Chapter 15 Notes

1. 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

2. 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.

3. 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

4. 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-

5. 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

6. Chapter 15 Notes • Draw a sample electrochemical cell