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NEET AIPMT SOLVED PAPER 1998

  • 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:

    A)                                                                                                                                                            \[\ln \,({{C}_{1}})\]

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

    C)                 \[\ln \,({{C}_{2}})\]                         

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

    Correct Answer: B

    Solution :

                    \[\Delta G=-n{{E}^{o}}\,F\]                 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 \[\ln \,{{C}_{2}}/{{C}_{1}}\]


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