Question

Give reason for the following?
Chlorine water on standing loses its yellow colour.

Answer 1

Chlorine water is made by adding chlorine into the water. Actually this process is known as chlorination. This is done to prevent water from the harmful airborne disease and make the water free of the deadly microbes.

Complete answer:
Chlorination is the process of adding chlorine or chlorinated compounds like sodium hypochlorite into the water. This process is done to make water safe and free of unnecessary microbes or germs.
Now, we know that chlorine water is slightly yellow in colour and has a distinctive smell from ordinary water.
Also, the chlorinated water or chlorine water loses its yellow colour, this is due the fact that standing chlorine water undergoes reaction and produces different products.
So, the reaction is:
$C{l_2} + {H_2}O \to HCl + HOCl$
Hence, chlorine undergoes reaction and produces hydrochloric acid and hypochlorous acid and this is the reason why it loses its yellow colour.

Note:
Often this question is asked, if the chlorinated water is safe for drinking or not. So, according to survey agencies, it is found that the chlorinated water is safe to use and drink. But keep in mind the chlorine level in water. Chlorine should be added in water in the amount that is only enough to kill harmful microbes. So, until and unless chlorine is in limit, there is no long-term adverse effect on human health. But excessively high levels of chlorine in the water can be a health problem.