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### Identifying Which Half-Reaction to Reverse

Posted: Fri Jan 29, 2016 2:07 pm
In lecture today, Professor Lavelle said that you reverse the half-reaction that, after you reverse, will cause you to get a positive value of voltage. So, does this mean the voltage always has to end up as a positive value?

### Re: Identifying Which Half-Reaction to Reverse

Posted: Fri Jan 29, 2016 2:37 pm
In these problems you want to get a positive voltage. From lecture today, Lavelle mentioned that if there is a negative voltage, then the reaction is not favorable.

### Re: Identifying Which Half-Reaction to Reverse

Posted: Sun Jan 31, 2016 12:10 am
I think that statement mainly applies to the redox reactions having to do with batteries, since batteries never have a negative voltage. However, in the example on page 52 in the course reader, the $E^{\circ}$ is -0.54 V, showing that negative cell potentials are possible in certain cases.

### Re: Identifying Which Half-Reaction to Reverse

Posted: Sun Jan 31, 2016 1:46 pm
Of course a negative net voltage is possible for a galvanic cell, it simply means so many volts of electricity need to be put into the system in order to have the reaction proceed in the set direction.