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NEET NEET SOLVED PAPER 2016 Phase-I

  • question_answer
    Which of the following statement about the composition of the vapour over an ideal a 1 : 1 molar mixture of benzene and toluene is correct?  Assume that the temperature is constant at \[\text{25}{{\,}^{\text{o}}}\text{C}\text{.}\] (Given : Vapour Pressure Data at \[\text{25}{{\,}^{\text{o}}}\text{C,}\] benzene = 12.8 kPa, Toluene = 3.85 kPa)                                              

    A)  The vapour will contain a higher percentage of benzene

    B)  The vapour will contain a higher percentage of toluene

    C)   The vapour will contain equal amounts of benezene and toluene

    D)   Not enough information is given to make a predication

    Correct Answer: A

    Solution :

                     A\[\to \] benzene, \[\to \] toluene 1 : 1 molar mixture of A and B \[\therefore \]  \[{{x}_{A}}=\frac{1}{2}\]and \[{{x}_{B}}=\frac{1}{2}\] \[P{{}_{s}}=P_{A}^{0}{{X}_{A}}+P_{B}^{0}{{X}_{B}}\] \[{{P}_{s}}=12.8\times \frac{1}{2}+3.85\times \frac{1}{2\,}=8.325\,\text{kPa}\] \[{{Y}_{A}}=\frac{P_{A}^{0}{{X}_{A}}}{{{P}_{s}}}=\frac{12.8\times \frac{1}{2}}{8.325}=0.768\] \[\therefore \] \[{{Y}_{B}}=1-{{Y}_{A}}=1-0.768=0.232\] so, the vapour will contain higher percentage of benzene.


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