Write down the reactions involved during the formation of photochemical smog.

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Photochemical smog, commonly found in urban areas with high levels of air pollution, is primarily formed through a series of complex chemical reactions involving pollutants emitted from various sources such as vehicles, industrial processes, and natural sources. These reactions typically occur in the presence of sunlight and involve nitrogen oxides (NOx), volatile organic compounds (VOCs), and oxygen molecules (O2).

Here are the key reactions involved:

1. Formation of Nitrogen Dioxide (NO2):

   • Nitric oxide (NO), a primary pollutant emitted from vehicle exhaust and industrial processes, reacts with oxygen (O2) in the atmosphere to form nitrogen dioxide (NO2).
   • Reaction: 2NO+O2→2NO22NO+O2→2NO2

2. Formation of Ozone (O3):

   • Oxygen molecules (O2) in the atmosphere are split apart by ultraviolet (UV) radiation from sunlight, forming oxygen atoms (O).
   • Oxygen atoms (O) then react with oxygen molecules (O2) to form ozone (O3).
   • Reaction: O2+UV→2OO2+UV→2O and O+O2→O3O+O2→O3

3. Reaction between Nitrogen Dioxide and Oxygen Radicals:

   • Nitrogen dioxide (NO2) reacts with oxygen radicals (O) to form nitric oxide (NO) and oxygen molecules (O2).
   • Reaction: NO2+O→NO+O2NO2+O→NO+O2

4. Formation of Peroxyacetyl Nitrate (PAN):

   • Peroxyacetyl radicals (CH3C(O)O2) are formed through reactions involving VOCs.
   • These radicals then react with nitrogen dioxide (NO2) to form peroxyacetyl nitrate (PAN) and other compounds.
   • Reaction: CH3C(O)O2+NO2→PAN+other productsCH3C(O)O2+NO2→PAN+otherproducts

5. Ozone Formation:

   • Ozone (O3) is continuously formed through the reactions involving oxygen atoms and oxygen molecules in the presence of sunlight.

These reactions lead to the accumulation of ozone, nitrogen oxides, volatile organic compounds, and other pollutants in the atmosphere, resulting in the formation of photochemical smog. UrbanPro provides excellent resources and expert tutors who can further elucidate these concepts and help you grasp them effectively.