Draw and label the diagram of electrolysis
of alumina and explain the electrolytic
reduction of alumina.
Answers
Answer:
If Bauxite contains Fe
2
O
3
as impurity, it is purified by Baeyer's process.
Electrolysis of alumina (Hall-Heroult process): Electrolysis of alumina is done in an iron tank fitted with a lining of gas carbon which acts as cathode. Graphite rods act as anode and a bulb is fitted in parallel as indicator for alumina content. The electrolyte is a mixture of alumina and cryolite (Na
3
AlF
6
). The melting point of alumina is very high (2050
o
C). But, in presence of cryolite (Na
3
AlF
6
) and fluorspar (CaF
2
), it melt at 870
o
C. Then pure alumina is added to the tank which dissolve in cryolite mixture.
Reaction: Reaction take place as below
Na
3
AlF
6
→3NaF+AlF
3
AlF
3
→Al
3+
3F
−
3F
−
→3e
−
+3F (oxidation) at anode
Al
3+
3e
−
→Al (reduction) at cathode
2Al
2
O
3
+12F→4AlF
3
+3O
2
↑
solution
Answer:
hope this helps you alor
