Application ofElectrolytic Cells
Lesson 11
Electrolysis describes what happens in an electrolytic cell andmeans to use electricity to make chemicals.
Many elements are made by electrolysis
Pb Al Zn Na K Li H2 Cl2 F2
I2 O2
Pb2+ + 2e- → Pb(s)
2Cl- → Cl2(g) + 2e-
This is sometimes called electrowinning- the element is won from its ion
Making Aluminum by ElectrolysisAlcan (70,000 employees in 55 countries) Kitimat B.C. 2.7 MT 7 % world production
Aluminum
Aluminum Production by Electrolysis
Name of the Ore imported from (Guinea and Brazil)Bauxite Al2O3
.3H2O
Heating drives off the waterAl2O3
.3H2O + Heat → Al2O3 + 3H2O
Melting point of Bauxite is 2045 0C
This is too hot!Cryolite is added Lowers the melting point to 1000 0C
Reduction of water
You cannot reduce Aluminum in water!It must be molten!
CC
DC Power
- +
Al3+
O2-
-
Reduction
Cathode
Al3+ + 3e- → Al(s)
+
Oxidation
Anode
O2- → 1/2O2(g) + 2e-
Liquid Al floats to the top and is removed
Oxygen gas
Al2O3(l)
Cation Cathode Reduction Anion Anode Oxidation
Au+
CN-
Au+
CN-
Electroplating
Au plating a Cu pennyElectroplating is the process of reducing a metal on to the surface of anotherElectrolyte: Must contain the ion of the metal that platesCathode: The metal to be covered with a new metalAnode: Metal to be plated on top the other metal
DC Power- +
DC Power- +
Au
+OxidationAnodeAu(s) → Au+ + 1e-
e--ReductionCathodeAu+ + e- → Au(s)
CuCu
AuCN
-ve+ve
stainless steel or Au
Au plated
Copper Ring Gold Plated
Tanya’s Ring Gold Plated
Ag+
NO3-
Electroplating
Ag plating a Loonie
DC Power- +
DC Power- +
Ag
+OxidationAnodeAg(s) → Ag+ + 1e-
e--ReductionCathodeAg+ + e- → Ag(s)
$1
Electrorefinning Lead Trail, B.C.Teck 16 mines in BCMajor World Producer of Zn, Cu, Pb, and Coal
Lead Refinery-Trail
The Electrorefinning of Lead
Electrorefining is the process of purifying a metal by electrolysis.The electrolyte must contain PbImpure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating.
DC Power- +
DC Power- +
Pb2+
NO3-
-ReductionCathode
Pb2+ + 2e- → Pb(s)
Cathode: Pure Pb
Anode: Impure Pb
The impurities in Pb are:AuAgZn
Zn oxidizes
Ag does not oxidize
Pb oxidizes
Au does not oxidizeAt the Anode
The voltage is controlled so that:
Pb2+ reduces
At the Cathode
Zn2+ does not reduce
The voltage is controlled so that:
The Electrorefinning of Lead Electrorefining is the process of purifying a metal by electrolysis.The electrolyte must contain PbImpure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating.
DC Power- +
DC Power- +
Pb2+
NO3-
-ReductionCathode
Pb2+ + 2e- → Pb(s)
Cathode: Pure Pb Anode: Impure Pb
+OxidationAnodeZn(s) → Zn2+ + 2e-
Pb(s) → Pb2+ + 2e-
Zn2+
Au Ag
Solid Au and Cu are released from the anode and fall to the bottom
Video of the thermite reaction used to make Iron
The Thermite reaction is very exothermic and produces white hot molten iron.
Fe2O3 + 2Al(s) → Al2O3(s) + 2Fe(l) + energy
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