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Gibbs Energy Change and Maximum Work

  1. May 3, 2013 #1
    1. The problem statement, all variables and given/known data

    I am trying to understand the implications of the principle that the maximum non-expansion work, dwadd is equal to the Gibbs energy change for a reversible process.

    2. Relevant equations

    For a reversible process, dwadd = dG.

    This is provided that the process takes place at constant pressure and temperature.

    3. The attempt at a solution

    The source of my confusion is to do with the fact that if the Gibbs energy change of a system, dG, is zero at constant temperature and pressure, then that system is at equilibrium. When a system undergoes a reversible change, it passes through a series of equilibrium states before attaining its final state. Hence, for a reversible process,

    dG = 0

    But, dG = dw add

    So that seems to imply that for any reversible process, the non-expansion work available is always zero, which doesn't seem to be true.

    Would greatly appreciate any clarifications. Thanks in advance.
  2. jcsd
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