Question

How much less pH of rain water is called 'Acid rain'?
1. 5.6
2. 6.0
3. 7.0
4. 7.5

Answer 1

Correct Answer - Option 1 : 5.6

The correct answer is 5.6.

• Normally rainwater has a pH of 5.6 due to the presence of H⁺ ions formed by the reaction of rainwater with carbon dioxide present in the atmosphere.
• When the pH of the rainwater drops below 5.6, it is called acid rain.

• Acid rain is produced from the emission of sulfur dioxide (SO₂) and nitrogen oxides (the combination of NO and NO₂) from human activities, mostly the combustion of fossil fuels. 
• SO₂ and NO₂ after oxidation and reaction with water are major contributors to acid rain because polluted air usually contains particulate matter that catalyzes the oxidation.

• Effects of Acid Rain:
  • Acid rain is harmful to agriculture, trees, and plants as it dissolves and washes away nutrients needed for their growth.
  • It causes respiratory ailments in human beings and animals.
  • It affects plants and animal life in the aquatic ecosystem as the acid rain flows as groundwater to reach rivers, lakes, etc.
  • Acid rain damages buildings and other structures made of stone or metal. The Taj Mahal has been affected by acid rain.