CHEMISTRY COMMUNITY

Hi!
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?

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.