BCECE Medical BCECE Medical Solved Papers-2010

  • question_answer
    The enthalpies of combustion of carbon, and carbon monoxide are -393.5 and \[-285\,\,kJ\,\,mo{{l}^{-1}}\] respectively. The enthalpy of formation of carbon monoxide per mole is

    A)  110.5 kJ        

    B)  676.5 kJ

    C)  -676.5 kJ      

    D)  -110.5 kJ

    Correct Answer: D

    Solution :

    I. \[C(s)+{{O}_{2}}(g)\xrightarrow{{}}C{{O}_{2}}(g);\]                  \[\Delta H=-393.5\,kJ\] II. \[CO(g)+\frac{1}{2}{{O}_{2}}(g)\xrightarrow{{}}C{{O}_{2}}(g);\]                  \[\Delta H=-283.0\,kJ\]     On subtracting Eq. (II) from Eq. (I), we get III. \[C(s)+\frac{1}{2}{{O}_{2}}(g)\xrightarrow{{}}CO(g);\]                  \[\Delta H=-110.5\,kJ\] The equation III also represents formation of 1 mole of CO and thus, enthalpy change, ie, -110.5 kJ, is the heat of formation of \[CO(g)\].


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