Electrolytic Cells

Electrolytic Cells electricity used to force non-spontaneous reactions to occur = Endothermic electrolytic cells identified by presence of battery or power supply many kinds of electrolytic cells

Galvanic Cell Chemical Potential Energy Electrical Potential Energy Electrolytic Cell

Electrolytic Decomposition of H2O H2 produced at one electrode, O2 at other 2H2O + energy 2H2 + O2 Can you tell from the picture which electrode is producing H2?

Reversing a Galvanic Cell This time: Zn is reduced & Cu is oxidized

Two kinds of electrolytic cells Fused Salt Cells – purify metals (Fused means melted!) Plating Cells – designing surface to have specific properties

Electroplating Move desired coating from anode onto object to be plated Solution contains ions of element to be plated

Electroplating: Cu onto Al Al above Cu in Table J reaction will not happen spontaneously use external energy source (power supply or battery) to force reaction to occur

An Ox ate a Red Cat Anode: electrode at which oxidation occurs Cathode: electrode at which reduction occurs Polarity electrodes different than galvanic cell! Anode is positive Cathode is negative

A POX on Electrolytic Cells Anode – Positive – Oxidation electrolytic cell, polarity determined by outside power supply anode hooked up to (+) terminal cathode hooked up to (-) terminal Look at drawings in Regents questions

(+) (-) (+) (-) Anode = Oxidation Cu  Cu+2 + 2e- Battery Cathode = Obj being Plated = Reduction Cu+2 + 2e-  Cu (-) Note: just moving Cu around Cu+2 and SO4-2

Plating Cathode = object to be plated Anode - made of metal want to plate on object Solution: contains ions of plating metal Plating

Fused Salt Cells Process used to purify metals from their ores

Schematic of fused salt cell + - + - Ox: 2Cl-  Cl2 + 2e- Red: Na+ + 1e-  Na

Why does NaCl have to be molten? Which electrode will Na+1 ions be attracted to? Which electrode will Cl-1 ions be attracted to?