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Gibbs Free Energy for non-standard conditions

  1. Jul 8, 2015 #1
    ΔG=ΔG°+RTlnQ are for reactions that are not under standard conditions. What does it mean under non-standard conditions for the ΔG?

    And what is the Q in this case? Is it Qp where it is based on the partial pressure of the gas or Qc which is based on the concentration?

  2. jcsd
  3. Jul 8, 2015 #2


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    Standard conditions are a convention and differ for solids liquids and gasses, as well as for solutes and solvents. Also, in biological systems other standard conditions are chosen than in chemistry.
    A gas is under standard conditions when its fugacity (which is equal to its partial pressure in a good approximation for not too high pressures) is 1 bar. For a solution, standard condition of the solute is an activity of 1 mol/kg. For the solvent, the standard state is the pure solvent. For a solid, the pure solid.
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