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JEE Main & Advanced Sample Paper JEE Main Sample Paper-20

  • question_answer
    At 300K, the vapour pressure of an ideal solution containing 3 mole of A and 2 mole of B is 600 torr. At the same temperature, if \[1.5\]mole of A and \[1.5\] mole of C (non-volatile) are added to this solution the vapour pressure of solution increases by 30 torr. What is the value of \[P_{B}^{0}\]?

    A)  940                             

    B)  405

    C)  90                  

    D)  None of these

    Correct Answer: C

    Solution :

      \[P=P_{A}^{o}{{x}_{A}}+P_{B}^{o}{{x}_{B}}\] \[600=P_{A}^{o}\left( \frac{3}{3+2} \right)+P_{B}^{o}\left( \frac{2}{2+3} \right);\,\,3P_{A}^{o}+\,2P_{B}^{o}=3000\]\[630=P_{A}^{o}\left( \frac{4.5}{4.5+2+0.5} \right)+P_{B}^{o}\left( \frac{2}{4.5+2+0.5} \right)\] \[4.5P_{A}^{o}+2P_{B}^{o}=4410\] \[1.5P_{A}^{o}=1410;\,P_{A}^{o}=940\] and \[P_{B}^{o}=90\]


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