Question

Acid rain is primarily caused by the emission of which two gases into the atmosphere?

• A. Nitrogen oxides and sulfur dioxide
• B. Carbon monoxide and methane
• C. Ozone and carbon monoxide
• D. Hydrogen sulfide and ammonia

Hint:

• Acid rain is mainly caused by sulfur dioxide (SO$_2$) and nitrogen oxides (NO$_x$). % Corrected
• These gases are released from burning fossil fuels and other industrial/natural processes.
• In the atmosphere, SO$_2$ converts to sulfuric acid (H$_2$SO$_4$). % Corrected
• NO$_x$ converts to nitric acid (HNO$_3$). % Corrected
• These acids lower the pH of precipitation.

Answer 1

The Correct Option is A

Acid rain is primarily caused by the emission of two specific gases: nitrogen oxides (NOx) and sulfur dioxide (SO₂). When these gases are released into the atmosphere, they react with water vapor, oxygen, and other chemicals to form acidic compounds. This process can be elucidated by the following reactions:

• Sulfur Dioxide (SO₂): SO₂, once in the atmosphere, can be oxidized to form sulfur trioxide (SO₃), which subsequently reacts with water to produce sulfuric acid (H₂SO₄). The chemical reactions can be represented as:
  SO₂ + O₂ → SO₃
  SO₃ + H₂O → H₂SO₄
• Nitrogen Oxides (NOx): Nitrogen oxides, primarily nitrogen monoxide (NO) and nitrogen dioxide (NO₂), participate in forming nitric acid (HNO₃). This process involves the oxidation of NO to NO₂, followed by reacting with water:
  2NO + O₂ → 2NO₂
  3NO₂ + H₂O → 2HNO₃ + NO

As a result, these acids precipitate onto the earth's surface, causing environmental harm to ecosystems, buildings, and infrastructure. Therefore, the correct answer is "Nitrogen oxides and sulfur dioxide".