NEET Chemistry NEET PYQ-Electrochemistry

  • question_answer
    The standard emf of a galvanic cell involving cell reaction with \[n=2\] is found to be 0.295 V at \[25{}^\circ \text{ }C\]. The equilibrium constant of the reaction would be:                         [AIPMT (S) 2004] (Given: \[F=96500\,\,C\,mo{{l}^{-1}};\]\[R=8.314\,J{{K}^{-1}}mo{{l}^{-1}})\]

    A) \[2.0\times {{10}^{11}}\]

    B) \[4.0\times {{10}^{12}}\]

    C) \[1.0\times {{10}^{2}}\]

    D) \[1.0\times {{10}^{10}}\]

    Correct Answer: D

    Solution :

    [d] By Nernst equation,
    \[{{E}_{cell}}={{E}^{0}}_{cell}-\frac{2.303RT}{nF}{{\log }_{10}}K\]
    At equilibrium \[{{E}_{cell}}=0\]
    Given that
    \[\therefore \,\,\,\,\,\,\,\,\,\,R=8.315\,J{{K}^{-1}}\,mo{{l}^{-1}}\]
    \[\text{T}=\text{25}{}^\circ \text{C}+\text{273}=\text{298 K}\]
    \[\text{F}=\text{965}00\text{ C and n}=\text{2}\]
    \[\therefore \]\[{{E}^{0}}_{cell}=\frac{2.303\times 8.314\times 298}{2\times 96500}\]\[{{\log }_{10}}K\]
    \[=\frac{0.0591}{2}{{\log }_{10}}K\]
    \[\because \]Given that \[{{E}^{0}}_{cell}\,\,=0.295\,\,V\]
    \[\therefore \]\[0.295=\frac{0.0591}{2}{{\log }_{10}}K\]
    \[{{\log }_{10}}K=\frac{0.295\times 2}{0.0591}=10\]
    or         antilog of\[{{\log }_{10}}K=anti\log \,10\]
                \[K=1\times {{10}^{10}}\]


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