Aluminium is an important metal in modern society. It is found widely distributed over the Earth and is extracted in several stages. Explain the following:
i. How is the aluminium in bauxite ore extracted and converted into pure aluminium oxide?
The aluminium oxide is reduced to pure metallic aluminium by adding cryolite, melting the mixture and using electrolysis.
ii. Why is cryolite added to the aluminium oxide?
iii. The cathode for this process is a graphite-lined, steel tank. Explain what is used for the anodes and why they need regular replacing.
iv. Write chemical equations for the electrolytic reactions at each electrode.