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VMMC VMMC Medical Solved Paper-2005

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

    A)  \[180\,\text{kJmo}{{\text{l}}^{-1}}\]  

    B) \[360\,\text{kJmo}{{\text{l}}^{-1}}\]     

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

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

    Correct Answer: D

    Solution :

    The formation of one mole of \[HCl\] can be represented as, \[\frac{1}{2}(H-H)+\frac{1}{2}(Cl-Cl)\,\xrightarrow{{}}H-Cl;\] \[\Delta H=-90\,kJ\] Hence, for the reaction, Heat evolved = Heat evolved in bond formation - Heat required for bond-breaking \[\therefore \]  \[90\,kJ=\][\[H-Cl\] bond energy] \[-\left( \frac{1}{2}\times 430\times \frac{1}{2}\times 240 \right)\] \[\therefore \]  (\[H-Cl\] bond energy) = 90 + (215 + 120) \[=425\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\]


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