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. It involves the electrolysis of a fused mixture of NaCl and ` CaCl_ 2 ` at 873 K. During electrolysis, sodium is discharged at the cathode while ` Cl _ 2 ` is obtained at the anode as a bye - product.
` " " NaCl(l)overset ("Electrolysis")to Na^(+) ("melt ") + Cl^( - )("melt" ) `
At cathode : ` Na^(+) ("melt" ) + e ^(- ) to Na (s) `
At anode: ` " " Cl^( - )("melt") to Cl(g) + e ^( - ) , 2 Cl (g) to Cl_ 2 (g)`
If, however, an aqueous solution of NaCl is electrolysed, `H_2 ` is evolved at the cathode while ` Cl_ 2 ` is obtained at the anode. The reason being that the `E^(@) ` of ` Na^(+)//Na ` redox couple is much lower ` (E^(@) = - 2*71V) ` than that of ` H_2O (E^(@)""_(H_2 O // H_2) = - 0*83 V) `and hence water is reduced to ` H_ 2 ` in preference to `Na^(+) ` ions.
NaOH is, however, obtained in the solution.
`" " NaCl (aq) overset ("Electrolysis") to Na^(+) (aq) + Cl^(- ) (aq)`
At anode : ` Cl^( - ) (aq) to Cl (g) + e ^(-), 2 Cl (g) to Cl_ 2 (g) `
At cathode : ` 2 H_2O (l) + 2 e^( - ) to H_ 2 (g) + 2 OH^(- ) (aq) `