Nernst Equation for Concentration Cells


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005290099
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Nernst Equation for Concentration Cells

Postby 005290099 » Fri Mar 06, 2020 5:31 am

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

Postby Jasmine Kim 1L » Fri Mar 06, 2020 7:45 am

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 , 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

Postby 805312064 » Fri Mar 06, 2020 8:21 am

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

Postby Jessica Li 4F » Fri Mar 06, 2020 9:45 am

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

Postby Hope Hyland 2D » Fri Mar 06, 2020 8:52 pm

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

Postby Jasmine Kim 1L » Sat Mar 07, 2020 10:48 am

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

Postby 705302428 » Sat Mar 07, 2020 12:14 pm

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


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