Question

Consider the following perhalate ions in acidic medium
$Cl{O}_4^{-}(I),Br{O}_4^{-}(II),I{O}_4^{-}(III)$
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.
$Cl{O}_4^{-}+2H^{+}+2e^{-}\to Cl{O}_3^{-}+H_{2}O$
$E^{\circ }=+1.19V$
$Br{O}_4^{-}+2H^{+}+2e^{-}\to Br{O}_3^{-}+H_{2}O$
$E^{\circ }=+1.74V$
$I{O}_4^{-}+2H^{+}+2e^{-}\to I{O}_3^{-}+H_{2}O$
$E^{\circ }=+1.65V$
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.