Question

(a) Name one main ore of Aluminium. Write its formula. Which two main impurities are associated with this ore? (b) Describe with chemical equations, the method employed for the enrichment of the above named ore.

Answer 1

(a) Bauxite is one main aluminium ore. The chemical formula of bauxite is Al2H2O4. The impurities are largely iron oxide, silica, and titania.

(b) The method employed for enrichment of bauxite is called asa Bayer's process.

Explanation:

(a) 1. Aluminum is the third most abundant element on Earth’s surface. The chemical formula of bauxite is Al2H2O4.

2. Bauxite is best defined as an aluminium ore of varying degrees of purity in which aluminium in the form of aluminium hydroxide or aluminium oxide is the largest single constituent.

3. The impurities are largely iron oxide, silica, and titania. Bauxite varies greatly in physical appearance, depending on its composition and impurities.

(b) The process used for refinement of bauxite is Bayer's process.

                   Al2O3 + 2 NaOH → 2 NaAlO2 + H2O

1. Digestion: This treatment also dissolves silica, forming sodium silicate.

                2 NaOH + SiO2 → Na2SiO3 + H2O

2. Clarification:

                  2 NaAlO2 + 3 H2O + CO2 → 2 Al(OH)3 + Na2CO3

3. Precipitation:

                 2 H2O + NaAlO2 → Al(OH)3 + NaOH

4. Calcination:

                   2 Al(OH)3 → Al2O3 + 3 H2O

Answer 2

(a) Bauxite is one main aluminium ore. The chemical formula of bauxite is Al2OH2O4. The impurities are largely iron oxide, silica, and titania.

(b) The method employed for enrichment of bauxite is called asa Bayer's process.

Explanation:

1. Aluminum is the third most abundant element on Earth’s surface. The chemical formula of bauxite is Al2OH2O4.

2. Bauxite is best defined as an aluminium ore of varying degrees of purity in which aluminium in the form of aluminium hydroxide or aluminium oxide is the largest single constituent.

3. The impurities are largely iron oxide, silica, and titania. Bauxite varies greatly in physical appearance, depending on its composition and impurities.

(b) The process used for refinement of bauxite is Bayer's process.

                  Al2O3 + 2 NaOH → 2 NaAlO2 + H2O

1. Digestion: This treatment also dissolves silica, forming sodium silicate.

               2 NaOH + SiO2 → Na2SiO3 + H2O

2. Clarification:

                 2 NaAlO2 + 3 H2O + CO2 → 2 Al(OH)3 + Na2CO3

3. Precipitation:

                2 H2O + NaAlO2 → Al(OH)3 + NaOH

4. Calcination:

                          2 Al(OH)3 → Al2O3 + 3 H2O