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

Sodium metal is prepared by Down's process, which involves the electrolysis of fused `NaCl` and `CaCl_(2)` mixture, at 873K. During electrolysis, sodium is discharged at the cathode, while `Cl_(2)` is obtained at the anode as a by-product.
`NaCl(l) overset("Electrolysis")rarr Na^(+)("melt")+Cl^(-)("melt")`
`"At cathode: "Na^(+)("melt")+e rarr Na(s)`
`"At anode:" Cl^(-)("melt")rarr Cl(g)+e, 2Cl(g)rarr Cl_(2)(g)`
However electrolysis of an aqueous `NaCl` solution leads to evolution of `H_(2)` at the cathode and `Cl_(2)` at the anode. This is because, `E^(@)` of `Na^(+)//Na` redox couple `(E^(@)=-2.71V)` is much lower than that of `H_(2)O(E_(H_(2)O //H_(2))^(@)=-0.83V).`
So, in reduction of water of `H_(2)` is preferred to `Na^(+)` ions.
In this case, `NaOH` is formed in the solution.
`NaCl(aq)overset("Electrolysis")rarr Na^(+)(aq)+Cl^(-)(aq)`
`"At anode: "Cl^(-)(aq) rarr Cl(g) +e, 2Cl(g)rarr Cl_(2)(g)`
`"At cathode: "2H_(2)O(l)+2e rarr H_(2)(g)+2OH^(-)(aq)`