Which Chloramine is formed, when the pH range is less than 4.4?

Explanation:

Treatment with chlorine:

(i) Chlorine is powerful oxidising agent, which when dissolved in water yields the following reaction:

At pH < 5, chlorine does not react with water and remains as free chlorine or unreacted chlorine.

Reaction of chlorine with water

(ii) (HOCL + OCl- and Cl2) are combinedly called freely availabe chlorine.

(iii) Out of these forms freely available chlorine hypochlorous acid HOCl is most destructive. It is 80% more effective than OCl- ion. Hence, pH of water should be maintained slightly below 7.

(iv) Moreover, chlorine will immediately react with ammonia in water to form chloramines.

\(C{l_2} + N{H_3}\overset{pH>7.5}{\longrightarrow} N{H_2}Cl + HCl \)

\(C{l_2} + N{H_2}Cl\overset {pH=(5-6.5)}{\longrightarrow} NHC{l_2} + HCl \)

\(C{l_2} + NHCl_{2} \overset{pH<4.4}{\longrightarrow} NC{l_3} + HCl \) -- [ From the reaction it is clear that Trichloroamine is formed when pH is less than 4.4]

 Additional Information(v) The chloramines are the combined residuals. They more stable than free residuals but less effective as disinfectant and remains in water for greater duration.

(vi) In the usual chlorine treatment, in which pH is kept slightly less than 7, diachloramine (NHCl2) is most predominant.