## changing sign of of standard cell potentials

Ishan Saha 1L
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

### changing sign of of standard cell potentials

Are we allowed to change the sign (as in multiply by -1) of the standard cell potentials of the half reactions if we are looking for the standard cell potential of the reverse half reaction? I had thought that this was not possible because reversing a reduction half reaction makes it an oxidation reaction since the e- would be on the products side.

Chem_Mod
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### Re: changing sign of of standard cell potentials

Technically, you can flip a reaction and change the $\Delta G$ by multiplying it by negative 1, as you said. Thus, by using the equation of $\Delta G = - nFE^{o}$, you can see that the standard cell potentials for reactions and their reverse counterparts are equal and opposite.

Anna Okabe
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

### Re: changing sign of of standard cell potentials

Yes, because the reverse half reaction of the reduction reaction that you are looking for is the oxidation reaction. Therefore you want the e- to be on the opposite side.

andrewr2H
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

### Re: changing sign of of standard cell potentials

Yes you can flip the reaction and the sign of Eo, but if in the case you are determining cell potentials and you happen to be using the equation Ecell = Ecathode - Eanode, you would just keep the signs of the E cathode and E anode as given because the negative sign in the equation accounts for the sign flip.

905022356
Posts: 48
Joined: Mon Oct 02, 2017 7:19 am

### Re: changing sign of of standard cell potentials

So, if we are using the reduction electrode potentials, we do not change the sign when we imput the voltages into the equation?