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NEET Chemistry NEET PYQ-Electrochemistry

  • question_answer
    For the cell reaction,             \[C{{u}^{2+}}({{C}_{1}}\,aq)+Zn(s)\rightleftharpoons Z{{n}^{2+}}({{C}_{2}}\,aq)+Cu(s)\] of an electrochemical cell. The change in free energy \[(\Delta G)\] at a given temperature is a function of: [AIPMT 1998]

    A) In \[({{C}_{1}})\]

    B) In \[({{C}_{2}}/{{C}_{1}})\]

    C) In\[({{C}_{2}})\]

    D) In \[({{C}_{1}}+{{C}_{2}})\]

    Correct Answer: B

    Solution :

    [b] \[\Delta G=-n{{E}^{o}}\,F\]
                For concentration cell
                            \[E=\frac{RT}{nF}\ln \,\frac{{{C}_{2}}}{{{C}_{1}}}\]
                In it R, T, n and F are constant.
                So E is based upon- In \[{{C}_{2}}/{{C}_{1}}\]
                            \[\Delta G=-nEF\]
                            \[=-nF\times \frac{RT}{nF}\ln \frac{{{C}_{2}}}{{{C}_{1}}}=-RT\,\ln \,\frac{{{C}_{2}}}{{{C}_{1}}}\]
                So, at constant temperature \[\Delta G\] depends upon In \[{{C}_{2}}/{{C}_{1}}\]


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