Q. ${2Fe}^{3 +}\ + \ {3I}^{-}\ \ \rightleftharpoons \ {2Fe}^{2 +}\ + \ I_{3}^{-}\ \ \ \ \$ The standard reduction potentials in acidic conditions are 0.77 and 0.54 V respectively for$\ {Fe}^{3 +}\ /\ {Fe}^{2 +}$ and $I_{3}^{-}\ \ /\ \ I^{-}$ couples. The equilibrium constant for the reaction is

A) $6.26\ \times \ 10^{- 7}$
B) $5.33\ \times \ 10^{- 4}$
C) $6.26\ \times \ 10^{7}$
D) $5.33\ \times \ 10^{4}$
Explanation

(c)
For the change , ${2Fe}^{3 +} + \ {3I}^{-}\ \rightleftharpoons \ {2Fe}^{2 +}\ + \ I_{3}^{-}$
$E_{cell}^{{^\circ}}$ = 0.77 – 0.54 = 0.23 V
$E^{{^\circ}} = \ \frac{0.059}{2}\log K_{c}\$
$0.23\ = \ \frac{0.0591}{2}\log K_{c}\ \$
$K_{c}\ = \ 6.26\ \times \ 10^{7}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.