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General Principles and Processes of Isolation of Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryGeneral Principles and Processes of Isolation of Elements1 Mark
MCQ
Aluminium is used in thermite welding because:
  • A
    Aluminium is a light metal.
  • ✓
    Aluminium has more affinity for oxygen.
  • C
    Aluminium is a strong oxidizing agent.
  • D
    Aluminium 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.

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