Which one of the following statements is not true?
Dissolved oxygen (DO) in cold water can reach a concentration upto 10 ppm.
Clean water would have a BOD value of 5ppm
Fluoride deficiency in drinking water is harmful.Soluble fluoride os often used to bring its concentration upto 1 ppm
When the pH of rainwater is higher than 6.5, it is called acid rain
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
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