Determining the potential in a cell that is not at equilibrium concentrations.

[JustinLiang]

Homework Statement

I attached a picture and I am confused by Part C.
The standard potential is given Eo=1.21

Homework Equations

Ecell=Eocell-RTlnQ/nF
R=8.3145
T=298.15
F=96485
Q=activity products/ activity reactants

The Attempt at a Solution

My problem with this question is finding Q.

Fe(s) -> Fe2+(aq) + 2e-
Fe3+(aq) + e- -> Fe2+(aq)

Balanced equation (is this right?):
2Fe3+(aq) + Fe(s) -> 3Fe2+(aq)


As suggested in the problem, the [Fe2+] of both half cells are different. Thus I do not know how to set up my Q, assuming that my balanced equation is correct.

 

[Borek]

You can derive overall Nernst equation for the system starting with separate Nernst equations for each half cell. Just assume two separate potentials for each half cell initially, and combine them in the final equation - this will be the potential given as a standard one.