Question

Which Nernst equation is true to find out the potential of non-standard electrochemical cell from the following? $ Fe(s)|F{{e}^{2+}}(aq\,XM)|\,|\,{{I}^{-}}(aq){{I}_{2}}(s)Pt $

• A. $ {{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.592}{n}{{\log }_{10}}[F{{e}^{2+}}]\,{{[{{I}^{-}}]}^{2}} $
• B. $ {{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}[F{{e}^{2+}}]\,\,{{[{{I}^{-}}]}^{2}} $
• C. $ {{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}[F{{e}^{2+}}]\,\,[{{I}^{-}}] $
• D. $ {{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}\frac{[F{{e}^{2+}}]\,\,{{[{{I}^{-}}]}^{2}}}{[Fe]\,\,[{{I}_{2}}]} $

Answer 1

Answer: (B)

Cell reaction of a given cell is $ \begin{align} & \underline{\begin{align} & \,\,\,\,\,\,\,\,\,\,\,\,Fe\xrightarrow{{}}F{{e}^{2+}}+2{{e}^{-}} \\ & {{I}_{2}}+2{{e}^{-}}\xrightarrow{{}}2{{I}^{-}} \\ \end{align}} \\ & \,\,Fe+{{I}_{2}}\xrightarrow{{}}F{{e}^{2+}}+2{{I}^{-}} \\ \end{align} $ According to Nernst equation $ {{E}_{cell}}=E_{cell}^{\text{o}}+\frac{0.0592}{n}{{\log }_{10}}\frac{[Fe]\,[{{I}_{2}}]}{[F{{e}^{2+}}]\,{{[{{I}^{-}}]}^{2}}} $ $ [Fe]=[{{I}_{2}}]=1 $ $ {{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}[F{{e}^{2+}}]\,{{[{{I}^{-}}]}^{2}} $