Question

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

Answer 1

a) True

b) True

c) False

d)True

Answer 2

Answer:

In the below given statements the statement which is not true is When the pH of rain water is higher than 6.5, It is called acid rain.

Explanation:

In the below given statements the statement which is not true is When the pH of rain water is higher than 6.5, It is called acid rain.

The statement is false because normal pH value of rain is slightly acidic that is 5.5 approximately.

But for acid rain the pH alters to nearly 4.5. This occurs when rain water mixes up with acids like sulphur oxide and nitrogen oxide.