Question

Assertion:In the electrolytic reduction of $A{l_2}{O_3}$ cryolite is used.
Reason:Cryolite is an ore of aluminium.
(A) Both Assertion and Reason are correct and Reason is correct explanation for Assertion
(B) Both Assertion and Reason are correct and but Reason is not the correct explanation for Assertion
(C) Assertion is correct but Reason is incorrect
(D) Assertion is incorrect and Reason is correct

Answer 1

Hint: To solve this question, we must first understand the basic concepts of Extraction of Aluminium. Then we need to assess the information related to extraction and electrolytic reduction of $A{l_2}{O_3}$ and then only we can conclude the correct answer.

Complete step-by-step answer:Before we move forward with the solution of this given question, let us first understand some basic concepts:
As we have studied that, In the metallurgy of aluminium, the metal is to be isolated from alumina $(A{l_2}{O_3})$ by carrying out its electrolytic reduction. The melting point of alumina is very high $(2323\,K)$. It is therefore mixed with cryolite $N{a_3}Al{F_6}$ which lowers its melting point to $1173\,K$ . Moreover, cryolite also increases the electrical conductivity of alumina.
Since, electrolysis of pure alumina is not feasible because it is a bad conductor of electricity and its fusion temperature is high. Cryolite and fluorspar are added to alumina which lowers the fusion temperature to $1140\,K$ and makes alumina a good electrical conductor.
And then, the electrolysis of fusion mixture is carried out.
So finally we can say that, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

So, clearly we can conclude that the correct answer is Option (B).

Note:Cryolite ( $N{a_3}Al{F_6}$ , sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, depleted by 1987. Due to its rarity it is possibly the only mineral on Earth ever to be mined to commercial extinction.