Question

Aluminium is extracted from alumina $(A{l_2}{O_3})$ by electrolysis of a molten mixture of:
$
  A.\,A{l_2}{O_3} + HF + NaAl{F_4} \\
  B.\,A{l_2}{O_3} + Ca{F_2} + NaAl{F_4} \\
  C.\,A{l_2}{O_3} + N{a_3}Al{F_6} + Ca{F_2} \\
  D.\,A{l_2}{O_3} + KF + N{a_2}Al{F_6} \\
$

Answer 1

Hint: In order to do electrolysis of alumina we need to overcome some of the problems like the metal aluminium should not be evaporated or disappeared from alumina. We need to use such chemicals which can conduct electricity or which have ions.

Complete step-by-step answer:
Electrolysis, the mechanism by which electrical current is passed through a material to induce a chemical change. Chemical transition is one in which the material loses or obtains an electron (oxidation or reduction). The procedure is carried out in an electrolytic cell, a device consisting of positive and negative electrodes kept apart and dipped into a solution containing positive and negatively charged ions. The electrolysis of pure alumina is difficult to do. As pure alumina is a bad conductor and does not conduct electricity, it is a bad conductor.
Alumina fuse at the temperature of 2000 degrees Celsius and at this point electrolysis is carried on the fused mass of alumina and as the boiling point of aluminium is 1800 degrees of Celsius so the metal vaporizes.
But we can overcome these difficulties when we use Alumina $A{l_2}{O_3}$, Cryolite $N{a_3}Al{F_6}$ and fluorspar $Ca{F_2}$.
So, the chemicals we will be using is $A{l_2}{O_3} + N{a_3}Al{F_6} + Ca{F_2}$.
So, the correct option is C.

Note – To get such problems solved we need to read the term electrolysis and electrolysis of some of the common compounds. Doing this will also help you further to solve problems and various questions also arise in terms of electrolysis of some of the common compounds. Here students should learn which compounds are needed for which use. For example the compound fluorspar in this problem will reduce the temperature from 2000 degrees Celsius to 1000 degrees Celsius. So, that the metal did not vaporize.