C-10-Q095mediumsingle_mcqAt the cathode of copper refining, the reaction is—aCu2++2e−→Cu\mathrm{Cu^{2+} + 2e^- \to Cu}Cu2++2e−→Cu (reduction)bCu→Cu2++2e−\mathrm{Cu \to Cu^{2+} + 2e^-}Cu→Cu2++2e−c2H2O→O2+4H++4e−\mathrm{2H_2O \to O_2 + 4H^+ + 4e^-}2H2O→O2+4Hd2Cl−→Cl2+2e−\mathrm{2Cl^- \to Cl_2 + 2e^-}2Cl−→Cl2+2e−