Answer: iron(II) oxide.
- A copper oxide
- B silica itself
- C sulfur dioxide
- D iron(II) oxide
Correct answer: D. iron(II) oxide
Explanation: Silica combines with iron(II) oxide to form ferrous silicate slag (FeSiO<sub>3</sub>), separating the iron impurity from the copper matte.
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.