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

Answer 1

The correct option is B

aluminium has more affinity for oxygen.

The explanation for correct option B:

• Reducing agents are the species that reduces other substance and undergoes oxidation in the process.
• In thermite process, the metal oxide undergoes reaction with Aluminum $\left(\mathrm{Al}\right)$ powder to form metal along with Aluminium oxide $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$.
• Aluminium reacts with Iron(III) oxide$\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ in the thermite welding process to form Aluminium oxide along with Iron $\left(\mathrm{Fe}\right)$.
• Since for oxygen affinity of Aluminum is higher than Iron, Aluminum reduces Iron(III) oxide to Iron and acts as the reducing agent in the process.

${\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+2\mathrm{Al}\left(\mathrm{s}\right)\to {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+2\mathrm{Fe}\left(\mathrm{s}\right)$

Final Answer: Hence, option B is correct. Aluminium is used in thermite welding because aluminium has more affinity for oxygen.