Class 11 Chemistry The S Block Elements Preparation of Caustic soda

Preparation of Caustic soda

  • It is commercially prepared by electrolysis of sodium chloride in Castner-Kellner cell.

  • Brine solution is first electrolyzed.
  • Mercury is made the cathode.
  • Carbon is made the anode.
  • Sodium metal gets discharged at cathode.
  • This discharged sodium combines with mercury and forms sodium amalgam.
  • Chlorinegas is evolved at the anode.

  • The amalgam then reacts with water and produces sodium hydroxide and hydrogen gas.

2Na-amalgam + 2H2O --> 2NaOH+ 2Hg +H2

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