Write in brief how aluminium is …

The extraction of the metal from bauxite involves the three main steps.

• Concentration of Bauxite (Al₂​O_3​.2H_2​O)

Concentration of ore is done by leaching which helps in removing impurities like Fe₂​O₃​,SiO_2​, etc. Bauxite is treated with NaOH to form sodium aluminate which on further reaction with CO₂​ gives pure Alumina.

Al₂​O₃​+2NaOH+3H₂​O⟶2Na[Al(OH)₄​]2CO₂​−2NaHCO₃​​Al₂​O_3​.xH₂​OΔ1470K​Pure aluminaAl2​O3​​+xH2​O

• Electrolytic reduction of Alumina (Al₂​O₃​)

Electrolytic reduction of pure alumina takes place in iron box (cathode) with cryolite (Na3​AlF6​) and fluorspar (CaF2​) which lowers the melting point and increases the conductivity of electrolyte. Graphide rods act as anode.

At cathode:-

Al³⁺+3e⁻⟶Al

At anode:- The oxygen liberated at anode reacts with the carbon of anode to produce CO and CO2​.

C+O²⁻⟶CO+2e⁻

C+2O²⁻⟶CO₂​+4e⁻

By this process 98.8% pure aluminium is obtained.