Application of electrolysis

1. Manufacturing of chlorine.
Cathode
a) Mercury cathode Electrolyte : cell brine/salt water
Anode (graphite): Cl- -> 1/2 Cl2 + e
Cathode(mercury): Na+ +e --> Na
Na +Hg --> Na-Hg
Na-Hg +H2O -->NaOH+1/2H2 +Hg

b) Diaphragm cell Electrolyte: brine/conc NaCl
Anode(graphite): Cl- -> 1/2Cl2 +e
Cathode(steel): H2O + e --> OH- + 1/2H2
Besides chlorine, side product NaOH and H2.
For same quantity of electricity, say 1F,
ratio Cl2 : NaOH : H2
ratio 1/2 : 1 : 1/2