Question

Consider the following: Statement-I: In the extraction of Al by Hall-Heroult process, pure \( Al_2O_3 \) mixed with \( Na_3AlF_6 \) lowers its melting point and increases conductivity. Statement-II: Zirconium metal is purified by zone refining method. The correct answer is:

• A. Both statement-I and statement-II are correct
• B. Both statement-I and statement-II are not correct
• C. Statement-I is correct, but statement-II is not correct
• D. Statement-I is not correct, but statement-II is correct

Hint:

Cryolite is essential in aluminum extraction, while zirconium purification uses the van Arkel method, not zone refining.

Answer 1

The Correct Option is C

Step 1: Verifying Statement-I In the Hall-Heroult process, aluminum oxide (\( Al_2O_3 \)) has a high melting point (~2000 K), making electrolysis inefficient. To reduce this, cryolite (\( Na_3AlF_6 \)) is added: - Lowers the melting point to ~1000 K, making electrolysis easier. - Enhances conductivity, allowing efficient ion migration in the molten electrolyte. Thus, Statement-I is correct. Step 2: Verifying Statement-II The zone refining method is used for purification of semiconductor metals, such as silicon and germanium, not zirconium. Zirconium is purified using the van Arkel method, which involves thermal decomposition of zirconium tetraiodide (\( ZrI_4 \)). Thus, Statement-II is incorrect. Conclusion Thus, the correct answer is: \[ \text{Statement-I is correct, but Statement-II is not correct} \]