Aluminium's Extraction and Reactivity Properties

Steps:

• Evaluate extraction: Aluminium is extracted via electrolysis of Al2O3 in molten cryolite, not by heating with carbon.
• Identify production site: In electrolysis, Al metal forms at the cathode, while oxygen gas forms at the anode.
• Assess reactivity: Aluminium appears unreactive due to a protective oxide layer (Al2O3) that prevents further reaction.
• Examine uses: Aluminium's low density and good conductivity make it ideal for overhead cables, not high density.

Why C is correct:

• Aluminium forms a thin, impermeable Al2O3 coating via 4Al + 3O2 → 2Al2O3, passivating the metal and reducing reactivity despite its position in the reactivity series.

Why the others are wrong:

• A: Heating Al2O3 with carbon does not reduce it to aluminium; carbon reduces less stable oxides like iron(III) oxide.
• B: Aluminium deposits at the cathode during electrolysis; the anode produces oxygen gas.
• D: Aluminium has low density (2.7 g/cm³), aiding its use in lightweight cables despite good conductivity.

Final answer: C