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BITSAT2018ChemistryGeneral Principles and Processes of Isolation of MetalsActual

In the context of the Hall-Heroult process for the extraction of Al , Which of the following statements is incorrect.

Options

  1. ACO and CO 2 are produced in the process.
  2. BAl 2 O 3 is mixed with CaF 2 which lowers the melting point of the mixture and brings conductivity.
  3. CAl 3 + is reduced at the cathode to form Al .
  4. DNa 3 AlF 6 serves as the electrolyte.

Correct answer

D. Na 3 AlF 6 serves as the electrolyte.

Step-by-step solution

(i) In Hall-Heroult process for extraction of Al , carbon anode is oxidised to CO and CO 2 . (ii) When Al 2 O 3 is mixed with CaF 2 , it lowers the melting point of the mixture and brings conductivity. (iii) Al 3 + is reduced at cathode to form Al . (iv) Al 2 O 3 serves as the electrolyte, undergoing the redox process. Na 3 AlF 6 although is an electrolyte but serves as a solvent, not electrolyte.

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