Answer: Electrolysis of brine (NaCl solution) using mercury cell.
- A Electrolysis of brine (NaCl solution) using mercury cell
- B The Solvay process, which instead yields sodium carbonate from brine
- C Electrolysis of molten anhydrous NaCl to give metallic sodium
- D Direct reaction of sodium carbonate with slaked lime
Correct answer: A. Electrolysis of brine (NaCl solution) using mercury cell
Explanation: The Castner-Kellner (mercury cell) electrolyses brine to give Cl<sub>2</sub> at anode and Na amalgam at cathode; the amalgam reacts with water to give NaOH.
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.