Action of Heat on Aluminium Hydroxide

When aluminium hydroxide (Al(OH)3Al(OH)3​) is heated, it undergoes thermal decomposition to form aluminium oxide (Al2O3Al2​O3​) and water (H2OH2​O). The reaction can be represented as:

2Al(OH)3→ΔAl2O3+3H2O2Al(OH)3​Δ​Al2​O3​+3H2​O

Detailed Steps of the Reaction:

1. Initial Heating:
   • Upon initial heating, begins to lose water molecules. This process starts at relatively low temperatures around 180-200°C.
2. Formation of Aluminium Oxide:
   • As the temperature increases, more water is released, and converts to aluminium oxide. The complete conversion typically occurs at temperatures around 300-400°C.

Characteristics of the Decomposition:

• Endothermic Process: The decomposition of AL(OH)3 is endothermic, meaning it absorbs heat from its surroundings during the reaction.
• Release of Water Vapor: The water produced in the reaction is released as steam, contributing to the endothermic nature of the process.
• Formation of Stable Product: The aluminium oxide formed (Al2O3Al2​O3​) is a stable, white, crystalline solid known as alumina. This compound has high thermal stability and is often used in ceramics, refractories, and as a catalyst support.

Applications:

• Fire Retardants: Due to the endothermic decomposition and release of water vapor, aluminium hydroxide is used as a fire retardant. When exposed to heat, it helps to cool the material and release water vapor, which dilutes flammable gases.
• Production of Alumina: The thermal decomposition of aluminium hydroxide is a crucial step in the production of alumina, which is further used in the manufacture of aluminium metal and various industrial products.

In summary, heating aluminium hydroxide results in its decomposition into aluminium oxide and water, a process utilized in various industrial applications due to the properties of the resultant compounds.