Answer: Carbon monoxide (CO) formed from coke.
- A Carbon monoxide (CO) formed from coke
- B Hydrogen gas injected directly into the furnace
- C Molten aluminium added as a reducing agent
- D Calcium metal added as a reducing agent
Correct answer: A. Carbon monoxide (CO) formed from coke
Explanation: CO (from coke combustion in limited air) reduces Fe2O<sub>3</sub>: Fe2O<sub>3</sub> + 3CO → 2Fe + 3CO<sub>2</sub>.
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.