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KCET · Chemistry · General Principles and Processes of Isolation of Metals

The incorrect statement about Hall -Heroult process is

  1. A carbon anode is oxidised to CO and \(\mathrm{CO}_2\).
  2. B \(\mathrm{Na}_3 \mathrm{AlF}_6\) helps to decrease the melting point of the electrolyte.
  3. C \(\mathrm{CaF}_2\) helps to increase the conductivity of the electrolyte.
  4. D oxidation state of oxygen changes in the overall cell reaction.
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Answer & Solution

Correct Answer

(D) oxidation state of oxygen changes in the overall cell reaction.

Step-by-step Solution

Detailed explanation

The incorrect statement about Hall-Heroult process is given in option (d). It is because in this process oxidation state of oxygen remains same in the overall cell reaction.
\(2 \mathrm{Al}_2 \mathrm{O}_3+3 \mathrm{C} \longrightarrow 4 \mathrm{Al}+3 \mathrm{CO}_2\)