## Concentration cells

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

N Jew 2E
Posts: 3
Joined: Wed Sep 21, 2016 2:58 pm

### Concentration cells

In the concentration cell example in the course reader (Ag+ (1.0 M) -> Ag+ (0.1 M)), why does n=1? If someone could also post a diagram of what is happening, that would be lovely.

Christina_F_3F
Posts: 21
Joined: Fri Jul 22, 2016 3:00 am

### Re: Concentration cells

n=1 because if you look at the half reactions there is 1 mol of electrons involved in the reaction.

Ag(s) --> Ag+(0.1M) + e-
e- + Ag+(1.0M) --> Ag (s)

Because there is the same number of mols of electrons in both reactions, you do not need to multiply by any coefficients. Therefore, just one mol of electrons (n=1) will suffice to make the final reaction happen. The final reaction (after canceling terms) is:

Ag+(1.0M) --> Ag+(0.1M)

In different examples where you had a different number of moles of electrons, n would be different.
Hope this helps! Let me know if anything is unclear.

LeontyneHenderson2E
Posts: 16
Joined: Wed Sep 21, 2016 2:57 pm

### Re: Concentration cells

What is a concentration cell exactly?

Megan Yabumoto 3K
Posts: 42
Joined: Fri Jul 22, 2016 3:00 am

### Re: Concentration cells

LeontyneHenderson2E wrote:What is a concentration cell exactly?

A concentration cell is a galvanic cell that has two equivalent half cells of the same composition. The only thing that is different between the two half cells is the concentration, whereas in a galvanic cell there is an anode that differs in composition from the cathode.

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