State that the main ore of aluminium is bauxite and that aluminium is extracted by electrolysis

Metals – Extraction of Metals

Aluminium

Main ore of aluminium: bauxite 🏭

Bauxite is a soft, earthy rock that contains a high percentage of aluminium oxide (Al₂O₃) along with iron oxides, silica, and other impurities.

Think of bauxite as a raw cake batter – you need to “bake” it (process it) to get the final aluminium “cake” that we use in everyday life.

Extraction by Electrolysis (Hall–Héroult Process) ⚡️

Aluminium is extracted from molten alumina (Al₂O₃) dissolved in cryolite (Na₃AlF₆) using a powerful electric current.

The overall reaction can be written as:

\$\mathrm{Al2O3 + 3e^- \rightarrow 2Al + 3O^{2-}}\$

In the electrolytic cell, aluminium ions gain electrons at the cathode to form liquid aluminium, while oxygen ions lose electrons at the anode to form oxygen gas.

⚡️ Analogy: Imagine the electrolytic cell as a super‑charged kitchen where the electric current acts like a chef, turning the “batter” (Al₂O₃) into a shiny, liquid “cake” (Al) and releasing a small puff of “steam” (O₂).

Key Steps in the Hall–Héroult Process

  1. Mine and refine bauxite to obtain pure alumina (Al₂O₃).

  2. Heat alumina to 950 °C and dissolve it in molten cryolite to lower the melting point.

  3. Apply a strong electric current through the molten mixture.

  4. Aluminium ions migrate to the cathode and deposit as liquid aluminium.

  5. Oxygen ions migrate to the anode and evolve as oxygen gas.

Quick Reference Table

OreExtraction Method
Bauxite (Al₂O₃)Electrolysis (Hall–Héroult)

Exam Tip: Remember that aluminium is extracted by electrolysis of molten alumina in cryolite. Write the key reaction and the role of the cathode and anode. Use the Hall–Héroult process name to show you know the specific industrial method.