VMMC VMMC Medical Solved Paper-2013

  • question_answer
    On burning 4.0 g of iron to ferric oxide at constant pressure, the heat evolved is 29.28 kJ. The enthalpy of formation of ferric oxide is (At\[\omega t.Fe=56\])

    A) \[81.98\text{ }kJ\text{ }mo{{1}^{-1}}\]       

    B)  \[-\text{ }81.98\text{ }kJ\text{ }mo{{1}^{-1}}\]

    C) \[\text{ }819.8\text{ }kJ\text{ }mo{{1}^{-1}}\]      

    D)  \[-819.8\,kJ\,mo{{l}^{-1}}\]

    Correct Answer: D

    Solution :

     \[\underset{\text{2}\,\text{mol}}{\mathop{2Fe}}\,(s)+\frac{3}{2}{{O}_{2}}(g)\xrightarrow{{}}\underset{\text{1}\,\text{mol}}{\mathop{F{{e}_{2}}{{O}_{3}}(S)}}\,\] Moles of \[Fc=\frac{4}{56}=\frac{1}{14}mol\] Moles of \[F{{e}_{2}}{{O}_{3}}\]formed \[=\frac{1}{28}\,mol\] Heat released = 29.28 kJ \[\Delta {{H}^{o}}f(F{{e}_{2}}{{O}_{3}})=-\frac{29.28}{1/28}kJ\,mo{{l}^{-1}}\] \[=-819.84\,kJ\,mo{{l}^{-1}}\]


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