1. Application of
Electrolytic Cells
Lesson 11

3. Electrolysis describes what happens in an electrolytic cell and
means to use electricity to make chemicals.
Many elements are made by electrolysis
Pb Al Zn Na K Li H2 Cl2 F2
I2 O2
Pb e- → Pb(s)
2Cl- → Cl2(g) + 2e-
This is sometimes called electrowinning- the element is won from its ion

4. Making Aluminum by Electrolysis
Alcan (70,000 employees in 55 countries)
Kitimat B.C MT 7 % world production

5. Aluminum

6. Aluminum Production by Electrolysis
Name of the Ore imported from (Guinea and Brazil)
Bauxite
Al2O3.3H2O
Heating drives off the water
Al2O3.3H2O + Heat → Al2O3 + 3H2O
Melting point of Bauxite is C
This is too hot!
Cryolite is added
Lowers the melting point to C

7. Reduction of water
You cannot reduce
Aluminum in water!
It must be molten!

8. Liquid Al floats to the top and is removed
DC Power
Oxygen gas C C -
Reduction
Cathode
Al3+ + 3e- → Al(s) +
Oxidation
Anode
O2- → 1/2O2(g) + 2e-
Al3+
O2-
Al2O3(l)
Cation Cathode Reduction
Anion Anode Oxidation

9. Electroplating e- - Reduction Au Cathode Au+ + e- → Au(s) + Au+
Au plating a Cu penny
Electroplating is the process of reducing a metal on to the surface of another
Electrolyte: Must contain the ion of the metal that plates
Cathode: The metal to be covered with a new metal
Anode: Metal to be plated on top the other metal
DC Power e- -
Reduction
Cathode
Au+ + e- → Au(s) Au +
Oxidation
Anode
Au(s) → Au e-
Au+
CN- Cu Cu

10. +ve
-ve
stainless steel or Au
AuCN

13. Au plated

14. Copper Ring
Gold Plated

15. Tanya’s Ring Gold Plated

16. Electroplating e- - Reduction Ag Cathode Ag+ + e- → Ag(s) + Ag+
Ag plating a Loonie
DC Power e- -
Reduction
Cathode
Ag+ + e- → Ag(s) Ag +
Oxidation
Anode
Ag(s) → Ag e-
Ag+
NO3- $1 $1

17. Electrorefinning Lead
Trail, B.C.
Teck 16 mines in BC
Major World Producer of Zn, Cu, Pb, and Coal

18. Lead Refinery-Trail

19. The Electrorefinning of Lead
Electrorefining is the process of purifying a metal by electrolysis.
The electrolyte must contain Pb
Impure metal is oxidized at the anode and pure metal is reduced at the cathode.
This is the same as electroplating.
DC Power
Cathode: Pure Pb
Anode: Impure Pb -
Reduction
Cathode
Pb e- → Pb(s)
Pb2+
NO3-

20. The impurities in Pb are:Au Ag Zn

21. At the Anode
Au does not oxidize
The voltage is controlled so that:
Ag does not oxidize
Pb oxidizes
Zn oxidizes

22. At the Cathode
The voltage is controlled so that:
Pb2+ reduces
Zn2+ does not reduce

23. The Electrorefinning of Lead
Electrorefining is the process of purifying a metal by electrolysis.
The electrolyte must contain Pb
Impure metal is oxidized at the anode and pure metal is reduced at the cathode.
This is the same as electroplating.
DC Power
Cathode: Pure Pb
Anode: Impure Pb -
Reduction
Cathode
Pb e- → Pb(s) +
Oxidation
Anode
Zn(s) → Zn e-
Pb(s) → Pb e-
Pb2+
NO3-
Zn2+ Au Ag
Solid Au and Cu are released from the anode and fall to the bottom

24. Video of the thermite reaction used to make Iron
The Thermite reaction is very exothermic and produces white hot molten iron.
Fe2O Al(s) → Al2O3(s) Fe(l) + energy