Question

Consider the following perhalate ions in acidic medium
$ClO_4^-(I),BrO_4^- (II),IO_4^-(III)$
Arrange these in the decreasing order of oxidizing power

• A. $I > II > III$
• B. $I > III > II$
• C. $II > I > III$
• D. $II > III > I$

Answer 1

Answer: (D)

Standard reduction potential (in volts) of the perhalate ions are given as below.
$ClO^-_4 + 2H^+ + 2e^- \rightarrow ClO_3^- + H_2O$
$E^{\circ} = + 1.19\,V$
$BrO_4^- + 2H^+ + 2e^- \rightarrow BrO_3^- + H_2O$
$E^{\circ} = + 1.74 \,V$
$IO_4^- + 2H^+ + 2e^- \rightarrow IO_3^- + H_2O$
$E^{\circ} = + 1.65\,V$
More the standard reduction potential the more is tendency of perhalite ion to undergo reduction and more stronger it will be as an oxidising agent.