How can you tell which way a reaction shifts?

Question

In electrochemistry, how can you tell which way a reaction proceeds spontaneously at standard state conditions? I believe the Gibbs free energy is required. Can someone please explain or give an example? Thanks!

Answer 1

Figure out the two half reactions and find their Eo values.

Combine the Eo values. If the answer is positive  the reaction is spontaneous; if the answer is negative  the reaction is not spontaneous.