Final answer:
In hydrogen peroxide (H2O2), oxygen has an oxidation state of -1, and in potassium superoxide (KO2), oxygen has an oxidation state of -1/2.
Step-by-step explanation:
The oxidation state of oxygen in H2O2 (hydrogen peroxide) is -1. This is because each hydrogen atom has an oxidation number of +1, and the sum of the oxidation numbers must equal zero for a neutral compound. Therefore, each oxygen atom in H2O2 has an oxidation number of -1 to balance the 2(+1) from the hydrogen atoms.
As for KO2 (potassium superoxide), oxygen has an oxidation state of -1/2. KO2 is a superoxide, which is a special case where the oxygen molecule (O2) gains one extra electron, leading to each oxygen atom having a -1/2 oxidation state to account for the single extra electron over the O2 unit. This results in the potassium ion (K+) balancing with an oxidation number of +1.