Components of Air

We all are aware of the vital role that air plays in our survival. But what is air? Air which is also commonly known as the atmosphere is a mixture of various gases. The first thing that pops up in our mind when we think about air is Oxygen, which is essential for the existence of life on Earth. But oxygen is not the only element that air is composed of. Other gasses also play an important role in sustaining life. Let’s get a thorough look at the composition of air due to which life is possible on Earth. 

Composition of Air

Air is made up of 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and other gases in meagre amounts. Water vapour is also a constituent of air in varying amounts, along with dust particles. The molar mass of dry air or air with no/low quantity of water vapour in it is 28.97g/mol. We can find out the average molar mass of a mixture of gases by using a simple formula in which we take the summation of the molar mass of each gaseous component multiplied by its mole fraction.

Fig: Composition of air

M mixture = x₁M₁+.....+x_nM_n, where,

x_i= mole fraction of each gas

M_i= the molar mass of each gas

Mole fraction or x_i= Number of Moles of that ComponentTotal Number of Moles in the Mixture

Mole fraction or x_i = \[\frac{\text{Number of moles of that Component}}{\text{Total Number of Moles in Mixture}}\]

Main Components of Air

The main components of air are given as,

Oxygen

Oxygen is the most important chemical elements of which air is composed. It has the symbol O and has an atomic number of 8. Oxygen is a highly reactive gas that readily forms bonds known as oxides with other elements. It is also highly combustible (quick to catch fire). In terms of mass, after hydrogen and helium, oxygen is the most copious element in the universe. If we consider the standard temperature, which is 273.15K, and the standard pressure, being 1atm, then two atoms of oxygen combine to form one molecule of oxygen known as dioxygen (O₂). Dioxygen is used for cellular respiration or breathing.

Oxygen is needed not only for respiration and combustion, but it is also a major component in many other crucial organic molecules that make up a living organism; for example, carbohydrates, proteins, fats all comprise oxygen in some amount. Oxygen has its use not only in terms of sustainability of life but also in recreational activities. For example, scuba divers depend upon artificially produced oxygen for underwater respiration. Even the mountaineers climbing much higher altitudes require a supply of artificial dioxygen in oxygen cylinders. Strangely enough, oxygen also has mild euphoric effects, due to which oxygen bars are quite popular in the United States. Apart from the above-mentioned, oxygen also has industrial applications, like smelting of iron ore into steel. This is a process in which dioxygen is administered into molten iron to remove impurities. 

This process consumes about 55% of commercially produced oxygen.

Carbon Dioxide

Carbon dioxide is a trace gas with a concentration of just about 0.04%. The gases which are present in the atmosphere in very small amounts are known as trace gases. It has the chemical symbol CO₂ and atomic number 6. Carbon dioxide is produced through respiration and also through the decomposition of organic materials. It is also produced through some natural sources like geysers, volcanoes, and hot springs. During the combustion of petroleum and natural gases, carbon dioxide is evolved. CO₂ has a variety of applications. It is used in the food industry as an additive in order to regulate acidity. It is used in soft drinks and some candies. It is also used in fire extinguishers. We know that oxygen is required for combustion, so when we use carbon dioxide to extinguish a fire, it surrounds the fire and cuts off the supply of oxygen required for burning and hence quenches the fire. It is an important ingredient in the production of the fertilizer, urea. It is also used as a refrigerant during transportation as well as storage of frozen foods.

Even though carbon dioxide is a trace element, its amount in the air is constantly increasing, leading to what is known as air pollution. Various human activities like deforestation, burning of fossil fuels, and industrialization lead to tremendous amounts of carbon dioxide emission in the atmosphere. It causes lung diseases as well when inhaled in large quantities. It is a greenhouse gas which means that it absorbs and emits harmful ultraviolet light, thus, increasing the surrounding temperature. This increase in atmospheric temperature on a much larger scale is what is commonly known as global warming.

Nitrogen

The most abundant, pure component of air is nitrogen, with a concentration of 78%. It has the symbol N and atomic number 7. Nitrogen is produced through a process called nitrogen fixation, which is a continuous cycle between living organisms and the atmosphere. It is also produced in industries by fractional distillation of air in its liquid form. Dinitrogen is a molecule of two nitrogen atoms bonded by a strong triple bond. Due to the triple bond, the decomposition of N2 is difficult and hence the process of its decomposition, which includes processes like exploding, produces a huge amount of useful energy. Nitrogen is present in living organisms in classes like nucleic acid, amino acids. Artificially produced nitrogen is also a very important component in fertilizers. Nitrogen also has its applications in the field of medicine, primary usage being in various drugs and even in antibiotics. Nitrogen is a non-toxic gas, but when it is emitted in an enclosed area, then it can displace oxygen which can lead to a situation of asphyxia. 

Argon

With a concentration of 0.93%, argon is the third most abundant element in the atmosphere. It is a noble gas. Argon has the symbol Ar and the atomic number is 18. Naturally, argon is produced due to an isotope of potassium, K-40. Industrially, it is produced by fractional distillation of liquid air. The application of argon is mainly in the environment where the substances which are normally unreactive become reactive; for example, it is used in graphite furnaces to prevent the combustion of graphite itself. It is also used as a fluorescent lamp. In order to prevent the oxidation of filaments at high temperatures, they are filled with argon. Since argon is a colourless, tasteless as well as odourless gas, it is often very difficult to detect its presence. In medical applications, argon is used as a blue laser in order to cure eye defects and often to destroy tumours. It is also used to produce a bluish-green laser.

Water Vapour

The water vapour concentration in the atmosphere varies from about 0.01% to 4.24%, depending upon the temperature. When we respire, we also release some amount of water vapour. In many chemical reactions, water vapour is evolved as a by-product. Apart from carbon dioxide and methane, water vapour also contributes to the greenhouse effect as it absorbs and emits radiation. Water vapour is used as steam which helps in cooking and also in producing energy. Water vapour is also used as a "lifting gas" as its density is lower than that of air. For example, it is used in hot air balloons in the form of steam so that its vapour pressure is much more than that of the surrounding atmosphere so that the shape of the balloon can be maintained.

Dust Particles

Fine solid particles are known as dust particles. Atmospheric dust is also known as Aeolian. These particles comprise particles that originate from volcanic eruptions, pollution or soil. These dust particles also contain pollens, hair of humans and animals, soot particles in small amounts. The dust settled on the roads also became airborne due to the constant movement of vehicles. Coal dust is responsible for respiratory diseases. The dust particles also have allergic effects on some people. If a large number of dust particles are present in the atmosphere, then it can also reduce visibility and is a safety hazard. Dust particles can also clog the filters of an automobile and affect its efficiency. In order to reduce the amount of dust present in the atmosphere, various methods can be adopted. The use of air filtering appliances is one of the methods used to provide clean air. Nowadays dust resistant materials are also used so as to prevent the settling of dust on substances. Sweepers and vehicles with installed vaccum cleaners are used to clean the dust particles settled on the road. 

The above are the major constituents of air. Apart from these, there are several other gases that make up our atmosphere, like sulfur, neon, helium. Often, the properties of the above-mentioned major constituents of air vary with different factors such as altitude, temperature, and air pressure. For life to exist on earth as we know, it is important that there should exist a balance among the different constituents and that those which have harmful effects on the environment should be eliminated or controlled.