Answer: Their oxide formation Delta_G is too large; no chemical reducing agent (not even C) can reduce them at practical temperatures.
- A Their oxide formation Delta_G is too large; no chemical reducing agent (not even C) can reduce them at practical temperatures
- B These particular metals are generally too rare in nature to ever justify any chemical reduction step in typical laboratory settings
- C These particular metals are inexpensive enough that electrolysis is preferred for cost reasons regardless under usual circumstances
- D These particular metals form unusually volatile oxide compounds that evaporate away before reduction begins according to most researchers
Correct answer: A. Their oxide formation Delta_G is too large; no chemical reducing agent (not even C) can reduce them at practical temperatures
Explanation: Al, Mg, and Na oxides have very large negative Delta_G of formation; on the Ellingham diagram, no chemical reductant's line passes below these even at the highest temperatures.
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.