Answer: Lower the melting point from 800°C to ~600°C making electrolysis practical.
- A Lower the melting point from 800°C to ~600°C making electrolysis practical
- B Simply raise the ionic conductivity without affecting melting point
- C Form a protective layer that prevents oxidation of the sodium product
- D Serve as a catalyst that speeds the electrode reactions
Correct answer: A. Lower the melting point from 800°C to ~600°C making electrolysis practical
Explanation: Pure NaCl melts at 800°C; adding CaCl<sub>2</sub> lowers the melting point (~600°C), reducing energy consumption and preventing Na vaporisation.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.