Ecell values

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Sarah Blake-2I
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Ecell values

Postby Sarah Blake-2I » Wed Mar 11, 2020 2:32 pm

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.

Christine Honda 2I
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Re: Ecell values

Postby Christine Honda 2I » Wed Mar 11, 2020 2:33 pm

The higher Ecell value is usually reduced!

Nicholas Chin 1G
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Re: Ecell values

Postby Nicholas Chin 1G » Wed Mar 11, 2020 2:42 pm

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.

Amanda Lin 2I
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Joined: Sat Aug 17, 2019 12:15 am

Re: Ecell values

Postby Amanda Lin 2I » Wed Mar 11, 2020 2:52 pm

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.

jisulee1C
Posts: 149
Joined: Thu Jul 25, 2019 12:17 am

Re: Ecell values

Postby jisulee1C » Wed Mar 11, 2020 3:10 pm

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.

Deena Doan 2F
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Joined: Sat Aug 17, 2019 12:17 am

Re: Ecell values

Postby Deena Doan 2F » Wed Mar 11, 2020 3:29 pm

the one that has a higher (more positive) value is usually the one that is reduced aka the cathode

Ryan Yee 1J
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Joined: Sat Aug 17, 2019 12:16 am

Re: Ecell values

Postby Ryan Yee 1J » Wed Mar 11, 2020 8:17 pm

The more positive value is reduced so that when you subtract the anode's value it'll remain positive

Simon Dionson 4I
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Re: Ecell values

Postby Simon Dionson 4I » Sat Mar 14, 2020 12:11 am

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

Rafsan Rana 1A
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Joined: Sat Aug 24, 2019 12:16 am

Re: Ecell values

Postby Rafsan Rana 1A » Sun Mar 15, 2020 3:40 pm

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.

Rhea Shah 2F
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Joined: Thu Jul 25, 2019 12:17 am

Re: Ecell values

Postby Rhea Shah 2F » Sun Mar 15, 2020 11:52 pm

The more positive E cell value corresponds to the reaction that is reduced. This reaction occurs at the cathode.

Diana A 2L
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Re: Ecell values

Postby Diana A 2L » Mon Mar 16, 2020 12:06 am

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??

Aiden Metzner 2C
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Re: Ecell values

Postby Aiden Metzner 2C » Mon Mar 16, 2020 1:36 am

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.

Charysa Santos 4G
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Joined: Wed Sep 18, 2019 12:21 am

Re: Ecell values

Postby Charysa Santos 4G » Mon Mar 16, 2020 11:58 am

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).


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