MCQ
Aluminium is used in thermite welding because:
- AAluminium is a light metal.
- ✓Aluminium has more affinity for oxygen.
- CAluminium is a strong oxidizing agent.
- DAluminium is a reactive metal.
✓
Answer
Correct option: 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,
$\mathrm{Fe}_2 \mathrm{O}_3+2 \mathrm{Al} \rightarrow 2 \mathrm{Fe}+\mathrm{Al}_2 \mathrm{O}_3$
$\mathrm{Cr}_2 \mathrm{O}_3+2 \mathrm{Al} \rightarrow 2 \mathrm{Cr}+\mathrm{Al}_2 \mathrm{O}_3$
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.
$\mathrm{Fe}_2 \mathrm{O}_3+2 \mathrm{Al} \rightarrow 2 \mathrm{Fe}+\mathrm{Al}_2 \mathrm{O}_3$
$\mathrm{Cr}_2 \mathrm{O}_3+2 \mathrm{Al} \rightarrow 2 \mathrm{Cr}+\mathrm{Al}_2 \mathrm{O}_3$
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.
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