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Question

Given below are two statements. One labelled as Assertion (A) and the other labelled as Reason (R) :
Assertion (A) : Chlorine, which is widely used as an effective and relatively inexpensive disinfectant in water, generates toxic organochlorine compounds in water.
Reason (R) : Hypochlorous acid reacts rapidly with humic acids and hydroxobenzenes.
Choose the correct answer :

The correct answer is
Both (A) and (R) are correct and (R) is the correct explanation of (A).

Chlorine Disinfection: Analyzing Assertion and Reason

Assertion (A) Analysis

The assertion states that chlorine, used as a water disinfectant, generates toxic organochlorine compounds. This is factually correct. When chlorine reacts with naturally occurring organic matter present in water, it can form various disinfection byproducts (DBPs), some of which are organochlorines and can be toxic.

Reason (R) Analysis

The reason explains that hypochlorous acid ($HOCl$), the active form of chlorine in water, reacts rapidly with substances like humic acids and hydroxobenzenes. This is also factually correct. Humic acids and hydroxobenzenes (phenols) are common organic precursors found in natural waters, and $HOCl$ readily reacts with them, leading to the formation of DBPs.

Connecting Assertion and Reason

The rapid reactions described in Reason (R) between hypochlorous acid and organic precursors (humic acids, hydroxobenzenes) are the direct chemical mechanism responsible for the generation of the toxic organochlorine compounds mentioned in Assertion (A).

Conclusion

Based on the analysis:

  • Assertion (A) is correct.
  • Reason (R) is correct.
  • Reason (R) correctly explains the mechanism behind Assertion (A).

Therefore, the correct option is that both (A) and (R) are correct, and (R) is the correct explanation of (A).

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Important Questions from Environmental Chemistry - Teaching

  1. Which of the following chemicals is used to cause artificial rain (cloud seeding)?

  2. Which is not a preferable characteristics of water to be used as green solvent ?
  3. Which of the following reaction involves the principle of green chemistry ?
  4. For a green synthesis strategy choose the one which is not applicable.
  5. Out of the following two statements, identify the correct one(s) :
    (a) An aqueous solution of sodium carbonate is alkaline.
    (b) An aqueous solution of carbon dioxide is acidic.
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