1. Limited time only! Sign up for a free 30min personal 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!

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


    User Avatar
    Science Advisor

    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook