Question

Explain how, a reduction reaction of aluminium can be used for welding cracked machine parts of iron. Write a chemical equation for the reaction involved.

Answer 1

When iron (III) oxide and aluminium powder are heated together, aluminium acts as a reducing agent and reduces iron (III) oxide to iron metal. It also gets oxidised to aluminium oxide with the liberation of excess heat.  As excess heat is liberated in the reaction, the product, i.e., iron metal  is formed in molten state.  This reaction is an oxidation-reduction reaction and its chemical equation is:

This reaction is called as thermite reaction. This reaction is widely used to weld cracked machine parts of iron. This is called thermite welding.