General Guidelines for Writing Half Reactions

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General Guidelines for Writing Half Reactions

Postby Junghyuk_Park_1I » Thu Feb 09, 2017 1:00 am

What exactly are the general guidelines for writing the half reactions to determine E (standard) of the cell? Also, why is the half reaction method recommended over the use of the equation E (standard) cell= E (standard) cathode- E (standard) anode? Thanks in advance!

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Joined: Wed Sep 21, 2016 2:58 pm

Re: General Guidelines for Writing Half Reactions

Postby NinaSheridan » Thu Feb 09, 2017 3:10 am

As I understand it, you split up the equation into the oxidation reaction and the reduction reaction. First, put them in their reduction form because E(standard) values are given for reduction reactions. Then, depending on which reaction is actually an oxidation reaction in the equation (you can find this from looking at the charges of the reactants and products or finding whatever reaction has a lower E(standard) value), flip the sign for the voltage of that reaction and now you simply add the two to get the E(standard) of the cell.

As to why its easier than the cathode - anode method, I'm not exactly sure. My TA preferred the half reaction method and I've been using it for the homework and it has actually increased my understanding of a couple concepts. If someone else could provide some clarity on that though, that would be greatly appreciated!

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