Aluminium is produced on a large scale by which of the following methods?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Electrolysis of aluminium oxide in the presence of cryolite
Metals such as Na, Mg and Al are produced on a large scale by electrochemical reduction of their cations, because no suitable chemical reducing agents are available for them. Sodium and magnesium come from the electrolysis of their fused chlorides, but aluminium is obtained by the electrolysis of aluminium oxide in the presence of cryolite:
\( \ce{Al^3+ + 3e^- -> Al} \)
Why the other options are incorrect
Option (1) Electrolysis of an aqueous solution of aluminium chloride — Incorrect. In an aqueous solution, water is reduced at the cathode in preference to a cation of a very reactive metal, so hydrogen, not aluminium, would be formed.
Option (2) Electrolysis of fused aluminium chloride — Incorrect. Electrolysis of the fused chloride is the method for sodium and magnesium, not for aluminium.
Option (4) Reduction of aluminium oxide by heating it with a chemical reducing agent — Incorrect. Electrolysis is used for these metals because no suitable chemical reducing agent is available.
NCERT (2026-27 edition):
2.5 Electrolytic Cells and Electrolysis – “…Many metals like Na, Mg, Al, etc. are produced on large scale by electrochemical reduction of their respective cations where no suitable chemical reducing agents are available for this purpose.”
“Sodium and magnesium metals are produced by the electrolysis of their fused chlorides and aluminium is produced by electrolysis of aluminium oxide in presence of cryolite.”