Question

Which of the following statements is wrong? (A) Ozone is not responsible for green house effect. (B) Ozone can oxidise sulphur dioxide present in the atmosphere to sulphur trioxide. (C) Ozone hole is thinning of ozone layer present in stratosphere. (D) Ozone is produced in upper stratosphere by the action of UV rays on oxygen.

Short answer

The incorrect statement is (D) Ozone is produced in the upper stratosphere by the action of UV rays on oxygen. Ozone is actually produced in the lower stratosphere, not the upper stratosphere.

Step-by-step solution

(A) Ozone is not responsible for green house effect.

Ozone itself is not a significant greenhouse gas, and it's not responsible for the major portion of the greenhouse effect on Earth. Greenhouse gases like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are more significant contributors to the Earth's greenhouse effect. Therefore, this statement is correct.

(B) Ozone can oxidize sulfur dioxide present in the atmosphere to sulfur trioxide.

Ozone (O3) is a powerful oxidizing agent and can react with sulfur dioxide (SO2) to form sulfur trioxide (SO3) in the atmosphere. The chemical equation for this reaction is: \[O_3 + SO_2 \rightarrow SO_3 + O_2\] So, this statement is also correct.

(C) Ozone hole is thinning of the ozone layer present in the stratosphere.

The term "ozone hole" refers to the depletion of ozone in the stratosphere, primarily over Antarctica. This depletion, or thinning, of the ozone layer allows more ultraviolet (UV) radiation to reach the Earth's surface. Thus, this statement is correct as well.

(D) Ozone is produced in the upper stratosphere by the action of UV rays on oxygen.

Ozone is formed in the Earth's upper atmosphere when ultraviolet (UV) radiation from the sun dissociates molecular oxygen (O2) into individual oxygen atoms (O), which then react with other molecular oxygen to form ozone (O3). However, this process mainly occurs in the lower stratosphere, not in the upper stratosphere as the statement suggests. The chemical reactions involved in ozone formation are: \[O_2 + UV \rightarrow 2O\] and \[O + O_2 \rightarrow O_3\] So, based on the discrepancy in the location of ozone production, statement (D) is the wrong statement among the given options.

Key concepts

Greenhouse Effect

The Greenhouse Effect is essential for life on Earth, creating a habitable climate by trapping heat from the sun. This natural phenomenon is orchestrated by greenhouse gases like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

These gases allow sunlight to enter the atmosphere freely. When sunlight strikes the Earth's surface, some of it is reflected back towards space as infrared radiation (heat). Greenhouse gases absorb this infrared radiation, heating the atmosphere, which in turn warms the surface of the Earth.

Importance of the Greenhouse Effect

Without the greenhouse effect, our planet would be too cold to support most forms of life. In contrast, too much greenhouse gas can cause the Earth's atmosphere to trap more heat, leading to an enhanced greenhouse effect and global warming, which disrupts Earth's climate systems.

Oxidation-Reaction

Oxidation-reactions are chemical processes where an element or compound loses electrons. This can occur through the transfer of electrons to another substance or when oxygen combines with a substance. Ozone (O3), a triatomic molecule of oxygen, is a powerful oxidant in the stratosphere.

For instance, ozone can react with sulfur dioxide (SO2) to produce sulfur trioxide (SO3), as in the equation \(O_3 + SO_2 \rightarrow SO_3 + O_2\). This reaction is significant because sulfur trioxide can further react with water to form sulfuric acid (H2SO4), which is a component of acid rain and has various environmental impacts.

Oxidants in the Atmosphere

Oxidants like ozone are crucial in the atmospheric chemistry as they help to remove pollutants by oxidizing them. However, this also means they can be harmful to living organisms, including humans, by causing respiratory issues and other health problems when present in lower areas of the atmosphere.

Stratospheric Chemistry

Stratospheric chemistry involves the study of the chemical composition and reactions in the Earth's stratosphere. This layer of the atmosphere stretches from about 10 to 50 kilometers above the Earth's surface and contains the ozone layer.

Ozone in the stratosphere is critical for life because it absorbs the majority of the harmful ultraviolet (UV) radiation from the sun. The production and destruction of ozone molecules (\(O_3\)) in this region involve complex processes driven primarily by solar radiation.

Dynamic Balance in the Ozone Layer

The ozone layer is sustained by a dynamic equilibrium between the production of ozone, through the reaction of oxygen molecules with individual oxygen atoms, and the natural destruction of ozone. Human-made chemicals, such as chlorofluorocarbons (CFCs), can disturb this balance, leading to ozone layer depletion, commonly referred to as the 'ozone hole'.

Ultraviolet Radiation

Ultraviolet (UV) radiation is a type of energy emitted from the sun, categorized based on its wavelength into three types: UVA, UVB, and UVC. Of these, UVC is the most harmful but is completely absorbed by the ozone layer in the atmosphere.

Exposure to UV radiation can lead to various health issues, such as skin cancer and cataracts, and is also implicated in damaging plant life and aquatic ecosystems. The ozone layer plays an indispensable role in filtering out the majority of ultraviolet radiation.

Increased UV Exposure Due to Ozone Depletion

If the ozone layer gets depleted, as is currently happening with the ozone hole phenomenon, more UVB and UVA can reach the Earth's surface, leading to increased risks of the aforementioned health and environmental issues. Monitoring and protecting the ozone layer is therefore crucial for minimizing UV radiation exposure on Earth.