Question

Which among the following is the active form of chlorine in chlorination?

• A. Hypochlorite ion
• B. Hydrogen chloride
• C. Hypochlorous acid
• D. Chloride ion

Hint:

The uncharged species is far stronger than the hypochlorite ion.

Answer 1

The Correct Option is C

Step 1: When chlorine is added to water for disinfection, it reacts to form hypochlorous acid and the hypochlorite ion, which together make up free residual chlorine.

Step 2: The disinfecting action of chlorine is predominantly due to hypochlorous acid, the most effective form.

Step 3: Hypochlorous acid is about 70 to 80 times more effective as a germicide than the hypochlorite ion because it is uncharged and penetrates the bacterial cell wall easily.

Step 4: Therefore the active form responsible for disinfection is hypochlorous acid (option C); the hypochlorite ion and chloride ion are far less or non-active.