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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3mt044

Select the correct statement(s) about the electrolytic extraction of aluminium.

  1. AA mixture of alumina with cryolite and fluorspar melts well below the melting point of pure alumina and conducts current
  2. BThe anode is an inert electrode on which oxygen is evolved and is not consumed
  3. CLiquid aluminium is denser than the melt, collects at the bottom of the graphite-lined tank and is tapped from there
  4. DAlumina dissolves in the molten cryolite mixture and is the species that is electrolysed

Answer: A, C, D

Alumina melts near 2300 K and is a poor conductor, whereas the cryolite-fluorspar melt works at about 1200 K or below and conducts (true). Alumina dissolves in the melt and its ions are discharged (true). The carbon anodes are consumed by the liberated oxygen, forming and , so statement 3 is false. Molten aluminium is denser than the bath and sinks to the cathode lining (true).
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