Gce Model Questions Vol1 2020 Chemistry Question 48

The following standard reduction potentials (25 °C) are given for stepwise reductions of chlorine oxyanions:\n\[\begin{aligned} \mathrm{ClO_{4}^{-} + 2H^{+} + 2e^{-} &\rightarrow ClO_{3}^{-} + H_{2}O}\quad E^{\circ}=+1.20\ \text{V}\\ \mathrm{ClO_{3}^{-} + 2H^{+} + 2e^{-} &\rightarrow ClO_{2}^{-} + H_{2}O}\quad E^{\circ}=+0.90\ \text{V}\\ \mathrm{ClO_{2}^{-} + 2H^{+} + 2e^{-} &\rightarrow ClO^{-} + H_{2}O}\quad E^{\circ}=+0.60\ \text{V}\\ \mathrm{ClO^{-} + 2H^{+} + 2e^{-} &\rightarrow Cl^{-} + H_{2}O}\quad E^{\circ}=+0.30\ \text{V} \end{aligned}\]\nAssuming each half‑reaction corresponds to the deprotonation of the conjugate oxoacid (i.e. \(\mathrm{HClO_{4}},\ \mathrm{HClO_{3}},\ \mathrm{HClO_{2}},\ \mathrm{HClO}\)), rank the four acids from strongest to weakest in terms of their acid dissociation constant \(K_a\). Justify your ranking using the given potentials.