JEE Main & Advanced Chemistry Electrochemistry / विद्युत् रसायन Question Bank Electrode potential Ecell Nernst equation and ECS

  • question_answer
    The e.m.f. of the cell \[Zn|Z{{n}^{2+}}(0.01M)||F{{e}^{2+}}(0.001M)|Fe\] at 298 K is 0.2905 then the value of equilibrium for the cell reaction is             [IIT-JEE Screening  2004]

    A)                 \[\frac{0.32}{{{e}^{0.0295}}}\]   

    B)                 \[\frac{0.32}{{{10}^{0.0295}}}\]

    C)                 \[\frac{0.26}{{{10}^{0.0295}}}\] 

    D)                 \[\frac{0.32}{{{10}^{0.0591}}}\]

    Correct Answer: B

    Solution :

               For this cell, reaction is: \[Zn+F{{e}^{2+}}\to Z{{n}^{2+}}+Fe\]                    \[E={{E}^{0}}-\frac{0.0591}{n}\log \frac{{{c}_{1}}}{{{c}_{2}}}\]; \[{{E}^{0}}=E+\frac{0.0591}{n}\log \frac{{{c}_{1}}}{{{c}_{2}}}\]                    \[=0.2905+\frac{0.0591}{2}\log \frac{{{10}^{-2}}}{{{10}^{-3}}}=0.32\ V\].                    \[{{E}^{0}}=\frac{0.0591}{2}\log {{K}_{c}}\]; \[\log {{K}_{c}}=\frac{0.32\times 2}{0.0591}=\frac{0.32}{0.0295}\]                                 \[\therefore \ \ {{K}_{c}}=\frac{0.32}{{{10}^{0295}}}\].


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