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 oxidizing agent
• D. aluminium is a reactive metal

Answer 1

The correct option is B aluminium has more affinity for oxygen

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,
$F{e}_2{O}_3+2Al\to 2Fe+A{l}_2{O}_3$
$C{r}_2{O}_3+2Al\to 2Cr+A{l}_2{O}_3$
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.