# So I'm about to tear my hair out

1. Dec 9, 2003

### Maxwell

So far I have done 14 out of 15 questions on the LAST problem set of the semester.

I am stuck on one question, and no matter what I try, it wont accept my answer (the problem set is electronic).

Here is the problem:

"A galvanic cell consists of a Pt cathode inmmersed in a solution containing Fe2+ at 2.15 M and Fe3+ at unknown concentration, as well as a Cu anode immersed in a 2.30 M solution of Cu2+. The cell voltage is 0.09 V. What is the concentration of Fe3+ ions? Enter your answer in M."

Since I tried the problem so many times, the computer gave me a hint:

"Hint: The platinum is acting as the cathode, and the copper is acting as the anode in this cell. Calculate the Eo for this cell, and given the actual emf, work backwards with the Nernst equation to calculate concentrations. Don't forget to count the number of electrons being transferred."

Anytime I ask someone in my class how they did it, I get a generic answer like "my friend did it".

Thank you..

2. Dec 9, 2003

### GCT

First write the correct balanced equation. It is important that your equation is correct. Remember that you need to arrange the half cell reactions so that the differences in the half cell potential is of a positive magnitude. I am sure you know how to do the rest. It is most likely that you did not write out the correct balanced equation or in dealing with Q.

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General Chemistry Homework
http://groups.msn.com/GeneralChemistryHomework

3. Dec 9, 2003

### Maxwell

Maybe you are right, let me give it a few more tries.. Thanks for your help!

I will post my results as soon as i get them. Thanks again.

4. Dec 9, 2003

### Maxwell

I got 5.8892383931813e-6.

The computer is not accepting it for some reason?

5. Dec 9, 2003

### Maxwell

Nevermind! I got it, the stupid computer was expecting sig figs, and it wouldn't accept anything close.

Thanks again.