Formula of air in chemistry. Chemical composition of air and its hygienic importance

How fresh the winter air is to breathe. How easy and pleasant it is to breathe deeply in the forest, near the sea or in the mountains. It is in such places that we strive to spend our weekends or our next vacation. But the percentage of air in paradise of our planet is the same as in the cities where you and I live. So what's the deal? Why don’t we feel the same purity of air at home, far from our dreamed forests, mountains and seas? Let's talk about the composition of air in percentage terms and its quality.

21% oxygen (O2), 0.03% carbon dioxide (CO2), the rest is 79% nitrogen (N2) and a small amount of impurities.

As one of mine said school teachers: “The dog is buried in impurities.” The fact is that over the past 150 years, a huge amount of arsenic, cobalt, silicon, oxides of sulfur, nitrogen, carbon and other impurities harmful to health have entered the atmosphere.

Obviously, the concentration of these pollutants in the air of rural areas is much lower than in cities and towns. And all, first of all, because of vehicles, which fog everything around with their exhausts. The degree of pollution of precious air is determined mainly by geographical conditions.

This is the percentage composition of the air, friends. Obviously, a person should think about its quality and not pollute the atmosphere. Next we will discuss some interesting facts.

Why does it feel bad in a stuffy room?

A person inhales air and exhales carbon dioxide and something else in the form gaseous substances– that’s what we were taught at school. There we also studied the composition of the air. Remember a time when, for no apparent reason, you felt ill in a closed room (if such a case occurred). Why do you think? You would be right if you assume that this room has not been ventilated for a long time.

You felt unwell due to the high concentration of the same gaseous substances that you, along with the people around you, inhaled. The mixture exhaled by a person contains no more than 16-18 percent oxygen and 4-6 percent carbon dioxide. And this is 130-200 times more than in the air you inhale.

There are also other bad compounds present there. So the advice to regularly ventilate your homes and offices should not seem inappropriate. You will be healthier. Since then, he is responsible for their cleanliness and order.

Natural air purification

In the summer, we sweep and spray the asphalt of the streets with water in order not to breathe in fine dust particles. But in winter the composition of the air is cleaner, if only because this very dust and dirt hangs under the drifts of snowfall.

Trees planted so intensively in populated areas, act as filters, clearing the atmosphere of excess carbon dioxide. So they change the composition of the air for our benefit. Green plants absorb it and saturate the city air with oxygen. Everyone in the same schools taught us that this process is called photosynthesis.

5 thousand cubic meters of air are purified by one tree, and a small park frees us from 200 tons of dust. That is, the more greenery is planted on Earth, the better the quality of the air we inhale. It’s not for nothing that plants are called the lungs of this planet.

Have you ever heard of ionization? So, a high concentration of negatively charged particles (ions) in the air has a beneficial effect on our bodies. Mountain seaside resorts and pine forests are famous for their highly ionized air.

Also, if you are lucky enough to live near a waterfall or fast-flowing mountain river, then air ions will give you good health.

The healing climate of such places does its job. Therefore, people living in or near these areas are less likely to get sick and are famous for their longevity. And yes, I almost forgot, to the required level. Especially in winter. Breathe deliciously, friends!

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It is probably not entirely correct to talk about air as a chemical compound. Rather, it is a mixture of gases in which water vapor is present. The main composition of air is nitrogen-oxygen in a volume ratio of 78-21%. The rest belongs to hydrogen, carbon dioxide, argon, helium, etc. The composition of the air can vary depending on the geography of the place (city, forest, mountains, sea) within 2% for each gas.

Many people sometimes wonder what air is made of and what its formula is. Air is a mixture of gases that envelops our Earth in the atmosphere. So the main components are nitrogen and oxygen, the rest are gases that simply add a little air

Air is a mixture of gases. The composition of the air is not a constant value and varies depending on the area, region and even the number of people near you. Basically, air consists of about 78% nitrogen and 21% oxygen, the rest is impurities of various compounds.



Vladimir! There is no chemical formula for air as such.

Air is a MIXTURE of various gases - oxygen, carbon monoxide, nitrogen and other gases.

It is difficult to name the exact proportion of these gases in the atmosphere...

Air is essentially a mixture of nitrogen (about 80%) and oxygen (about 20%), with other gases making up about 1% or less. As such, there is no chemical formula for air, since it is a mixture of various compounds in different percentages.

Air is not a chemical compound. Air is a mixture of gases, and its composition is not constant and depends directly on the place in which we will analyze the composition of the air, the presence of certain contaminants.

98-99% of the air composition is nitrogen and oxygen. Air also contains

It is impossible to create a single integral formula for the Earth's atmosphere. But you can determine what gases are in the air:

• Nitrogen N2 - 78.084%.
• Oxygen (which we breathe) O2 - 20.9476%.
• Argon Ar - 0.934%.
• Carbon dioxide CO2 - 0.0314%.
• Neon Ne - 0.001818%.
• Methane CH4 - 0.0002%.
• Helium He - 0.000524%.
• Krypton Kr - 0.000114%.
• Hydrogen H2 - 0.00005%.
• Xenon Xe - 0.0000087%.
• Ozone O3 - 0.000007%.
• Nitrogen dioxide NO2 - 0.000002%.
• Iodine I2 - 0.000001%.
• The amount of carbon monoxide CO and ammonium NH3 is negligible.

• Air cannot be called a chemical compound, because it consists of a mixture of various gases, which constantly changes its composition. Moreover, this change is both qualitative and quantitative in nature. So, if up to a height of 13 kilometers, the composition of the atmosphere changes little, then the ozone layer appears higher, that is, in the atmosphere there is a large number of triatomic oxygen. On the contrary, at the surface, the composition of the atmosphere is greatly influenced by pollution, both man-made (emissions from enterprises, cars) and natural (volcanic activity). A chemical compound is usually permanent; the atoms of the elements in it are connected by various bonds and are in strict proportions.

  Here is the composition of the atmosphere at the surface:

  

  Here are the changes that occur in the atmosphere with altitude:

  

  You won't be able to find any chemical formula air. The whole point is that air in its composition has a huge amount of different gas impurities, so you can only provide a list of these impurities with an approximate percentage, and here is that list.

It cannot be touched and cannot be seen, but the main thing we owe to him is life. Of course, this is the air that was not occupied last place in the folklore of every nation. How the people of antiquity imagined it, and what it really is - I will write about this below.

Gases that make up air

Natural mixture of gases called air. Its necessity and importance for living things can hardly be underestimated - it plays an important role in oxidative processes, which are accompanied by the release of energy necessary for all living things. Through experiments, scientists were able to determine its exact composition, but the main thing that needs to be understood is it is not a homogeneous substance, but gas mixture . About 99% of the composition is a mixture of oxygen and nitrogen, and in general air forms the atmosphere of our planet. So, the mixture consists of the following gases:

• methane;
• krypton;
• helium;
• xenon;
• hydrogen;
• neon;
• carbon dioxide;
• oxygen;
• nitrogen;
• argon.

It should be noted that composition is not constant and may vary significantly from one area to another. For example, big cities characterized by a high content of carbon dioxide. In the mountains it will be observed decreased oxygen levels, since this gas is heavier than nitrogen, and as it rises its density will decrease. Science says the composition may differ depending on the different parts planets from 1% to 4% for each gas.

Except percentage gases, air is characterized by the following parameters:

• humidity;
• temperature;
• pressure.

The air is constantly in motion, forming vertical flows. Horizontal - winds, depend on certain natural conditions, so they may have different characteristics speed, force and direction.

Air in folklore

Legends of every people endow the air with certain “living” qualities. As a rule, the spirits of this element were elusive and invisible creatures. According to legends, they inhabited mountain tops or clouds, and differed in their predisposition to humans. They were the ones who were thought to be created snowflakes and collected clouds in the clouds, flying across the sky on the winds.

The Egyptians counted the air symbol of life, and the Indians believed that Brahma's exhalation is life, and inhalation, accordingly, means death. As for the Slavs, air (wind) occupied almost a central place in the legends of this people. He could hear and sometimes even fulfill small requests. However, he was not always kind, sometimes siding with the forces of evil. in the form of an evil and unpredictable wanderer.

The main components of atmospheric air are oxygen (about 21%), nitrogen (78%), carbon dioxide (0.03-0.04%), water vapor, inert gases, ozone, hydrogen peroxide (about 1%).

Oxygen is the most component air. With its direct participation, all oxidative processes occur in the human and animal body. At rest, a person consumes approximately 350 ml of oxygen per minute, and in severe physical work the amount of oxygen consumed increases several times.

Inhaled air contains 20.7-20.9% oxygen, and exhaled air contains about 15-16%. Thus, body tissues absorb about 1/4 of the oxygen present in the inhaled air.

In the atmosphere, the oxygen content does not change significantly. Plants absorb carbon dioxide and, breaking it down, assimilate carbon, and release the released oxygen into the atmosphere. The source of oxygen formation is also the photochemical decomposition of water vapor in the upper layers of the atmosphere under the influence of ultraviolet radiation from the sun. In ensuring a constant composition of atmospheric air, mixing of air flows in the lower layers of the atmosphere is also important. The exception is hermetically sealed rooms, where, due to prolonged stay of people, the oxygen content can be significantly reduced (submarines, shelters, pressurized aircraft cabins, etc.).

For the body, the partial pressure of oxygen is important, and not its absolute content in the inhaled air. This is due to the fact that the transition of oxygen from alveolar air to blood and from blood to tissue fluid occurs under the influence of differences in partial pressure. The partial pressure of oxygen decreases with increasing altitude above sea level (Table 1).

Table 1. Partial pressure of oxygen at different altitudes

Great importance has the use of oxygen for the treatment of diseases accompanied by oxygen starvation (oxygen tents, inhalers).

Carbon dioxide. The carbon dioxide content in the atmosphere is fairly constant. This constancy is explained by its cycle in nature. Despite the fact that the processes of decay and vital activity of the body are accompanied by the release of carbon dioxide, a significant increase in its content in the atmosphere does not occur, since carbon dioxide is absorbed by plants. In this case, carbon is used to build organic matter, and oxygen enters the atmosphere. Exhaled air contains up to 4.4% carbon dioxide.

Carbon dioxide is a physiological stimulant of the respiratory center, therefore during artificial respiration it is added to the air in small quantities. IN large quantities it can have narcotic effects and cause death.

Carbon dioxide also has hygienic significance. Based on its content, the cleanliness of the air in residential and public premises (i.e., premises where people are present) is judged. When people gather in poorly ventilated rooms, parallel to the accumulation of carbon dioxide in the air, the content of other human waste products increases, the air temperature rises and its humidity increases.

It has been established that if the carbon dioxide content in indoor air exceeds 0.07-0.1%, then the air acquires an unpleasant odor and can disrupt the functional state of the body.

The parallelism of the changes in the listed properties of air in residential premises and the increase in the concentration of carbon dioxide, as well as the ease of determining its content, make it possible to use this indicator for the hygienic assessment of air quality and the efficiency of ventilation of public premises.

Nitrogen and other gases. Nitrogen is basic integral part atmospheric air. In the body, it is dissolved in the blood and tissue fluids, but does not take part in chemical reactions.

It has now been experimentally established that under conditions of high pressure, air nitrogen causes a disorder of neuromuscular coordination in animals, followed by agitation and a narcotic state. Researchers observed similar phenomena among divers. The use of a helio-oxygen mixture for breathing by divers makes it possible to increase the depth of descent to 200 m without pronounced symptoms of intoxication.

During electrical lightning discharges and under the influence of ultraviolet rays from the sun, small amounts of other gases are formed in the air. Their hygienic value is relatively small.

* The partial pressure of a gas in a mixture of gases is the pressure that a given gas would produce if it occupied the entire volume of the mixture.

Given in table. 1.1 the composition of atmospheric air undergoes various changes in enclosed spaces. Firstly, the percentage of individual required components, and, secondly, additional impurities appear that are not characteristic of clean air. This paragraph will discuss changes gas composition and about its permissible deviations from the normal.

The most important gases for human life are oxygen and carbon dioxide, which participate in gas exchange between humans and environment. This gas exchange occurs mainly in the human lungs during breathing. Gas exchange occurring through the surface of the skin is approximately 100 times less than through the lungs, since the surface of the adult human body is approximately 1.75 m2, and the surface of the alveoli of the lungs is about 200 m2. The breathing process is accompanied by the formation of heat in the human body in an amount from 4.69 to 5.047 (on average 4.879) kcal per 1 liter of absorbed oxygen (converted into carbon dioxide). It should be noted that only a small part of the oxygen contained in the inhaled air is absorbed (approximately 20%). So, if in atmospheric air contains approximately 21% oxygen, then in the air exhaled by a person it will be about 17%. Typically, the amount of carbon dioxide exhaled is less than the amount of oxygen absorbed. The ratio of the volumes of carbon dioxide emitted by a person and the oxygen absorbed is called the respiratory coefficient (RQ), which usually ranges from 0.71 to 1. However, if a person is in a state of strong excitement or performs very hard work, the RQ can be even greater than one.

Amount of oxygen necessary for a person to maintain normal life functions, mainly depends on the intensity of the work performed and is determined by the degree of nervous and muscular tension. The absorption of oxygen in the blood occurs best at a partial pressure of about 160 mmHg. Art., which at an atmospheric pressure of 760 mm Hg. Art. corresponds to the normal percentage of oxygen in atmospheric air, i.e. 21%.

Due to the human body's ability to adapt, normal breathing can be observed even with smaller amounts of oxygen.

If the reduction in oxygen content in the air occurs due to inert gases (for example, nitrogen), then a significant reduction in the amount of oxygen is possible - up to 12%.

However, in enclosed spaces, a decrease in oxygen content is accompanied not by an increase in the concentration of inert gases, but by the accumulation of carbon dioxide. Under these conditions, the maximum permissible minimum oxygen content in the air should be much higher. Typically, the oxygen content of 17% by volume is taken as the norm for this concentration. Generally speaking, in enclosed spaces the percentage of oxygen never decreases to this norm, since the concentration of carbon dioxide reaches the limit value much earlier. Therefore, it is practically more important to establish the maximum acceptable standards the content in enclosed spaces is not oxygen, but carbon dioxide.

Carbon dioxide CO2 is a colorless gas with a faint sour taste and odor; it is 1.52 times heavier than air and slightly poisonous. The accumulation of carbon dioxide in the air of enclosed spaces leads to headaches, dizziness, weakness, loss of sensitivity and even loss of consciousness.

It is believed that the amount of carbon dioxide in atmospheric air is 0.03% by volume. This is true for rural areas. In the air of large industrial centers its content is usually higher. For calculations, a concentration of 0.04% is taken. The air exhaled by humans contains approximately 4% carbon dioxide.

Without any harmful consequences for the human body, carbon dioxide concentrations significantly higher than 0.04% can be tolerated in the air of enclosed spaces.

The maximum permissible concentration of carbon dioxide depends on the length of stay of people in a particular enclosed space and on the type of their occupation. For example, for sealed shelters, when placed in them healthy people for a period of no more than 8 hours, the norm of 2% can be accepted as the maximum permissible CO2 concentration. For short-term stays, this rate may be increased. The possibility of a person staying in an environment with high concentrations of carbon dioxide is due to the ability human body adapt to different conditions. When the CO2 concentration is higher than 1%, a person begins to inhale significantly more air. Thus, at a CO2 concentration of 3%, breathing doubles even at rest, which in itself does not cause noticeable negative consequences during a relatively short stay in such air. If a person stays in a room with a CO2 concentration of 3% for a long enough time (3 or more days), he is at risk of losing consciousness.

When people stay in sealed rooms for a long time and when people perform this or that work, the maximum permissible concentration of carbon dioxide should be significantly less than 2%. It is allowed to fluctuate from 0.1 to 1%. A carbon dioxide content of 0.1% can be considered acceptable for ordinary unsealed premises of buildings and structures for various purposes. A lower concentration of carbon dioxide (about 0.07-0.08) should be prescribed only for the premises of medical and children's institutions.

As will be clear from what follows, the requirements for the content of carbon dioxide in the indoor air of above-ground buildings are usually easily met if the sources of its emission are people. The question is different when carbon dioxide accumulates in production premises as a result of certain technological processes, occurring, for example, in yeast, brewing, hydrolysis workshops. In this case, 0.5% is taken as the maximum permissible concentration of carbon dioxide.