87.12 Basic principal and application of electrolysis 1. Cathode reaction: discharge potential For liberation of metal, the overpotential is usually very low, and the reversible potential can be used in stead of irreversible potential 0.799V For evolution of gas, the overpotential is relatively large, PeAg*/Ag therefore, the overpotential should be taken into consideration 0.337V pe Cu2+/Cu Ag, Cu, H, and Pbzt will liberates at 0. 799 V;0.337 V: 0.000 0.000 V;-0126 V, respectively without consideration of P H*/H overpotential -0.126 Overpotential of hydrogen liberation on Cu is 0.6 V, on Pb P Pb+/pb is 1.56VFor evolution of gas, the overpotential is relatively large, therefore, the overpotential should be taken into consideration. Ag+ , Cu2+ , H+ , and Pb2+ will liberates at 0.799 V; 0.337 V; 0.000 V; -0.126 V, respectively without consideration of overpotential; Overpotential of hydrogen liberation on Cu is 0.6 V, on Pb is 1.56 V 0.337 V ⊖ Cu2+/Cu -0.126 ⊖ Pb2+/Pb 0.799 V ⊖ Ag+ /Ag 0.000 ⊖ H+ /H2 For liberation of metal, the overpotential is usually very low, and the reversible potential can be used in stead of irreversible potential. 1. Cathode reaction: discharge potential §7.12 Basic principal and application of electrolysis