Identifying cathode & anode in electrolytic cells

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Ashley Wang 4G
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Joined: Wed Sep 11, 2019 12:16 am

Identifying cathode & anode in electrolytic cells

Postby Ashley Wang 4G » Sun Mar 01, 2020 10:02 pm

Hi,

As I understand it, when identifying the cathode and anode in electrolytic cells, we would still take the cathode to be the electrode where reduction would naturally occur (more positive reduction potential), and anode where oxidation would occur, regardless of which way the electron actually flows when an external power supply is added. Can someone confirm whether my understanding is correct?

So by the same idea, Ecell would still be E(cathode) - E(anode) of the naturally preferred reduction and oxidation sites, and not the electrode which actually gains & loses electrons when external potential is supplied, correct?

Thank you so much!

JonathanS 1H
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

Re: Identifying cathode & anode in electrolytic cells

Postby JonathanS 1H » Sun Mar 01, 2020 10:10 pm

Yes I believe your understanding is correct. When calculating Eo of a cell, we use the natural Eo of reduction values for Eocell = EoR - EoL. This applies even when the cell is unfavorable but you add a current to cause a redox reaction. Reduction always occurs at the cathode and oxidation always occurs at the anode.

Vinita Saxena 2I
Posts: 58
Joined: Fri Aug 09, 2019 12:16 am

Re: Identifying cathode & anode in electrolytic cells

Postby Vinita Saxena 2I » Sun Mar 01, 2020 10:25 pm

Yup, cathode is reduced and anode is oxidized!

Prasanna Padmanabham 4I
Posts: 111
Joined: Thu Jul 25, 2019 12:17 am

Re: Identifying cathode & anode in electrolytic cells

Postby Prasanna Padmanabham 4I » Sun Mar 01, 2020 10:27 pm

Vinita Saxena 2I wrote:Yup, cathode is reduced and anode is oxidized!


My TA taught us an easy way to remember this: "an ox" for anode is oxidized and a "red cat" for reduction happens at the cathode.

Gerald Bernal1I
Posts: 102
Joined: Thu Jul 11, 2019 12:16 am

Re: Identifying cathode & anode in electrolytic cells

Postby Gerald Bernal1I » Sun Mar 01, 2020 10:51 pm

For electrolytic cells, the cathode is still the reaction getting reduced and the anode is the reaction being oxidized. You would still use the reduction cell potentials given but you will notice that when you calculate Ecell= E cathode -E anode you get a negative cell potential which further emphasizes that it is an electrolytic cell. The cell will still flow like a galvanic from anode to cathode and the reduction still corresponds to the cathode and the oxidation to the anode. However, the electric current supply used to drive the reaction must be greater than the cell potential.


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