Determining the sign of a cell potential

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Aya Shokair- Dis 2H
Posts: 58
Joined: Fri Sep 29, 2017 7:07 am

Determining the sign of a cell potential

Postby Aya Shokair- Dis 2H » Mon Feb 19, 2018 5:43 pm

In the attached pictures, the textbook is using the standard hydrogen electrode to determine the standard cell potentials of different electrodes.
How did they determine one to be positive and one to be negative?
I understand that if the cathode is on the right of the cell, then the cell potential is positive.
However, the reduction processes for both the picture occurs in the electrodes on the right of both cell diagrams.\

Why is the cell potential for one negative and the other positive?
Screen Shot 2018-02-19 at 5.39.05 PM.png
Screen Shot 2018-02-19 at 5.38.49 PM.png

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Re: Determining the sign of a cell potential

Postby Chem_Mod » Mon Feb 19, 2018 7:33 pm

All the potentials are reduction potentials. These are potentials for reduction reactions. The higher a reduction potential is for a reaction, the more favorable the reaction is as a reduction reaction. Thus, if you have two half reactions depicted as reductions, the reaction with a lower reduction potential will be the oxidation half reaction.

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