1. Electrochemistry f

2. I. Electrochemistry:
a) Definition: the branch of chemistry dealing with electricity and redox reactions

3. b) Types of Cells
a) Electrochemical (Voltaic) Cell – the type of cell where a separated redox reaction gives you electricity (spontaneous Redox  Electricity)
Voltaic = Battery
b) Electrolytic Cell – the type of cell where electricity is used to cause a redox reaction to occur. (Electricity  Redox)

5. Electrochemical Cell Identifying The Parts Of A Voltaic Cell Electrode

6. Identifying The Parts Of A Voltaic Cell
Identifying the Anode and Cathode
Go to Table J- the element that is most reactive is the anode and the other is the cathode
Zn = anode Cu = cathode
2. Writing the reaction that occurs at each cell. (An Ox Red Cat)
Anode is oxidation – Metal  Ion
Zn  Zn+2 + 2e
Cathode is reduction - Ion in solution  Atom
Cu+2 + 2e  Cu

7. Identifying The Parts Of A Voltaic Cell
Showing the flow of electricity
Anode  Cathode
Zn Cu
Finding the charge of each electrode
Anode = Negative(-)
Cathode = Positive (+)
Purpose of the salt bridge
Keeps a balance of charge by allowing the migration of ions and completes the circuit

8. Electrochemical Cell Working

9. Using The Cell Below Answer The Following Questions
1. Which is the cathode and anode ?
Mg = anode and Ag = cathode
2. What is the direction of the electron flow?
Mg  Ag
3. What is the reaction that occurs at the anode?
Mg Mg+2 +2e (An Ox Red Cat)

10. Using The Cell Below to Answer The Following Questions
Which electrode is the anode ? Mg
What is the direction of the electron flow?
Mg  Zn
What is the reaction that occurs at the Cathode?
Zn+2 + 2e  Zn

11. Summary of Electrochemical (Voltaic) Cell

12. Summary of Electrochemical (Voltaic) Cells
Redox Electricity
Anode the most reactive metal (see Table J)
Reactions that occur (An ox Red cat)
Anode = Oxidation (-)(loses weight)
Metal  Ion
Cathode = Reduction (+) (gains weight)
Ion  Metal
Electrons flow from anode to cathode
Salt Bridge permits the migration of ions to keep a balance of charge

13. Tell Me Everything You Know About The Cell Below

14. Possible Answers Pb anode; Cu cathode Electrons flow from Pb to Cu
Salt Bridge allows ions to migrate
Pb - electrode ; Cu + electrode
Reaction at the anode: Pb  Pb+2 +2e
Reaction at the cathode:Cu+2 + 2e  Cu
Pb loses weight and Cu gains weight
Remember : An Ox Red Cat: Metal  (+) ion
& (+) ion to Metal

15. Electrolytic Cell Electrodes
Electricity causes a reaction to take place
Electrodes

16. What happens in the Electrolytic Cell ?
An Ox Red Cat
Anode= (+) positive electrode
Silver (Ag):
Ag  Ag+ + 1e
Cathode= (-) negative electrode
Key
(+) Ion is attracted to the key Atom plates the key
Ag+ + 1e  Ag0 _ +

17. Answer the following What is the cathode ?
Spoon - because its is negative
What is the anode ?
Ni (because its positive)
What reaction occurs at the cathode? Red Cat
Ni+2 + 2e Ni (plating)

19. Comparison of Two Cells
Electrochemical (Voltaic)
Electrolytic (plating)
Electrons flow from anode to cathode
Redox Reaction Electricity
Electricity Redox Reaction
+ Electrode Cathode
- Electrode Anode
- Electrode Cathode
+ Electrode Anode
An Ox Red Cat (plating is reduction and it occurs at the cathode) Ag+ Ag
An Ox Red Cat
Atom + ion & Ion  atom

20. How Does Electrolysis (Electrolytic cell) Work ?
Electrolysis – using electricity to change a compound into its element.
Negative Ion migrates to the positive electrode (anode) and is oxidized to its atom
Cl-  Cl0 + 1e
Positive Ion migrates to the (– ) electrode (cathode) and is reduced to its atom
K+ +1e K - +

21. Answer the following
What takes place at the negative electrode during electrolysis ?
Special note: during electrolysis Ions  Atoms
1. - ion migrates to the – electrode and is reduced
2. + ion migrates to the – electrode and is oxidized
3. + ion migrates to the – electrode and is reduced
4. – ion migrates to the – electrode and is oxidized
Why ?
Opposites attract and +  0 is reduction

22. Try one more:
What takes place at the positive electrode during electrolysis ?
1. - ion migrates to the + electrode and is reduced
2. + ion migrates to the + electrode and is oxidized
3. + ion migrates to the + electrode and is reduced
4. – ion migrates to the + electrode and is oxidized
Why ?
- ion is attracted to the positive electrode and becomes the atom( – to 0 is up = oxidized)

23. Applications of Electrochemical Cells
Batteries
Primary Cells
"dry" cell & alkaline cell 1.5 v/cell
mercury cell v/cell
fuel cell 1.23v/cell
Secondary Cells
lead-acid (automobile battery) 2 v/cell
NiCad v/cell

24. Applications of Electrochemical Cells
Batteries
device that converts chemical energy to electricity
Primary Cells
non-reversible electrochemical cell
non-rechargeable cell
Secondary Cells
reversible electrochemical cell
rechargeable cell

25. “Dry” Cell

26. “Dry” Cell

27. “Flash Light” Batteries
"Dry" Cell
Zn(s) MnO2(s) NH >
Zn+2(aq) MnO(OH)(s) NH3
Alkaline Cell
Zn(s) MnO2(s) ---> ZnO(s) + Mn2O3(s)

28. Lead-Acid (Automobile Battery)

29. Nickel-Cadmium (Ni-Cad)
Cd(s) Ni(OH)3(s) = Cd(OH)2(s) Ni(OH)2(s)
NiCad v/cell