Question:

Electrolytic reduction of alumina to aluminium by Hall-Heroult process is carried out

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Cryolite acts as a solvent for alumina and does not decompose during electrolysis.
Updated On: Apr 16, 2026
  • in the presence of NaCl
  • in the presence of Honcite
  • in the presence of cryolite which forms a melt with lower melting temperature
  • in the presence of cryolite which forms a melt with higher melting temperature
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The Correct Option is C

Solution and Explanation


Step 1:
Understanding the Concept:
The Hall-Heroult process is the primary industrial process for smelting aluminum.

Step 2:
Detailed Explanation:
Alumina (Al\(_2\)O\(_3\)) has a very high melting point (over 2000°C). To make the electrolysis economically feasible, it is dissolved in molten cryolite (Na\(_3\)AlF\(_6\)), which lowers the melting point of the mixture to about 950°C. Cryolite also increases the conductivity of the melt.

Step 3:
Final Answer:
Cryolite is used to lower the melting temperature of the mixture, which corresponds to option (C).
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