RAJASTHAN ­ PET Rajasthan PET Solved Paper-2012

  • question_answer The enthalpy of combustion of\[{{H}_{2}},\]cyclohexene\[({{C}_{6}}{{H}_{10}})\]and  cyclohexane\[({{C}_{6}}{{H}_{12}})\]are\[-241,~-3800\] and\[-3920\text{ }kJ\]per  mol respectively. Heat of hydrogenation of cyclohexene is

    A)  \[-121\text{ }kJ\] per mol

    B)  \[+121\text{ }kJ\] per mol

    C)  \[+242\text{ }kJ\] per mol

    D)  \[-242\text{ }kJ\] per mol

    Correct Answer: A

    Solution :

      \[\Delta H=?\] \[\Delta H=[\Delta H\]of combustion of cyclohexan\[-(\Delta H\] of combustion of cyclohexene\[+\Delta H\]of combustion of\[{{H}_{2}}\])] \[=-[-3920-(3800-24)]\text{ }kJ\] \[=-[3920+4041]\] \[=-[121]kJ\] \[=-121kJ\]


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