# Redox equations

1. Aug 22, 2007

### big man

1. The problem statement, all variables and given/known data
Write the half equation for the cathodic reaction of oxygen

3. The attempt at a solution
Now I know that the cathodic reaction will be reduction and so the oxygen will be gaining electrons. I thought I had the answer from the lecture notes, but then I thought of another possible equation that would work too and I don't know which one is right??

The two equations are as follows:
equation from notes( the notes say that this is the most common)
$$O_2 + 2H_2O + 4e^- ->4OH^-$$

the equation I came up with
$$O_2 + 4H^+ + 4e^- ->2H_2O$$

Are these just two possible half equations for the cathodic reaction of oxygen or is one wrong??