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AFMC AFMC Solved Paper-2000

  • question_answer
    The enthalpy of combustion of \[{{C}_{6}}{{H}_{6}}\]is \[-3250\,kJ\]when 0.39g of \[{{C}_{6}}{{H}_{6}}\]is burnt in excess of oxygen in an open vessel, the amount of heat evolved is:

    A) 8.32 kJ                                  

    B) 12.36 kJ

    C) 16.25 kJ                               

    D) 20.74 kJ

    Correct Answer: C

    Solution :

    Combustion of benzene can be represented as follows \[{{C}_{6}}{{H}_{6}}+{{O}_{2}}\xrightarrow{{}}6C{{O}_{2}}+{{H}_{2}}O+3250\,kJ\] 78 g of \[{{C}_{6}}{{H}_{6}}\]produce 3250 kJ heat 1 g will produce \[\frac{3250}{78}\]kJ heat 39 g will produce \[=\frac{3250}{78}\times 0.39\,\text{kJ}\] NOTE: Enthalpy of combustion is the amount of heat liberated when one mole of a substance is burnt in excess of air.


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