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Ecell values

Posted: Wed Mar 11, 2020 2:32 pm
by Sarah Blake-2I
How can you tell which half reaction is being reduced or oxidized based on the Ecell value? There was a question like this on test 2 and I am confused as to how you would distinguish this based on just the standard potential value.

Re: Ecell values

Posted: Wed Mar 11, 2020 2:33 pm
by Christine Honda 2I
The higher Ecell value is usually reduced!

Re: Ecell values

Posted: Wed Mar 11, 2020 2:42 pm
by Nicholas Chin 1G
You can use the appendix to look at the E values for the two half reactions. Since the equation for Ecell is E(c) = E(cath) - E(anode), then you can determine which reaction is cathode and which one is anode.

Re: Ecell values

Posted: Wed Mar 11, 2020 2:52 pm
by Amanda Lin 2I
The one with a higher, more positive Ecell value is usually reduced while the one with a lower, more negative Ecell value is usually oxidized.

Re: Ecell values

Posted: Wed Mar 11, 2020 3:10 pm
by jisulee1C
Since most tables give the reduction potential for the half reaction, the higher (more positive) reduction potential determines the cathode which is the species that will undergo reduction.

Re: Ecell values

Posted: Wed Mar 11, 2020 3:29 pm
by Deena Doan 2F
the one that has a higher (more positive) value is usually the one that is reduced aka the cathode

Re: Ecell values

Posted: Wed Mar 11, 2020 8:17 pm
by Ryan Yee 1J
The more positive value is reduced so that when you subtract the anode's value it'll remain positive

Re: Ecell values

Posted: Sat Mar 14, 2020 12:11 am
by Simon Dionson 4I
along with the responses above, I also try to consider which assignment of the cathode or anode will result in a positive Eº cell value

Re: Ecell values

Posted: Sun Mar 15, 2020 3:40 pm
by Rafsan Rana 1A
In addition to the answers given, the reason we want to have a positive E cell is because it leads to a negative standard gibbs free energy which in turn means a positive value for entropy meaning the process is spontaneous.

Re: Ecell values

Posted: Sun Mar 15, 2020 11:52 pm
by Rhea Shah 2F
The more positive E cell value corresponds to the reaction that is reduced. This reaction occurs at the cathode.

Re: Ecell values

Posted: Mon Mar 16, 2020 12:06 am
by Diana A 2L
If you take the reverse of a reaction, does the sign of the Ecell also flip, or does it remain? For example, when constructing redox reactions from redox couples you are given, you determine which couple is at the anode and at the cathode by examining Ecell values. You set up the reaction in a way that yields a positive Ecell based on the corresponding cell potentials. Determining which redox couple is the anode and cathode also allows you to figure out what is being oxidized and what is being reduced.

Once you know which half-reaction is being oxidized, you flip it for the overall reaction (ex: Zn(2+) + 2e- ==> Zn(s) becomes Zn(s) ==> Zn(2+) + 2e) When the reaction is flipped, does the cell potential sign change too??

Re: Ecell values

Posted: Mon Mar 16, 2020 1:36 am
by Aiden Metzner 2C
The higher Ecell value is usually reduced because the E cell values are the standard values of reduction. One that produces a higher value that is reduced is more likely to be reduced in a reaction.

Re: Ecell values

Posted: Mon Mar 16, 2020 11:58 am
by Charysa Santos 4G
The more positive/less negative Ecell value is typically correlated to the cathode (reduced), and the more negative Ecell value is correlated to the anode (oxidized).