Question

Acid rain is chiefly due to atmospheric pollution by
1. SO₂
2. H₂S
3. HCl
4. N₂

Answer 1

Correct Answer - Option 1 : SO₂

Along with harming human health, air pollution can cause a variety of environmental effects that affect the overall environment, acid rain being one of them.

Acid Rain:  

• Acid rain means the precipitation of acidic components such as Sulfuric or Nitric acid.
• Sulfur dioxide and oxides of nitrogen get into the upper atmosphere by wind or air currents and get mixed with water.
• The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.
• Normal rain has a pH value of 5.6.
• It is slightly acidic due to the presence of carbon dioxide which gets dissolved into the water forming weak carbonic acid.
• However, acid rain usually has a pH between 4.2 and 4.4 because of the large quantity of acids. 
• The major sources of sulphuric dioxide and oxides of nitrogen are the burning of fossil fuels, emission from vehicles, oil refineries, etc. 

Thus, acid rain is chiefly due to atmospheric pollution by SO2.

​Controlling Acid rain:

• Reducing the amount of SO2 and NO2 being released into the atmosphere decreases the chances of acid rain.
• The main source of SO2 is coal fuel power plants in which SO2 emission can be reduced by new combustion techniques.
• Whereas the main source of NO2 in the atmosphere is through vehicular exhaust which can be controlled by using internal combustion engines.