Answer: Magnetic (e.g., magnetite Fe 3 O 4 ) to separate from non-magnetic gangue.
- A Magnetic (e.g., magnetite Fe<sub>3</sub>O<sub>4</sub>) to separate from non-magnetic gangue
- B Generally denser than the surrounding gangue material overall in most cases
- C Sulfide ores best separated instead by froth flotation under typical conditions
- D Carbonate ores best separated instead by gravity methods according to standard textbooks
Correct answer: A. Magnetic (e.g., magnetite Fe<sub>3</sub>O<sub>4</sub>) to separate from non-magnetic gangue
Explanation: Magnetic ores (like magnetite) are separated from non-magnetic gangue by passing the crushed mixture over a magnetic roller.
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.