[Chemistry Class Notes] on Ozone Layer Pdf for Exam

Ozone is a highly reactive gas that is basically composed of three oxygen atoms. In Earth’s atmosphere, more precisely in the stratosphere layer and lower atmosphere layer that is the troposphere this ozone occurs. It can be both natural as well as man-made. Ozone affects life on earth, either in a good way or bad way it depends where it is situated in the atmosphere of the earth.

The stratospheric ozone is formed naturally from the interaction of solar ultraviolet radiation with molecular oxygen. This layer of ozone protects the earth’s surface from harmful ultraviolet radiation.

The troposphere ozone layer is formed from photochemical reactions primarily. These reactions occur between two major classes of air pollutants that are not orphan oxide and Volatile organic compounds. These reactions are traditionally being dependent upon heat and light resulting in a greater concentration of ozone in the atmosphere during the summer season. Ozone can be both advantageous as well as hazardous; it is completely dependent upon its location. This article will give you a brief knowledge about the ozone layer. The topics that you are going to study here include the definition of ozone, elemental Properties of ozone as a whole, properties layer, importance of the ozone e layer, depletion of the ozone layer, and other information. At the end of this article, you are being provided with the Frequently Asked Questions related to the ozone layer. It will help you to clear your queries. has designed this article especially for you to understand the basics of our ozone layer.

What is Ozone?

Ozone is a natural gas present within the atmosphere of our planet. Well, how is ozone formed? Three oxygen atoms form the ozone layer on the upper atmosphere of the Earth’s surface. The layer of atmosphere in which the ozone layer lies is called the stratosphere. Hence, you get the ozone layer formula – O3. The ozone structure indicates that it is quite unstable and much more reactive as compared to oxygen (O₂). It implies it is easy to form and decompose when interacting with other compounds. The O₃ can deplete and decompose when it collaborates with human-made compounds in the stratosphere.

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Diagram showing where the Ozone layer lies and distance between different layers in Earth’s atmosphere.

On the other hand, Ozone gas also exists near the Earth’s surface, in the lower atmosphere called the troposphere. Here chemical responses between air pollutants from gasoline smoke, vehicle exhaust, and other emissions create O₃ that is, however, toxic to people and plants alike.

Today this protective ozone layer is depleting because of the presence of chlorofluorocarbon compounds (CFC) in the atmosphere. These compounds mix with other gases present in the environment and enter the Earth’s stratosphere. In the presence of ultraviolet rays, these agents deliver chlorine radicals in the air to produce oxygen molecules and chlorine monoxide. As a result, the ozone layer depleted. The ultraviolet radiation from the sun is able to enter the Earth’s atmosphere directly. These ultraviolet radiations can cause a lot of harm to humans as well as other organisms living on earth. As for Humans, they are prone to diseases such as skin cancer, cataract, and other immune weakening diseases.

Element Properties

Symbol: O₃

Atomic Weight: 48

Solubility: 570 mg/l bij 20 °C

Energy: 142,3 KJ/mol (34,15 kcal/mol)

Melting Point: -192.2 °C

Boiling Point: -112 °C

Critical Temperature: -12,1 °C

Binding Degree: 116 °

Critical Pressure: 5460 kPa

Density: 2,14 kg O₃/m³ bij 0°C 1013 mbar

Relative Density (in air): 1,7 kg/m³

Electrochemical Potential: 2,07 volt

Properties of O₃

Ozone is a form of oxygen called a triatomic allotrope of oxygen. The molecule in the ozone structure comprises three atoms.

This form of oxygen is a pale blue and irritating gas that even at low concentrations is combustible and lethal in nature.

O₃ absorbs solar ultraviolet radiation when naturally produced in the Earth’s stratosphere in little quantities. Otherwise, the UV sunlight could lead to drastic destruction to living organisms on our planet. Ozone can control the ultraviolet range extending between 220 – 290 nm of the atmospheric spectrum.

Another significant property of O₃ is that it is highly reactive, especially when exposed to heat. In the presence of heat, it even decomposes back to oxygen, which is known as the thermal decomposition process. This process can spontaneously happen at roughly 300 degrees Celsius. When the temperature rises, it creates an exothermic reaction that causes the breakdown of ozone to an oxygen atom as well as an oxygen molecule. 

The boiling point of ozone is −112 °C (−169.6 °F) that turns into violet-blue crystals on solidifying whereas its melting point is -192.2 (−314 °F).

Preparation of Ozone Layer

You might be wondering how the ozone layer is formed? Don’t worry; here we will clear out all your confusion regarding the preparation of ozone.

The preparation of ozone is done in a two-step reactive method in the stratosphere region of the earth’s surface. Firstly, an oxygen molecule decomposes by sunlight into two oxygen atoms. Afterward, the oxygen atoms interact with another oxygen atom to form O₃.

However, is this the only way you get ozone? Definitely not, men, today can even create ozone gas. So, how is the ozone formed by us? All you require for the preparation of ozone is a machine and oxygen molecules to create ozone gas. The ozone-producing machine is called an ozonizer, which is an apparatus generally used as a water or air purifier. The O₃ in this device swoops bacteria to eliminate them. 

Scientists use a similar methodology in the laboratory for the preparation of ozone. Instead of sunlight just use a high voltage electric current. The dry oxygen is placed in an ozonizer in this process. Then a salient electric current, which is a high voltage electrical current zaps through the oxygen molecule that transforms the oxygen molecule into O₃ gas.

The equation for ozone formation is as follows:

3O₂ + energy = 2O₃

Importance of Ozone Layer

One of the most important uses of the ozone layer for our environment is that it saves every single living being on the planet from the harmful UV rays of the sun. As a shield to Earth, it protects us from physical and environmental damage that UV radiation can cause.

Further, human-produced ozone gas is used for water and air purification.

Other uses of ozone layer gas are to help eliminate any unwanted toxic substances from the environment. It is suitable for various industrial purposes.

Ozone Layer Depletion

Halogen gases
are the reasons behind ozone layer depletion. Bromide, halons, Chlorofluorocarbons, hydrochlorofluorocarbons, methyl, and chloride are called ozone-depleting substances or ODS. They release at the surface, spread all over in the air, and go from the lower atmosphere to the upper atmosphere through wind transport patterns. These gases further create chlorine and/or bromine that are capable of ozone layer depletion by destroying the stratosphere in the presence of ultraviolet rays. 

Apart from the natural factors, scientists believe that somewhat stratospheric ozone is also damaging because of human actions such as human-made chemicals.

Fun Facts

Volcanic eruptions may shoot substances into the stratosphere, which causes an increased risk of ozone layer depletion. And if this layer keeps depleting it will be very difficult for humans to survive on earth as most of the rays may enter the earth’s surface. Along with it, many human activities are also responsible for the depletion of oxygen.

Zone layer: In Antarctica, there is a hole in the ozone layer. This hole is known as an ozone hole. Due to various human activities, there is depletion of the ozone layer and in Antarctica, due to its depletion, a complete hole is formed.

In 1840 Schönbein first made an electrical ozone generating machine