Question

Write the reactions of \[{{\rm{F}}_{\rm{2}}}\] and \[{\rm{C}}{{\rm{l}}_{\rm{2}}}\] with water.

Answer 1

Hint: Fluorine is a strong oxidising agent. Chlorine undergoes disproportionation reaction.

Complete step by step answer:
Fluorine is a strong oxidising agent. It oxidises water to oxygen or ozone.

\[\begin{array}{l}
 {\rm{2 }}{{\rm{F}}_{\rm{2}}}\left( g \right) + {\rm{2 }}{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( l \right) \to 4{\rm{ }}{{\rm{H}}^ + }\left( {aq} \right){\rm{ + }}4{\rm{ }}{{\rm{F}}^ - }\left( {aq} \right){\rm{ + }}{{\rm{O}}_{\rm{2}}}\left( g \right) \\
 {\rm{3 }}{{\rm{F}}_{\rm{2}}}\left( g \right) + 3{\rm{ }}{{\rm{H}}_{\rm{2}}}{\rm{O}}\left( l \right) \to 6{\rm{ }}{{\rm{H}}^ + }\left( {aq} \right){\rm{ + 6 }}{{\rm{F}}^ - }\left( {aq} \right){\rm{ + }}{{\rm{O}}_{\rm{3}}}\left( g \right) \\
 \end{array}\]

The oxidation state of oxygen in water is -2. The oxidation state of oxygen in \[{{\rm{O}}_{\rm{2}}}\] is 0. Thus, fluorine oxidises water to dioxygen.
The oxidation state of oxygen in water is -2. The oxidation state of oxygen in \[{{\rm{O}}_{\rm{3}}}\] is 0. Thus, fluorine oxidises water to ozone.

Chlorine reacts with water to form hydrochloric acid and hypochlorous acid. Due to this, the chlorine water loses its yellow color on standing.

\[\begin{array}{l}
 {\rm{ C}}{{\rm{l}}_2} + {{\rm{H}}_{\rm{2}}}{\rm{O}} \to {\rm{HCl}} + {\rm{HOCl}} \\
 {\rm{ HOCl }} \to {\rm{ HCl + }}\left[ {\rm{O}} \right] \\
 \end{array}\]

The nascent oxygen released during the process gives oxidising and bleaching properties to chlorine.
The reaction of chlorine with water is a disproportionation reaction. In this reaction, the oxidation state of chlorine in \[{\rm{C}}{{\rm{l}}_{\rm{2}}}\] is 0. The oxidation states of chlorine in HCl and HOCl are -1 and +1 respectively. Thus, in this disproportionation reaction, one chlorine atom is oxidised to HOCl and another chlorine atom is reduced to HCl.

Note:
\[{{\rm{F}}_{\rm{2}}}\] and \[{\rm{C}}{{\rm{l}}_{\rm{2}}}\] will give different reactions with water. The rate of the reaction of fluorine with water is much higher than the rate of reaction of chlorine with water. Bromine and iodine do not react with water because bromine and iodine have smaller reduction potential than oxygen. Fluorine and chlorine have larger reduction potential than water. Hence, fluorine and chlorine react with water.