Free Energy and Chemical Energy

[MedGrl@2022]

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I am currently learning about Free Energy and Chemical Energy and the equation (change in)G=(change in)Gº+RTln(Q) where Q is the reaction quotient and Q=[Products]/[Reactants]. I understand that (change in)Gº is for standard conditions and (change in)G. Examkrackers states that standard conditions could be at any temperature with a 1 molar concentration. However, it stated that "Notice that if we use only one molar concentrations for Q, then Q=1, and RTln(Q)=0, leaving us with (change in)G=(change in)Gº."

How does having a 1 molar concentration of anything mean that Q=1? Doesn't the reaction need to be in equilibrium in order for Q=K? Perhaps, I am really confused...

Also, if we are at equilibrium why does only (change in)G=0 and not (change in)Gº?

Thank you for helping me sort this out. 🙂

 

[sdm33]

Standard-state conditions
The partial pressures of any gases involved in the reaction is 0.1 MPa.
The concentrations of all aqueous solutions are 1 M.
Standard-state thermodynamic data are generally for a temperature of 25C (298 K)
Under standard Conditions (change in)G=(change in)Gº+RTln(Q) where Q is the reaction quotient and Q=[Products]/[Reactants] = 1/1 = Ln 1 = 0 , therefore change G = Change G0
EQUILIBRIUM: G = 0 (Keq = 1)

 

[MedGrl@2022]

Standard-state conditions
The partial pressures of any gases involved in the reaction is 0.1 MPa.
The concentrations of all aqueous solutions are 1 M.
Standard-state thermodynamic data are generally for a temperature of 25C (298 K)
Under standard Conditions (change in)G=(change in)Gº+RTln(Q) where Q is the reaction quotient and Q=[Products]/[Reactants] = 1/1 = Ln 1 = 0 , therefore change G = Change G0
EQUILIBRIUM: G = 0 (Keq = 1)

I am still having some difficulties understanding the difference between (change in)Gº and (change in)G. I know that (change in)Gº is for standard state conditions and (change in)G is for non-standard state conditions. But, why doesn't (change in)Gº=0 at equilibrium conditions? Why is it that ONLY (change in)G=0? I know that (change in)G=(change in)Gº+RTln(Q) but I do not understand it. Why does (change in)Gº=-RTln(K) at equilibrium and not 0?

Thank you for all your help. Let me know if there any good resources that I should check out to better understand this topic.

Thank you once again! 🙂