Final answer:
Nitrogen oxides and hydrocarbons combine in the presence of sunlight to cause:
4) photochemical smog
Step-by-step explanation:
Photochemical smog is the result of the interaction between nitrogen oxides (NOx) and hydrocarbons in the presence of sunlight. The primary components of photochemical smog are ground-level ozone and other secondary pollutants. When NOx and hydrocarbons, often released from vehicle emissions and industrial activities, react in the presence of sunlight, they form a complex mixture of pollutants, including ozone, aldehydes, and peroxyacetyl nitrate (PAN).
The chemical reactions involved in the formation of photochemical smog include the photochemical reaction of nitrogen oxides and hydrocarbons. For example, nitrogen dioxide (NO₂) and volatile organic compounds (VOCs) react in the presence of sunlight to produce ozone (O₃) and other secondary pollutants. This ozone, at ground level, contributes to the formation of smog and can have harmful effects on human health, causing respiratory problems and other health issues.
In summary, the combination of nitrogen oxides and hydrocarbons, when exposed to sunlight, leads to the formation of photochemical smog. This phenomenon is a significant environmental concern in urban areas with high levels of vehicle emissions and industrial activities, where the concentration of NOx and hydrocarbons is elevated. OPTION 4