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Delta G and delta Gr

Posted: Wed Feb 19, 2020 7:01 pm
by Julie_Reyes1B
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!

Re: Delta G and delta Gr

Posted: Wed Feb 19, 2020 9:19 pm
by CNourian2H
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.

Re: Delta G and delta Gr

Posted: Fri Feb 21, 2020 12:04 am
by 005324438
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?

Re: Delta G and delta Gr

Posted: Sat Feb 22, 2020 4:26 pm
by Dina Marchenko 2J
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.