Q49 / 200 · Manipal (MET) 2013 · Chemistry

Consider the following redox reaction occurring in acidic medium Figure
The unknown standard reduction potential is

  • A
    $-1.6 \mathrm{~V}$
  • B
    1.6 V
  • C
    $-1.52 \mathrm{~V}$
  • Correct answer
    D
    1.52 V

Solution

The given half reactions are $\mathrm{BrO}_3^{-}+4 e^{-}+4 \mathrm{H}^{+} \rightarrow E^{\circ}(\mathrm{inV}) \Delta G^{\circ}=-n F E^{\circ}$ $\mathrm{BrO}^{-}+2 \mathrm{H}_2 \mathrm{O} \quad 1.50 \quad-6 \mathrm{~F}$ $\mathrm{BrO}^{-}+\mathrm{e}^{-}+2 \mathrm{H}^{+} \longrightarrow 1.60 \quad-1.6 \mathrm{~F}$ $\frac{1}{2} \mathrm{Br}_2+\mathrm{H}_2 \mathrm{O}$ Adding $\mathrm{BrO}_3^{-}+5 \mathrm{e}^{-}+6 \mathrm{H}^{+} \longrightarrow \frac{1}{2} \mathrm{Br}_2+3 \mathrm{H}_2 \mathrm{O}$ $\begin{gathered}\Delta G^{\circ}=-7.6 \mathrm{~F}=-5 E^{\circ} \mathrm{F} \\ E^{\circ}=\frac{7.6}{5}=1.52 \mathrm{~V}\end{gathered}$

Hence, the correct answer is option: 'D'.

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