Atomic mass of nitrogen. Being in nature, receiving. Origin and distribution
home Nitrogen is a chemical element, atomic number 7, atomic mass 14.0067. In the air, free nitrogen (in the form of N2 molecules) is 78.09%. Nitrogen is slightly lighter than air, density 1.2506 kg/m 3 at zero temperature and normal pressure . Boiling point -195.8°C. The critical temperature is -147°C and the critical pressure is 3.39 MPa. Nitrogen is a colorless, odorless, tasteless, non-toxic, non-flammable, non-explosive and non-flammable gas in the gaseous state when normal temperature has high inertia. Chemical formula
- N. Under normal conditions, the nitrogen molecule is diatomic - N 2. Nitrogen production in industrial scale
based on obtaining it from the air (see). There is still debate about who was the discoverer of nitrogen. In 1772, a Scottish doctor Daniel Rutherford (Daniel Rutherford) passing air through a hot coal, and then through water solution alkali - he received a gas, which he called “poisonous gas.” It turned out that a burning splinter brought into a vessel filled with nitrogen goes out, and Living being
in the atmosphere of this gas it quickly dies. At the same time, while conducting a similar experiment, a British physicist obtained nitrogen Henry Cavendshin (Henry Cavendish) calling it "suffocating air", the British naturalist Joseph Priestley (Joseph Priestley) gave it the name "dephlogisticated air", a Swedish chemist Karl Wilhelm Scheele
(Carl Wilhelm Scheele) - “spoiled air.” The final name “nitrogen” was given to this gas by a French scientist Antoine Laurent Lavoisier (Antoine Laurent de Lavoisier). The word "nitrogen" Greek origin.
and means "lifeless"
A logical question arises: “If nitrogen forms, what is the point of using it for welding stainless steels that contain carbide-forming elements?” The thing is that even a relatively small nitrogen content increases the thermal power of the arc . Because of this feature, nitrogen is most often used.
not for welding, but for plasma cutting
Nitrogen is a non-toxic gas, but can act as a simple asphyxiant (asphyxiant gas). Asphyxiation occurs when nitrogen levels in the air reduce oxygen levels to 75% or below normal concentrations. They release nitrogen in gaseous and liquid forms. For 1st (99.6% nitrogen) and 2nd (99.0% nitrogen) grades.
It is stored and transported in a compressed state in steel cylinders. The cylinders are painted black and have “NITROGEN” written in yellow letters on the top cylindrical part.
(according to Pauling)
| N | 7 |
| 14,00674 | |
| 2s 2 2p 3 | |
| Nitrogen | |
Nitrogen, in the form of diatomic N2 molecules, makes up most of the atmosphere, where its content is 75.6% (by mass) or 78.084% (by volume), that is, about 3.87 10 15 tons.
The mass of nitrogen dissolved in the hydrosphere, taking into account that the processes of dissolution of atmospheric nitrogen in water and its release into the atmosphere simultaneously occur, is about 2 10 13 tons, in addition, approximately 7 10 11 tons of nitrogen are contained in the hydrosphere in the form of compounds.
Biological role
Nitrogen is an element necessary for the existence of animals and plants; it is part of proteins (16-18% by weight), amino acids, nucleic acids, nucleoproteins, chlorophyll, hemoglobin, etc. In the composition of living cells, the number of nitrogen atoms is about 2%, according to mass fraction- about 2.5% (fourth place after hydrogen, carbon and oxygen). In this regard, a significant amount of fixed nitrogen is contained in living organisms, “dead organic matter” and dispersed matter of the seas and oceans. This amount is estimated at approximately 1.9 10 11 tons. As a result of the processes of rotting and decomposition of nitrogen-containing organic matter, subject to favorable factors environment, natural deposits of minerals containing nitrogen can form, for example, “Chilean nitrate” (sodium nitrate with admixtures of other compounds), Norwegian, Indian nitrate.
Nitrogen cycle in nature
Nitrogen cycle in nature
Fixation of atmospheric nitrogen in nature occurs in two main directions - abiogenic and biogenic. The first pathway involves mainly reactions of nitrogen with oxygen. Since nitrogen is chemically very inert, large amounts of energy are required for oxidation ( high temperatures). These conditions are achieved during lightning strikes when the temperature reaches 25,000 °C or more. In this case, the formation of various nitrogen oxides occurs. There is also the possibility that abiotic fixation occurs as a result of photocatalytic reactions on the surface of semiconductors or broadband dielectrics (desert sand).
However, the main part of molecular nitrogen (about 1.4·10 8 t/year) is fixed biotically. For a long time it was believed that only a small number of species of microorganisms (albeit widespread on the Earth’s surface) could bind molecular nitrogen: bacteria Azotobacter And Clostridium, nodule bacteria of leguminous plants Rhizobium, cyanobacteria Anabaena, Nostoc etc. It is now known that many other organisms in water and soil have this ability, for example, actinomycetes in the tubers of alder and other trees (160 species in total). All of them convert molecular nitrogen into ammonium compounds (NH 4 +). This process requires significant costs energy (to fix 1 g of atmospheric nitrogen, bacteria in legume nodules consume about 167.5 kJ, that is, they oxidize approximately 10 g of glucose). Thus, the mutual benefit from the symbiosis of plants and nitrogen-fixing bacteria is visible - the former provide the latter with a “place to live” and supply the “fuel” obtained as a result of photosynthesis - glucose, the latter provide the nitrogen necessary for plants in a form that they can absorb.
Nitrogen in the form of ammonia and ammonium compounds, resulting from biogenic nitrogen fixation processes, is quickly oxidized to nitrates and nitrites (this process is called nitrification). The latter, not connected by plant tissues (and further along the food chain herbivores and predators) do not remain in the soil for long. Most nitrates and nitrites are highly soluble, so they are washed away by water and eventually end up in the world's oceans (this flow is estimated at 2.5-8·10 7 t/year).
Nitrogen included in the tissues of plants and animals, after their death, undergoes ammonification (decomposition of nitrogen-containing complex compounds with the release of ammonia and ammonium ions) and denitrification, that is, the release of atomic nitrogen, as well as its oxides. These processes occur entirely due to the activity of microorganisms under aerobic and anaerobic conditions.
In the absence of human activity, the processes of nitrogen fixation and nitrification are almost completely balanced by the opposite reactions of denitrification. Some nitrogen enters the atmosphere from the mantle with volcanic eruptions, some is firmly fixed in soils and clay minerals In addition, there is a constant leakage of nitrogen from the upper layers of the atmosphere into interplanetary space.
Toxicology of nitrogen and its compounds
Atmospheric nitrogen itself is inert enough to have a direct effect on the human body and mammals. However, when high blood pressure it causes narcosis, intoxication or suffocation (due to lack of oxygen); When pressure decreases rapidly, nitrogen causes decompression sickness.
Many nitrogen compounds are very active and often toxic.
Receipt
In laboratories it can be obtained by the decomposition reaction of ammonium nitrite:
NH 4 NO 2 → N 2 + 2H 2 O
The reaction is exothermic, releasing 80 kcal (335 kJ), so the vessel must be cooled while it occurs (although ammonium nitrite must be heated to start the reaction).
In practice, this reaction is performed by adding dropwise a saturated solution of sodium nitrite to a heated saturated solution of ammonium sulfate, and the ammonium nitrite formed as a result of the exchange reaction instantly decomposes.
The gas released in this case is contaminated with ammonia, nitrogen oxide (I) and oxygen, from which it is purified by successively passing through solutions of sulfuric acid, iron (II) sulfate and over hot copper. The nitrogen is then dried.
Another laboratory method for producing nitrogen is heating a mixture of potassium dichromate and ammonium sulfate (in a ratio of 2:1 by weight). The reaction proceeds according to the equations:
K 2 Cr 2 O 7 + (NH 4) 2 SO 4 = (NH 4) 2 Cr 2 O 7 + K 2 SO 4
(NH 4) 2 Cr 2 O 7 →(t) Cr 2 O 3 + N 2 + 4H 2 O
The purest nitrogen can be obtained by decomposition of metal azides:
2NaN 3 →(t) 2Na + 3N 2
The so-called “air” or “atmospheric” nitrogen, that is, a mixture of nitrogen with noble gases, is obtained by reacting air with hot coke:
O 2 + 4N 2 + 2C → 2CO + 4N 2
This produces so-called “generator” or “air” gas - raw materials for chemical synthesis and fuel. If necessary, nitrogen can be separated from it by absorbing carbon monoxide.
Molecular nitrogen is produced industrially by fractional distillation of liquid air. This method can also be used to obtain “atmospheric nitrogen”. Nitrogen plants that use adsorption and membrane gas separation methods are also widely used.
One of the laboratory methods is passing ammonia over copper (II) oxide at a temperature of ~700°C:
2NH 3 + 3CuO → N 2 + 3H 2 O + 3Cu
Ammonia is taken from its saturated solution by heating. The amount of CuO is 2 times greater than calculated. Immediately before use, nitrogen is purified from oxygen and ammonia by passing over copper and its oxide (II) (also ~700°C), then dried with concentrated sulfuric acid and dry alkali. The process is quite slow, but it is worth it: the gas obtained is very clean.
Properties
Physical properties
Optical line emission spectrum of nitrogen
Under normal conditions, nitrogen is a colorless gas, odorless, and slightly soluble in water (2.3 ml/100g at 0 °C, 0.8 ml/100g at 80 °C).
In the liquid state (boiling point -195.8 °C) it is a colorless, mobile liquid like water. When in contact with air, it absorbs oxygen from it.
At -209.86 °C, nitrogen turns into a solid state in the form of a snow-like mass or large snow-white crystals. Upon contact with air, it absorbs oxygen from it and melts, forming a solution of oxygen in nitrogen.
Three crystalline modifications of solid nitrogen are known. In the range 36.61 - 63.29 K there is a β-N 2 phase with hexagonal close packing, space group P6 3/mmc, lattice parameters a=3.93 Å and c=6.50 Å. At temperatures below 36.61 K, the α-N 2 phase with a cubic lattice is stable, having space group Pa3 or P2 1 3 and period a = 5.660 Å. Under a pressure of more than 3500 atmospheres and a temperature below 83 K, the hexagonal γ-N 2 phase is formed.
Chemical properties, molecular structure
Nitrogen in the free state exists in the form of diatomic N 2 molecules, the electronic configuration of which is described by the formula σ s ²σ s *2 π x, y 4 σ z ², which corresponds to the triple bond between nitrogen molecules N≡N (bond length d N≡N = 0.1095 nm). As a result, the nitrogen molecule is extremely strong for the dissociation reaction N 2 ↔ 2N specific enthalpy of formation ΔH° 298 =945 kJ, reaction rate constant K 298 =10 -120, that is, dissociation of nitrogen molecules practically does not occur under normal conditions (equilibrium is almost completely shifted to the left). The nitrogen molecule is nonpolar and weakly polarized, the interaction forces between molecules are very weak, therefore, under normal conditions, nitrogen is gaseous.
Even at 3000 °C, the degree of thermal dissociation of N 2 is only 0.1%, and only at a temperature of about 5000 °C reaches several percent (at normal pressure). In high layers of the atmosphere, photochemical dissociation of N 2 molecules occurs. In laboratory conditions, it is possible to obtain atomic nitrogen by passing gaseous N 2 under strong discharge through the field of a high-frequency electric discharge. Atomic nitrogen is much more active than molecular nitrogen: in particular, at ordinary temperatures it reacts with sulfur, phosphorus, arsenic and a number of metals, for example, co.
Due to the great strength of the nitrogen molecule, many of its compounds are endothermic, the enthalpy of their formation is negative, and nitrogen compounds are thermally unstable and quite easily decompose when heated. That is why nitrogen on Earth is mostly in a free state.
Due to its significant inertness, nitrogen reacts only with lithium under normal conditions:
6Li + N 2 → 2Li 3 N,
when heated, it reacts with some other metals and non-metals, also forming nitrides:
3Mg + N 2 → Mg 3 N 2,
Greatest practical significance has hydrogen nitride (ammonia):
Industrial fixation of atmospheric nitrogen
Nitrogen compounds are extremely widely used in chemistry; it is impossible even to list all the areas where substances containing nitrogen are used: this is the industry of fertilizers, explosives, dyes, medicines, etc. Although colossal quantities of nitrogen are available literally “from the air,” due to the strength of the nitrogen molecule N 2 described above, the problem of obtaining nitrogen-containing compounds from the air has long remained unsolved; most of nitrogen compounds were extracted from its minerals, such as Chilean saltpeter. However, the reduction in reserves of these minerals, as well as the growing need for nitrogen compounds, forced work on the industrial fixation of atmospheric nitrogen to be accelerated.
The most common ammonia method of fixing atmospheric nitrogen. Reversible reaction of ammonia synthesis:
3H 2 + N 2 ↔ 2NH 3
exothermic (thermal effect 92 kJ) and comes with a decrease in volume, therefore, to shift the equilibrium to the right in accordance with the Le Chatelier-Brown principle, cooling of the mixture and high pressures are necessary. However, from a kinetic point of view, lowering the temperature is unfavorable, since this greatly reduces the reaction rate - already at 700 °C the reaction rate is too low for practical use.
In such cases, catalysis is used because a suitable catalyst allows the reaction rate to be increased without shifting the equilibrium. In the process of searching for a suitable catalyst, about twenty thousand different compounds were tried. Based on a combination of properties (catalytic activity, resistance to poisoning, low cost) greatest application received a catalyst based on metallic iron with admixtures of aluminum and potassium oxides. The process is carried out at temperatures of 400–600°C and pressures of 10–1000 atmospheres.
It should be noted that at pressures above 2000 atmospheres, the synthesis of ammonia from a mixture of hydrogen and nitrogen occurs with high speed and without a catalyst. For example, at 850 °C and 4500 atmospheres, the product yield is 97%.
There is another, less common method for the industrial binding of atmospheric nitrogen - the cyanamide method, based on the reaction of calcium carbide with nitrogen at 1000 °C. The reaction occurs according to the equation:
CaC 2 + N 2 → CaCN 2 + C.
The reaction is exothermic, its thermal effect is 293 kJ.
Every year, approximately 1·10 6 tons of nitrogen are removed industrially from the Earth's atmosphere. The process of obtaining nitrogen is described in detail here GRASYS
Nitrogen compounds
The oxidation states of nitrogen in compounds are −3, −2, −1, +1, +2, +3, +4, +5.Nitrogen compounds in the −3 oxidation state are represented by nitrides, of which ammonia is practically the most important;
Nitrogen compounds in the −2 oxidation state are less typical, represented by pernitrides, of which the most important is hydrogen pernitride N2H4 or hydrazine (there is also an extremely unstable hydrogen pernitride N2H2, diimide);
Nitrogen compounds in the oxidation state −1 NH2OH (hydroxylamine) is an unstable base used, along with hydroxylammonium salts, in organic synthesis;
Nitrogen compounds in oxidation state +1 nitric oxide (I) N2O (nitrous oxide, laughing gas);
Nitrogen compounds in oxidation state +2 nitric oxide (II) NO (nitrogen monoxide);
Nitrogen compounds in the oxidation state +3 nitrogen oxide (III) N2O3, nitrous acid, derivatives of the anion NO2-, nitrogen trifluoride NF3;
Nitrogen compounds in oxidation state +4 nitrogen oxide (IV) NO2 (nitrogen dioxide, brown gas);
Nitrogen compounds in the oxidation state +5 - nitric oxide (V) N2O5, nitric acid and its salts - nitrates, etc.
Use and application
Low-boiling liquid nitrogen in a metal beaker.
Liquid nitrogen is used as a refrigerant and for cryotherapy.
Industrial applications of nitrogen gas are due to its inert properties. Gaseous nitrogen is fire and explosion-proof, prevents oxidation and rotting. In petrochemistry, nitrogen is used to purge tanks and pipelines, check the operation of pipelines under pressure, and increase the production of fields. IN mining Nitrogen can be used to create an explosion-proof environment in mines and to expand rock layers. In electronics manufacturing, nitrogen is used to purge areas that do not allow the presence of oxidizing oxygen. If, in a process traditionally carried out using air, oxidation or putrefaction occurs negative factors- Nitrogen can successfully replace air.
An important area of application of nitrogen is its use for the further synthesis of a wide variety of compounds containing nitrogen, such as ammonia, nitrogen fertilizers, explosives, dyes, etc. Large quantities nitrogen are used in coke production (“dry quenching of coke”) when unloading coke from coke oven batteries, as well as for “pressing” fuel in rockets from tanks to pumps or engines.
In the food industry, nitrogen is registered as a food additive E941, as a gaseous medium for packaging and storage, a refrigerant, and liquid nitrogen is used when bottling oils and non-carbonated drinks to create excess pressure and an inert environment in soft containers.
Liquid nitrogen is often shown in movies as a substance that can instantly freeze fairly large objects. This is a common mistake. Even freezing a flower requires quite a long time. This is partly due to the very low heat capacity of nitrogen. For the same reason, it is very difficult to cool, say, locks to −196 °C and split them with one blow.
A liter of liquid nitrogen, evaporating and heating to 20 °C, forms approximately 700 liters of gas. For this reason, liquid nitrogen is stored in special open-type vacuum-insulated Dewar vessels or cryogenic pressure tanks. The principle of extinguishing fires with liquid nitrogen is based on the same fact. By evaporating, nitrogen displaces the oxygen necessary for combustion, and the fire stops. Since nitrogen, unlike water, foam or powder, simply evaporates and disappears, nitrogen fire extinguishing is the most effective fire extinguishing mechanism in terms of preserving valuables.
Freezing living beings with liquid nitrogen with the possibility of their subsequent defrosting is problematic. The problem is the inability to freeze (and unfreeze) a creature quickly enough so that the inhomogeneity of freezing does not affect its vital functions. Stanislaw Lem, fantasizing about this topic in his book “Fiasco,” came up with an emergency nitrogen freezing system in which a nitrogen hose, knocking out teeth, was thrust into the astronaut’s mouth and a copious stream of nitrogen was supplied inside.
Cylinder marking
Nitrogen cylinders are painted black and must have the inscription yellow color and a brown stripe (normal
Nitrogen is a chemical element with atomic number 7. It is an odorless, tasteless and colorless gas.
Thus, a person does not feel the presence of nitrogen in earth's atmosphere, while it consists of 78 percent of this substance. Nitrogen is one of the most common substances on our planet. You can often hear that without nitrogen there would be no food, and this is true. After all, the protein compounds that make up all living things necessarily contain nitrogen.
Nitrogen in nature
Nitrogen is found in the atmosphere in the form of molecules consisting of two atoms. In addition to the atmosphere, nitrogen is found in the Earth's mantle and in the humus layer of the soil. The main source of nitrogen for industrial production These are minerals.
However, in recent decades, when mineral reserves began to deplete, an urgent need arose to separate nitrogen from the air on an industrial scale. This problem has now been solved, and huge volumes of nitrogen for industrial needs are extracted from the atmosphere.
The role of nitrogen in biology, the nitrogen cycle
On Earth, nitrogen undergoes a number of transformations in which both biotic (life-related) and abiotic factors. Nitrogen enters plants from the atmosphere and soil, not directly, but through microorganisms. Nitrogen-fixing bacteria retain and process nitrogen, converting it into a form that can be easily absorbed by plants. In the plant body, nitrogen is converted into complex compounds, in particular proteins.
Through the food chain, these substances enter the bodies of herbivores and then predators. After the death of all living things, nitrogen returns to the soil, where it undergoes decomposition (ammonification and denitrification). Nitrogen is fixed in the soil, minerals, water, enters the atmosphere, and the circle repeats.
Application of nitrogen
After the discovery of nitrogen (this happened in the 18th century), the properties of the substance itself, its compounds, and the possibility of using it on the farm were well studied. Since the reserves of nitrogen on our planet are huge, this element has become extremely actively used. 
Pure nitrogen is used in liquid or gaseous form. Liquid nitrogen has a temperature of minus 196 degrees Celsius and is used in the following areas:
— in medicine. Liquid nitrogen is a refrigerant in cryotherapy procedures, that is, cold treatment. Flash freezing is used to remove various tumors. Tissue samples and living cells (in particular, sperm and eggs) are stored in liquid nitrogen. Low temperature allows you to preserve biomaterial for a long time, and then defrost and use it.
The possibility of storing entire living organisms in liquid nitrogen, and, if necessary, defrosting them without any harm, was expressed by science fiction writers. However, in reality it has not yet been possible to master this technology;
— in the food industry Liquid nitrogen is used when bottling liquids to create an inert environment in the container.
In general, nitrogen is used in areas where a gaseous environment without oxygen is required, e.g.
— in fire fighting. Nitrogen displaces oxygen, without which combustion processes are not supported and the fire goes out.
Nitrogen gas has found application in the following industries:
— food production. Nitrogen is used as an inert gas medium to maintain the freshness of packaged products;
— in the oil industry and mining. Pipelines and tanks are purged with nitrogen, it is injected into mines to form an explosion-proof gas environment;
— in aircraft manufacturing The chassis tires are inflated with nitrogen.
All of the above applies to the use of pure nitrogen, but do not forget that this element is the starting material for the production of a mass of various compounds:
- ammonia. An extremely sought-after substance containing nitrogen. Ammonia is used in the production of fertilizers, polymers, soda, and nitric acid. It is itself used in medicine, in the manufacture of refrigeration equipment;
— nitrogen fertilizers;
- explosives;
- dyes, etc. 
Nitrogen is not only one of the most common chemical elements, but also a very necessary component used in many branches of human activity.
Nitrogen
Nitrogen— element of the main subgroup of the fifth group of the second period periodic table chemical elements of D.I. Mendeleev, with atomic number 7. Denoted by the symbol N (lat. Nitrogenium). Simple substance nitrogen - a diatomic gas, quite inert under normal conditions, without color, taste and smell (formula N2), of which three-quarters of the earth’s atmosphere consists.
It was “discovered” several times and different people. It was called differently, attributing almost mystical properties - “phlogisticated air”, and “mephitic air”, and “atmospheric mofett”, and simply “asphyxiating substance”. Until now, it has several names: English Nitrogen, French Azote, German Stickstoff, Russian “nitrogen”...
The history of “spoiled air”
Nitrogen(from Greek word azoos - lifeless, in Latin Nitrogenium) - the fourth most common element solar system(after hydrogen , helium And oxygen ). Nitrogen compounds - saltpeter, nitric acid, ammonia - were known long before nitrogen was obtained in a free state.
In 1777, Henry Cavendish repeatedly passed air over hot coal and then treated it with lye. The result was a residue that Cavendish called suffocating (or mephitic) air. From the standpoint of modern chemistry, it is clear that in the reaction with hot coal, air oxygen was bound into carbon dioxide, which then reacted with alkali. The remainder of the gas was mostly nitrogen. Thus, Cavendish isolated nitrogen, but failed to understand that it was a new simple substance (chemical element).
That same year, Cavendish reported this experience to Joseph Priestley. Priestley at this time conducted a series of experiments in which he also bound atmospheric oxygen and removed the resulting carbon dioxide, that is, he also received nitrogen, however, being a supporter of the phlogiston theory that was dominant at that time, he completely misinterpreted the results obtained (in his opinion, the process was the opposite - it was not oxygen that was removed from the gas mixture, but on the contrary, as a result of firing, the air was saturated with phlogiston; he called the remaining air (nitrogen) saturated phlogiston, that is, phlogisticated).
It is obvious that Priestley, although he was able to isolate nitrogen, failed to understand the essence of his discovery, and therefore is not considered the discoverer of nitrogen. At the same time, similar experiments with the same result were carried out by Karl Scheele.
Even before that time, in 1772, Daniel Rutherford, burning phosphorus and other substances in a glass bell, saw that the gas remaining after combustion, which he called “suffocating air,” did not support respiration and combustion. Only in 1787 did Antoine Lavoisier establish that the “vital” and “asphyxiating” gases that make up the air are simple substances, and suggested the name “nitrogen”.
Earlier, in 1784, G. Cavendish showed that nitrogen is part of nitrate; this is where it comes from Latin name nitrogen (from the Late Latin nitrum - saltpeter and Greek genna - I give birth, I produce). By the beginning of the 19th century. The chemical inertness of nitrogen in the free state and its exclusive role in compounds with other elements as bound nitrogen were clarified.
"Non-life-sustaining" is vital
Although the title " nitrogen " means "non-life-sustaining", in fact it is an element necessary for life. Animal and human protein contains 16-17% nitrogen. In the organisms of carnivorous animals, protein is formed due to the consumed protein substances present in the organisms of herbivorous animals and in plants. Plants synthesize protein by assimilating nitrogenous substances contained in the soil, mainly inorganic. Significant amounts of nitrogen enter the soil thanks to nitrogen-fixing microorganisms that are capable of converting free nitrogen from the air into nitrogen compounds. As a result of extraction from the soil by plants huge amount of bound nitrogen (especially with intensive farming), soils become depleted.
Nitrogen deficiency is typical for agriculture in almost all countries. Nitrogen deficiency is also observed in animal husbandry (“protein starvation”). On soils poor in available nitrogen, plants develop poorly. In the last century, a fairly rich source of fixed nitrogen was discovered in nature. This is Chilean nitrate, the sodium salt of nitric acid. For a long time, nitrate was the main supplier of nitrogen for industry. Its deposit in South America unique, practically the only one in the world. And it is not surprising that in 1879, a war broke out between Peru, Bolivia and Chile over the possession of the rich saltpeter border province of Tarapaca. The winner was Chile. However, the Chilean deposit, of course, could not satisfy the world demand for nitrogen fertilizers.
“Nitrogen starvation” of the planet
The Earth's atmosphere contains almost 80% nitrogen, earth's crust- only 0.04%. The problem of “how to fix nitrogen” is old, it is the same age as agrochemistry. The possibility of binding nitrogen in the air with oxygen in an electric discharge was first seen by the Englishman Henry Cavendish. This was back in the 18th century. But the process of controlled synthesis of nitrogen oxides was carried out only in 1904. In 1913, the Germans Fritz Haber and Carl Bosch proposed the ammonia method for nitrogen fixation. Now, using this principle, hundreds of factories on all continents produce more than 20 million tons of fixed nitrogen per year from the air. Three quarters of it goes to the production of nitrogen fertilizers. However, nitrogen deficiency in crop areas globe amounts to more than 80 million tons per year. The Earth clearly does not have enough nitrogen. The bulk of the free nitrogen produced is used for the industrial production of ammonia, which is then processed in significant quantities into nitric acid, fertilizers, explosives, etc.
Application of nitrogen
Free nitrogen used in many industries: as an inert medium in various chemical and metallurgical processes, for filling free space in mercury thermometers, when pumping flammable liquids, etc.
A liquid nitrogen used as a coolant and for cryotherapy. Industrial applications of nitrogen gas are due to its inert properties. Gaseous nitrogen is fire and explosion-proof, prevents oxidation and rotting.
IN petrochemicals nitrogen used for purging tanks and pipelines, checking the operation of pipelines under pressure, increasing the production of fields. In mining nitrogen can be used to create an explosion-proof environment in mines and to expand rock layers.
IN electronics production nitrogen used for purging areas that do not allow the presence of oxidizing oxygen. If in a process traditionally carried out using air, oxidation or putrefaction are negative factors - nitrogen can successfully replace air.
Important area of application nitrogen is his use for further synthesis a wide variety of compounds containing nitrogen , such as ammonia, nitrogen fertilizers, explosives, dyes, etc. Large quantities nitrogen used in coke production (“dry quenching of coke”) when unloading coke from coke batteries, as well as for “pressing” fuel in rockets from tanks to pumps or engines.
Misconceptions: nitrogen is not Santa Claus
IN Food Industry nitrogen registered as a food additive E941, as a gaseous medium for packaging and storage, refrigerant. Liquid nitrogen It is often demonstrated in films as a substance that can instantly freeze fairly large objects. This is a common mistake. Even freezing a flower requires quite a long time, which is partly due to the very low heat capacity nitrogen .
For the same reason, it is very difficult to cool, say, locks to −180 °C and split them with one blow. Liter of liquid nitrogen , evaporating and heating up to 20 °C, forms approximately 700 liters of gas. For this reason, you should not store nitrogen in closed vessels not suitable for high pressures. The principle of extinguishing fires with liquid is based on the same fact. nitrogen . Evaporating nitrogen displaces the air needed for combustion and the fire stops.
Because nitrogen , unlike water, foam or powder, simply evaporates and disappears, nitrogen fire extinguishing is the most effective fire extinguishing mechanism from the point of view of preserving valuables. Freezing liquid nitrogen living creatures with the possibility of their subsequent defrosting is problematic. The problem is the inability to freeze (and unfreeze) a creature quickly enough so that the inhomogeneity of freezing does not affect its vital functions. Stanislav Lem, fantasizing about this topic in the book “Fiasco,” came up with an emergency freezing system nitrogen , in which a hose with nitrogen, knocking out teeth, was thrust into the astronaut’s mouth and a copious stream was supplied inside him nitrogen .
As already stated above, nitrogen liquid and gaseous are obtained from atmospheric air deep cooling method.
Quality indicators of gaseous nitrogen GOST 9293-74
| Indicator name | Special | Increased | Increased | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2nd grade | 1st grade |
2nd grade |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Volume fraction of nitrogen, not less | 99,996 |
99,99 |
99,95 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Oxygen, no more | 0,001 |
0,001 |
0,05 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Water vapor in nitrogen gas, no more | 0,0007 |
0,0015 |
0,004 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Hydrogen, no more | 0,001 | Not standardized |
Not standardized | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Sum of carbon-containing compounds in terms of CH 4, no more | 0,001 | Not standardized |
Properties elements V-A subgroups
1. Structure of atoms of chemical elements
The presence of three unpaired electrons at the outer energy level explains that in a normal, unexcited state, the valence of elements of the nitrogen subgroup is three. Atoms of elements of the nitrogen subgroup (except for nitrogen - the outer level of nitrogen consists of only two sublevels - 2s and 2p) have vacant cells of the d-sublevel at the outer energy levels, so they can vaporize one electron from the s-sublevel and transfer it to the d-sublevel . Thus, the valency of phosphorus, arsenic, antimony and bismuth is 5. Elements of the nitrogen group form compounds of the composition RH 3 with hydrogen, and oxides of the type R 2 O 3 and R 2 O 5 with oxygen. Oxides correspond to acids HRO 2 and HRO 3 (and ortho acids H 3 PO 4, except nitrogen). The highest oxidation state of these elements is +5, and the lowest is -3.
Since the charge of the nucleus of atoms increases, the number of electrons in the outer level is constant, the number energy levels in atoms increases and the atomic radius increases from nitrogen to bismuth, the attraction of negative electrons to the positive nucleus weakens and the ability to give up electrons increases, and, consequently, in the nitrogen subgroup, with increasing atomic number, non-metallic properties decrease, and metallic properties increase.
Nitrogen is a non-metal, bismuth is a metal. From nitrogen to bismuth, the strength of RH 3 compounds decreases, and the strength of oxygen compounds increases. The most important among the elements of the nitrogen subgroup are nitrogen and phosphorus . Nitrogen, physical and Chemical properties, receipt and application 1. Nitrogen is a chemical element
N +7) 2) 5 1 s 2 2 s 2 2 p 3 unfinished external level, p -element, non-metal Ar(N)=14 2. Possible oxidation states Due to the presence of three unpaired electrons, nitrogen is very active and is found only in the form of compounds. Nitrogen exhibits oxidation states in compounds from “-3” to “+5”
3. Nitrogen is a simple substance, molecular structure, physical properties Nitrogen (from Greek ἀ ζωτος - lifeless, lat. Nitrogenium), instead of the previous names (“phlogisticated”, “mephitic” and “spoiled” air) proposed in 1787 Antoine Lavoisier . As shown above, it was already known at that time that nitrogen supports neither combustion nor respiration. This property was considered the most important. Although it later turned out that nitrogen, on the contrary, is essential for all living beings, the name was preserved in French and Russian. N 2 – covalent nonpolar bond, triple (σ, 2π), molecular crystal lattice
Conclusion: 1. Low reactivity at normal temperature 2. Gas, colorless, odorless, lighter than air
Mr ( B air)/ Mr ( N 2 ) = 29/28 4. Chemical properties of nitrogen
5. Receipt: In industry nitrogen is obtained from the air. To do this, the air is first cooled, liquefied, and the liquid air is subjected to distillation. Nitrogen has a slightly lower boiling point (–195.8°C) than the other component of air, oxygen (–182.9°C), so when liquid air is gently heated, nitrogen evaporates first. Nitrogen gas is supplied to consumers in compressed form (150 atm. or 15 MPa) in black cylinders with a yellow “nitrogen” inscription. Store liquid nitrogen in Dewar flasks. In the laboratorypure (“chemical”) nitrogen is obtained by adding a saturated solution of ammonium chloride NH 4 Cl to solid sodium nitrite NaNO 2 when heated: NaNO 2 + NH 4 Cl = NaCl + N 2 + 2H 2 O. You can also heat solid ammonium nitrite: NH 4 NO 2 = N 2 + 2H 2 O. EXPERIMENT 6. Application: In industry, nitrogen gas is used mainly to produce ammonia. As a chemically inert gas, nitrogen is used to provide an inert environment in various chemical and metallurgical processes, when pumping flammable liquids. Liquid nitrogen is widely used as a refrigerant; it is used in medicine, especially in cosmetology. Nitrogen mineral fertilizers are important in maintaining soil fertility. 7. Biological role Nitrogen is an element necessary for the existence of animals and plants; it is part ofproteins (16-18% by weight), amino acids, nucleic acids, nucleoproteins, chlorophyll, hemoglobin etc. In the composition of living cells, the number of nitrogen atoms is about 2%, and the mass fraction is about 2.5% (fourth place after hydrogen, carbon and oxygen). In this regard, a significant amount of fixed nitrogen is contained in living organisms, “dead organic matter” and dispersed matter of the seas and oceans. This amount is estimated at approximately 1.9 10 11 tons. As a result of the processes of rotting and decomposition of nitrogen-containing organic matter, subject to favorable environmental factors, natural mineral deposits containing nitrogen can form, for example, “Chilean saltpeterN 2 → Li 3 N → NH 3 No. 2. Write down equations for the reaction of nitrogen with oxygen, magnesium and hydrogen. For each reaction, create an electronic balance, indicate the oxidizing agent and the reducing agent. No. 3. One cylinder contains nitrogen gas, another contains oxygen, and the third contains carbon dioxide. How to distinguish these gases? No. 4. Some flammable gases contain free nitrogen as an impurity. Can nitrogen (II) oxide be formed during the combustion of such gases in ordinary gas stoves? Why?
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