Question

Mention names and chemical formulae of two ores of aluminium.

Answer 1

Hint: Aluminium is the most abundant metal in the earth’s crust. It does not occur in the free State and it is very reactive metal also. Ore is a naturally occurring solid material from which a valuable material or a metal also can be extracted.

Complete step by step answer: Following are the ores of aluminium:
${\text{-}}$ Bauxite having chemical formula ${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{.2}}{{\text{H}}_{\text{2}}}{\text{O}}$. It is hydrated aluminium oxide. Bauxite consists mostly of the aluminium minerals gibbsite; it is a mixture of the aluminium clay mineral. Basically Bauxite is the chief ore of aluminium. Moreover it is used for aluminium production and it is the principle ore of aluminium. So the first step in producing aluminium is to crush the bauxite and then we have to purify it by the Bayer process. In Bayer’s process, we have to wash the Bauxite in a hot solution of sodium hydroxide which then bleaches aluminium from the bauxite. Chemical name of bauxite is hydrate aluminium ore.
$-$ Corundum having chemical formula ${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}$. It is an extremely hard crystallized alumina; basically it is used as an abrasive. In addition, it is used as a precious gem, also used for grinding optical glass and polishing metals also. It also has been made into the sandpapers and grinding wheels. Ruby and sapphire are varieties of corundum.

Note: Point to be noted that many people are surprised to learn that bauxite is not a mineral. It is a rock composed mainly of aluminium bearing minerals. It does not have a definite crystal system where corundum has hexagonal crystal family.