Question

In electrolysis of \[A{l_2}{O_3}\] ​ Hall-Heroult’s process:
A.Cryolite Na3[AlF6] lowers the melting point of \[A{l_2}{O_3}\] and increases its electrical conductivity
B. Al is obtained at the cathode and probably \[C{O_2}\] at the anode
C. Both (a) and (b) are correct
D.None of the above is correct

Answer 1

Hint: To answer this question, you should recall the concept of Hall-Heroult’s process. This is used in the extraction of aluminium using electrolysis.

Complete step by step answer:
The electrolysis of alumina through the process of Hall and Heroult is carried by utilising a fusion mixture of alumina and cryolite in the presence of minor quantities of aluminium fluoride and fluorspar. The addition of cryolite and fluorspar leads to an increase in the electrical conductivity of alumina and lowers the fusion temperature. Thus, option A is correct.
At the anode, alumina reacts with fluorine to give oxygen. The oxygen gas released undergoes a chemical reaction with carbon to form \[CO\] and \[C{O_2}\]​ . These gases are liberated at the anode. Thus, option B is also correct.

Hence, the correct answer to this question is option C.

Additional information:
Aluminium is a highly reactive metal, belonging to the IIIA group of the periodic table. In nature, aluminium is generally found as oxides. Some of these few important oxide ores include:
Bauxite \[A{l_2}{O_3}.2{H_2}O\]
Corundum \[A{l_2}{O_3}\]
Cryolite \[N{a_3}Al{F_6}\]
Aluminium is mostly extracted from its bauxite ore. The bauxite ore contains ferric oxide and silica as impurities. It is first concentrated by gravity separation of ferric oxide impurities. As these impurities are magnetic, they are separated by the process of magnetic separation. The ore is then concentrated by the chemical process.

Note:
Aluminium ions are created at the adverse cathode from the aluminium oxide and then sink because they are heavier than the cryolite solution. Then, the liquid shape of the aluminium that has sunk to the bottom. On the other side, at the positive anode, the oxygen from the aluminium oxide forms and responds to carbon dioxide \[C{O_2}\] with the graphite carbon.