Answer: Lowers the melting point from 800°C to ~600°C and increases conductivity.
- A Lowers the melting point from 800°C to ~600°C and increases conductivity
- B Produces calcium metal as the main electrolysis product instead
- C Acts as an oxidising agent that consumes the sodium metal formed
- D Directly reduces sodium ions to sodium metal without electrolysis
Correct answer: A. Lowers the melting point from 800°C to ~600°C and increases conductivity
Explanation: CaCl<sub>2</sub> acts as a flux; the NaCl/CaCl<sub>2</sub> mixture melts at ~600°C vs 800°C for pure NaCl, saving energy and preventing Na vaporisation.
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.