Electrodes in Hall-Héroult Aluminum Extraction

Steps:

• Bauxite ore is purified and dissolved in molten cryolite as the electrolyte for electrolysis.
• Carbon-based electrodes are used: anode oxidizes, releasing oxygen that reacts with carbon to form CO2.
• Anode must be inert and heat-resistant to avoid contamination.
• Cathode reduces aluminum ions to molten aluminum metal.

Why A is correct:

• Graphite serves as the inert anode, conducting electricity and resisting oxidation at high temperatures (around 950°C), per the electrolysis cell design.

Why the others are wrong:

• B: Steel corrodes rapidly due to oxygen evolution at the anode.
• C: Bauxite is the aluminum ore (Al2O3 source), not an electrode material.
• D: Cryolite (Na3AlF6) is the flux to lower melting point of the electrolyte, not an electrode.

Final answer: A