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GATE 2020 CE (CE1) – Question 26

Water and Waste Water Quality and Treatment · Unit processes and operations · 1 mark · Multiple choice

Aqueous chlorine reacts with water: $Cl_2+H_2O\rightleftharpoons HOCl+Cl^-+H^+$. Which is the most active disinfectant?

  1. $H^+$
  2. $HOCl$
  3. $Cl^-$
  4. $H_2O$

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Correct answer: (B) $HOCl$

Explanation

Hypochlorous acid HOCl is the active molecular disinfectant formed by chlorine hydrolysis. Chloride is the reduced,non-disinfecting form;hydrogen ions and water are not chlorine disinfectants. **Answer:B**.