Problem 55 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following is mainly responsible for depletion of ozone layer? (a) water (b) carbon dioxide (c) chlorofluorocarbons (d) methane

Step-by-Step Solution

Answer

Chlorofluorocarbons (CFCs) are mainly responsible for ozone layer depletion.

Step 1: Identifying the Problem

The problem at hand is to identify which compound from the given options is mainly responsible for the depletion of the ozone layer.

Step 2: Understanding Ozone Layer Depletion

The ozone layer is a protective shield in Earth's stratosphere, and its depletion is primarily due to certain chemicals released into the atmosphere.

Step 3: Evaluating the Options

Let's analyze each option: (a) Water is not known for destroying ozone; (b) Carbon dioxide contributes to the greenhouse effect rather than ozone depletion; (c) Chlorofluorocarbons (CFCs) are known to break down ozone molecules; (d) Methane primarily impacts greenhouse gas levels rather than directly damaging the ozone layer.

Step 4: Selecting the Correct Option

Based on our analyses, chlorofluorocarbons are the substances linked to ozone layer depletion as they release chlorine atoms that break down ozone molecules.

Key Concepts

Chlorofluorocarbons (CFCs)

Chlorofluorocarbons, commonly abbreviated as CFCs, are compounds once widely used in refrigeration, air conditioning, and as propellants in aerosol sprays. They are composed of carbon, chlorine, and fluorine atoms. Despite their past utility, CFCs have a significant environmental downside. When released into the atmosphere, they eventually reach the stratosphere, where they are broken down by ultraviolet (UV) radiation. This process releases chlorine atoms, highly reactive species that can catalytically destroy ozone molecules. The destruction of ozone in the stratosphere raises concern because the ozone layer protects life on Earth by blocking harmful UV radiation from the sun. Thus, CFCs play a critical role in ozone layer depletion, which is why international agreements like the Montreal Protocol have aimed to phase out their use.

Stratosphere

The stratosphere is the second major layer of Earth's atmosphere, sitting above the troposphere and extending from approximately 10 to 50 kilometers above Earth's surface. This layer is crucial because it contains the ozone layer, which absorbs and scatters the sun's harmful ultraviolet radiation. The stability of this layer is vital for life on Earth.
One of the distinctive features of the stratosphere is its temperature profile. Unlike the troposphere, the stratosphere experiences an increase in temperature with altitude, owing to the absorption of UV radiation by ozone. This heating effect provides stability, reducing turbulence and convection. However, the delivery of ozone-depleting substances like CFCs to the stratosphere has disrupted its delicate balance, thinning the protective ozone shield and allowing more UV radiation to reach the Earth's surface.

Environmental Chemistry

Environmental chemistry is a scientific discipline focused on the chemical processes occurring in the environment and their effects on human health and ecosystems. This field studies the sources, reactions, transport, and fate of chemicals in the soil, water, and air.
One key area within environmental chemistry is the study of atmospheric reactions, like those causing ozone layer depletion. Scientists in this field investigate how pollutants such as CFCs and other industrial chemicals impact the natural composition of the atmosphere. They utilize this knowledge to develop policies and technologies aimed at reducing pollution and mitigating its effects. The understanding gained through environmental chemistry is crucial for creating strategies to protect our planet from the long-term impacts of human activity, including climate change and biodiversity loss.