# Why does ozone reduce to oxygen?

The O's in ozone and in dioxygen all have oxidation states of 0. If this is the case, why is ozone considered to be reduced to form dioxygen (since there's no change in oxidation state)?

Would the half reaction for this reduction be $\ce{2 O3 -> 3 O2}$ ? Since there's no transfer of electrons, how would we combine this with an oxidation half reaction to cancel out the electrons transferred in the oxidation half?

• Ozone is not considered to be reduced to form dioxygen like $\ce{2 O3 -> 3 O2}$. As you correctly pointed out, there's neither transfer of electrons, nor a change in oxidation state, so this can't be and isn't considered a redox reaction. On the other hand, there is a good deal of true redox reactions where ozone attacks something and leaves $\ce{O2}$ as a byproduct, but that's another story. – Ivan Neretin Dec 7 '15 at 7:25