Answer: Very pure semiconductors (Si, Ge) by moving a molten zone through the material.
- A Very pure semiconductors (Si, Ge) by moving a molten zone through the material
- B Crude, completely unrefined metal straight from the original smelting furnace charge
- C Iron alloys specifically blended and cast for heavy structural construction purposes
- D Common table salt purified by recrystallisation directly from a saturated brine solution
Correct answer: A. Very pure semiconductors (Si, Ge) by moving a molten zone through the material
Explanation: Zone refining (zone melting) purifies metals/semiconductors by moving a molten zone; impurities concentrate in the melt and are swept to one end.
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.