Question

Which photochemical oxidants are formed by the action of sunlight on nitrogen oxides and reactive hydrocarbons?

• A. peroxyacetyl nitrate
• B. acid rain
• C. inorganic carbon
• D. particulate matter

Hint:

• Photochemical smog forms when sunlight acts on nitrogen oxides (NO$_x$) and volatile organic compounds (VOCs/reactive hydrocarbons).
• This produces secondary pollutants called photochemical oxidants.
• Key photochemical oxidants include ground-level ozone (O$_3$) and peroxyacetyl nitrate (PAN).
• PAN is known for causing eye irritation and damaging plants.

Answer 1

The Correct Option is A

To answer the question, let's explore the photochemical reactions involving sunlight, nitrogen oxides, and reactive hydrocarbons, which lead to the formation of various photochemical oxidants.

1. Understanding the Concepts:

- Photochemical Oxidants: These are harmful chemical compounds formed when sunlight interacts with certain pollutants in the atmosphere, particularly nitrogen oxides (NO_x) and reactive hydrocarbons (VOCs). The reaction between these compounds under sunlight leads to the production of various secondary pollutants, which are harmful to human health and the environment.

- Common Photochemical Oxidants: Some of the most significant photochemical oxidants include ozone (O₃), peroxyacetyl nitrate (PAN), and other related compounds. These are formed through complex chemical reactions in the atmosphere, especially in the presence of sunlight.

2. Breakdown of the Given Options:

• Peroxyacetyl Nitrate (PAN): This is the correct answer. PAN is a photochemical oxidant formed by the action of sunlight on nitrogen oxides and reactive hydrocarbons (VOCs). It is one of the key pollutants in photochemical smog and can cause respiratory problems.
• Acid Rain: While acid rain can result from the reaction of nitrogen oxides and sulfur oxides with water vapor, forming acids such as sulfuric and nitric acid, it is not directly a photochemical oxidant formed by sunlight. Acid rain is more related to the chemical transformation of pollutants in the atmosphere.
• Inorganic Carbon: Inorganic carbon (such as carbon dioxide) is not a photochemical oxidant. It is a greenhouse gas and does not form as a result of the reaction between nitrogen oxides and hydrocarbons under sunlight.
• Particulate Matter: Particulate matter (PM) refers to tiny particles or droplets suspended in the air. While particulate matter can be formed in various ways, it is not a photochemical oxidant created by the interaction of nitrogen oxides and hydrocarbons under sunlight.

3. Conclusion:

The photochemical oxidant formed by the action of sunlight on nitrogen oxides and reactive hydrocarbons is peroxyacetyl nitrate (PAN). It is a harmful secondary pollutant that contributes to the formation of smog and has adverse health effects.

Final Answer:

The photochemical oxidant formed by the action of sunlight on nitrogen oxides and reactive hydrocarbons is peroxyacetyl nitrate (PAN).