Question

The electrochemical extraction of aluminum from bauxite ore involves

• A. the reaction of $Al _2 O _3$ with coke (C) at a temperature $>2500^{\circ} C$.
• B. the neutralization of aluminate solution by passing $CO _2$ gas to precipitate hydrated alumina $\left( Al _2 O _3 .3 H _2 O \right)$
• C. the dissolution of $Al _2 O _3$ in hot aqueous $NaOH$.
• D. the electrolysis of $Al _2 O _3$ mixed with $Na _3 AlF _6$ to give $Al$ and $CO _2$.

Answer 1

The Correct Option is B, C, D

The electrochemical extraction of aluminum from bauxite involves several key processes. Let's analyze the given options:

• Option A: "The reaction of Al₂O₃ with coke (C) at a temperature > 2500°C."
  This is incorrect. High-temperature reactions involving coke are not part of the primary extraction methods for aluminum. Instead, the Hall-Héroult process uses electrolysis of alumina (Al₂O₃) in molten cryolite.
• Option B: "The neutralization of aluminate solution by passing CO₂ gas to precipitate hydrated alumina (Al₂O₃·3H₂O)."
  This is correct. In the Bayer process, sodium aluminate solution is neutralized by CO₂ to precipitate hydrated alumina, which is then converted into alumina (Al₂O₃) for further electrolysis.
• Option C: "The dissolution of Al₂O₃ in hot aqueous NaOH."
  This is correct. The Bayer process involves dissolving bauxite (Al₂O₃) in hot sodium hydroxide (NaOH), forming sodium aluminate, a key intermediate in alumina extraction. 
• Option D: "The electrolysis of Al₂O₃ mixed with Na₃AlF₆ to give Al and CO₂."
  This is correct. The Hall-Héroult process involves electrolysis of alumina (Al₂O₃) dissolved in molten cryolite (Na₃AlF₆), producing aluminum metal (Al) and carbon dioxide (CO₂).

Final Answer: The correct options are: B, C, D.