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Homework Help: Measurning the partial pressure of a component of a solution in equilibrium

  1. Nov 18, 2012 #1
    1. The problem statement, all variables and given/known data
    Suppose I have two substances in a solution, each forming an equilibrium with its corresponding vapor phase, and thus having its own partial pressure. How can I measure this partial pressure of one of the components, given the pressure of each component in its pure form.

    2. Relevant equations

    3. The attempt at a solution
    Using Henry's Law and assuming ideality, I know that the partial pressure of a component in the solution equals the product of the vapor pressure in the pure form multiplied by the mole fraction of the component in the solution.

    So I ultimately need some way of measuring the mole fraction of the component in the solution. How can I do this? What apparatus might I need? I assume I have distillation columns, condensers, thermometers, etc. but exactly how do I proceed?

  2. jcsd
  3. Nov 19, 2012 #2


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    Gold Member

    Raoult's Law? (If you know their amounts present in the mixture)
  4. Nov 19, 2012 #3


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    Staff: Mentor

    You want to measure or to calculate? Because what you wrote doesn't sound clear.
  5. Nov 19, 2012 #4


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    Gold Member

    I think he stated the Raoult's Law and he stated Henry's Law. So, in order to "calculate" the vapor pressures, he requires to measure the mole fraction.

    For that purpose, different techniques can be used. If you are assuming ideality (good enough for benzene toluene mixture), fractional distillation will do.
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