Problem 26 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere? (a) freons (b) ferrocene (c) fullerenes (d) polyhalogens

Step-by-Step Solution

Answer

Freons (a) are responsible for ozone layer depletion.

Step 1: Understanding the Chemistry Context

The ozone layer in the upper atmosphere protects the Earth from harmful ultraviolet radiation. However, certain chemicals can lead to its depletion.

Step 2: Analyzing the Options

Evaluate each option based on their chemical properties and their potential impact on the ozone layer. - Freons: Also known as chlorofluorocarbons (CFCs), are well-documented for their role in ozone depletion. - Ferrocene: An organometallic compound often used in fuels but not linked to ozone depletion. - Fullerenes: Carbon structures that do not affect the ozone layer. - Polyhalogens: Compounds with multiple halogens, but not specifically linked to the ozone layer.

Step 3: Identifying the Correct Answer

From the analysis, freons (CFCs) have a known role in breaking down ozone molecules in the stratosphere, leading to depletion of the ozone layer.

Key Concepts

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons, commonly referred to as CFCs, are compounds made up of chlorine, fluorine, and carbon. Historically, these substances were used in many everyday applications, including refrigeration and air conditioning, due to their non-flammable and non-toxic properties.
However, after extensive scientific research, it became clear that CFCs are extremely harmful to the environment, specifically the ozone layer.

• CFCs were first created in the 1920s and became widespread in the decades that followed.
• They are chemically stable, which allowed them to drift into the stratosphere intact.
• Once in the stratosphere, they release chlorine atoms, which catalyze the destruction of ozone molecules.

This chain reaction can lead to significant ozone layer thinning, known as depletion, especially over polar regions. Understanding and controlling the effects of CFCs was crucial for ozone protection efforts.

Chemical Impact on Atmosphere

The atmosphere is a delicate blend of gases that support life on Earth. Introducing certain chemicals, like CFCs, can cause significant disruptions to this balance, leading to environmental concerns like ozone depletion.
When CFCs reach the stratosphere, they release chlorine atoms, which can then interact with ozone molecules (O"]'). This interaction significantly decreases the efficiency of the ozone layer to block harmful ultraviolet (UV) radiation.

• For example, a single chlorine atom can destroy up to 100,000 ozone molecules before it is deactivated, showing the severe catalytic potential of these atoms.
• The decreased ozone levels result in higher amounts of UV radiation reaching the Earth's surface, which can cause health and environmental issues.

Issues like increased skin cancer rates, cataracts in humans, and negative impacts on animals and ecosystem health have been linked to heightened UV exposure due to ozone layer thinning.

Ozone Layer Protection

Protecting the ozone layer is vital as it plays a crucial role in safeguarding life on Earth. The ozone layer acts as a shield that absorbs the majority of the sun's harmful UV radiation.
Recognizing the threat caused by CFCs and other ozone-depleting substances, international efforts have been taken to protect and conserve this crucial part of the atmosphere.

• The Montreal Protocol, agreed upon in 1987, is a global treaty aimed at phasing out the production and consumption of ozone-depleting substances, including CFCs.
• Due to these coordinated efforts, global emissions of CFCs have drastically reduced, and studies show that the ozone layer is on a path to recovery.
• Continued adherence to these regulations and advancements in creating safer alternatives for industrial applications are essential for the ongoing protection of the ozone layer.

By understanding the importance of the ozone layer and the impact certain chemicals can have, societies can better protect the environment and ensure a healthier world for future generations.