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Is the Helmholez or Gibbs free energy every used outside of reactions?

  1. Jul 10, 2012 #1
    I'm trying to figure out if the Helmholtz & Gibbs free energy are ever used outside of chemical reactions (I suppose they could be used in nuclear reactions in a plasma as well.) It seems to me that they are not, as I can only recall using them for chemical reactions in my thermodynamics course way back when.
  2. jcsd
  3. Jul 10, 2012 #2
    Phase transitions.
  4. Jul 10, 2012 #3
    It seems to me that in a phase transition, the Gibbs function is constant. This is so because a phase transition takes place at constant T & P, so the heat transferred Q is equal to the change in H, so

    ΔH = Q

    ΔS = Q / T = ΔH / T

    A = H - T S

    ΔA = ΔH - T ΔS = Q - T ( Q / T ) = Q - Q = 0

    Is this accurate?
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