Problem 68 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements are incorrect about ozone layer? 1\. it is beneficial because ozone cuts-off the ultraviolet radiation of the sun 2\. it is harmful because ozone cuts out the important radiation of the sun which are vital for photosynthesis 3\. it is harmful because ozone is dangerous to living organisms 4\. it is beneficial because oxidation reaction can proceed faster in the presence of ozone (a) 1,2 and 3 (b) 1,2 and 4 (c) 3 and 4 only (d) 2,3 and 4

Step-by-Step Solution

Answer

Option (d) 2, 3, and 4 are incorrect statements.

Step 1: Evaluating Statement 1

Statement 1 claims that the ozone layer is beneficial because it cuts off the ultraviolet radiation of the sun. This statement is correct because the ozone layer absorbs and reduces harmful UV rays from reaching the Earth's surface, which protects living organisms from damage.

Step 2: Evaluating Statement 2

Statement 2 claims that the ozone layer is harmful because it cuts out important radiation necessary for photosynthesis. This statement is incorrect because photosynthesis primarily depends on visible light, not ultraviolet light, which the ozone layer filters.

Step 3: Evaluating Statement 3

Statement 3 claims that ozone is harmful because it is dangerous to living organisms. At ground level, ozone can indeed be harmful as it is a pollutant and can cause respiratory problems. However, in the stratosphere, ozone is protective. Therefore, this statement is context-dependent.

Step 4: Evaluating Statement 4

Statement 4 claims that the ozone layer is beneficial because oxidation reactions proceed faster in the presence of ozone. This statement is incorrect as it provides no significant benefit from the presence of ozone in relation to chemical reactions like oxidation.

Step 5: Identifying Incorrect Statements

Based on the evaluations, the incorrect statements are 2 and 4. Statement 3 is context-dependent, primarily suggesting harm at the ground level, while being beneficial in the stratosphere. Thus, according to the options provided, (d) 2, 3, and 4 are the incorrect statements.

Key Concepts

Ultraviolet Radiation

Ultraviolet (UV) radiation is a type of energy produced by the sun. It plays a fundamental role in our environment and affects both living organisms and atmospheric phenomena. The ozone layer in the Earth's stratosphere serves as a protective shield by absorbing a significant portion of the harmful ultraviolet radiation before it reaches the surface. This protection is crucial since excessive exposure to UV radiation can lead to:

• Skin damage and increased risk of skin cancer.
• Eye injuries, such as cataracts.
• Suppression of the immune system.

Thanks to the ozone layer, these harmful effects are minimized, ensuring a safer environment for life on Earth. The filtering of UV radiation is not only beneficial for human health but also for other organisms and ecosystems as it prevents excessive UV exposure that can disrupt natural biological processes. Nonetheless, despite its detrimental potential, some UV radiation does play a positive role in environments requiring disinfection and in the synthesis of Vitamin D in the skin.

Photosynthesis

Photosynthesis is a fundamental process that allows plants, algae, and some bacteria to convert light energy, typically from the sun, into chemical energy. This process is vital for life on Earth as it is the primary source of energy and oxygen for all living organisms.Contrary to some misconceptions, photosynthesis does not rely on ultraviolet radiation. Instead, it primarily harnesses visible light, particularly blue and red wavelengths, to fuel the conversion of carbon dioxide and water into glucose and oxygen. The reaction can be summarized by the equation:\[ 6CO_2 + 6H_2O + light \enspace energy \rightarrow C_6H_{12}O_6 + 6O_2 \]This demonstrates that visible light, not UV light, is the critical energy source that facilitates this process.The ozone layer's filtering of UV radiation does not impede photosynthesis. Rather, it ensures that the harmful effects of excessive UV exposure do not affect plants' ability to photosynthesize effectively. Therefore, while UV radiation is largely blocked by the ozone layer, the wavelengths essential for photosynthesis pass through, supporting photosynthetic organisms and the life forms relying on them.

Oxidation Reaction

Oxidation reactions are a category of chemical reactions involving the transfer of electrons. In many contexts, these are reactions where a substance loses electrons, often involving oxygen from the surrounding environment. A common misconception is that the ozone layer affects the rate of oxidation reactions. However, the presence of ozone neither accelerates nor substantially influences these chemical processes. While ozone is a reactive form of oxygen, it is not prominent in influencing everyday oxidation reactions like rusting or the metabolism of food in cells. In general, oxidation reactions are essential in various processes, including:

• Combustion, such as burning gasoline for energy.
• Metabolism, where nutrients in food are converted to energy in living organisms.
• Corrosion, like the rusting of iron when exposed to moist air.

While the ozone layer is beneficial in absorbing harmful radiation, it does not play a notable role in enhancing or assisting oxidation reactions at the ground level, where these processes typically take place.