Problem 23 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Photochemical smog consists of excessive amount of \(\mathrm{X}\), in addition to aldehydes, ketones, peroxyacetyl nitrate (PAN), and so forth \(X\) is : (a) \(\mathrm{CO}\) (b) \(\mathrm{CH}_{4}\) (c) \(\mathrm{O}_{3}\) (d) \(\mathrm{CO}_{2}\)

Step-by-Step Solution

Answer

The component \(X\) is \(\mathrm{O}_{3}\), so the answer is (c).

Step 1: Understanding Photochemical Smog Components

Photochemical smog refers to a type of air pollution created, particularly in urban areas, due to the reaction between sunlight and pollutants such as hydrocarbons and nitrogen oxides. This reaction largely produces ozone \( (\mathrm{O}_{3}) \), which is one of the principal components responsible for the formation of smog.

Step 2: Identifying Key Component

The exercise states that the smog consists of a particular component \(X\) in excessive amounts. From background knowledge on photochemical smog, we know that ozone \( (\mathrm{O}_{3}) \) is one of the primary constituents found in higher concentrations compared to other pollutants like aldehydes or ketones.

Step 3: Analyzing Given Options

Here, we need to locate the component \(X\) from the provided options. The options given are \(\mathrm{CO}\), \(\mathrm{CH}_{4}\), \(\mathrm{O}_{3}\), and \(\mathrm{CO}_{2}\). Among these, \(\mathrm{O}_{3}\), or ozone, is widely recognized as a major component of photochemical smog.

Step 4: Concluding the Solution

Conclusively, based on the comprehension of photochemical smog and the analysis of options, the component \(X\) present in excess in photochemical smog is \(\mathrm{O}_{3}\), which corresponds to option (c).

Key Concepts

Ozone

Ozone, denoted as \( \mathrm{O}_{3} \), is a molecule composed of three oxygen atoms. It is a crucial component of the Earth's atmosphere but plays different roles depending on its location. In the stratosphere, ozone forms a protective layer that shields the Earth from the Sun's harmful ultraviolet radiation. However, when it is found near the ground in the troposphere, it becomes a significant air pollutant. This ground-level ozone is harmful to human health and environmental quality. It is the key ingredient in the formation of photochemical smog, as it results from chemical reactions involving sunlight, nitrogen oxides, and volatile organic compounds.

Air Pollution

Air pollution is a troubling environmental issue that occurs when harmful substances are released into the atmosphere. These can be in the form of gases, solids, or liquids, and they have detrimental effects on health and the environment. Common sources include industrial emissions, vehicle exhaust, and chemical solvents. The pollutants can cause respiratory problems in humans, harm wildlife, damage ecosystems, and lead to the formation of acid rain.

• Gaseous air pollutants, like nitrogen oxides and sulfur dioxide, are particularly problematic.
• Particulate matter, such as dust and soot, can cause respiratory ailments.
• Persistent organic pollutants can accumulate in living organisms, leading to long-term health effects.

Understanding and controlling air pollution is vital to ensuring clean air and a healthy environment for everyone.

Chemical Reactions in Smog

Chemical reactions in smog formation are complex but fascinating. Photochemical smog arises when sunlight interacts with pollutants in the atmosphere, specifically hydrocarbons and nitrogen oxides.
When these chemicals mix with sunlight, they undergo a series of reactions that lead to the production of secondary pollutants, such as ozone. The process involves:

• Emission of nitrogen oxides (NOx) and volatile organic compounds (VOCs) from sources like vehicles and industrial activities.
• The interaction of these pollutants with sunlight, facilitating chemical transformations.
• Formation of secondary pollutants like ozone, which is a significant component of smog.

These reactions are more prevalent on sunny days, which can make urban areas particularly susceptible to high levels of smog.

Urban Pollution

Urban pollution refers to the contamination of the environment within cities and densely populated areas. This is a significant problem due to the high concentration of vehicles, industrial activities, and energy consumption found in metropolitan regions. Photochemical smog is prevalent in these areas due to the abundance of pollutants from numerous sources:

• High traffic volumes contribute significantly to urban pollution through exhaust emissions.
• Industrial activities release large quantities of gases, including sulfur dioxide and nitrogen oxides.
• The widespread use of fossil fuels increases the emission of carbon-based pollutants.

The dense concentration of buildings and human activities in cities means pollutants can accumulate, affecting both air quality and public health.

Nitrogen Oxides

Nitrogen oxides (NOx) are a group of gases composed of nitrogen and oxygen atoms. They are significant contributors to atmospheric pollution and are key players in the formation of photochemical smog.
NOx gases primarily derive from:

• Combustion processes, particularly from motor vehicles and power plants.
• Industrial processes that involve burning of fossil fuels.

Once in the atmosphere, nitrogen oxides can react with other compounds to form harmful pollutants such as ozone and fine particles. This makes controlling NOx emissions crucial for reducing air pollution and the prevalence of smog in urban environments.