Answer
$4OH^{-} (aq) → O_{2} (g) + 2H_{2}O + 4e^{-}$
This is an oxidation reaction.
Work Step by Step
First we double OH- to balance the # of Oxygen; then we add 2H+ on the right side to balance the number of H; next we add 2OH- on both side to neutralize the 2H+ that we just added.
There are 4 OH- on the left side, and 2 H2O(H+ and OH- combined) on the right side.
Finally, we add 4 e- on the right side to balance the charge.
Since e- are on the right side, it is losing e-, thus it’s an oxidation reaction.
