Units G=-nFE


Moderators: Chem_Mod, Chem_Admin

805312064
Posts: 50
Joined: Thu Jul 11, 2019 12:16 am

Units G=-nFE

Postby 805312064 » Fri Mar 06, 2020 8:17 am

I'm not sure if this is common sense, but if the units for F are coulombs and the units for E are volts, how do we get joules for G?

Jessica Li 4F
Posts: 115
Joined: Fri Aug 09, 2019 12:16 am

Re: Units G=-nFE

Postby Jessica Li 4F » Fri Mar 06, 2020 9:44 am

The units cancel out because volts, coulombs, and joules are all interrelated -- one joule is equal to one volt times one coulomb.

Rodrigo2J
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

Re: Units G=-nFE

Postby Rodrigo2J » Fri Mar 06, 2020 10:32 am

The units of Volts are actually equivalent to Joules/Coulomb. So, if you work out the math, the units should all cancel and you will get Joules.

Zaynab Hashm 2I
Posts: 110
Joined: Wed Sep 11, 2019 12:15 am
Been upvoted: 1 time

Re: Units G=-nFE

Postby Zaynab Hashm 2I » Fri Mar 06, 2020 1:01 pm

1 Volt = 1 J/C so the units cancel out when you multiply;

substituting the units in for -nFE, you get
-(mol)x(C/mol)x(V=J/C), and you’re left with J for G

Nathan Nakaguchi 1G
Posts: 102
Joined: Wed Sep 18, 2019 12:22 am
Been upvoted: 1 time

Re: Units G=-nFE

Postby Nathan Nakaguchi 1G » Fri Mar 06, 2020 3:15 pm

Volts = Joules/Coulomb so in deltaG=-nFE the Coulombs cancel out from the multiplication between E (J/C) and F (C/mol), and n has no units so the final units will be J/mol.

Betania Hernandez 2E
Posts: 107
Joined: Fri Aug 02, 2019 12:15 am

Re: Units G=-nFE

Postby Betania Hernandez 2E » Fri Mar 06, 2020 8:31 pm

F is also Coulombs/mol and Volts is Joules/Coulomb. When multiplied together, the units cancel out leaving Joules for deltaG

Diana Chavez-Carrillo 2L
Posts: 122
Joined: Fri Sep 28, 2018 12:18 am

Re: Units G=-nFE

Postby Diana Chavez-Carrillo 2L » Fri Mar 06, 2020 9:10 pm

Zaynab Hashm 2I wrote:1 Volt = 1 J/C so the units cancel out when you multiply;

substituting the units in for -nFE, you get
-(mol)x(C/mol)x(V=J/C), and you’re left with J for G


Does n have units? I have seen some TAs and UAs write mole of e- when plugging in the numbers into n in that equation. But I have also heard that n does not have units and that is why we end up with J/mol as our final units for delta G. Could someone clarify this for me, please?


Return to “Work, Gibbs Free Energy, Cell (Redox) Potentials”

Who is online

Users browsing this forum: No registered users and 1 guest