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Posted: Thu Feb 09, 2017 11:49 pm
by Cowasjee_Sanaea_3E
14.35: determine the equilibrium constants for the following reaction:

Mn (s) + Ti^2+ (aq) --> Mn^2+ (aq) + Ti (s)

I don't understand why when you solve for the cell potential it is negative?? I thought you always make it so that the cell potential is positive, even if that means reversing the cathode versus the anode?

Re: 14.35

Posted: Fri Feb 10, 2017 12:50 pm
by Paul Adkisson 1D
The cell potential is always positive when making a battery or an electrical system that can do work. However, in some reactions, electrical work is required to drive the reaction. In these cases, Eo is negative. In this question, we are using E(cell) to determine the equilibrium constant for a reaction based on the relationship k = e^(nFEo/RT). Thus since k can change if the reaction is written forward or reverse, Eo can be positive or negative correspondingly.