Question

The number of species of the following that can act both as Bronsted acids and bases is $HCl , ClO _{4}^{-},{ }^{-} OH , H ^{+}, H _{2} O , HSO _{4}^{-}, SO _{4}^{2-}$, $H _{2} SO _{4}, Cl ^{-}$

• A. 4
• B. 3
• C. 1
• D. 2

Answer 1

Answer: (D)

2

Answer 2

The correct answer is option (D): 2
(i) $HCl \to H ^{+}+ Cl ^{-}$ (Bronsted acid)
(ii) $ClO _{4}^{-}+ H ^{+} \to HClO _{4}$ (Bronsted base)
(iii) $\bar{ O } H + H ^{+} \to H _{2} O$ (Bronsted base)
(iv) $H _{3} O ^{+} \to H ^{+}+ H _{2} O$ (Bronsted acid)
(v) $H ^{+}+ SO _{4}^{2-}\to HSO _{4}^{-}$ (Bronsted base)
(vi) $H _{2} SO _{4} \to H ^{+}+ HSO _{4}^{-}$ (Bronsted acid)
(vii) $Cl ^{-}+ H ^{+} \longrightarrow HCl$ (Bronsted base)
Hence, $H _{2} O$ and $HSO _{4}^{-}$ (two species act as acid as well as base)