Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Aluminium is extracted from bauxite by the electrolysis of molten mixture of \( \text{Al}_2\text{O}_3 \) with cryolite.
Reason (R) : The oxidation state of Al in cryolite is +3.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Cryolite and Fluorspar (\( \text{CaF}_2 \)) are the two common additives in the electrolytic extraction of Aluminum used to manage melting points and conductivity.

Answer 1

The Correct Option is B

To evaluate the given assertion and reason, let's break down the statements and assess their accuracy and relationship with each other.

1. Understanding the Assertion (A): Aluminium is extracted from bauxite by the electrolysis of a molten mixture of \(\text{Al}_2\text{O}_3\) with cryolite.
   • Bauxite is the primary ore of aluminium, containing mainly aluminium oxide, \(\text{Al}_2\text{O}_3\), along with impurities.
   • The extraction of aluminium involves the Hall-Héroult process, where bauxite is dissolved in molten cryolite (Na₃AlF₆) to lower the melting point and facilitate electrolysis. 
   • Thus, the assertion is true as the extraction process indeed relies on this mixture for more efficient aluminium production.
2. Understanding the Reason (R): The oxidation state of Al in cryolite is +3.
   • Cryolite is represented as Na₃AlF₆.
   • In cryolite, Al is in the +3 oxidation state. This is consistent with aluminium’s valency in most of its compounds where it exhibits a +3 oxidation state.
   • Therefore, the reason is also correct.
3. Evaluating the Relationship:
   • While both the assertion and reason are correct, the reason provided is not the correct explanation for the assertion.
   • The assertion deals with the process of extracting aluminium using cryolite to dissolve \(\text{Al}_2\text{O}_3\), which helps reduce the melting point and improve efficiency during electrolysis.
   • The reason, though true, does not explain why cryolite is used in this process. Cryolite's role is more about its physical properties than the oxidation state of aluminium.
4. Conclusion: The most appropriate option is: Both (A) and (R) are correct but (R) is not the correct explanation of (A).