BCECE Engineering BCECE Engineering Solved Paper-2013

  • question_answer
    \[\Delta {{G}^{o}}\]and \[\Delta {{H}^{o}}\]for a reaction at 300 K is \[-66.9\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\] and\[-41.8\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\] respectively. \[\Delta {{G}^{o}}\]for the same reaction at 330 K is

    A) \[-25.1\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\]

    B)        \[+\,25.1\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\]

    C)        \[18.7\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\]

    D)        \[-69.4\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\]

    Correct Answer: D

    Solution :

    \[\because \]\[\Delta {{H}^{o}}\]and\[\Delta {{S}^{o}}\]remain constant in the given temperature range. \[\therefore \] \[\Delta {{S}^{o}}=-\frac{\Delta {{G}^{o}}-\Delta {{H}^{o}}}{T}\]                 \[=-\left( -\frac{66.9+41.8}{300} \right)\]                 \[=0.08367\,kJ\,{{K}^{-1}}\,mo{{l}^{-1}}\] \[\therefore \]  \[\Delta G_{330}^{o}=\Delta {{H}^{o}}-T\Delta {{S}^{o}}\]                 \[=-41.8-330\times 0.08367\]                 \[=-69.4\,kJ\,mo{{l}^{-1}}\]


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