Question

How can electrolysis be used to produce Chlorine?

Answer 1

The word Electrolysis literally means Breaking in presence of electricity therefore clearly it is a process where we break compounds into their constituent ions using electricity in an electrolytic cell setup. Chlorine is useful in many industries and its production is generally done via electrolysis, specially the electrolysis of Brine solution i.e.$25 - 30\% NaCl$.

Complete answer:
Production of Chlorine is done by an electrolytic process named as Chlorine-Alkali electrolysis. It takes place via the following changes on electrodes:
At Cathode: $2{H_2}O + 2{e^ - } \to 2H{O^ - } + {H_2}$
At Anode: $2C{l^ - } \to C{l_2} + 2{e^ - }$and
$2{H_2}O + C{l^ - } \to 2H{O^ - } + {H_2} + C{l_2}$
As clear from above the byproducts obtained during the process of preparation of Chlorine are Hydrogen and Hydroxide which in the case of brine solution forms Sodium hydroxide.
We generally use an Iron$\left( {Fe} \right)$cathode and a Graphite$\left( C \right)$anode for the preparation of Chlorine.
Certain precautions have to be kept in mind during the whole process such as avoiding contact between$C{l_2}$and$H{O^ - }$as that leads to consumption of Chlorine formed to yield an undesired$Cl{O^ - }$like compound via the following reaction:
$C{l_2} + 2O{H^ - } \to Cl{O^ - } + C{l^ - } + {H_2}O$
To accomplish separation between chlorine and hydroxide ion we insert a porous wall between the electrodes or replace Iron cathode by Liquid mercury cathode wherein instead of hydroxide free sodium metal is discharged into the medium.
Chlorine production via electrolysis can also be done by using electrolysis of molten$NaCl$, electrolysis of Magnesium Chloride etc.

Note: The Chloro-alkali process is one which is used in industries extensively for production of Chlorine however when doing this type of electrolysis we should always be wary about the type of electrode we use for the process as this is essential in order to avoid any less useful byproduct or lose any yield.