Question

The species among the following, which can act as acid as well as base is?

• A. $HS{O}_4^{-}$
• B. $S{O}_4^{2-}$
• C. $H_3{O}^{+}$
• D. $C{l}^{-}$

Answer 1

Answer: (A)

$HS{O}_4^{-}$

$HS{O}_4^{-}+H^{+}\leftrightharpoons H_{2}S{O}_4$
$HS{O}_4^{-}\leftrightharpoons S{O}_4^{2-}+H^{+}$
Species which can accept as well as donate $H^{+}$ ion can act both as acid and base.

$S{O}_4^{2-}$ can accept $H^{+}$ ion hence it can act only as base.

$H_3{O}^{+}$ act as proton donor, hence it can act only as acid.

$C{l}^{-}$ can accept $H^{+}$ ion hence can act only as base.