Ions present: H+,Cl- from HCL
H+, OH- from H2O
During electrolysis, hydrogen ions move to the cathode while Cl- and OH- ions move to the anode.
At the cathode, the hydrogen ions are discharged as hydrogen gas.
The hydrogen gas then passes through tube B and is collected over saturated of calcium chloride.
At the anode: chloride ion are discharged in preference to OH- ion because of their high concentration in solution. The Cl- ion are discharged as chlorine gas.
The chlorine gas passes through tube ‘a’ and is collected over saturated solution of calcium chloride.