Answer: Silver, gold, and platinum group metals collect as anode mud.
- A Silver, gold, and platinum group metals collect as anode mud
- B Iron, which dissolves alongside copper and deposits at the cathode
- C Zinc, which collects together with the precious metals in the anode mud
- D Aluminium, which is recovered from the copper sulfate electrolyte
Correct answer: A. Silver, gold, and platinum group metals collect as anode mud
Explanation: Noble metals (Ag, Au, Pt) do not dissolve from the anode during Cu electrolytic refining; they fall off as anode sludge/mud and are recovered.
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.