In a thermite process, the reducing agent is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Al
In the thermite process (aluminothermy) a metal oxide is reduced by powdered aluminium. Aluminium has a very high affinity for oxygen: the formation of \( \ce{Al2O3} \) has a large negative Gibbs energy, so aluminium takes oxygen away from oxides such as \( \ce{Fe2O3} \) and \( \ce{Cr2O3} \).
\(\ce{Fe2O3 + 2Al -> Al2O3 + 2Fe}\)
\(\ce{Cr2O3 + 2Al -> Al2O3 + 2Cr}\)
The reaction is so exothermic that the metal formed is molten; molten iron from the thermite reaction is used to weld railway tracks and broken machine parts. Aluminium is oxidised (0 to +3) and is the reducing agent.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.