swapping signs of E values

$\Delta G^{\circ} = -nFE_{cell}^{\circ}$

Miranda 1J
Posts: 51
Joined: Fri Sep 29, 2017 7:06 am

swapping signs of E values

When we are trying to find the Ecell how do we know which one of the two equations we swap the sign of?

Cooper1C
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

Re: swapping signs of E values

If you use the formula $E_{cell}^{\circ} = E_{cathode}^{\circ} - E_{anode}^{\circ}$ you do not need to change the sign of $E^{\circ}$ for either half reaction because the minus sign does it for you.

Diego Zavala 2I
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Re: swapping signs of E values

You can also use the equation $E=E_{oxidation}+E_{reduction}$

Rachel Formaker 1E
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Re: swapping signs of E values

I think Dr. Lavelle prefers that we use:
Eocell = Eocathode - Eoanode
so that we don't have to switch the sign of either standard reduction potential

sahiltelang-Discussion 1J
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Re: swapping signs of E values

The main thing you have to remember when you use the Cathode-Anode equation is that both the Enaught values that you use have to be reduction half reaction potential values.

Jennie Fox 1D
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Joined: Sat Jul 22, 2017 3:01 am

Re: swapping signs of E values

I use Eo(cell) = Eo(cathode) - Eo(anode) so that way I do not need to flip any signs.

Ridhi Ravichandran 1E
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Joined: Sat Jul 22, 2017 3:01 am

Re: swapping signs of E values

You usually swap the sign of the equation that needs to be oxidized. Since the back of the book only lists reduction potentials, and a redox reaction has both reduction and oxidation half reactions, we need to flip one of the equations to turn it into an oxidation. Turning a half reaction from a reduction to an oxidation basically means you are reversing the equation, in which case you need to change the sign of E naught.

Shane Simon 2K
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Joined: Fri Sep 29, 2017 7:05 am

Re: swapping signs of E values

Yeah I also do what Ridhi does which is flipping the sign of the oxidation reaction since the appendix contains the reduction potentials. Either way works though, it all just depends on what way works best for you.

Abby Ellstrom 1I
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Joined: Fri Sep 29, 2017 7:04 am

Re: swapping signs of E values

You swipe the sign on the anode by using the equation Ecell=Ecathode-Eanode