Question

Hall-Heroult's process is given by :

• A. ${Cr2O3 + 2Al -> Al2O3 + 2Cr}$
• B. ${Cu^{2+} (a) + H_2(g) \to Cu(s) + 2H^{+} (aq)}$
• C. ${ZnO + C ->[Coke, 1673 K] Zn + CO}$
• D. ${2 Al_2 O_3 + 3C \to 4Al + 3CO_2 }$

Answer 1

The Correct Option is D

The Hall-Heroult process is a key step in the extraction of aluminum metal from its ore, bauxite. This process involves the electrolytic reduction of alumina (Al₂O₃) to aluminum. Let's examine the given options:

1. {Cr_2O_3 + 2Al \rightarrow Al_2O_3 + 2Cr} - This reaction describes the thermite reduction of Cr₂O₃, not the process for aluminum extraction.
2. {Cu^{2+} (aq) + H_2(g) \rightarrow Cu(s) + 2H^{+} (aq)} - This is the reduction of copper ions, not related to aluminum extraction.
3. {ZnO + C \xrightarrow{Coke, 1673 K} Zn + CO} - This is the reduction of zinc oxide with carbon, typical for zinc extraction.
4. {2Al_2O_3 + 3C \rightarrow 4Al + 3CO_2} - This reaction describes the electrolytic reduction of alumina, which is a crucial part of the Hall-Heroult process.

Therefore, the correct option is the fourth one: {2Al_2O_3 + 3C \rightarrow 4Al + 3CO_2}. Here's why this is the Hall-Heroult process:

• In the Hall-Heroult process, alumina is dissolved in molten cryolite and subjected to electrolytic reduction.
• Carbon acts as an electrode, and it gets consumed during the process, forming carbon dioxide as a by-product, which matches the overall reaction.
• This electrolytic reduction is integral to producing aluminum from its ore in an industrial context.

In conclusion, the correct answer is the option: {2Al_2O_3 + 3C \rightarrow 4Al + 3CO_2}, accurately representing the Hall-Heroult process for aluminum extraction.