Brainlag PlusExtracting aluminium with cryolite and carbon anodes, half equations at each electrode, masses of products, and the required practical on electrolysing solutions.
Extracting aluminium
Aluminium is above carbon in the reactivity series, so its oxide cannot be reduced with carbon.
It is extracted by electrolysis of aluminium oxide.
- Aluminium oxide melts above 2000 °C, so it is dissolved in molten cryolite. This lowers the melting point and saves energy.
- At the cathode, Al³⁺ ions gain electrons and molten aluminium collects at the bottom.
- At the anode, O²⁻ ions lose electrons and oxygen forms. The anodes are carbon: the oxygen reacts with them to make carbon dioxide, so they burn away and are replaced regularly.
- The huge current and the heating make the process expensive.
- Al₂O₃ is 2 × 27 + 3 × 16 = 102
- fraction that is aluminium = 54 ÷ 102 = 52.9%
The rest of this lesson and its 14 practice questions are in Plus.
Screen 1 of 4, free to read.
- 14 exam-style questions, marked as you go, each with a worked solution
- The Molar Mass Calculator beside every question
- Anything you get wrong is saved to your flashcards