Chapter 15 Notes Oxidation number - number of electrons an element wants to gain or lose to become stable. Determining oxidation number: Ex. CaSO4 CCl4 AlPO4

Chapter 15 Notes Reduction Vs Oxidation Reduction – Called this because charge gets reduced (more negative) Gaining of electrons Oxidation - Losing of electrons becomes more positive. LEO the lion goes GER When you have a reaction in which both reduction and oxidation occur is known as a redox reaction.

Chapter 15 Notes Cathode vs Anode Cathode is where reduction occurs, builds up because metal ions gain electrons and become neutral metals (Metal plating) Anode is where oxidation occurs and the electrode will break down into ions in solution. Electrode is the part of the conductor that touches the solution An Ox Loses…Red Cats Gain

Chapter 15 Notes There are two big topics in electrochemistry: Electrolysis—in which electricity (moving electrons) causes chemical change Electrochemical Cells—in which chemical changes cause a flow of electrons (electricity). When water undergoes electrolysis (memorize how to derive these). (-) cathode: 2 H2O(l) + 2 e-  H2(g) + 2 OH- (+) anode: 2 H2O(l)  O2(g) + 4 H+ + 4 e-

Chapter 15 Notes You should be able to use a reduction potential chart to determine which of two substances are more likely to be reduced or oxidized. Pg 585 Example Calculate the Cell Potential (voltage) for ZnlZn+2llCa+2lCa

Chapter 15 Notes Draw a sample electrochemical cell