JEE Main & Advanced Chemistry Thermodynamics / रासायनिक उष्मागतिकी Question Bank Bond energy

  • question_answer
    The \[H-H\] bond energy is 430 kJ \[mol\] and \[Cl-Cl\] bond energy is \[240\,kJ\,mo{{l}^{-1}}.\,\,\Delta H\] for \[HCl\] is \[-90\,kJ\]. The \[H-Cl\] bond energy is about [BVP 2003]

    A)                 \[180\,kJ\,mo{{l}^{-1}}\]              

    B)                 \[360\,kJ\,mo{{l}^{-1}}\]

    C)                 \[213\,kJ\,mo{{l}^{-1}}\]              

    D)                 \[425\,kJ\,mo{{l}^{-1}}\]

    Correct Answer: D

    Solution :

           \[\frac{1}{2}{{H}_{2}}+\frac{1}{2}C{{l}_{2}}\to HCl,\,\,\,\Delta H=-90\,KJ\]            \[\therefore \Delta H=\frac{1}{2}{{E}_{H-H}}+\frac{1}{2}{{E}_{Cl-Cl}}\]            or \[-90=\frac{1}{2}\times 430+\frac{1}{2}\times 240-{{E}_{HCl}}\]                                 \[\therefore {{E}_{H-Cl}}=425\,kJ\,mo{{l}^{-1}}\].


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