Question

Which of the following species act as an amphiprotic species in the following reactions?
$HCl\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons H_3{O}^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$

$N{H}_3\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons N{H}_4^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$

• A. $N{H}_3$
• B. $H_{2}O$
• C. $O{H}^{-}$
• D. $C{l}^{-}$

Answer 1

The correct option is B $H_{2}O$

Amphiprotic Species:
Species which can accept $H^{+}$ as well as donate $H^{+}$.
As per Bronsted-Lowry’s theory, species which can act as an acid as well as a base.

Water is amphiprotic in the following reactions,

$HCl\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons H_3{O}^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$, here $H_{2}O\left(aq\right)$ is accepting $H^{+}$

$N{H}_3\left(aq\right)+H_{2}O\left(aq\right)\rightleftharpoons N{H}_4^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$, here $H_{2}O\left(aq\right)$ is giving $H^{+}$
Therefore water is amphiprotic.