1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Thermodynamics Question (Maxwell Equal Area Construct)

  1. Mar 18, 2012 #1
    1. The problem statement, all variables and given/known data

    The problem is a long one. Basically we have to use Maxwell's Equal Area Construction. "With Mathcad, find Psat and the corresponding saturation volumes at T=400K for n-hexane based on the van der Waals' equation of state. Furthermore, turn Psat into a function of temperature T, i.e., define Psat(T) and identify the temperature range within which your Psat function works. Plot Psat versus T"

    2. Relevant equations

    Work done through a hypothetical reversible path under "dome" = Work done by expanding at constant Psat across "dome"

    ∫P(V)*dV = Psat*(Vv-Vl)dV

    Equivalently, two areas enclosed by Psat and P(V) are equal; thus, the name "Maxwell's equal areas rule".

    ∫(Psat-P(V))*dV = ∫(P(V)-Psat)*dV

    The integrals are from Vl to Vm, and Vm to Vv, respectively

    3. The attempt at a solution

    So this is all done with MathCad. First I defined all the parameters for Van der Waals (what Tc, Pc, a, and b were... and eventually what the filled in Van der Waals equation was). I have a couple questions...

    Should I use Antoine Equation to find Psat? I did that already and found what Psat was at there temperature specified.

    Secondly, I think I have to use the "find" function in MathCad. I'm definitely doing something wrong. I defined the second integral in the given equations and use a Bullian equal sign. I set up a matrix where each solution was a row, and then did find(Vv, Vl) to no avail.

    Can someone please shed some light?
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?



Similar Discussions: Thermodynamics Question (Maxwell Equal Area Construct)
Loading...