Question

Water is considered an amphoteric substance. Which of following other substances can also be considered amphoteric?

• A. $H_{2}S{O}_4$
• B. $HS{O}_4^{-}$
• C. $S{O}_4^{2-}$
• D. $C{O}_3^{2-}$

Answer 1

The correct option is B $HS{O}_4^{-}$

Substances that can act as acid is one reaction and as a base in another are called amphoteric substances.

In the first reaction the bisulfate ion,$HS{O}_4^{-}$ acts as a base. In the second reaction it acts as an acid:

1. $HS{O}_4^{-}+H_3{O}^{+}\to H_{2}S{O}_4+H_{2}O$

$HS{O}_4^{-}$ accepts a proton from $H_3{O}^{+}$

2. $HS{O}_4^{-}+OH\to H_{2}O+S{O}_4^{-2}$

$HS{O}_4^{-}$ gives (donates) a proton to $O{H}^{-}$