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NEET Sample Paper NEET Sample Test Paper-44

  • question_answer
    If two substances A and B have \[{{\operatorname{P}}^{o}}_{A} : {{P}^{o}}_{B}\]and have mole fraction in solution 1 : 2, then mole fraction of A in vapours is:

    A) 0.33                             

    B) 0.25     

    C) 0.52                             

    D) 0.2

    Correct Answer: D

    Solution :

    0.2 \[\operatorname{In} a solution if {{x}_{A}}^{o} = x~~, {{X}_{B}} = 2x\] \[\operatorname{and}\,\,it {{P}_{A}}^{o}=p, {{P}_{B}}^{o}=2p\] \[\therefore  pA = x \times  p\] \[\operatorname{pB}=2x\times 2p=4xp\] \[\therefore p=pA+pB\] \[= xp + 4xp = 5xp\] Mole fraction in vapour phase, \[{{\operatorname{y}}_{A}}=\frac{pA}{{{p}_{total}}}\] \[=\frac{xp}{5xp}=\frac{1}{5}=0.2\]


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