm{NH}_4 \mathrm{CN}$ turns red litmus blue as HCN is a weak acid.