Problem 77 - A Complete Resource Book in Chemistry for JEE Main

Question

Smog is essentially caused by presence of (a) \(\mathrm{O}_{2}\) and \(\mathrm{N}_{2}\) (b) \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) (c) \(\mathrm{O}_{3}\) and \(\mathrm{N}_{2}\) (d) oxides of sulphur and nitrogen

Step-by-Step Solution

Answer

Smog is mainly caused by oxides of sulfur and nitrogen (option d).

Step 1: Identify Common Smog Components

Smog is commonly associated with industrial and automotive emissions. It typically involves a combination of various gases like nitrogen oxides (NOx), sulfur oxides (SOx), volatile organic compounds (VOCs), and particulate matter. The presence of these chemicals, especially in sunny urban settings, leads to the development of smog.

Step 2: Evaluate Each Option

Let's examine each option:- (a) \(\mathrm{O}_{2}\) and \(\mathrm{N}_{2}\) do not directly contribute to smog as they are normal constituents of clean air.- (b) \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\): \(\mathrm{O}_{3}\), or ozone, can be a component of smog, but \(\mathrm{O}_{2}\) is not a direct contributor.- (c) \(\mathrm{O}_{3}\) and \(\mathrm{N}_{2}\): Ozone is often present in smog, but nitrogen \(\mathrm{N}_{2}\) is not a reactive compound contributing to smog formation.- (d) Oxides of sulfur and nitrogen are primary contributors of smog as they react in the atmosphere forming acidic compounds and enhancing ozone formation.

Step 3: Choose the Correct Answer

Considering the components known to cause smog, option (d) 'oxides of sulphur and nitrogen' aligns with the known contributors to smog formation. These compounds are notably part of the chemical reactions that result in the smog phenomenon, especially in urban and industrial areas.

Key Concepts

Nitrogen Oxides (NOx)

Nitrogen oxides, commonly referred to as NOx, are significant contributors to air pollution. These gases are primarily produced from combustion processes, like those seen in vehicles and power plants. The main components are nitric oxide (NO) and nitrogen dioxide (NO₂).

NOx gases are not only a major part of the smog formation process, but they also have direct health impacts. They can lead to respiratory issues and aggravate conditions like asthma. Furthermore, they participate in atmospheric reactions that lead to the formation of ozone, a significant smog component.

• Produced mainly from fuel combustion
• Consist of NO and NO₂
• Contribute to ozone formation and respiratory issues

Sulfur Oxides (SOx)

Sulfur oxides, or SOx, are another critical component of air pollution and smog. These compounds, mainly sulfur dioxide (SO₂), are produced when sulfur-containing fuels are burned, such as in electricity generation and industrial processes.

SOx compounds are harmful as they can lead to acid rain and are involved in forming particulate matter. They have a significant impact on air quality and public health. In urban and industrial areas, their concentration can be quite high, enhancing smog formation and contributing to environmental harm.

• Mainly consist of sulfur dioxide (SO₂)
• Originates from burning sulfur-containing fuels
• Leads to acid rain and worsens smog conditions

Volatile Organic Compounds (VOCs)

Volatile organic compounds, or VOCs, play a critical role in smog formation. They are a group of carbon-based compounds that easily evaporate into the air. You can find VOCs in products like paints, cleaners, and fuels.

These compounds react with NOx in the presence of sunlight to form ground-level ozone, a primary constituent of smog. Thus, controlling VOC emissions is crucial to reduce smog in urban environments.

• Highly evaporative carbon-based compounds
• Found in products like paints and fuels
• React with NOx to create ground-level ozone

Particulate Matter

Particulate matter (PM) consists of tiny particles suspended in the air. These particles can be solid or liquid droplets and vary widely in size. Sources of particulate matter include motor vehicles, industrial processes, and natural sources like wildfires and dust storms.

Particulate matter is a serious concern as it affects both health and the environment. Fine particles can penetrate deep into the lungs, leading to health issues like heart and lung diseases. Additionally, PM contributes to the haziness and reduced visibility associated with smog.

• Composed of tiny solid or liquid particles
• Emitted by vehicles and industrial activities
• Affects respiratory health and reduces visibility

Urban Air Pollution

Urban air pollution is a severe issue impacting regions worldwide, especially in densely populated areas. This pollution is comprised mainly of emissions from vehicles, industries, and other urban activities.

One of the most visible manifestations of urban air pollution is smog, which occurs when emissions from transportation, industrial activity, and other sources mingle in the air under certain conditions. High traffic, industrial discharge, and geographical factors can exacerbate the concentration of pollutants, leading to more severe smog events.

• Prominent in highly populated areas
• Caused by vehicles and industrial emissions
• Leads to smog and deteriorates air quality