application electrolytic cells

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 H
2
Cl
2
F
2

I
2
O
2
Pb
2+
+ 2e
-
→ Pb
(s)

2Cl
-
→ Cl
2(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. 2.7 MT 7 % world production

5. Aluminum

6. Aluminum Production by Electrolysis
Name of the Ore imported from (Guinea and Brazil)
Bauxite
Al
2
O
3
.
3H
2
O
Heating drives off the water
Al
2
O
3
.
3H
2
O + Heat → Al
2
O
3
+ 3H
2
O

Melting point of Bauxite is 2045
0
C
This is too hot!
Cryolite is added
Lowers the melting point to 1000
0
C

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

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

9. Au
+
CN
- Au
+
CN
-
Electroplating

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
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DC Power
- +

Au
+
Oxidation
Anode
Au
(s)
→ Au
+
+ 1e
-

e
-
-
Reduction
Cathode
Au
+
+ e
-
→ Au
(s)
Cu Cu

10. AuCN
-ve
+ve
stainless steel or Au

13. Au plated

14. Copper Ring Gold Plated

15. Tanya’s Ring Gold Plated

16. Ag
+
NO
3
-
Electroplating

Ag plating a Loonie
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DC Power
- +

Ag
+
Oxidation
Anode
Ag
(s)
→ Ag
+
+ 1e
-

e
-
-
Reduction
Cathode
Ag
+
+ e
-
→ Ag
(s)
$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.



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DC Power
- +
Pb
2+
NO
3
-
-
Reduction
Cathode
Pb
2+
+ 2e
-
→ Pb
(s)
Cathode: Pure Pb
Anode: Impure Pb

20. The impurities in Pb are:
Au
Ag
Zn

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

22. Pb
2+
reduces
At the Cathode
Zn
2+
does not reduce
The voltage is controlled so that:

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.



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DC Power
- +
Pb
2+
NO
3
-
-
Reduction
Cathode
Pb
2+
+ 2e
-
→ Pb
(s)
Cathode: Pure Pb Anode: Impure Pb
+
Oxidation
Anode
Zn
(s)
→ Zn
2+
+ 2e
-

Pb
(s)
→ Pb
2+
+ 2e
-

Zn
2+
AuAg
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.
Fe
2
O
3
+ 2Al
(s)
→ Al
2
O
3(s)
+ 2Fe
(l)
+ energy