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JEE Main & Advanced Chemistry Thermodynamics / रासायनिक उष्मागतिकी Sample Paper Topic Test - Thermo Chemistry (Thermodynamics)

  • question_answer
    A 1 g sample of octane \[{{C}_{8}}{{H}_{18}}\] is burned in excess of oxygen in a bomb calorimeter. The temperature of the calorimeter rises from 294 K to 300 K. If heat capacity of the calorimeter is 8 kJ/K, the enthalpy of combustion of octane is

    A) 5472 kJ/mol      

    B) 48 kJ/mol

    C) 684 kJ/mol

    D) 4281 kJ/mol

    Correct Answer: A

    Solution :

    [a] Rise in temperature = 300 - 294 = 6 K
    Heat given to the calorimeter
    = Heat capacity \[\times \,\Delta T\]\[=8\times 6\]
    = 48 kJ
    Molar mass of octane \[({{C}_{8}}{{H}_{18}})=114\]
    1 g of octane gives = 48 kJ heat
    114 g of octane = 1 mol of octane gives
    \[=48\times 114\,\,kJ\]   
    = 5472 kJ/mol


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