Question

Which of the following cannot act both as Bronsted acid and as Bronsted base?

• A. $HC{O}_3^{-}$
• B. $N{H}_3$
• C. $HC{l}^{-1}$
• D. $HS{O}_4^{-}$

Answer 1

Answer: (C)

$HCl$ can only act as Bronsted acid because it can only donate proton.
$\underset{\text{Acid}}{\mathrm{HCl}}+\underset{\text{Base}}{H_{2}O}\rightleftharpoons H_3{O}^{+}+C{l}^{-}$
The remaining options contains substances which act both as Bronsted acid and Bronsted base.
(a) $HC{O}_3^{-}+HC{O}_3^{-}\rightleftharpoons H_{2}C{O}_3+C{O}_3^{2-}$
(b) $N{H}_3+N{H}_3\rightleftharpoons N{H}_4^{+}+N{H}_2^{-}$
(c) $HS{O}_4^{-}+HS{O}_4^{-}\rightleftharpoons H_{2}S{O}_4+S{O}_4^{2-}$