The number of species of the following that can act both as Bronsted acids and bases is \(\mathrm{HCl}, \mathrm{ClO}_4^{-},-\mathrm{OH}, \mathrm{H}^{+}, \mathrm{H}_2 \mathrm{O}, \mathrm{HSO}_4^{-}, \mathrm{SO}_4^{2-}\), \(\mathrm{H}_2 \mathrm{SO}_4, \mathrm{Cl}^{-}\)

• A

  4
• B

  3
• C

  1
• Correct answer
  D

  2

Solution

(i) \(\mathrm{HCl} \longrightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}\) (Bronsted acid) (ii) \(\mathrm{ClO}_4^{-}+\mathrm{H}^{+} \longrightarrow \mathrm{HClO}_4\) (Bronsted base) (iii) \(\mathrm{O} \mathrm{H}+\mathrm{H}^{+} \longrightarrow \mathrm{H}_2 \mathrm{O}\) (Bronsted base) (iv) \(\mathrm{H}_3 \mathrm{O}^{+} \longrightarrow \mathrm{H}^{+}+\mathrm{H}_2 \mathrm{O}\) (Bronsted acid)
(vii) \(\mathrm{H}^{+}+\mathrm{SO}_4^{2-} \longrightarrow \mathrm{HSO}_4^{-} \quad\) (Bronsted base) (viii) \(\mathrm{H}_2 \mathrm{SO}_4 \longrightarrow \mathrm{H}^{+}+\mathrm{HSO}_4^{-} \quad\) (Bronsted acid) (ix) \(\mathrm{Cl}^{-}+\mathrm{H}^{+} \longrightarrow \mathrm{HCl}\) (Bronsted base) Hence, \(\mathrm{H}_2 \mathrm{O}\) and \(\mathrm{HSO}_4^{-}\)(two species act as acid as well as base).

Hence, the correct answer is option: 'D'.