Test #2: Question #4, Parts A and B

[Sophia Diaz - Dis 1B]

Hi everyone!

For test #2, I got both parts of #4 completely wrong. Can anyone explain to me how you are meant to solve the problem and what the answers are?

For reference, I thought that the NO3- equation was the anode and the Zn2+ was the cathode which got me an Ecell of -1.56V.
and my Cell diagram was NO3- I NO2 II Zn2+ I Zn

[Matthew Tran 1H]

I have a slightly different version of the test so I can't give you the exact answers, but where you went wrong was that you made a cell that had a negative cell potential. If you are asked to construct a galvanic cell, you have to make sure that the cell potential is positive so that it can do useful work. If you switch the anode and cathode, you should get a positive cell potential. In your cell diagram, you need to make sure that there always is a conducting solid on both sides (add Pt(s) if there isn't), have the conducting solid on the outside, aqueous closest to the salt bridge, and include everything except water in the cell diagram.

[lukezhang2C]

The balanced overall cell reaction that I got was 2N02 + 2H20 + Zn2+ --> Zn (S) + NO3- + 4H+, and I also got the cell diagram wrong. However from what I can ascertain you needed to flip No3 and Zn, and include a solid for the NO3 side.