Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Second derivative of Pressure with respect to moles?

  1. Dec 1, 2009 #1
    binary mixture.
    Na=moles of a
    Nb=moles of b

    (using Peng Robinson Equation of state)

    (second order partial derivative below)

    d^2P/(dNa^2) holding T, molar volume, Nb constant

    I can't figure out how to do this?

    I know that Peng Robinson is a function of concentration of Na and Nb... but I tried to substitute all molar fractions with Na/(Na+Nb) & Nb/(Na+Nb) put the complete expression in Mathcad (was huge!) and it gives 0 as the first derivative of Na or Nb so something went wrong or it decided not to do it...

    Attached is/was my Mathcad input and also the whole equation I am trying to get an expression of (this partial derivative is just part of it; don't mind the cursor on the right)
     

    Attached Files:

  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?
Draft saved Draft deleted



Similar Discussions: Second derivative of Pressure with respect to moles?
  1. Vapor Pressure (Replies: 1)

  2. Vapour pressure (Replies: 2)

Loading...