O₃(g) + Cu(s) → Cu²⁺(aq) + O₂(g)

acidic environment

O₃(g) + 2 H⁺(aq) + 2 e^– → O₂(g) + H₂O(l)

Cu(s) → Cu²⁺(aq) + 2 e^–

sum and eliminate electrons

O₃(g) + Cu(s) + 2 H⁺(aq) → Cu²⁺(aq) + O₂(g) + H₂O(l)