Question

How would you write the balanced equation for the reaction of elemental chlorine with liquid water?

Answer 1

When a chemical reaction is written using the chemical formulae of the compound or species involved in the reaction then it is known as a chemical equation.
When there are the same numbers of atoms of elements on the reactant as well as the product side of the chemical equation then it is a balanced chemical equation.
The reaction between water and chlorine gas is the disproportionation reaction.

Complete answer:
When chlorine gas reacts with water, a disproportionation reaction takes place.
In disproportionation, the reaction element is present in three oxidation states. Here, chlorine is disproportionate in presence of the water and reaction takes place are as follows:
Here, the oxidation reaction of chlorine is as follows:
$\dfrac{1}{2}{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{\text{Cl}}{{\text{O}}^ - }\,{\text{ + }}\,{{\text{e}}^ - }\,{\text{ + 2}}{{\text{H}}^ + }$
Here, chlorine from zero oxidation state changes to +1 oxidation state, thus oxidation of chlorine takes place.
Here, chlorine is reduced also and the reaction is as follows:
$\dfrac{1}{2}{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}\,{{\text{e}}^ - }\, \to {\text{C}}{{\text{l}}^ - }$
Here, chlorine from zero oxidation state changes to -1 oxidation state, thus reduction of chlorine takes place.
The overall reaction is obtained by addition oxidation and the reduction reaction as follows:
$\dfrac{1}{2}{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}\,{\text{ + }}\dfrac{{\text{1}}}{{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{e}}^{\text{ - }}} \to {\text{Cl}}{{\text{O}}^ - }\,{\text{ + }}\,{{\text{e}}^ - }\,{\text{ + 2}}{{\text{H}}^ + } + {\text{C}}{{\text{l}}^ - }$
${\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{\text{Cl}}{{\text{O}}^ - }\,{\text{ + 2}}{{\text{H}}^ + } + {\text{C}}{{\text{l}}^ - }$
This reaction also can be written as follows:
${\text{C}}{{\text{l}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{\text{HClO}}\,{\text{ + HCl}}$
This is the balanced chemical equation for the reaction between water and chlorine gas that leads to producing hypochlorous acid and hydrochloric acid.

Note: When a chemical reaction is written using the chemical formulae of the compound or species involved in the reaction then it is known as a chemical equation.The balanced chemical equation is very important to determine the stoichiometry of the reaction. The stoichiometric ratio obtained between the reactants and products is important to determine the yield of the species formed in the reaction.Oxidation is the process where an electron is lost by the species while reduction is the process in which electrons are gained by the species.The reaction in which oxidation, as well as reduction, takes place are known as redox reactions.