Question

Acid rain is caused by the pollution of environment by
1. carbon dioxide and nitrogen
2. carbon monoxide and carbon dioxide
3. ozone and carbon dioxide
4. nitrous oxide and sulphur dioxide

Answer 1

Correct Answer - Option 4 : nitrous oxide and sulphur dioxide

The correct answer is nitrous oxide and sulphur dioxide.

• Definition of Acid Rain - Rain or any other form of precipitation that has a higher level of hydrogen ions (i.e. low pH < 5.6), is termed as Acid Rain.
• Oxides of sulphur and nitrogen which are acidic in nature are responsible for causing Acid Rain.
• Human activities like the burning of fossil fuels, volcanic activities, etc. result in the formation of sulphur dioxide and nitrogen oxides.
• These oxides after oxidation and reaction with water are the major contributors to Acid Rain.
• Following chemical reactions occur:

1. 2SO₂ (g) + O₂ (g) + 2H₂O (l) → 2H₂SO₄ (aq)
2. 4NO2 (g) + O2 (g) + 2H2O (l) → 4HNO₃ (aq)

Aftermaths of Acid Rain:

1. Deteriorates plant and animal life in the aquatic ecosystem.
2. It corrodes water pipes resulting in the leaching of heavy metals (iron, lead, copper) into drinking water.
3. It damages buildings and other structures made of metal or stone (eg. Taj Mahal)
4. Chemical reaction occurring at the surface of Taj Mahal: CaCO₃ + H2SO4 → CaSO₄ + H2O + CO₂

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• The term Acid Rain was first coined by Scottish chemist Robert Angus Smith in the year 1852.
• Normal rainwater is weakly acidic due to the presence of carbonic acid, which is formed due to the absorption of carbon dioxide from the atmosphere.