Answer: Electrolytic refining (crude Cu anode, pure Cu cathode, CuSO 4 electrolyte).
- A Electrolytic refining (crude Cu anode, pure Cu cathode, CuSO<sub>4</sub> electrolyte)
- B Simple distillation of the molten metal under vacuum in most textbook accounts
- C Zone refining by passing a molten zone along a copper rod during normal conditions
- D The thermite process used instead to refine iron oxide as generally observed
Correct answer: A. Electrolytic refining (crude Cu anode, pure Cu cathode, CuSO<sub>4</sub> electrolyte)
Explanation: In electrolytic refining, Cu dissolves from the crude anode and deposits as pure Cu on the cathode; impurities collect as anode mud.
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.