Question

Account for the acidic nature of HClO₄ in terms of Bronsted – Lowry theory, identify its conjugate base.

Answer 1

\[\ce{HClO4 ⇌ H^+ + ClO^-_4}\]

1. According to Lowry – Bronsted concept, a strong acid has a weak conjugate base and a weak acid has a strong conjugate base.

2. Let us consider the stabilities of the conjugate bases \[\ce{ClO^-_4}\], \[\ce{ClO^-_3}\], \[\ce{ClO^-_2}\] and ClO^– formed from these acid HClO₄, HClO₃, HCIO₂, HOCI respectively.

These anions are stabilized to a greater extent, it has a lesser attraction for proton and therefore, will behave as a weak base.

Consequently, the corresponding acid will be strongest because the weak conjugate base has strong acid and the strong conjugate base has weak acid.

3. The charge stabilization mercases in the order, \[\ce{ClO^- < ClO^-_2 < ClO^-_3 < ClO^-_4}\].

This means \[\ce{ClO^-_4}\] will have maximum stability and therefore will have a minimum attraction for W. Thus \[\ce{ClO^-_4}\] will be the weakest base and its conjugate acid HCIO₄ is the strongest acid.

4. \[\ce{ClO^-_4}\] is the conjugate base of the acid HClO₄.