Question

Chlorine water on standing loses its colour and forms:
(A) $HOCl\text{ }and\text{ }HOC{{l}_{2}}$
(B) $HCl$ only
(C) $HCl\text{ and HCl}{{\text{O}}_{2}}$
(D) $HCl$ and $HOCl$

Answer 1

Basically Chlorine is a chemical element which is yellowish in colour. Since it’s a halogen, it’s highly reactive and also a strong oxidizing agent. When the chlorine is dissolved in water, chlorine water is formed.

Complete step by step solution:
- As we know, chlorine is a fairly soluble element in water. When it is dissolved in water, a strongly smelling, yellow solution called chlorine water is being formed.
- When chlorine water is exposed to sunlight, the solution loses its yellow colour. The loss of colour of yellow solution is due to the formation of a mixture of hypochlorous acid and hydrochloric acid. The corresponding reaction can be written as follows
$C{{l}_{2}}+{{H}_{2}}O\to HCl+HOCl$
- The given reaction is an example of a disproportionation reaction. The hypochlorous acid decomposes into a nascent oxygen and hydrochloric acid. This reaction can be represented as follows
$HOCl\to HCl+\left[ O \right]$
- This newly formed nascent oxygen is accountable for the oxidizing and bleaching properties of chlorine.
- From the above discussions it’s clear that the Chlorine water on standing loses its colour and forms hydrochloric acid and hypochlorous acid.

Therefore the answer is option (D) $HCl$ and $HOCl$.

Note: Do not confuse hypochlorous acid with other oxyacids of chlorine. Hypochlorous acid has the formula $HOCl$, Chlorous acid has the formula $HCl{{O}_{2}}$, chloric acid has the formula $HCl{{O}_{3}}$ and perchloric acid ha the formula $HCl{{O}_{4}}$. Also it is found that chlorine water can cause several skin problems when used in excess in the process of chlorination.