1. Topic: Redox Aim: What are electrochemical cells? Do Now: Which of the following ions is most easily reduced? 1)Li+ 2) K+ 3) Ca 2+ 4) Na+ HW:

2. Types of Cells

3. Electrochemical Cells Practical uses for redox reactions Involve: –Chemical rxns –Flow of e- 2 types: –Voltaic (galvanic) –Electrolytic

4. Voltaic Cell produce electricity as a result of chemical rxns These rxns are spontaneous These rxns cause the flow of e-. Therefore, electricity is produced. Parts of a voltaic cell (drawn on board)

5. Voltaic Cell

6. Parts of Voltaic Cell 1.Two Half Cells: -Each half of the redox reaction takes place in a separate container. -The 2 containers (2 half cells) are connected by a SALT BRIDGE. -Allows ions to move, but does not allow the solutions to mix! 2.Electrodes a. Anode – where oxidation occurs (LEO) An Ox b. Cathode – where reduction occurs (GER) Red Cat

7. Parts, cont. 3.Salt Bridge 4.Switch 5.Wire 6.Voltmeter 7.Solutions in Both Half Cells

8. Voltaic Cell Info ANODE is NEGATIVE CATHODE is POSITIVE (Think: they are in alphabetical order!) Electrons flow from anode to cathode b/c opposites attract (e- are negative, cathode is positive) –Also, anode is oxidation – loss of e-, cathode is reduction – gain of e- This spontaneous flow produces electricity.

9. Voltaic Cell Info When given a voltaic cell, how do you know which metal electrode is the anode and which is the cathode? The metal HIGHER ON TABLE J will be the ANODE and LOSE ELECTRONS b/c it is MORE EASILY OXIDIZED than the other metal (below it)!

10. Review Questions In the reaction: Zn  Zn 2+ + 2e - Is Zn oxidized or reduced? In the reaction: Zn + Cu 2+  Zn 2+ + Cu Which is reduced, Cu 2+, Cu, Zn 2+, or Zn? Which one has a stronger tendency to lose electrons when they are in contact with an electrolyte, Cu 2+, Cu, Zn 2+, or Zn?

11. Review Questions What is responsible for the conduction of electricity in the solution? The salt-bridge is the path for what to move?

12. Examples of Voltaic Cells Batteries –a dry cell battery is what you find in your typical electronic device. –The reason you often need more than one battery is because a single battery doesn’t provide enough volts of power. When connected in a series (end to end), the voltage is multiplied.

13. Electrolytic Cells produce chemical reactions as a result of electric current These rxns are non-spontaneous These rxns use the flow of e-. Therefore, electricity is used. Parts of an electrolytic cell (drawn on board)

14. Electrolytic Cell

15. Parts of Electrolytic Cell 1.One Cell: -Both halves of the redox reaction take place in the same container. 2.Electrodes a. Anode – where oxidation occurs (LEO) An Ox b. Cathode – where reduction occurs (GER) Red Cat

16. Parts, cont. 3.Wire 4.Battery/power source 5.Solution in Cell

17. Electrolytic Cell Info ANODE is POSITIVE CATHODE is NEGATIVE Electrons still flow from anode to cathode b/c opposites attract (e- are negative, cathode is positive) –Also, anode is oxidation – loss of e-, cathode is reduction – gain of e-

18. Electroplating