Reactions of Alumina

Alumina is also known as aluminium oxide since it is a chemical compound of aluminium and oxide. The chemical formula of Alumina is Al2O3 . Alumina is extracted from bauxite ore by the Bayer process. It is a white or nearly colourless crystalline substance with a molar mass of 101.96gm/mol and a density of 3.95gm/cm3. The melting point of Alumina is 2,072 °C, and the boiling point of Alumina is 2,977 °C. It is a well known fine ceramic material with high resistance and high thermal conductivity. Alumina can react with acids and bases, so it is called amphoteric.

The Reaction of Alumina With Water

 As Alumina is amphoteric, it can react with acid and base, but not with water. This is because the oxide ions in alumina (Al2O3) are held too firmly in its solid lattice. Like other metallic oxides, aluminium oxide does not react with water. This makes alumina (Al2O3) insoluble in water.

 Reactions of Alumina With Different Chemicals

Alumina reacts differently with different chemicals and produces compounds accordingly.

• The reaction of alumina with sodium hydroxide:

The reaction of alumina with sodium hydroxide as a base gives an example of amphoteric alumina. It neutralises another substance and produces a salt, which is sodium aluminate.

Al2O3+2NaOH+3H2 2NaAl(OH)4

• The reaction of alumina with hydrochloric acid (HCL):

The reaction of alumina with hydrochloric acid takes place at room temperature. It reacts with hydrochloric acid to produce aluminium chloride and water.

Al2O3+ 6HCl 2AlCl3+3H₂O

• The reaction of alumina with nitric acid:

The reaction of alumina with nitric acid is an acid-base reaction. The base, Al2O3, which is a colourless crystalline substance that reacts with nitric acid(HNO3), a colourless-to-yellow with suffocating odour, produces aluminium nitrate(Al(NO)3)3, a solid white crystal and water(H₂O).

Al2O3+ 6HNO3 2Al(NO3)3 +3H₂O

• The reaction of alumina with sulphuric acid: 

The reaction of alumina with sulfuric acid at room temperature produces aluminium sulfate and water. This is a neutralisation reaction as alumina is amphoteric.

Al2O3+3H2SO4Al2(SO4)3+3H2O

• The reaction of alumina with hydrogen bromide (bromoderma):

When alumina reacts with hydrogen bromide acid (HBr),  the resulting product is bromide of aluminium (AlBr3) and water (H2O).

Al2O3+6HBr2AlBr3+3H2O

• The reaction of Alumina with Potassium Hydroxide:

The reaction of alumina with potassium hydroxide occurs between 900-1100 oC. It reacts with dry potassium hydroxide (KOH). The product of the reaction is potassium aluminate (KAlO2 ) salt and water.

Al2O3+2KOH2KAlO2+H2O (T = 900-1100 °C).

• The reaction of alumina with calcium oxide:

The reaction of alumina with potassium hydroxide occurs between 1200-1300 °C.  The product of the reaction is calcium aluminate ( Ca(AlО2)2) salt and water.

CaO+Al2O3Ca(AlO2)2 (T = 1200-1300 °C).

• The reaction of aluminium oxide with ammonia:

The reaction of alumina with ammonia takes place at 1000 °C. The product of the reaction is salt of aluminium nitride and water.

Al2O3+2NH32AlN+3H2O (T = 1000 °C).

Uses of Alumina

Alumina or aluminium oxide is one of the most suitable materials. It is widely used in producing various products or components in multiple industries. Some of the primary uses of alumina are- 

• Owing to its chemical properties and hardness, many medical appliances are made by alumina.

• Alumina is widely used in the microchip industry. 

• Alumina is used to form two precious gems: rubies and sapphires.

• It is also used as a high-temperature electric insulator. 

• More than 90% of alumina is used to manufacture aluminium metal through electrolysis.

Conclusion 

Alumina is one of the most popular materials of bauxite ore. When reacting with sodium hydroxide, Alumina makes salt. When reacting with hydrogen chloride at room temperature, it gives aluminium chloride. Alumina is widely used in many different forms, such as it is used as a high electric insulator. Alumina is used in almost all ceramic products. Alumina is superbly resistant to abrasion and chemical attacks. The ceramic tile industry needs Alumina almost for every purpose, be it the manufacture of chips, stains, anti-slip coating, or grinding inputs.