Question

Rain water is called 'acid rain' when its ______.

Options

• pH falls below 7.2.

• pH falls below 14.

• pH is above 7.

• pH falls below 5.6.

Answer 1

Rain water is called ‘acid rain’ when its pH falls below 5.6.

Explanation:

Normal rainwater has a pH of about 5.6 because it reacts with carbon dioxide to form weak carbonic acid. It is officially classified as acid rain only when its pH drops below this level due to pollutants like sulphur and nitrogen oxides.