Question

Aluminium is used in thermite welding because-

• A. aluminium is a light metal
• B. aluminium has more affinity for oxygen
• C. aluminium is a strong oxidising agent
• D. aluminium is a reactive metal

Answer 1

Answer: (B)

aluminium has more affinity for oxygen

Answer 2

The affinity for oxygen in the case of aluminium is higher than that of iron and therefore, it acts as a strong reducing agent with iron, $Fe _{2} O _{3}+2 Al \rightarrow 2 Fe + Al _{2} O _{3}$ $Cr _{2} O _{3}+2 Al \rightarrow 2 Cr + Al _{2} O _{3}$ This is an important application in the melting of metals. The reaction, being exothermic, produces large amount of heat, thus melting the metal and the process is called thermite welding.