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Homework Help: What is Maxwell's Principle (Thermodynamics)?

  1. Dec 19, 2011 #1
    1. The problem statement, all variables and given/known data

    I'm trying to calculate the saturation pressure and the densities of a liquid and vapor using an equation of state. I figured out how to do it and know how to proceed except that I don't understand Maxwell's Principle which is stated in number 2 below.

    2. Relevant equations

    ∫P.dV - Psat (Vg - Vl) = 0
    integration limits of the ∫P.dV are from Vl to Vg

    Where P is the pressure,
    Psat is the saturation pressure,
    Vg is the gas volume,
    Vl is the liquid volume

    3. The attempt at a solution

    I don't understand how principle is derived. The only equation which comes to mind that relates Pressure and Saturation Pressure is Raoult's Law which is y*P=x*Psat (y is the gas mole fraction and x is the liquid mole fraction).

    I would also appreciate it if I can be guided to some references which explains this prinicple, the book lacks this principle.
  2. jcsd
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