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 caused by the presence of oxides of sulphur and nitrogen, so the answer is (d).

Step 1: Understand Smog

First, let's understand what smog is. Smog is a type of air pollution characterized by a visible haze or fog in the atmosphere, typically found in urban areas. It results from the combination of pollutants such as industrial emissions, car exhaust fumes, and other chemical reactions in the atmosphere.

Step 2: Identify Key Components

The primary components responsible for the formation of smog are oxides of nitrogen (NO) and volatile organic compounds (VOCs). When these compounds react in the presence of sunlight, they form ground-level ozone (O_3) and fine particles, which contribute to smog.

Step 3: Evaluate Each Option

Now, evaluate each given option: (a) O_2 and N_2: While oxygen and nitrogen are abundant in the atmosphere, they do not directly contribute to smog formation. (b) O_2 and O_3: Oxygen is a major component, but in isolation with ozone, it doesn't directly cause smog. (c) O_3 and N_2: Ozone is part of smog, but nitrogen gas (N_2) itself doesn't cause it. (d) Oxides of sulphur (SO_x) and nitrogen (NO_x): These are key contributors to smog formation as sulfur and nitrogen oxides react in the atmosphere to form secondary pollutants.

Step 4: Select the Correct Answer

Based on the components that typically cause smog, option (d), 'oxides of sulphur and nitrogen,' is the correct answer since these oxides play a significant role in smog formation.

Key Concepts

Air Pollution

Air pollution is when harmful substances, introduced by human activity or natural processes, contaminate the atmosphere. These pollutants come from various sources like factories, vehicles, and even agricultural activities.

The two main types of pollutants are:

• Primary Pollutants: Directly emitted pollutants like carbon monoxide from cars or sulfur oxides from factories.
• Secondary Pollutants: Not emitted directly but formed when primary pollutants react in the atmosphere, such as ground-level ozone.

These pollutants can harm our health, the environment, and contribute to phenomena like smog. Reducing air pollution involves controlling emissions and introducing cleaner technologies.

Industrial Emissions

Industrial emissions are pollutants released into the air from factories and manufacturing processes. These include gases and particles that often result from the burning of fossil fuels like coal and oil.

Common emissions from industries are:

• Particulate Matter (PM): Tiny particles that can penetrate deep into the lungs.
• Sulfur Dioxide (SO₂): Can lead to acid rain and respiratory problems.
• Nitrogen Oxides (NOₓ): Contribute to smog and acid rain formation.

Efforts to reduce industrial emissions include using scrubbers or filters and shifting to renewable energy sources like wind or solar power.

Ground-Level Ozone

Ground-level ozone is a harmful air pollutant and a key component of smog. It forms when oxides of nitrogen (NOₓ) and volatile organic compounds (VOCs) react under sunlight.

Unlike the protective ozone layer high above the Earth, ground-level ozone can cause respiratory issues and damage crops. Its formation is especially pronounced in urban areas with heavy traffic and industrial activities.

Preventative measures include reducing emissions of NOₓ and VOCs and promoting cleaner transportation options like biking or public transit.

Oxides of Nitrogen

Oxides of nitrogen, abbreviated as NOₓ, are a group of gases that play a significant role in air pollution. They are primarily produced from burning fuels in cars and power plants.

These gases include:

• Nitric Oxide (NO): A colorless gas that can oxidize to form other pollutants.
• Nitrogen Dioxide (NO₂): A reddish-brown gas contributing to respiratory issues and smog.

Reducing NOₓ emissions can be achieved through catalytic converters in vehicles and cleaner industrial processes.

Volatile Organic Compounds

Volatile Organic Compounds, or VOCs, are organic chemicals that can easily become vapors or gases. They are emitted from various sources including paints, cleaning supplies, and automotive exhausts.

Common sources of VOCs are:

• Industrial Solvents: Used in manufacturing processes.
• Gasoline Vapors: Released during fueling of vehicles.
• Household Products: Such as aerosols and cleansers.

Since VOCs contribute to smog formation and can be harmful indoors and outdoors, reducing their use and choosing safer alternatives is crucial.