March 30, 2015

Homework Help: Electrochemistry

Posted by Donna on Friday, May 16, 2008 at 1:00am.

In lab, we did an experiment with electrochemical cells with solutions of ZnSO4, CuSO4, Al2(SO4)3 and MgSO4 and their respective metal electrodes.

There are a couple of post-lab questions that I'm not sure about:
(1) Summarize Part A with a data table containing the headings: Anode, Cathode, Overall Cell Reaction, Cell Potential. For each of cell combination, write the anode half reaction, the cathode half reaction, the overall reaction in cell notation (all concentrations of solutions are 0.1M) and the potential in volts.

Cell Potential is the same as Voltage Potential, right?

I'm not completely sure about writing half reactions, so I wanted to post a couple of the ones I wrote and if anybody could check these over for me, that would be completely helpful:

anode: Zn(s) --> Zn^2+(aq) + 2 e-
cathode: Cu^2+(aq) + e- --> Cu(s)

anode: Mg(s)---> Mg^2+(aq) + 2 e-
cathode: Cu^2+(aq) + e- --> Cu(s)

anode: Al(s) --> Al^3+(aq) + 3 e-
cathode: Zn^2+(aq) + 2 e- --> Zn(s)

For example, for the cell combination of Cu/Zn I got a voltage potential of 0.515V. So is this the cell potential?

I'm not really clear on how to write overall reactions either. Would these be correct?

Zn(s)|Zn^2+(aq, 0.1M)||Cu^2+(aq, 0.1M)|Cu(s)

Al(s)|Al^3+(aq, 0.1M)||Zn^2+(aq, 0.1M)|Zn(s)

(2) Create a Reduction Potential Table with the cells containing copper. Assume the reduction potential for Cu^2+ + 2e- --> Cu is 0.00V and calculate the remaining reduction potentials relative to Cu^2+/Cu. List the reactions in order of decreasing reduction potential.

So...I would just compare voltages?
Cu/Zn is 0.515 V
Cu/Mg is 1.728 V
Cu/Al is 0.729 V

Does that mean I make the assumptions that Eo(V)
Zn|Zn^2+ is 0.515 V
Mg|Mg^2+ is 1.728 ?

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