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Mole fraction

  1. Dec 19, 2004 #1
    does anyone know how to do this problem?
    The total vapor pressure above a solution of [tex]C_6H_6(l)[/tex] and [tex]C_7H_8(l)[/tex] is 0.485 atm. What is the mole fraction of [tex]C_6H_6(l)[/tex] in the liquid solution?
    [tex]P^o C6H6(l) = 0.526 atm[/tex]
    [tex]P^o C7H8(l) = 0.188 atm[/tex]

    the answer is 0.879 but i'm not sure how to get that using the formula [tex]P_A = (X_A)(P^o _A)[/tex]
    Last edited: Dec 19, 2004
  2. jcsd
  3. Dec 19, 2004 #2


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    It's a direct substitution problem.

    [tex]P_{tot} = P_A + P_B = (X_A)(P^o _A) + (X_B)(P^o _B) = (X_A)(P^o _A) + (1-X_A)(P^o _B)[/tex]

    Now just plug in the given numbers and solve for [itex]X_A [/itex]
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