Problem 47 - A Complete Resource Book in Chemistry for JEE Main

Question

The absorption of ultraviolet radiation by \(\mathrm{O}_{3}\) (a) makes both the function effective (b) makes no function effective (c) maintains an equilibrium between the concentrations of \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) (d) protects the inhabitants of out planet from injurious radiation

Step-by-Step Solution

Answer

(d) protects the inhabitants of our planet from injurious radiation

Step 1: Understand the Role of Ozone

Ozone (\(\mathrm{O}_3\)) is located in the Earth's stratosphere and plays a crucial role in absorbing the majority of the Sun's harmful ultraviolet (UV) radiation before it reaches the Earth's surface. This absorption is a protective function that is essential for life on Earth.

Step 2: Identify the Effects of UV Absorption by Ozone

When ozone absorbs ultraviolet radiation, it prevents harmful UV rays from reaching the Earth's surface, which could otherwise cause skin cancer, cataracts, and other harmful effects to living organisms including humans.

Step 3: Match the Effects with Given Options

Review the provided options: (a) makes both the function effective, (b) makes no function effective, (c) maintains an equilibrium between the concentrations of \(\mathrm{O}_2\) and \(\mathrm{O}_3\), (d) protects the inhabitants of our planet from injurious radiation. The option that correctly describes the protective role of ozone by absorbing UV radiation is option (d).

Step 4: Confirm with Definitions and Scientific Role

From scientific understanding, the primary function of ozone absorption is protection from UV radiation. This aligns with option (d), confirming it as the correct answer by its definition and role in the stratosphere.

Key Concepts

Ultraviolet Radiation

Ultraviolet (UV) radiation is a form of electromagnetic energy that comes from the Sun. It is invisible to the naked eye and is classified into three types:
**UVA:** Long-wave ultraviolet radiation, which can penetrate deeper into the skin.
**UVB:** Medium-wave ultraviolet radiation, responsible for causing sunburn and playing a role in skin cancer.
**UVC:** Short-wave ultraviolet radiation, which is absorbed completely by the Earth's atmosphere and does not reach the surface.

• UV radiation can cause significant harm to living organisms. It can damage skin cells, lead to sunburn, and increase the risk of skin cancers.
• The harmful effects also extend to the eyes, as excessive UV exposure can lead to cataracts and other eye conditions.

Despite these dangers, UV radiation is essential for the production of vitamin D in humans. However, it is crucial that we rely on the ozone layer to absorb the majority of UV rays and shield us from their harmful effects, ensuring a balance between exposure and protection.

Ozone Absorption

Ozone absorption occurs in the ozone layer, where ozone molecules (O\(_3\)) play a key role in protecting life on Earth by absorbing around 98% of the Sun's UV radiation. This occurs primarily in the stratosphere, which is a layer of the Earth's atmosphere that contains higher concentrations of ozone.

• When UV radiation encounters an ozone molecule, energy is absorbed.
• This process breaks the O\(_3\) molecule into an O\(_2\) molecule and an individual oxygen atom.
• The free oxygen atom can then combine with an O\(_2\) molecule to reform ozone, maintaining a dynamic equilibrium.

This cycle is essential for sustaining life, as it reduces the amount of harmful UV radiation reaching the Earth's surface. Without this absorption, the planet would be exposed to significantly higher levels of UV radiation, increasing health risks and affecting ecosystems adversely.

Stratosphere

The stratosphere is the second major layer of Earth's atmosphere, located above the troposphere and below the mesosphere. It extends from about 10 km to 50 km above the Earth's surface and houses the ozone layer.
The stratosphere is characterized by a temperature increase with altitude, which is unusual compared to the layers above and below it. This warming trend is a result of ozone absorption of UV radiation, which releases energy.

• The absorption of UV radiation by ozone is crucial for maintaining a stable temperature structure within the stratosphere.
• This layer acts as a shield, protecting all life forms by preventing the majority of harmful UV radiation from reaching the surface.

The presence of ozone in the stratosphere is vital for both environmental stability and the health of all living organisms, serving as a natural filter against UV radiation.