Delta G and delta Gr


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Julie_Reyes1B
Posts: 105
Joined: Sat Jul 20, 2019 12:16 am

Delta G and delta Gr

Postby Julie_Reyes1B » Wed Feb 19, 2020 7:01 pm

Hi!
Just wondering the difference in the two equations listed in the book for Gibbs free energy:
ΔG=-nFEcell
ΔGr=-nrFEcell
They look very similar but the book states the second is in "molar form", so that the units are KJ/mol. Not really sure what this means or when to use one instead of the other. Thank you!

CNourian2H
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

Re: Delta G and delta Gr

Postby CNourian2H » Wed Feb 19, 2020 9:19 pm

when do we know when to write delta G r (with r as the subscript)? I see both but never understand when to write what when calculating it.

005324438
Posts: 51
Joined: Sat Aug 24, 2019 12:16 am

Re: Delta G and delta Gr

Postby 005324438 » Fri Feb 21, 2020 12:04 am

If the book says its in molar form, then I'm pretty sure we would take deltaG and divide it by the number of electrons being transferred in the reaction. This would turn the energy from KJ into KJ/mol, however I'm not sure, could someone confirm?

Dina Marchenko 2J
Posts: 54
Joined: Thu Jul 25, 2019 12:16 am

Re: Delta G and delta Gr

Postby Dina Marchenko 2J » Sat Feb 22, 2020 4:26 pm

I believe the subscript r just stands for reaction, so if you're using r then you're accounting for the stoichiometric coefficients (ie moles) within the reaction. I don't think that you need to worry much about which of the two equations to pick, I think the r is more symbolic and reminding you what to account for.


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