cell potential


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Ruiting Jia 4D
Posts: 65
Joined: Fri Sep 28, 2018 12:27 am

cell potential

Postby Ruiting Jia 4D » Sat Mar 16, 2019 10:55 pm

When choosing which half reaction to flip, do we choose the one in which plugging in Ecathode - Eanode will produce the greatest positive number? If so, how does one do that when we want to keep the sign of E values for each half reaction the same? I'm just kinda confused on which reaction we reverse and how to determine it.

Samantha Pacheco 2K
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

Re: cell potential

Postby Samantha Pacheco 2K » Sat Mar 16, 2019 11:02 pm

You reverse the half reaction that will given help produce the desired overall reaction. If you are using the Ecathode-Eanode then you do not need to flip the sign of E.
Ex our reaction is Fe3+ + Cu ---> Cu2+ + Fe2+

our half reactions are
Fe3+ + e- ---> Fe2+ E= .77V
Cu2+ + 2e- -----> Cu E= .34 V
We would flip the 2nd half reaction so that the Cu would be on the left hand side like it is in the given eqaution and we would not flip the sign of E because the eqaution accounts for it

hazelyang2E
Posts: 57
Joined: Fri Sep 28, 2018 12:23 am

Re: cell potential

Postby hazelyang2E » Sat Mar 16, 2019 11:03 pm

I believe that if you are flipping one of the half reactions you also need to reverse the sign of the reduction potentials, and then you would add the potentials together instead of subtracting them. If you are using the equation E(cathode)-E(anode) to find the cell potential, you do not reverse the signs of either of the half reactions


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