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JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Morning)

  • question_answer
    The standard electrode potential \[E{}^\circ \]and its temperature coefficient \[\left( \frac{d{{E}^{o}}}{dT} \right)\]for a cell are 2 V and \[-5\times {{10}^{-4}}V\,{{K}^{-1}}\]at 300 K respectively.
    The cell reaction is
     \[Z{{n}_{(s)}}+Cu_{(aq)}^{2+}\xrightarrow[{}]{{}}Zn_{(aq)}^{2+}+C{{u}_{(s)}}\]
    The standard reaction enthalpy \[({{\Delta }_{r}}{{H}^{o}})\]at 300 K in \[kJ\,mo{{l}^{-1}}\]is, [Use \[R=8\,J\,{{K}^{-1}}mo{{l}^{-1}}\]and \[F=96,000\,C\,mo{{l}^{-1}}\]] [JEE Main Online Paper Held On 12-Jan-2019 Morning]

    A) \[-412.8\]       

    B) 192.0

    C) \[-384.0\]                      

    D)   206.4

    Correct Answer: A

    Solution :

    \[{{\Delta }_{r}}{{H}^{o}}=-nF{{E}^{o}}+nFT\left( \frac{\Delta {{E}^{o}}}{\Delta T} \right)\] \[=-2\times 96000\times 2+2\times 96000\times 300(-5\times {{10}^{-4}})\] \[=-384000-28800=-412.8kJ\,mo{{l}^{-1}}\]                 


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