CMC Medical CMC-Medical Ludhiana Solved Paper-2012

  • question_answer
    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)  \[{{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}\frac{[F{{e}^{2+}}]\,\,{{[{{I}^{-}}]}^{2}}}{[Fe]\,\,[{{I}_{2}}]}\]

    Correct Answer: B

    Solution :

                    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 \[{{E}_{cell}}=E_{cell}^{\text{o}}+\frac{0.0592}{n}{{\log }_{10}}\frac{[Fe]\,[{{I}_{2}}]}{[F{{e}^{2+}}]\,{{[{{I}^{-}}]}^{2}}}\] \[[Fe]=[{{I}_{2}}]=1\] \[{{E}_{cell}}=E_{cell}^{\text{o}}-\frac{0.0592}{n}{{\log }_{10}}[F{{e}^{2+}}]\,{{[{{I}^{-}}]}^{2}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner