JAMB - Chemistry (1979 - No. 23)
In the extraction of aluminum from purified bauxite by electrolysis, cryolite is used because
it makes bauxite a better conductor of electricity
it makes bauxite melt at a lower temperature
it makes aluminium purer
it prevents aluminium from getting oxidized
it protects the carbon electrodes used in the process
Vysvětlení
The bauxite is purified to yield a white powder, aluminium oxide, from which aluminium can be extracted. The extraction is done by electrolysis. ... Instead, it is dissolved in molten cryolite, an aluminium compound with a lower melting point than aluminium oxide.