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Standard XII
Chemistry
BOD and COD
AssertionIf B...
Question

Assertion
If BOD level of water in reservoir is less than 5 ppm it is not polluted.

Reason
High biological oxygen demand means low activity of bacteria in water.

A
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
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B
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
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C
Assertion is correct but Reason is incorrect
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D
Both Assertion and Reason are incorrect
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Solution

The correct option is C Assertion is correct but Reason is incorrect
Assertion
If the BOD level of water in the reservoir is less then 5 ppm it is not polluted.
Reason
High biological oxygen demand means a low activity of bacteria in water which is incorrect.

BOD indicates the amount of oxygen required by bacteria to break down organic matter present in a certain volume of a sample of water. Therefore, a low BOD is an indication of good quality water, while a high BOD indicates polluted water. Dissolved oxygen (DO) is consumed by bacteria when large amounts of organic matter from sewage or other discharges are present in the water.

Hence the correct answer is option (c).

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BOD and COD
Standard XII Chemistry
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