Question

The salt whose aqueous solution will turn blue litmus to red is :

(a) ammonium sulphate

(b) sodium acetate

(c) sodium chloride

(d) potassium carbonate

Answer 1

a). ammonium sulphate

Ammonium sulphate $\left[\right(N{H}_4{)}_{2}S{O}_4]$ is formed from a weak base, ammonium hydroxide $\left(N{H}_{4}OH\right)$, and a strong acid, sulphuric acid $\left(H_{2}S{O}_4\right)$. On dissolving in water, $\left[\right(N{H}_4{)}_{2}S{O}_4]$ undergoes hydrolysis to form more $H^{+}$ ions than $O{H}^{-}$ ions. As the aqueous solution of the salt $\left[\right(N{H}_4{)}_{2}S{O}_4]$ is acidic, it turns blue litmus red.