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

  • question_answer
    The first ionization energy for Li is 5.4 eV and electron affinity of Cl is 3.61eV. The \[\Delta H\] (in kJ/mol) for the reaction \[Li(g)+Cl(g)\to L{{i}^{+}}+C{{l}^{-}}\] is (if resulting ions do not combine with each other) \[(1\,eV=1.6\times {{10}^{-19}}J)\] [MP PMT 2000, 03]

    A)                 70          

    B)                 100

    C)                 170        

    D)                 270

    Correct Answer: C

    Solution :

           First ionization potential of \[Li=5.4eV\]            Electron affinity of \[Cl=3.61eV\]            We have \[\Delta H=I.P.-E.A.\]            \[=5.4-3.61=1.80eV=1.80\times 1.6\times {{10}^{-22}}kJ\]            \[\Delta H=2.86\times {{10}^{-22}}kJ,\]            for 1mol Avogadro?s number \[=6.02\times {{10}^{23}}\].                                 \[\Delta H=2.86\times {{10}^{-22}}\times 6.02\times {{10}^{23}}=170\,kJ/mole.\]


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