Name the processes from which chlorine is obtained as a by-product. What will happen if an aqueous solution of NaCl is subjected to electrolysis?

Explanation

Chlorine is obtained as the by-product in the manufacture of sodium by Down's process in which molten sodium chloride is subjected to electrolysis.
`NaCl(l) overset("Electrolysis") to Na^(+) +Cl^(-)`
At cathode: `" " Na^(+) e^(-) to Na , " At anode :" Cl^(-) to 1//2 Cl_(2)+e^(-)`
Sodium obtained by this method is almost pure while chlorine is the by-product.
Chlorine can also be obtained by carrying out the electrolysis of an aqueous solution of sodium chlorine. The process is carried in Nelson's cell. The various reactions which take place are as follows :
`NaCl overset((aq))to Na^(+) (aq)+Cl^(-)(aq)`
`H_(2)O harr H^(+)(aq)+OH^(-)(aq)`
At cathode. Both `Na^(+) " and " H^(+)` ions migrate towards the cathode but `H^(+)` ions are discharged in preference to `Na^(+)` ions since their discharge potential is less. `Na^(+)` ions remain in the solution.
`H^(+)+e^(-) to H , H+H to H_(2)(g)`
At anode : Both `Cl^(-) " and " OH^(-)` ions migrate towards the anode but `Cl^(-)` ions are discharged in preference to `OH^(-)` since their discharge potential is less. `OH^(-)` ions remain in the solution.
` Cl^(-) to Cl +e^(-) , Cl+ Cl to Cl_(2)(g)`
Thus, in the electrolysis of an aqueous NaCl solution,` H_(2)` gas is evolved at the cathode and chlorine at the anode. The solution contains NaOH and is therefore, basic in nature.
It is always better to prepare chlorine by Down's process.