2012 Final Q3A

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Shirley Wong 2E
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Joined: Fri Sep 25, 2015 3:00 am

2012 Final Q3A

Postby Shirley Wong 2E » Sat Mar 12, 2016 1:27 pm

In this question, we were asked to draw and label the galvanic cell of 0.0080M CrCl3 and 0.12M CuSO4 with a piece of copper wire and a chrome-plated piece of metal. How do we determine which one is the anode and cathode?

dmcclintick
Posts: 19
Joined: Wed Nov 11, 2015 3:00 am

Re: 2012 Final Q3A

Postby dmcclintick » Sat Mar 12, 2016 1:54 pm

First, figure out the half reactions. You have chromium and copper in the solid (and thus neutral) state, going to aqueous CrCl3 and CuSO4. So, the half reactions must be

Cr3+ + 3e- ----> Cr

and
Cu2+ ----> Cu

Then you look up their standard reduction potentials and you can see that the 1st is -.74 and the second is .34. The only way to add these and get a positive reaction is if the first is reversed, which means that the first would be the oxidation reaction and the second would be the reduction.


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