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: The question targets which chlorine species actually does the killing of microbes during water chlorination.

Step 2: Chlorine in water yields two free forms, hypochlorous acid and the hypochlorite ion, but their germicidal power differs greatly.

Step 3: Hypochlorous acid is the dominant disinfectant; being neutral and small, it slips through the microbial membrane and is many times stronger than the negatively charged hypochlorite ion.

Step 4: Hence the active disinfecting form is hypochlorous acid, while the hypochlorite and chloride ions contribute little or no disinfection. \[\boxed{\text{Hypochlorous acid}}\]