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प्रश्न
How is aluminium obtained from pure ore?
उत्तर
Aluminium is obtained from pure ore by Hall - Heroult's process as follows:
i. Electrolyte used :
a. Pure alumina
b. Cryolite
c. Aluminium fluoride
d. Calcium fluoride or Fluorspar
ii . Electrolytic cell : It is a rectangular steel tank with a thick inner lining of carbon .
iii . Electrodes used :
a. Cathode: inner lining of carbon
b. Anode: Thick carbon rods dipping into the fused electrolytes.
iv. Temperature of the electrolytic bath : 950°C
Reactions: On passage of electricity through electrolyte aluminium and oxide ions are formed.
At cathode: Aluminium ions get reduced as:
Al3+ + 3e- → Al
At anode: oxygen gas is liberated as:
O2- - 2e- → [ O ]
[ O ] + [ O ] → O2
The oxygen formed at anode oxidizes the carbon of the anode to carbon dioxide.
C + O2 → CO2
As a result the anode gets oxidized and it has to be replaced periodically.
Figure: Extraction of aluminium from pure ore.
APPEARS IN
संबंधित प्रश्न
Write the equation for the reaction that occurs at the cathode during the extraction of aluminum by electrolysis.
Name the constituents of Bronze.
For graphite, explain its significance in the extraction of aluminium.
Give reason for the following:
Aluminium oxide cannot be reduced by carbon.
In the Hall's process for extraction of aluminium, Sate the location of cathode and anode and explain what occurs at each electrode.
What is the role of cryolite (NaAlF6) in the electrolytic reduction of alumina in the Hall's process?
Aluminium is extracted from its chief ore bauxite. The ore is first purified and then the metal is extracted from it by electrolytic reduction.
Write three balanced equations for the purification of bauxite by Hall's process.
Explain why :
Iron sheets are coated with zinc during galvanization.
Write the constituents of the electrolyte for the extraction of aluminium.
State the relevant reason for the following:
Graphite anodes are continuously replaced during the electrolysis of alumina.
