Answer the question on the basis of the passage given below:

Molecular nitrogen is very little reactive chemically. During lightning discharge, atmospheric nitrogen and oxygen combine to form nitric acid which also combines with oxygen to form nitrogen dioxide. Both \(NO\) and \(NO_2\) constitute smog which is very poisonous. It can cause a burning sensation in the eyes and adversely affect the respiratory system.

What are the constituents of photochemical smog?

Photochemical smog are oxide of nitrogen, organic compounds like formaldehyde acrolein and peroxyacetyl nitrate (PAN)

The correct answer is option 1. Photochemical smog are oxide of nitrogen, organic compounds like formaldehyde acrolein, and peroxyacetyl nitrate (PAN).

Photochemical smog is a complex mixture of pollutants that are formed when primary pollutants, especially oxides of nitrogen (NOx) and volatile organic compounds (VOCs), undergo chemical reactions in the presence of sunlight. The formation of photochemical smog involves a series of complex reactions and the release of secondary pollutants. The constituents of photochemical smog include:

1. Oxides of Nitrogen (NOx): These are primary pollutants released from combustion processes, such as those in vehicles and industrial activities. Nitric oxide \((NO)\) and nitrogen dioxide (NO2) are common components of NOx.

2. Volatile Organic Compounds (VOCs): These are a group of organic chemicals that can easily evaporate into the air. Examples of VOCs involved in smog formation include:

I. Formaldehyde \((HCHO)\): A colorless gas with a pungent odor, formaldehyde is a VOC that contributes to the formation of photochemical smog.

II. Acrolein \((C_3H_4O)\):  Another VOC, acrolein is a highly reactive and irritating compound.

III. Peroxyacetyl Nitrate (PAN):  Formed as a secondary pollutant in the presence of NOx and VOCs, PAN is a key component of photochemical smog. It is an eye and respiratory irritant.

3. Sunlight: Sunlight, specifically ultraviolet (UV) radiation, plays a crucial role in the formation of photochemical smog. The energy from sunlight initiates and drives the complex chemical reactions among NOx and VOCs, leading to the formation of secondary pollutants.

The formation of photochemical smog involves several steps, including the photodissociation of nitrogen dioxide \((NO_2)\), the generation of ozone \((O_3)\), and the subsequent reactions with VOCs to produce a variety of secondary pollutants. These reactions are collectively known as photochemical reactions.

The presence of photochemical smog is often associated with urban areas and regions with high vehicular traffic and industrial activities. It can have adverse effects on human health, leading to respiratory problems and irritation of the eyes and throat. Additionally, photochemical smog contributes to environmental issues such as the formation of ground-level ozone, which is a key component of smog and a harmful air pollutant.