Answer: Fe2O 3 + 2Al → Al 2 O 3 + 2Fe (aluminium reduces iron oxide, highly exothermic).
- A Fe2O<sub>3</sub> + 2Al → Al<sub>2</sub>O<sub>3</sub> + 2Fe (aluminium reduces iron oxide, highly exothermic)
- B Fe + O<sub>2</sub> → Fe2O<sub>3</sub>, the simple rusting reaction of iron in air in general practice
- C Al + H<sub>2</sub>O → Al<sub>2</sub>O<sub>3</sub> + H<sub>2</sub>, the reaction of aluminium with water as frequently described
- D Al + Fe → alloy, a direct alloying reaction with little oxide involved
Correct answer: A. Fe2O<sub>3</sub> + 2Al → Al<sub>2</sub>O<sub>3</sub> + 2Fe (aluminium reduces iron oxide, highly exothermic)
Explanation: The thermite reaction produces molten iron in situ; used for welding railway tracks due to the extreme localised heat.
An Ellingham diagram plots ΔG° of oxide formation against temperature for different metals; whichever line is LOWER (more negative ΔG°) at a given temperature reduces the oxide of any metal whose line sits above it - the basis of carbon reduction (Fe, Zn) vs electrolytic reduction (Al, Mg, Na) decisions.
Concept context
The science of extracting metals from ores and refining them for use. Covers concentration methods, reduction techniques, refining processes, and the thermodynamic principles that govern metal extraction.