# Which species are oxidized and reduced when sufficient voltage is applied?

For example, you have two salts in a solution. Say one of the species half reaction requires 1V (standard electrode potential), and another requires 3V, and you have a current running through the solution at 4v.

Here are the possibilities I thought of, I don't know which or if any, are right:

1. Both species react simultaneously at the same rate.
2. Both species react simultaneously, but the one that requires 1V reacts faster.
3. The species that requires 1V reacts first, and once it is completely reacted, the species that requires 3V reacts after.

Am I completely off or what is the right answer?