Which one of the following statements is not true?

  • Option 1)

    Dissolved oxygen (DO) in cold water can reach a concentration upto 10 ppm.

  • Option 2)

    Clean water would have a BOD value of 5ppm

  • Option 3)

    Fluoride deficiency in drinking water is harmful.Soluble fluoride os often used to bring its concentration upto 1 ppm

  • Option 4)

    When the pH of rainwater is higher than 6.5, it is called acid rain

 

Answers (1)

As learnt in

Acid rain -

Rainfall and other precipitation with a pH of less than 5.6 . Acidic components, sulphuric acid and nitric acid,
are emitted into the atmosphere from thermal power plants, industries, automobiles.

- wherein

2SO_{2}(g)+O_{2}(g)+2H_{2}O(l)
ightarrow 2H_{2}SO_{4}(aq)

4NO_{2}(g)+O_{2}(g)+2H_{2}O(l)
ightarrow 4HNO_{3}(aq)

 

 


Option 1)

Dissolved oxygen (DO) in cold water can reach a concentration upto 10 ppm.

This option is incorrect

Option 2)

Clean water would have a BOD value of 5ppm

This option is incorrect

Option 3)

Fluoride deficiency in drinking water is harmful.Soluble fluoride os often used to bring its concentration upto 1 ppm

This option is incorrect

Option 4)

When the pH of rainwater is higher than 6.5, it is called acid rain

This option is correct

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