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CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2011

  • question_answer
    The enthalpy of vaporization of benzene is +35.3 kJ/mol at its boiling point, \[{{80}^{o}}C\]. The entropy change in the transition of vapour to liquid at its boiling point is

    A)  - 100                                    

    B)  + 100

    C)  + 342                                   

    D)  ? 342

    Correct Answer: A

    Solution :

    \[\Delta H=+35.3\,kJ/mol\] \[T={{80}^{o}}C=80+273=353\,K\] \[\Delta S=\frac{\Delta H}{T}=\frac{+\,35.3}{353}=0.1\,kJ/mol/K\] \[\Delta S=0.1\times {{10}^{3}}=100\,J/mol/K\] Entropy change in the transition of vapour to liquid is negative, \[\Delta S=-100\].


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