BCECE Medical BCECE Medical Solved Papers-2014

  • question_answer
    The enthalpy changes for the following processes are listed below
    \[C{{l}_{2}}(g)\xrightarrow{{}}2Cl(g),\,\,242.3\,kJ\,\,mo{{l}^{-1}}\]
    \[{{I}_{2}}(g)\xrightarrow{{}}2I(g),\,\,151.0\,\,kJ\,\,mo{{l}^{-1}}\]
    \[ICI(g)\xrightarrow{{}}I(g)+Cl(g),\,211.3\,\,kJ\,\,mo{{l}^{-1}}\]
    \[{{I}_{2}}(s)\xrightarrow{{}}{{I}_{2}}(g),\,\,62.76\,\,kJ\,\,mo{{l}^{-1}}\]
    Given that the standard states for iodine and chlorine are \[{{I}_{2}}(s)\] and \[C{{l}_{2}}(g)\], the standard enthalpy for the formation of \[ICl(g)\] is

    A)  \[-14.6\,\,kJ\,\,mo{{l}^{-1}}\]

    B)  \[-16.8\,\,kJ\,\,mo{{l}^{-1}}\]

    C)  \[+16.8\,\,kJ\,\,mo{{l}^{-1}}\]

    D)  \[+244.8\,\,kJ\,\,mo{{l}^{-1}}\]

    Correct Answer: C

    Solution :

    \[\frac{1}{2}{{l}_{2}}(s)+\frac{1}{2}C{{l}_{2}}(g)\xrightarrow{{}}lCl(g)\] \[\Delta H=\left[ \frac{1}{2}{{H}_{s\to g}}+\frac{1}{2}\Delta {{H}_{diss}}(C{{l}_{2}})+\frac{1}{2}\Delta {{H}_{diss}}({{l}_{2}}) \right]\] \[=\left( \frac{1}{2}\times 62.76+\frac{1}{2}\times 242.3+\frac{1}{2}\times 151.0 \right)-211.3\] = 228.03 - 211.3 \[\Delta H=16.73\]


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