Question

Give reasons for the following:

Chlorine water on standing loses its yellow colour

Answer 1

Chlorine:

• Chlorine($\mathrm{Cl}$) is a chemical element with a yellowish hue.
• Because it is a halogen, it is very reactive and a powerful oxidising agent.
• Chlorine water is generated when Chlorine is dissolved in water.

Reaction on chlorine water due to sunlight:

• When Chlorinated water is exposed to sunshine, its yellow colour fades.
• The loss of yellow solution colour is caused by the development of a combination of Hypochlorous acid ($\mathrm{HOCl}$) and Hydrochloric acid ($\mathrm{HCl}$).
• The associated reaction is as follows:

$\underset{\mathrm{Chorine}}{{\mathrm{Cl}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\stackrel{\mathrm{Sunlight}}{\to }\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{l}\right)}+\underset{\mathrm{Hypochlorous}\mathrm{acid}}{\mathrm{HOCl}\left(\mathrm{l}\right)}$

Thus, in this way, Chlorine water on standing loses its yellow colour.