Components of Air - Nitrogen, Oxygen, Carbon Dioxide, Water Vapor and Other Gases
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 vital element that air is composed of. Other gases 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.
The 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 meager amounts. Water vapor 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 vapor 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.
Mmixture= (x1*M1 + ......+ xn*Mn), where xi = mole fraction of each gas Mi = the molar mass of each gas Mole fraction or xi= number of moles of that component/ total number of moles in the mixture
The main components of air are:
Oxygen is the most important chemical element of which air is composed of. It has the symbol O and has an atomic number of 8. Oxygen is a highly reactive gas which 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 which make up a living organism, for example, carbohydrates, proteins, fats, all comprise of oxygen in some amount. Oxygen has its use not only in terms of sustainability of life but also in recreational activities. For example, the scuba divers depend upon the 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 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 the 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 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 leads to the 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 the 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.
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 the 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.
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 temperature, they are filled with argon. Since argon is a colorless, tasteless as well as odorless 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 tumors. It is also used to produce a bluish-green laser.
The water vapor 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 vapor. In many chemical reactions, water vapor is evolved as a by-product. Apart from carbon dioxide and methane, water vapor also contributes to the greenhouse effect as it absorbs and emits radiations. Water vapor is used as steam which helps in cooking and also in producing energy. Water vapor 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 vapor pressure is much more than that of the surrounding atmosphere so that the shape of the balloon could be maintained.
Fine solid particles are known as dust particles. Atmospheric dust is also known as Aeolian. These particles comprise of particles which originate from volcanic eruptions, pollution or soil. These dust particles also contain pollens, hair of humans and animals, soot particles, in small amounts. Dust settled on the roads also become 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. 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 vacuum 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 which 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.