Question

For each of the substance listed below, describe the role played in the extraction of aluminium. (1) Cryolite (2) Sodium hydroxide (3) Graphite

Answer 1

Extraction of Aluminium is done from Bauxite, a common are of aluminium.

1.Cryolite is added to extraction of aluminium to decrease the melting point of alumina.

1. The molten cryolite act as a solvent which reduced the energy costs in exacting aluminium.

ii. The ions of aluminium oxide are allowed to move freely at low temperature.

2. Sodium hydroxide($\mathrm{NaOH}$) is able to dissolve

i. Bauxite (${\mathrm{Al}}_2{\mathrm{O}}_3.2{\mathrm{H}}_2\mathrm{O}$)from sodium meta aluminate (${\mathrm{NaAlO}}_2$) that helps in removing the insoluble impurities from ${\mathrm{Al}}_2{\mathrm{O}}_3$ by forming red mud.

ii. Purification of Bauxite in Bayer's process is done by sodium hydroxide.

3. Graphite is an inert electrode act as anode.

i. It prevents the oxidation of aluminium.

ii. It makes the reduction process of aluminium oxide (${\mathrm{Al}}_2{\mathrm{O}}_3$) easy.