Deriving the Nernst Equation

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Annie Chantasirivisal_4G
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Joined: Wed Sep 18, 2019 12:21 am

Deriving the Nernst Equation

Postby Annie Chantasirivisal_4G » Sun Mar 01, 2020 4:35 pm


I was practicing how to derive the Nernst Equation and got a little confused...
I know you use ΔG°= -nFE° and ΔG= ΔG°+ RTlnQ in order to obtain the Nernst equation, E = E°- (RT/nF)lnQ, however I'm stuck on the difference between the E and E° in the equation. When obtaining E°(inside), I used ΔG°= -nFE, while for the E without the naught (outside), I used ΔG= -nFE. Is this valid? Can ΔG= -nFE still be assumed true for non-standard conditions, while ΔG°= -nFE°is for standard conditions? In other words, I guess I'm just confused on the implications of the naught...

Any help would be appreciated!

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Re: Deriving the Nernst Equation

Postby sbeall_1C » Sun Mar 01, 2020 4:48 pm

Hey! I think you are correct in your thought process. You just have to make sure that is you are using standard conditions for delta G, you use standard conditions for the remaining variables and this yields the standard cell potential. I believe as long as you are consistent, you can use both delta G=-nRE, and
delta G naught=-nFE naught.

Daniel Chen 2L
Posts: 101
Joined: Fri Aug 30, 2019 12:15 am

Re: Deriving the Nernst Equation

Postby Daniel Chen 2L » Sun Mar 01, 2020 4:51 pm

If it has the naught then that means it is at standard conditions. I think you can use the equation just fine not at standard conditions, you just have to do it without the naught?

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

Re: Deriving the Nernst Equation

Postby Ruby Richter 2L » Sun Mar 01, 2020 11:19 pm

So the equation is essentially the same but without the naught at standard conditions?

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