Question

Why does aluminium not react with water under ordinary conditions?

Answer 1

Hint: Aluminium does not react with water under ordinary conditions because of the presence of some other entities which are interfering in the chemical reaction and altering the results. The reaction is not conducted under special conditions like a vacuum. Thus, components present in the air can also react.

Complete step by step answer:
Here we need to know that the reaction of water with aluminium metal is not occurring in-situ or in a vacuum. Thus, there is a presence of air and moisture in the atmosphere which are also interfering in the reaction process. Due to the presence of moisture and oxygen, the aluminium metal reacts with them to form aluminium oxide \[\left( {A{l_2}{O_3}} \right)\]
Aluminium oxide \[\left( {A{l_2}{O_3}} \right)\] is commonly called Alumina. It is a white powder-like compound with a high melting point and chemical stability. Its structure is in the form of the crystalline framework (called corundum), in which the oxide ions are held very strongly in the solid lattice forming hexagonal close-packed structure and aluminium ions occupying two-thirds of the octahedral sites.
Due to this thermodynamic and chemical stability of the aluminium oxide, it becomes almost impossible for water molecules to react with alumina under ordinary conditions like room temperature and atmospheric pressure. and therefore, aluminium oxide is insoluble in water. Thus, to conclude we can say that aluminium does not react with water under ordinary conditions because of the formation of alumina \[\left( {A{l_2}{O_3}} \right)\] due to the presence of oxygen and moisture in the air.
\[A{l_2}{O_3} + {H_2}O \to \times \;(No{{ }}Reaction)\]

Note: Aluminium oxide is an amphoteric oxide which means it can behave as both acid and base during a specific reaction process. Unlike aluminium oxide, sodium oxide and magnesium oxide easily react with water to form the corresponding hydroxides. Thus, all the oxides are not water insoluble except aluminium oxide \[\left( {A{l_2}{O_3}} \right)\] and silicon dioxide \[\left( {Si{O_2}} \right)\]