Answer: Low melting points (like Sn, Bi, Pb) by gently heating on a slope so pure metal flows away from impurities.
- A Low melting points (like Sn, Bi, Pb) by gently heating on a slope so pure metal flows away from impurities
- B Unusually high melting points that instead require an electric arc furnace to process them in the majority of cases studied
- C Vacuum distillation of the molten metal carried out under significantly reduced pressure as widely reported
- D Zone refining mainly, with little thermal gradient on a heated slope involved in standard practice under most conditions encountered
Correct answer: A. Low melting points (like Sn, Bi, Pb) by gently heating on a slope so pure metal flows away from impurities
Explanation: Liquation heats impure low-melting-point metals on a sloped hearth; the pure metal melts and flows out, leaving higher-melting impurities behind.
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.