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Lec . 2Lec . 2Faraday’s LawsFaraday’s Laws
Lec . 2Lec . 2Faraday’s LawsFaraday’s Laws
Industrial Electrolytic ProcessesIndustrial Electrolytic Processes““Electrolysis”Electrolysis”
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What you should learn
• What is electrolysis? • Faraday's laws of
electrolysis• Industrial Applications of
electrolytic process
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It is used industrially in a number of ways:1. Electroplatig.2. The preparation of gases, notably
chlorine.3. Water decomposition.4. The extraction of metals, notably
aluminum, magnesium, and sodium. 5. The refining of metals, such as copper
and zinc.
2. Electrolysis of Molten 2. Electrolysis of Molten Salts and Production of Salts and Production of
Cl2Cl2
2. Electrolysis of Molten 2. Electrolysis of Molten Salts and Production of Salts and Production of
Cl2Cl2
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+-battery
Na (l)
Cathode
Anode
Molten NaCl
Na+
Cl-
Cl- Na+
Na+
Na+ + e- Na
2Cl- Cl2 + 2e-
Cl2 (g) escapes
Observe the reactions at the electrodes
NaCl (l)
(-)
Cl-
(+)
Molten NaCl Electrolytic Cell
cathode half-cell (-)REDUCTION Na+ + e- Na
anode half-cell (+)OXIDATION 2Cl- Cl2 + 2e-
overall cell reaction2Na+ + 2Cl- 2Na + Cl2
X 2
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Electrolysis of Diluted Electrolysis of Diluted NaClNaCl
battery+- power
source
e-
e-
NaCl (aq)
(-) (+)
cathodedifferent half-cell
Aqueous NaCl
Na+
Cl-
H2O
What could be reduced at the cathode?
Aqueous NaCl Electrolytic Cell
possible cathode half-cells (-)REDUCTION Na+ + e- Na
2H20 + 2e- H2 + 2OH-
possible anode half-cells (+)OXIDATION 2Cl- Cl2 + 2e-
2H2O O2 + 4H+ + 4e-
overall cell reaction2Cl- + 2H20 H2 + Cl2 + 2OH-
3. Water electrolysis3. Water electrolysis3. Water electrolysis3. Water electrolysis
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The Electrolysis of Watercontaining some sulfates
2 H2O + 2e- H2 (g) + 2 OH-
cathode reaction2H2O O2 (g) + 4H+ + 4e-
anode reaction
Cell diagram Battery, a source of direct currente- flow
Cathode Anode
e- flow
aqueous K2SO4
O2 gasH2 gas
+ pole of battery- pole of battery
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The Electrolysis ofwater
O 2H OH 2 isreaction overall The
OH 4 4H O H 2 OH 6reaction Cell
)2OH H2e- OH 2(2reaction Cathode
e 4 H 4 O OH 2 reaction Anode
2(g)2(g)2
OH 4
-2(g)2(g)2
-2(g)2
-2(g)2
2
4. Extraction of 4. Extraction of MetalsMetals
4. Extraction of 4. Extraction of MetalsMetals
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carbon-lined steel vesselacts as cathode
CO2 bubbles
Al (l)Al2O3 (l)
Drawoff Al (l)
-
+
Cathode: Al+3 + 3e- Al (l)
Anode: 2 O-2 + C (s) CO2 (g) + 4e-
frompowersource
Al+3
O-2
O-2
Al+3
O-2
graphite anodes
e-
e-
The Hall ProcessCathode: Al+3 + 3e- Al (l)
Anode: 2 O-2 + C (s) CO2 (g) + 4e-
4 Al+3 + 6 O-2 + 3 C (s) 4 Al (l) + 3 CO2 (g)
x 4
x 3
The graphite anode is consumed in the process.