Explain and write the reactions for the preparation of caustic soda by the method of castner kellner cell...
Answers
Principle — In castner-kellner method NaOH is prepared by the electrolysis of aqueous solution of NaCl (Brine).
Castner-kellner cell — It is a rectangular tank of steel. Inside of tank is lined with ‘ebonite.’ Anode is made of titanium. Flowing layer of mercury (Hg) at the bottom of tank serves as cathode.
Ionization of NaCl — 2NaCl e- 2Na+ + 2Cl-
When electric current is passed through brine, +ve and -ve ions migrate towards their respective electrodes. Na+ ions are discharged at mercury cathode. The sodium deposited at mercury forms Sodium Amalgam. Chlorine produced at the anode is removed from the top of the cell.
Reaction at cathode
2Na+ +2 e- à 2Na
(Na forms amalgam)
Na + Hg à Na/Hg
Na+ ions are discharged in preference to H+ ions due to high over voltage.
Reaction at anode
2Cl- à Cl2 + 2e-
- Kellner–Solvay cell consists of a rectangular trough, at the base of which there is a thin layer of mercury which flows from one end to the other acting as cathode. A concentrated brine solution flows slowly through the cell in the same direction as the mercury and is maintained at a constant level.
❤❤❤❤❤❤❤❤❤❤