The sBlock Elements - Result Question 17
####18. In Castner-Kellner cell for production of sodium hydroxide:
[NEET Kar. 2013]
(a) Brine is electrolyzed with Pt electrodes
(b) Brine is electrolyzed using graphite electrodes
(c) Molten sodium chloride is electrolysed
(d) Sodium amalgam is formed at mercury cathode
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Solution:
- (d) In castner kellner cell, sodium amalgam is formed at mercury cathode.
Sodium is discharged from brine at a mercury cathode in preference to hydrogen because of the high hydrogen overpotential at mercury surface. This is the reason of using mercury cathode instead of graphite or platinum in castner-kellner cell.
