Question

The correct statements regarding Hall-Héroult process are:

• [i.] Steel vessel with lining of carbon acts as anode.
• [ii.] Purified Al\(_2\)O\(_3\) is mixed with cryolite.
• [iii.] The overall reaction is \( 2\text{Al}_2\text{O}_3 + 3\text{C} \rightarrow 4\text{Al} + 3\text{CO}_2 \).

• A. \(i\), \(ii\), \(iii\)
• B. \(ii\), \(iii\) only
• C. \(i\), \(iii\) only
• D. \(i\), \(ii\) only

Hint:

Remember, the polarity of the electrodes in electrolytic processes is crucial; the cathode is where reduction occurs (aluminum production), and the anode is where oxidation occurs (carbon to carbon dioxide).

Answer 1

The Correct Option is B

Evaluate each statement for accuracy. 
Statement i: Incorrect. In the Hall-Héroult process, the steel vessel lined with carbon serves as the cathode, not the anode.
Statement ii: Correct. Purified alumina (Al\(_2\)O\(_3\)) is indeed mixed with cryolite to lower the melting point of alumina and increase the conductivity of the mixture.
Statement iii: Correct. The overall chemical reaction for the Hall-Héroult process involves the reduction of alumina to aluminum and the oxidation of carbon (as anode material) to carbon dioxide. 
Conclusion: Statements \(ii\) and \(iii\) are correct, making option (2) the correct choice.

Answer 2

To solve the problem, we need to determine the correct statements regarding the Hall-Héroult process, a method used for extracting aluminum from its ore.

1. Understanding the Hall-Héroult Process:
The Hall-Héroult process is the primary method of aluminum extraction. In this process:
A steel vessel lined with carbon acts as the anode.
Purified aluminum oxide (Al₂O₃) is mixed with cryolite (Na₃AlF₆) to lower the melting point and improve the conductivity.
The overall reaction involves the reduction of aluminum oxide to aluminum metal, with carbon dioxide produced at the anode.

2. Analyzing the Statements:
Now, let's evaluate each statement:

• Statement i: "Steel vessel with lining of carbon acts as anode" - This is true. The Hall-Héroult process uses carbon as the anode in the electrolysis cell.
• Statement ii: "Purified Al₂O₃ is mixed with cryolite" - This is also true. Cryolite is added to Al₂O₃ to reduce its melting point and improve the process efficiency.
• Statement iii: "The overall reaction is 2Al₂O₃ + 3C → 4Al + 3CO₂" - This is correct. The Hall-Héroult process involves the reduction of aluminum oxide (Al₂O₃) to produce aluminum and carbon dioxide.

Final Answer:
The correct answer is (B) ii, iii only.