Oxidation states of copper and redox behavior of H2O2

Steps:

• Calculate oxidation state in red oxide Cu₂O: O is -2, so 2Cu = +2, Cu = +1.
• Calculate oxidation state in black oxide CuO: O is -2, so Cu = +2.
• Compare: CuO has higher oxidation state (+2 > +1) than Cu₂O.
• Analyze H₂O₂ decomposition: 2H₂O₂ → 2H₂O + O₂; O in H₂O₂ (-1) reduces to -2 in H₂O, so H₂O₂ is reduced when forming water.

Why A is correct:

• Cu in CuO has higher oxidation state (+2) than in Cu₂O (+1), and H₂O₂'s oxygen reduces from -1 to -2 in H₂O per redox definition.

Why the others are wrong:

• B: H₂O₂ is reduced, not oxidised, in forming water.
• C: Cu oxidation state is higher, not lower, in black oxide.
• D: Cu oxidation state is higher, not lower, and H₂O₂ is reduced, not oxidised.

Final answer: A