## Nernst Equation for Concentration Cells

$E_{cell} = E_{cell}^{\circ}-\frac{RT}{nF}\ln Q$

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005290099
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### Nernst Equation for Concentration Cells

Can someone explain to me how concentration cells work? I'm having trouble understanding example 6N.3 and how the thought process works there?

Jasmine Kim 1L
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### Re: Nernst Equation for Concentration Cells

In concentrations cells, the two electrodes are the same except for their concentrations. Because the molecules are the same, the reactions on either side are the reverse reaction of the other, so Ecell will always be 0 because Ecathode and Eanode cancel out. So in the equation $E_{cell}=E^{\circ}_{cell}-\frac{RT}{nF}lnQ$, you just have to find n, the number of electrons being transferred, and Q, the concentration of the products over the reactants. Also, to make it easier, T is usually 298.15K, so RT/F = 0.025693

805312064
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### Re: Nernst Equation for Concentration Cells

E°cell is 0, Then like the person above me said, you just need to find n and Q since T is given and F and R are constants.

Jessica Li 4F
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### Re: Nernst Equation for Concentration Cells

In addition, if you want Ecell (not Enaught cell) to be positive, you would want Q to be less than 1 so that lnQ will be negative.

Hope Hyland 2D
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### Re: Nernst Equation for Concentration Cells

How do you know what n is when the half reactions have different numbers of electrons being transferred? Would you balance them and use that number?

Jasmine Kim 1L
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### Re: Nernst Equation for Concentration Cells

Hope Hyland 2D wrote:How do you know what n is when the half reactions have different numbers of electrons being transferred? Would you balance them and use that number?

Yeah, just find a common multiple for both of them and that's n
For example, if one half reaction is transferring 4 electrons and the other 2, you can multiply the latter reaction by 2 to get 4 electrons being transferred in total. For half reactions transferring 3 and 2 electrons, the total number would be 6 because that is the lowest common multiple of 3 and 2

705302428
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### Re: Nernst Equation for Concentration Cells

Yes you would balance them and use that number as your n.

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