Answer: Impurities have different solubility (distribution coefficient k) in solid vs liquid phases; most impurities are more soluble in the melt.
- A Impurities have different solubility (distribution coefficient k) in solid vs liquid phases; most impurities are more soluble in the melt
- B Impurities generally evaporate largely away from the metal rod as the heated molten zone slowly passes in routine practice overall in most cases
- C The molten heating zone is deliberately kept at a temperature below the metal's actual melting point under typical conditions according to standard textbooks
- D The specific impurities being removed by this process are inherently magnetic substances by nature in general practice as frequently described
Correct answer: A. Impurities have different solubility (distribution coefficient k) in solid vs liquid phases; most impurities are more soluble in the melt
Explanation: Distribution coefficient k = Cs/Cl (concentration in solid/liquid). For k < 1, impurities prefer the liquid zone and are swept toward one end of the ingot.
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.