A concentration cell consists of the same redox couples at the anode and the cathode,

Question

with different

concentrations of the ions in the respective compartments. Find the unknown concentration for the following cell.

Pt(s) I Fe^3 (aq. 0.1M) , Fe^2 (aq 1M) II Fe^3 (aq ?), Fe^2 (aq 0.001M) I Pt (s) E= 0.1 V. Answer should be in M

Answer 1

if you mean tosay that the anode compartment has:

Fe+2 (1M) --> Fe+3 (0.1M)  & 1 e-

and that the cathode compartment has:

Fe+3 (?M)  & 1 e- --> Fe+2 (0.001M)

==================

then nernst:

E = Eo - (0.0592 / n) (log Q)

0.1 = 0 - (0.0592/ 1) log [0.001Fe+2] [0.1Fe+3] / [1M] [?M]

0.1 / (-0.0592) = log (0.0001 / ?M)

- 1.689 = log (0.0001 / ?M)

10^x of both sides:

0.02046 = 0.0001/ (?M)

M = 0.0001 / 0.02046

M = 4.89 e-3 Molar

your answer is 0.005 Molar

==============================

my only concern was your listing of the oxidation:

"Pt(s) I Fe^3 (aq. 0.1M) , Fe^2 (aq 1M) II " for the anode side & whether you  meant:

Pt(s) I , Fe^2 (aq 1M), Fe^3 (aq. 0.1M)  II  (which I used...),

or whether you meant:

Pt(s) I , Fe^2 (aq 0.1M), Fe^3 (aq. 1M)  II  

================

you can e-mail me from a link by clicking  on my avatar