Give the theory of manufacture of caustic soda by Castner Kellner's process ?

Explanation

Sodium hydroxide is manufactured by the electrolysis of a saturated solution of sodium chloride in Castner-Kellner cell. It is also known as mercury cathode cell.
Working : The cell consists of a rectangular iron tank. Merucyr flows at the bottom of the cell. it is considered as a cathode. the brine solution flows in the same direction. number of graphite blocks act as anode. on passing electric current through the cell, the following reactions take place:
At anode: `NaCl to Na^(+)+Cl^(-)`, `Cl^(-)toCl+e^(-)`
At cathode: `Na^(+)+e^(-) to Na`, `Na+Hg to underset("Amalgam")(Na//Hg)`
Sodium atoms are produced at cathode where they form amalgam with mercury. this amalgam flows out and reacts with water and give NaOH
`2Na//Hg+2H_(2)O to 2NaOH+2Hg+H_(2)`