Interaction of dichloroethane with oxygen 9 gaseous state. Chemistry preparation for fever and dpa comprehensive edition

The content of the article

OXYGEN, O (oxygenium), a chemical element of the VIA subgroup of the periodic table of elements: O, S, Se, Te, Po - a member of the chalcogen family. This is the most common element in nature, its content in the Earth’s atmosphere is 21% (vol.), in the earth’s crust in the form of compounds of approx. 50% (wt.) and in the hydrosphere 88.8% (wt.).

Oxygen is necessary for the existence of life on earth: animals and plants consume oxygen during respiration, and plants release oxygen through photosynthesis. Living matter contains bound oxygen not only in body fluids (in blood cells, etc.), but also in carbohydrates (sugar, cellulose, starch, glycogen), fats and proteins. Clays, rocks, consist of silicates and other oxygen-containing inorganic compounds such as oxides, hydroxides, carbonates, sulfates and nitrates.

Historical reference.

The first information about oxygen became known in Europe from Chinese manuscripts of the 8th century. At the beginning of the 16th century. Leonardo da Vinci published data related to the chemistry of oxygen, not yet knowing that oxygen was an element. Reactions of oxygen addition are described in the scientific works of S. Geils (1731) and P. Bayen (1774). K. Scheele's research in 1771–1773 on the interaction of metals and phosphorus with oxygen deserves special attention. J. Priestley reported the discovery of oxygen as an element in 1774, a few months after Bayen's report of reactions with air. The name oxygenium (“oxygen”) was given to this element shortly after its discovery by Priestley and comes from the Greek words meaning “acid-producing”; this is due to the misconception that oxygen is present in all acids. The explanation of the role of oxygen in the processes of respiration and combustion, however, belongs to A. Lavoisier (1777).

The structure of the atom.

Any naturally occurring oxygen atom contains 8 protons in the nucleus, but the number of neutrons can be 8, 9, or 10. The most common of the three isotopes of oxygen (99.76%) is 16 8 O (8 protons and 8 neutrons). The content of another isotope, 18 8 O (8 protons and 10 neutrons), is only 0.2%. This isotope is used as a label or for identifying certain molecules, as well as for conducting biochemical and medico-chemical studies (a method for studying non-radioactive traces). The third non-radioactive isotope of oxygen, 17 8 O (0.04%), contains 9 neutrons and has a mass number of 17. After the mass of the carbon isotope 12 6 C was adopted as the standard atomic mass by the International Commission in 1961, the weighted average atomic mass of oxygen became 15. 9994. Until 1961, chemists considered the standard unit of atomic mass to be the atomic mass of oxygen, assumed to be 16,000 for a mixture of three naturally occurring isotopes of oxygen. Physicists took the mass number of the oxygen isotope 16 8 O as the standard unit of atomic mass, so on the physical scale the average atomic mass of oxygen was 16.0044.

There are 8 electrons in an oxygen atom, with 2 electrons in the internal level and 6 electrons in the outer level. Therefore, in chemical reactions, oxygen can accept up to two electrons from donors, building up its outer shell to 8 electrons and forming an excess negative charge.

Molecular oxygen.

Like most other elements, the atoms of which lack 1–2 electrons to complete the outer shell of 8 electrons, oxygen forms a diatomic molecule. This process releases a lot of energy (~490 kJ/mol) and, accordingly, the same amount of energy must be spent for the reverse process of dissociation of the molecule into atoms. The strength of the O–O bond is so high that at 2300° C only 1% of oxygen molecules dissociate into atoms. (It is noteworthy that during the formation of the nitrogen molecule N2, the strength of the N–N bond is even higher, ~710 kJ/mol.)

Electronic structure.

In the electronic structure of the oxygen molecule, as might be expected, the distribution of electrons in an octet around each atom is not realized, but there are unpaired electrons, and oxygen exhibits properties typical of such a structure (for example, it interacts with a magnetic field, being paramagnetic).

Reactions.

Under appropriate conditions, molecular oxygen reacts with almost any element except the noble gases. However, under room conditions, only the most active elements react with oxygen quickly enough. It is likely that most reactions occur only after the dissociation of oxygen into atoms, and dissociation occurs only at very high temperatures. However, catalysts or other substances in the reacting system can promote the dissociation of O 2 . It is known that alkali (Li, Na, K) and alkaline earth (Ca, Sr, Ba) metals react with molecular oxygen to form peroxides:

Receipt and application.

Due to the presence of free oxygen in the atmosphere, the most effective method for its extraction is the liquefaction of air, from which impurities, CO 2, dust, etc. are removed. chemical and physical methods. The cyclic process includes compression, cooling and expansion, which leads to air liquefaction. With a slow rise in temperature (fractional distillation method), first noble gases (the most difficult to liquefy) evaporate from liquid air, then nitrogen, and liquid oxygen remains. As a result, liquid oxygen contains traces of noble gases and a relatively large percentage of nitrogen. For many applications these impurities are not a problem. However, to obtain oxygen of extreme purity, the distillation process must be repeated. Oxygen is stored in tanks and cylinders. It is used in large quantities as an oxidizer for kerosene and other fuels in rockets and spacecraft. The steel industry uses oxygen gas to blow through the molten iron using the Bessemer method to quickly and effectively remove C, S and P impurities. Oxygen blast produces steel faster and of higher quality than air blast. Oxygen is also used for welding and cutting metals (oxy-acetylene flame). Oxygen is also used in medicine, for example, to enrich the respiratory environment of patients with difficulty breathing. Oxygen can be produced by various chemical methods, and some of them are used to obtain small quantities of pure oxygen in laboratory practice.

Electrolysis.

One of the methods for producing oxygen is the electrolysis of water containing small additions of NaOH or H 2 SO 4 as a catalyst: 2H 2 O ® 2H 2 + O 2. In this case, small hydrogen impurities are formed. Using a discharge device, traces of hydrogen in the gas mixture are again converted into water, the vapors of which are removed by freezing or adsorption.

Thermal dissociation.

An important laboratory method for producing oxygen, proposed by J. Priestley, is the thermal decomposition of heavy metal oxides: 2HgO ® 2Hg + O 2 . To do this, Priestley focused the sun's rays on mercury oxide powder. A well-known laboratory method is also the thermal dissociation of oxo salts, for example potassium chlorate in the presence of a catalyst - manganese dioxide:

Manganese dioxide, added in small quantities before calcination, allows maintaining the required temperature and dissociation rate, and the MnO 2 itself does not change during the process.

Methods for thermal decomposition of nitrates are also used:

as well as peroxides of some active metals, for example:

2BaO 2 ® 2BaO + O 2

The latter method was at one time widely used to extract oxygen from the atmosphere and consisted of heating BaO in air until BaO 2 was formed, followed by thermal decomposition of the peroxide. The thermal decomposition method remains important for the production of hydrogen peroxide.

Physical properties.

Oxygen under normal conditions is a colorless, odorless and tasteless gas. Liquid oxygen is pale blue in color. Solid oxygen exists in at least three crystalline modifications. Oxygen gas is soluble in water and probably forms weak compounds such as O2HH2O, and possibly O2H2H2O.

Chemical properties.

As already mentioned, the chemical activity of oxygen is determined by its ability to dissociate into O atoms, which are highly reactive. Only the most active metals and minerals react with O 2 at high rates at low temperatures. The most active alkali (IA subgroups) and some alkaline earth (IIA subgroups) metals form peroxides such as NaO 2 and BaO 2 with O 2 . Other elements and compounds react only with the dissociation product O2. Under suitable conditions, all elements, excluding the noble gases and the metals Pt, Ag, Au, react with oxygen. These metals also form oxides, but under special conditions.

The electronic structure of oxygen (1s 2 2s 2 2p 4) is such that the O atom accepts two electrons to the outer level to form a stable outer electron shell, forming an O 2– ion. In alkali metal oxides, predominantly ionic bonds are formed. It can be assumed that the electrons of these metals are almost entirely drawn to oxygen. In oxides of less active metals and non-metals, the electron transfer is incomplete, and the negative charge density on oxygen is less pronounced, so the bond is less ionic or more covalent.

When metals are oxidized with oxygen, heat is released, the magnitude of which correlates with the strength of the M–O bond. During the oxidation of some nonmetals, heat is absorbed, which indicates their weaker bonds with oxygen. Such oxides are thermally unstable (or less stable than oxides with ionic bonds) and are often highly reactive. The table shows for comparison the values ​​of the enthalpies of formation of oxides of the most typical metals, transition metals and nonmetals, elements of the A- and B-subgroups (the minus sign means the release of heat).

Several general conclusions can be drawn about the properties of oxides:

1. Melting temperatures of alkali metal oxides decrease with increasing atomic radius of the metal; So, t pl (Cs 2 O) t pl (Na 2 O). Oxides in which ionic bonding predominates have higher melting points than the melting points of covalent oxides: t pl (Na 2 O) > t pl (SO 2).

2. Oxides of reactive metals (IA–IIIA subgroups) are more thermally stable than oxides of transition metals and nonmetals. Oxides of heavy metals in the highest oxidation state upon thermal dissociation form oxides with lower oxidation states (for example, 2Hg 2+ O ® (Hg +) 2 O + 0.5O 2 ® 2Hg 0 + O 2). Such oxides in high oxidation states can be good oxidizing agents.

3. The most active metals react with molecular oxygen at elevated temperatures to form peroxides:

Sr + O 2 ® SrO 2 .

4. Oxides of active metals form colorless solutions, while the oxides of most transition metals are colored and practically insoluble. Aqueous solutions of metal oxides exhibit basic properties and are hydroxides containing OH groups, and non-metal oxides in aqueous solutions form acids containing the H + ion.

5. Metals and non-metals of A-subgroups form oxides with an oxidation state corresponding to the group number, for example, Na, Be and B form Na 1 2 O, Be II O and B 2 III O 3, and non-metals IVA–VIIA of subgroups C, N , S, Cl form C IV O 2, N V 2 O 5, S VI O 3, Cl VII 2 O 7. The group number of an element correlates only with the maximum oxidation state, since oxides with lower oxidation states of elements are possible. In combustion processes of compounds, typical products are oxides, for example:

2H 2 S + 3O 2 ® 2SO 2 + 2H 2 O

Carbon-containing substances and hydrocarbons, when heated slightly, oxidize (burn) to CO 2 and H 2 O. Examples of such substances are fuels - wood, oil, alcohols (as well as carbon - coal, coke and charcoal). The heat from the combustion process is utilized to produce steam (and then electricity or goes to power plants), as well as for heating houses. Typical equations for combustion processes are:

a) wood (cellulose):

(C6H10O5) n + 6n O 2 ® 6 n CO2+5 n H 2 O + thermal energy

b) oil or gas (gasoline C 8 H 18 or natural gas CH 4):

2C 8 H 18 + 25O 2 ® 16CO 2 + 18H 2 O + thermal energy

CH 4 + 2O 2 ® CO 2 + 2H 2 O + thermal energy

C 2 H 5 OH + 3O 2 ® 2CO 2 + 3H 2 O + thermal energy

d) carbon (coal or charcoal, coke):

2C + O 2 ® 2CO + thermal energy

2CO + O 2 ® 2CO 2 + thermal energy

A number of C-, H-, N-, O-containing compounds with a high energy reserve are also subject to combustion. Oxygen for oxidation can be used not only from the atmosphere (as in previous reactions), but also from the substance itself. To initiate a reaction, a small activation of the reaction, such as a blow or shake, is sufficient. In these reactions, combustion products are also oxides, but they are all gaseous and expand rapidly at the high final temperature of the process. Therefore, such substances are explosive. Examples of explosives are trinitroglycerin (or nitroglycerin) C 3 H 5 (NO 3) 3 and trinitrotoluene (or TNT) C 7 H 5 (NO 2) 3.

Oxides of metals or non-metals with lower oxidation states of an element react with oxygen to form oxides of high oxidation states of that element:

Natural oxides, obtained from ores or synthesized, serve as raw materials for the production of many important metals, for example, iron from Fe 2 O 3 (hematite) and Fe 3 O 4 (magnetite), aluminum from Al 2 O 3 (alumina), magnesium from MgO (magnesia). Light metal oxides are used in the chemical industry to produce alkalis or bases. Potassium peroxide KO 2 has an unusual use because in the presence of moisture and as a result of reaction with it, it releases oxygen. Therefore, KO 2 is used in respirators to produce oxygen. Moisture from the exhaled air releases oxygen in the respirator, and KOH absorbs CO 2. Production of CaO oxide and calcium hydroxide Ca(OH) 2 – large-scale production in ceramics and cement technology.

Water (hydrogen oxide).

The importance of water H 2 O both in laboratory practice for chemical reactions and in life processes requires special consideration of this substance WATER, ICE AND STEAM). As already mentioned, during the direct interaction of oxygen and hydrogen under conditions, for example, a spark discharge, an explosion and the formation of water occur, and 143 kJ/(mol H 2 O) is released.

The water molecule has an almost tetrahedral structure, the H–O–H angle is 104° 30°. The bonds in the molecule are partially ionic (30%) and partially covalent with a high density of negative charge on oxygen and, accordingly, positive charges on hydrogen:

Due to the high strength of H–O bonds, hydrogen is difficult to split off from oxygen and water exhibits very weak acidic properties. Many properties of water are determined by the distribution of charges. For example, a water molecule forms a hydrate with a metal ion:

Water donates one electron pair to an acceptor, which can be H +:

Oxoanions and oxocations

– oxygen-containing particles having a residual negative (oxoanions) or residual positive (oxocations) charge. The O 2– ion has high affinity (high reactivity) for positively charged particles such as H +. The simplest representative of stable oxoanions is the hydroxide ion OH –. This explains the instability of atoms with a high charge density and their partial stabilization as a result of the addition of a particle with a positive charge. Therefore, when an active metal (or its oxide) acts on water, OH– is formed, and not O 2–:

2Na + 2H 2 O ® 2Na + + 2OH – + H 2

Na 2 O + H 2 O ® 2Na + + 2OH –

More complex oxoanions are formed from oxygen with a metal ion or non-metallic particle that has a large positive charge, resulting in a low-charge particle that is more stable, for example:

Plan:

History of discovery

Origin of name

Being in nature

Receipt

Physical properties

Chemical properties

Application

10. Isotopes

Oxygen

Oxygen- element of the 16th group (according to the outdated classification - the main subgroup of group VI), the second period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 8. Denoted by the symbol O (lat. Oxygenium). Oxygen is a chemically active non-metal and is the lightest element from the group of chalcogens. Simple substance oxygen(CAS number: 7782-44-7) under normal conditions is a colorless, tasteless and odorless gas, the molecule of which consists of two oxygen atoms (formula O 2), and therefore it is also called dioxygen. Liquid oxygen has a light blue color, and solid crystals are light blue in color.

There are other allotropic forms of oxygen, for example, ozone (CAS number: 10028-15-6) - under normal conditions, a blue gas with a specific odor, the molecule of which consists of three oxygen atoms (formula O 3).

History of discovery

It is officially believed that oxygen was discovered by the English chemist Joseph Priestley on August 1, 1774 by decomposing mercuric oxide in a hermetically sealed vessel (Priestley directed sunlight at this compound using a powerful lens).

However, Priestley initially did not realize that he had discovered a new simple substance; he believed that he had isolated one of the constituent parts of air (and called this gas “dephlogisticated air”). Priestley reported his discovery to the outstanding French chemist Antoine Lavoisier. In 1775, A. Lavoisier established that oxygen is a component of air, acids and is found in many substances.

A few years earlier (in 1771), oxygen was obtained by the Swedish chemist Karl Scheele. He calcined saltpeter with sulfuric acid and then decomposed the resulting nitric oxide. Scheele called this gas “fire air” and described his discovery in a book published in 1777 (precisely because the book was published later than Priestley announced his discovery, the latter is considered the discoverer of oxygen). Scheele also reported his experience to Lavoisier.

An important step that contributed to the discovery of oxygen was the work of the French chemist Pierre Bayen, who published works on the oxidation of mercury and the subsequent decomposition of its oxide.

Finally, A. Lavoisier finally figured out the nature of the resulting gas, using information from Priestley and Scheele. His work was of enormous importance because thanks to it, the phlogiston theory, which was dominant at that time and hampered the development of chemistry, was overthrown. Lavoisier conducted experiments on the combustion of various substances and disproved the theory of phlogiston, publishing results on the weight of the burned elements. The weight of the ash exceeded the original weight of the element, which gave Lavoisier the right to claim that during combustion a chemical reaction (oxidation) of the substance occurs, and therefore the mass of the original substance increases, which refutes the theory of phlogiston.

Thus, the credit for the discovery of oxygen is actually shared between Priestley, Scheele and Lavoisier.

Origin of name

The word oxygen (also called “acid solution” at the beginning of the 19th century) owes its appearance in the Russian language to some extent to M.V. Lomonosov, who introduced the word “acid”, along with other neologisms; Thus, the word “oxygen”, in turn, was a tracing of the term “oxygen” (French oxygène), proposed by A. Lavoisier (from ancient Greek ὀξύς - “sour” and γεννάω - “giving birth”), which is translated as “generating acid”, which is associated with its original meaning - “acid”, which previously meant substances called oxides according to modern international nomenclature.

Being in nature

Oxygen is the most common element on Earth; its share (in various compounds, mainly silicates) accounts for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by mass), in the atmosphere the content of free oxygen is 20.95% by volume and 23.12% by mass. More than 1,500 compounds in the earth's crust contain oxygen.

Oxygen is part of many organic substances and is present in all living cells. In terms of the number of atoms in living cells, it is about 25%, and in terms of mass fraction - about 65%.

Receipt

Currently, in industry, oxygen is obtained from the air. The main industrial method for producing oxygen is cryogenic rectification. Oxygen plants operating on the basis of membrane technology are also well known and successfully used in industry.

Laboratories use industrially produced oxygen, supplied in steel cylinders under a pressure of about 15 MPa.

Small amounts of oxygen can be obtained by heating potassium permanganate KMnO 4:

The reaction of catalytic decomposition of hydrogen peroxide H2O2 in the presence of manganese(IV) oxide is also used:

Oxygen can be obtained by the catalytic decomposition of potassium chlorate (Berthollet salt) KClO 3:

Laboratory methods for producing oxygen include the method of electrolysis of aqueous solutions of alkalis, as well as the decomposition of mercury(II) oxide (at t = 100 °C):

In submarines it is usually obtained by the reaction of sodium peroxide and carbon dioxide exhaled by humans:

Physical properties

In the world's oceans, the content of dissolved O2 is greater in cold water and less in warm water.

Under normal conditions, oxygen is a gas without color, taste or smell.

1 liter of it has a mass of 1.429 g. Slightly heavier than air. Slightly soluble in water (4.9 ml/100 g at 0 °C, 2.09 ml/100 g at 50 °C) and alcohol (2.78 ml/100 g at 25 °C). It dissolves well in molten silver (22 volumes of O 2 in 1 volume of Ag at 961 ° C). Interatomic distance - 0.12074 nm. Is paramagnetic.

When gaseous oxygen is heated, its reversible dissociation into atoms occurs: at 2000 °C - 0.03%, at 2600 °C - 1%, 4000 °C - 59%, 6000 °C - 99.5%.

Liquid oxygen (boiling point −182.98 °C) is a pale blue liquid.

O2 phase diagram

Solid oxygen (melting point −218.35°C) - blue crystals. There are 6 known crystalline phases, three of which exist at a pressure of 1 atm:

α-O 2 - exists at temperatures below 23.65 K; bright blue crystals belong to the monoclinic system, cell parameters a=5.403 Å, b=3.429 Å, c=5.086 Å; β=132.53°.

β-O 2 - exists in the temperature range from 23.65 to 43.65 K; pale blue crystals (with increasing pressure the color turns pink) have a rhombohedral lattice, cell parameters a=4.21 Å, α=46.25°.

γ-O 2 - exists at temperatures from 43.65 to 54.21 K; pale blue crystals have cubic symmetry, lattice parameter a=6.83 Å.

Three more phases form at high pressures:

δ-O 2 temperature range 20-240 K and pressure 6-8 GPa, orange crystals;

ε-O 4 pressure from 10 to 96 GPa, crystal color from dark red to black, monoclinic system;

ζ-O n pressure more than 96 GPa, a metallic state with a characteristic metallic luster, at low temperatures it transforms into a superconducting state.

Chemical properties

A strong oxidizing agent, it interacts with almost all elements, forming oxides. Oxidation state −2. As a rule, the oxidation reaction proceeds with the release of heat and accelerates with increasing temperature (see Combustion). Example of reactions occurring at room temperature:

Oxidizes compounds that contain elements with less than the maximum oxidation state:

Oxidizes most organic compounds:

Under certain conditions, it is possible to carry out mild oxidation of an organic compound:

Oxygen reacts directly (under normal conditions, with heating and/or in the presence of catalysts) with all simple substances except Au and inert gases (He, Ne, Ar, Kr, Xe, Rn); reactions with halogens occur under the influence of an electrical discharge or ultraviolet radiation. Oxides of gold and heavy inert gases (Xe, Rn) were obtained indirectly. In all two-element compounds of oxygen with other elements, oxygen plays the role of an oxidizing agent, except for compounds with fluorine

Oxygen forms peroxides with the oxidation state of the oxygen atom formally equal to −1.

For example, peroxides are produced by the combustion of alkali metals in oxygen:

Some oxides absorb oxygen:

According to the combustion theory developed by A. N. Bach and K. O. Engler, oxidation occurs in two stages with the formation of an intermediate peroxide compound. This intermediate compound can be isolated, for example, when a flame of burning hydrogen is cooled with ice, hydrogen peroxide is formed along with water:

In superoxides, oxygen formally has an oxidation state of −½, that is, one electron per two oxygen atoms (O − 2 ion). Obtained by reacting peroxides with oxygen at elevated pressure and temperature:

Potassium K, rubidium Rb and cesium Cs react with oxygen to form superoxides:

In the dioxygenyl ion O 2 +, oxygen formally has an oxidation state of +½. Obtained by the reaction:

Oxygen fluorides

Oxygen difluoride, OF 2 oxidation state of oxygen +2, is prepared by passing fluorine through an alkali solution:

Oxygen monofluoride (dioxydifluoride), O 2 F 2, is unstable, the oxidation state of oxygen is +1. Obtained from a mixture of fluorine and oxygen in a glow discharge at a temperature of −196 °C:

By passing a glow discharge through a mixture of fluorine and oxygen at a certain pressure and temperature, mixtures of higher oxygen fluorides O 3 F 2, O 4 F 2, O 5 F 2 and O 6 F 2 are obtained.

Quantum mechanical calculations predict the stable existence of the trifluorohydroxonium ion OF 3 +. If this ion really exists, then the oxidation state of oxygen in it will be equal to +4.

Oxygen supports the processes of respiration, combustion, and decay.

In its free form, the element exists in two allotropic modifications: O 2 and O 3 (ozone). As Pierre Curie and Marie Skłodowska-Curie established in 1899, under the influence of ionizing radiation O 2 turns into O 3 .

Application

The widespread industrial use of oxygen began in the middle of the 20th century, after the invention of turboexpanders - devices for liquefying and separating liquid air.

INmetallurgy

The converter method of steel production or matte processing involves the use of oxygen. In many metallurgical units, for more efficient combustion of fuel, an oxygen-air mixture is used instead of air in the burners.

Welding and cutting of metals

Oxygen in blue cylinders is widely used for flame cutting and welding of metals.

Rocket fuel

Liquid oxygen, hydrogen peroxide, nitric acid and other oxygen-rich compounds are used as oxidizers for rocket fuel. A mixture of liquid oxygen and liquid ozone is one of the most powerful oxidizers of rocket fuel (the specific impulse of the hydrogen-ozone mixture exceeds the specific impulse for the hydrogen-fluorine and hydrogen-oxygen fluoride pairs).

INmedicine

Medical oxygen is stored in high-pressure metal gas cylinders (for compressed or liquefied gases) of blue color of various capacities from 1.2 to 10.0 liters under pressure up to 15 MPa (150 atm) and is used to enrich respiratory gas mixtures in anesthesia equipment, when breathing disorders, to relieve an attack of bronchial asthma, to eliminate hypoxia of any origin, for decompression sickness, to treat pathologies of the gastrointestinal tract in the form of oxygen cocktails. For individual use, special rubberized containers - oxygen cushions - are filled from cylinders with medical oxygen. Oxygen inhalers of various models and modifications are used to supply oxygen or an oxygen-air mixture simultaneously to one or two victims in the field or in a hospital setting. The advantage of an oxygen inhaler is the presence of a condenser-humidifier of the gas mixture, which uses the moisture of the exhaled air. To calculate the amount of oxygen remaining in the cylinder in liters, the pressure in the cylinder in atmospheres (according to the pressure gauge of the reducer) is usually multiplied by the cylinder capacity in liters. For example, in a cylinder with a capacity of 2 liters, the pressure gauge shows an oxygen pressure of 100 atm. The volume of oxygen in this case is 100 × 2 = 200 liters.

INFood Industry

In the food industry, oxygen is registered as a food additive E948, as a propellant and packaging gas.

INchemical industry

In the chemical industry, oxygen is used as an oxidizing agent in numerous syntheses, for example, the oxidation of hydrocarbons into oxygen-containing compounds (alcohols, aldehydes, acids), ammonia into nitrogen oxides in the production of nitric acid. Due to the high temperatures developing during oxidation, the latter are often carried out in combustion mode.

INagriculture

In greenhouse farming, for making oxygen cocktails, for weight gain in animals, for enriching the aquatic environment with oxygen in fish farming.

Biological role of oxygen

Emergency oxygen supply in a bomb shelter

Most living beings (aerobes) breathe oxygen from the air. Oxygen is widely used in medicine. In case of cardiovascular diseases, to improve metabolic processes, oxygen foam (“oxygen cocktail”) is injected into the stomach. Subcutaneous administration of oxygen is used for trophic ulcers, elephantiasis, gangrene and other serious diseases. Artificial ozone enrichment is used to disinfect and deodorize air and purify drinking water. The radioactive oxygen isotope 15 O is used to study blood flow speed and pulmonary ventilation.

Toxic oxygen derivatives

Some oxygen derivatives (so-called reactive oxygen species), such as singlet oxygen, hydrogen peroxide, superoxide, ozone and hydroxyl radical, are highly toxic. They are formed during the process of activation or partial reduction of oxygen. Superoxide (superoxide radical), hydrogen peroxide and hydroxyl radical can form in cells and tissues of humans and animals and cause oxidative stress.

Isotopes

Oxygen has three stable isotopes: 16 O, 17 O and 18 O, the average content of which is, respectively, 99.759%, 0.037% and 0.204% of the total number of oxygen atoms on Earth. The sharp predominance of the lightest of them, 16 O, in the mixture of isotopes is due to the fact that the nucleus of the 16 O atom consists of 8 protons and 8 neutrons (a double magic nucleus with filled neutron and proton shells). And such nuclei, as follows from the theory of the structure of the atomic nucleus, are particularly stable.

Radioactive isotopes of oxygen with mass numbers from 12 O to 24 O are also known. All radioactive isotopes of oxygen have a short half-life, the longest-lived of them is 15 O with a half-life of ~120 s. The shortest-lived isotope 12 O has a half-life of 5.8·10−22 s.

DEFINITION

Oxygen- the eighth element of the Periodic Table. Designation - O from the Latin “oxygenium”. Located in the second period, group VIA. Refers to non-metals. The nuclear charge is 8.

Oxygen is the most common element in the earth's crust. In a free state, it is found in the atmospheric air; in a bound form, it is part of water, minerals, rocks and all substances from which the organisms of plants and animals are built. The mass fraction of oxygen in the earth's crust is about 47%.

In its simple form, oxygen is a colorless, odorless gas. It is slightly heavier than air: the mass of 1 liter of oxygen under normal conditions is 1.43 g, and 1 liter of air is 1.293 g. Oxygen dissolves in water, although in small quantities: 100 volumes of water at 0 o C dissolve 4.9, and at 20 o C - 3.1 volumes of oxygen.

Atomic and molecular mass of oxygen

DEFINITION

Relative atomic mass A r is the molar mass of an atom of a substance divided by 1/12 of the molar mass of a carbon-12 atom (12 C).

The relative atomic mass of atomic oxygen is 15.999 amu.

DEFINITION

Relative molecular weight M r is the molar mass of a molecule divided by 1/12 the molar mass of a carbon-12 atom (12 C).

This is a dimensionless quantity. It is known that the oxygen molecule is diatomic - O 2. The relative molecular mass of an oxygen molecule will be equal to:

M r (O 2) = 15.999 × 2 ≈32.

Allotropy and allotropic modifications of oxygen

Oxygen can exist in the form of two allotropic modifications - oxygen O 2 and ozone O 3 (the physical properties of oxygen are described above).

Under normal conditions, ozone is a gas. It can be separated from oxygen by strong cooling; ozone condenses into a blue liquid, boiling at (-111.9 o C).

The solubility of ozone in water is much greater than that of oxygen: 100 volumes of water at 0 o C dissolve 49 volumes of ozone.

The formation of ozone from oxygen can be expressed by the equation:

3O 2 = 2O 3 - 285 kJ.

Isotopes of oxygen

It is known that in nature oxygen can be found in the form of three isotopes 16 O (99.76%), 17 O (0.04%) and 18 O (0.2%). Their mass numbers are 16, 17 and 18, respectively. The nucleus of an atom of the oxygen isotope 16 O contains eight protons and eight neutrons, and the isotopes 17 O and 18 O contain the same number of protons, nine and ten neutrons, respectively.

There are twelve radioactive isotopes of oxygen with mass numbers from 12 to 24, of which the most stable isotope 15 O with a half-life of 120 s.

Oxygen ions

The outer energy level of the oxygen atom has six electrons, which are valence electrons:

1s 2 2s 2 2p 4 .

The structure of the oxygen atom is shown below:

As a result of chemical interaction, oxygen can lose its valence electrons, i.e. be their donor, and turn into positively charged ions or accept electrons from another atom, i.e. be their acceptor and turn into negatively charged ions:

O 0 +2e → O 2- ;

O 0 -1e → O 1+ .

Oxygen molecule and atom

The oxygen molecule consists of two atoms - O 2. Here are some properties characterizing the oxygen atom and molecule:

Examples of problem solving

EXAMPLE 1

The earth's crust is 50% oxygen. The element is also present in minerals in the form of salts and oxides. Oxygen in bound form is included in the composition (the percentage of the element is about 89%). Oxygen is also present in the cells of all living organisms and plants. Oxygen is in the air in a free state in the form of O₂ and its allotropic modification in the form of ozone O₃, and occupies a fifth of its composition,

Physical and chemical properties of oxygen

Oxygen O₂ is a colorless, tasteless and odorless gas. Slightly soluble in water, boils at a temperature of (-183) °C. Oxygen in liquid form is blue; in solid form, the element forms blue crystals. Oxygen melts at a temperature of (-218.7) °C.

When heated, oxygen reacts with various simple substances (metals and non-metals), resulting in the formation of oxides - compounds of elements with oxygen. The interaction of chemical elements with oxygen is called an oxidation reaction. Examples of reaction equations:

4Na + О₂= 2Na₂O

S + O₂ = SO₂.

Some complex substances also interact with oxygen, forming oxides:

CH₄ + 2O₂= CO₂ + 2H₂O

2СО + О₂ = 2СО₂

Oxygen as a chemical element is obtained in laboratories and industrial plants. in the laboratory there are several ways:

• decomposition (potassium chlorate);
• decomposition of hydrogen peroxide when heating the substance in the presence of manganese oxide as a catalyst;
• decomposition of potassium permanganate.

Chemical reaction of oxygen combustion

Pure oxygen does not have special properties that oxygen in the air does not have, that is, it has the same chemical and physical properties. The air contains 5 times less oxygen than the same volume of pure oxygen. In the air, oxygen is mixed with large quantities of nitrogen - a gas that does not burn itself and does not support combustion. Therefore, if air oxygen has already been consumed near the flame, then the next portion of oxygen will make its way through nitrogen and combustion products. Consequently, more energetic combustion of oxygen in the atmosphere is explained by a faster supply of oxygen to the combustion site. During the reaction, the process of combining oxygen with the burning substance is carried out more energetically and more heat is released. The more oxygen is supplied to the burning substance per unit time, the brighter the flame burns, the higher the temperature and the stronger the combustion process.

How does the combustion reaction of oxygen occur? This can be verified experimentally. You need to take the cylinder and turn it upside down, then place a tube with hydrogen under the cylinder. Hydrogen, which is lighter than air, will completely fill the cylinder. It is necessary to ignite hydrogen near the open part of the cylinder and insert a glass tube into it through the flame, through which oxygen gas flows. A fire will break out at the end of the tube, while the flame will burn quietly inside the hydrogen-filled cylinder. During the reaction, it is not oxygen that burns, but hydrogen in the presence of a small amount of oxygen coming out of the tube.

What results from the combustion of hydrogen and what oxide is formed? Hydrogen is oxidized to water. Droplets of condensed water vapor are gradually deposited on the walls of the cylinder. The oxidation of two hydrogen molecules takes one oxygen molecule, and two water molecules are formed. Reaction equation:

2Н₂ + O₂ → 2Н₂O

If the oxygen flows out of the tube slowly, it burns completely in the hydrogen atmosphere, and the experiment proceeds calmly.

As soon as the supply of oxygen increases so much that it does not have time to burn completely, part of it goes beyond the flame, where pockets of a mixture of hydrogen and oxygen are formed, and individual small flashes similar to explosions appear. A mixture of oxygen and hydrogen is an explosive gas.

When detonating gas is ignited, a strong explosion occurs: when oxygen combines with hydrogen, water is formed and a high temperature develops. Water vapor with surrounding gases expands greatly, creating high pressure, at which not only a fragile cylinder, but also a more durable vessel can rupture. Therefore, it is necessary to work with an explosive mixture with extreme caution.

Oxygen consumption during combustion

For the experiment, a glass crystallizer with a volume of 3 liters must be filled 2/3 with water and a tablespoon of caustic soda or caustic potassium must be added. Tint the water with phenolphthalein or another suitable dye. Pour sand into a small flask and vertically insert a wire with cotton wool attached to the end into it. The flask is placed in a crystallizer with water. The cotton wool remains 10 cm above the surface of the solution.

Lightly moisten the cotton wool with alcohol, oil, hexane or other flammable liquid and set it on fire. Carefully cover the burning cotton wool with a 3-liter bottle and lower it below the surface of the lye solution. During the combustion process, oxygen passes into water and. As a result of the reaction, the alkali solution in the bottle rises. The cotton wool will soon go out. The bottle should be carefully placed on the bottom of the crystallizer. In theory, the bottle should be 1/5 full, since the air contains 20.9% oxygen. During combustion, oxygen turns into water and carbon dioxide CO₂, which is absorbed by the alkali. Reaction equation:

2NaOH + CO₂ = Na₂CO₃ + H₂O

In practice, combustion will stop before all the oxygen is consumed; part of the oxygen turns into carbon monoxide, which is not absorbed by the alkali, and part of the air leaves the bottle as a result of thermal expansion.

Attention! Do not try to repeat these experiments yourself!

Lump in throat is oxygen. It was found that in a state of stress, the glottis widens. It is located in the middle of the larynx, limited by 2 muscle folds.

They put pressure on nearby tissues, creating the sensation of a lump in the throat. The widening of the gap is a consequence of increased oxygen consumption. It helps cope with stress. So, the notorious lump in the throat can be called oxygen.

The 8th element of the table is familiar in the form. But it can also be liquid oxygen. Element In this state it is magnetic. However, we’ll talk about the properties of oxygen and the advantages that can be extracted from them in the main part.

Properties of oxygen

Due to its magnetic properties, oxygen is moved using powerful ones. If we talk about an element in its usual state, it itself is capable of moving, in particular, electrons.

Actually, the respiratory system is built on the redox potential of a substance. Oxygen in it is the final acceptor, that is, the receiving agent.

Enzymes act as donors. Substances oxidized by oxygen are released into the external environment. This is carbon dioxide. It produces from 5 to 18 liters per hour.

Another 50 grams of water comes out. So drinking plenty of fluids is a reasonable recommendation from doctors. Plus, about 400 substances are by-products of respiration. Among them is acetone. Its secretion increases in a number of diseases, for example, diabetes.

The breathing process involves the usual modification of oxygen – O 2 . This is a diatomic molecule. It has 2 unpaired electrons. Both are in antibonding orbitals.

They have a greater energy charge than the binders. Therefore, the oxygen molecule easily breaks down into atoms. The dissociation energy reaches almost 500 kilojoules per mole.

In natural conditions oxygen – gas with almost inert molecules. They have a strong interatomic bond. Oxidation processes occur barely noticeably. Catalysts are needed to speed up reactions. In the body they are enzymes. They provoke the formation of radicals, which initiate the chain process.

Temperature can be a catalyst for chemical reactions with oxygen. The 8th element reacts even to slight heating. Heat reacts with hydrogen, methane and other flammable gases.

Interactions occur with explosions. It’s not for nothing that one of the first airships in human history exploded. It was filled with hydrogen. The aircraft was called the Hindenburg and crashed in 1937.

Heating allows oxygen to form bonds with all elements of the periodic table except the noble gases, that is, argon, neon and helium. By the way, helium has become a replacement for filling airships.

The gas does not react, but it is expensive. But, let's return to the hero of the article. Oxygen is a chemical element, interacting with metals already at room temperature.

It is also sufficient for contact with some complex compounds. The latter include nitrogen oxides. But with simple nitrogen chemical element oxygen reacts only at 1,200 degrees Celsius.

For reactions of the hero of the article with non-metals, heating is required to at least 60 degrees Celsius. This is enough, for example, for contact with phosphorus. The hero of the article interacts with sulfur already at 250 degrees. By the way, sulfur is included in oxygen subgroup elements. She is the main one in the 6th group of the periodic table.

Oxygen interacts with carbon at 700-800 degrees Celsius. This refers to the oxidation of graphite. This mineral is one of the crystalline forms of carbon.

By the way, oxidation is the role of oxygen in any reaction. Most of them occur with the release of light and heat. Simply put, the interaction of substances leads to combustion.

The biological activity of oxygen is due to its solubility in water. At room temperature, 3 milliliters of the 8th substance dissociate in it. The calculation is based on 100 milliliters of water.

The element shows high levels in ethanol and acetone. 22 grams of oxygen dissolve in them. The maximum dissociation is observed in liquids containing fluorine, for example, perfluorobutitetrahydrofuran. Almost 50 grams of the 8th element are dissolved per 100 milliliters of it.

Speaking about dissolved oxygen, let's mention its isotopes. Atmospheric is number 160. There is 99.7% of it in the air. 0.3% are isotopes 170 and 180. Their molecules are heavier.

By contacting them, water hardly turns into a vapor state. So only the 160th modification of the 8th element rises into the air. Heavy isotopes remain in the seas and oceans.

Interestingly, in addition to gaseous and liquid states, oxygen can be solid. It, like the liquid version, is formed at sub-zero temperatures. Watery oxygen requires -182 degrees, and rock oxygen requires a minimum of -223.

The latter temperature produces a cubic crystal lattice. From -229 to -249 degrees Celsius, the crystal structure of oxygen is already hexagonal. Other modifications have also been obtained artificially. But, in addition to lower temperatures, they require increased pressure.

In a normal state oxygen belongs to the elements with 2 atoms, colorless and odorless. However, there is a 3-atomic variety of the hero of the article. This is ozone.

It has a distinctly fresh aroma. It's pleasant, but toxic. The difference from ordinary oxygen is also the large mass of molecules. Atoms come together during lightning discharges.

Therefore, the smell of ozone is felt after rainstorms. The aroma is also felt at high altitudes of 10-30 kilometers. There, the formation of ozone is provoked by ultraviolet radiation. Oxygen atoms capture radiation from the sun, combining into large molecules. This, in fact, protects humanity from radiation.

Oxygen production

Industrialists extract the hero of the article out of thin air. It is cleaned of water vapor, carbon monoxide and dust. Then, the air is liquefied. After cleaning, only nitrogen and oxygen remain. The first evaporates at -192 degrees.

Oxygen remains. But, Russian scientists discovered a storehouse of an already liquefied element. It is located in the Earth's mantle. It is also called the geosphere. The layer is located under the solid crust of the planet and above its core.

Install there oxygen element sign The laser press helped. We worked with him at the DESY synchrotron center. It is located in Germany. The research was carried out jointly with German scientists. Together, they calculated that the oxygen content in the supposed layer of mania is 8-10 times higher than in the atmosphere.

Let us clarify the practice of calculating deep oxygen rivers. Physicists worked with iron oxide. By squeezing and heating it, scientists obtained new metal oxides, previously unknown.

When it came to thousand-degree temperatures and pressure 670,000 times higher than atmospheric pressure, the compound Fe 25 O 32 was obtained. The conditions of the middle layers of the geosphere are described.

The oxide transformation reaction occurs with a global release of oxygen. It should be assumed that this is also happening inside the planet. Iron is a typical element for the mantle.

Combination of element with oxygen also typical. An atypical version is that atmospheric gas leaked from underground over millions of years and accumulated at its surface.

To put it bluntly, scientists have questioned the dominant role of plants in the production of oxygen. Greens may only provide some of the gas. In this case, you need to be afraid not only of the destruction of flora, but also of the cooling of the planet’s core.

A decrease in mantle temperature can block the formation process oxygen. Mass fraction its presence in the atmosphere will also decline, and at the same time life on the planet.

The question of how to extract oxygen from mania is not worth it. It is impossible to drill into the earth to a depth of more than 7,000-8,000 kilometers. All we have to do is wait until the hero of the article reaches the surface himself and extracts him from the atmosphere.

Application of oxygen

The active use of oxygen in industry began with the invention of turboexpanders. They appeared in the middle of the last century. The devices liquefy the air and separate it. Actually, these are production installations oxygen.

What elements is it formed by? the “social circle” of the hero of the article? Firstly, these are metals. This is not about direct interaction, but about the melting of elements. Oxygen is added to burners to burn fuel as efficiently as possible.

As a result, metals soften faster, mixing into alloys. For example, the convection method of steel production cannot do without oxygen. Ordinary air is ineffective as ignition. Metal cutting cannot do without liquefied gas in cylinders.

Oxygen as a chemical element was discovered and farmers. In liquefied form, the substance ends up in cocktails for animals. They are actively gaining weight. The connection between oxygen and the mass of animals can be traced in the Carboniferous period of the Earth's development.

The era is marked by a hot climate, an abundance of plants, and therefore the 8th gas. As a result, centipedes 3 meters long crawled around the planet. Insect fossils have been found. The scheme also works in modern times. Give the animal a constant supplement to the usual portion of oxygen, and you will get an increase in biological mass.

Doctors stock oxygen in cylinders to relieve, that is, stop asthma attacks. Gas is also needed to eliminate hypoxia. This is what is called oxygen starvation. The 8th element also helps with ailments of the gastrointestinal tract.

In this case, oxygen cocktails become the medicine. In other cases, the substance is given to patients in rubberized cushions, or through special tubes and masks.

In the chemical industry, the hero of the article is an oxidizing agent. Reactions in which the 8th element may participate have already been discussed. Characteristics of oxygen positively considered, for example, in rocket science.

The hero of the article was chosen as the oxidizer of ship fuel. The most powerful oxidizing mixture is the combination of both modifications of the 8th element. That is, rocket fuel interacts with ordinary oxygen and ozone.

Oxygen price

The hero of the article is sold in cylinders. They provide element connection. With oxygen You can purchase cylinders of 5, 10, 20, 40, 50 liters. In general, the standard step between container volumes is 5-10 liters. The price range for the 40-liter version, for example, is from 3,000 to 8,500 rubles.

Next to high price tags, as a rule, there is an indication of the compliance with GOST. His number is “949-73”. In advertisements with the budget cost of cylinders, GOST is rarely stated, which is alarming.

Transportation of oxygen in cylinders

Philosophically speaking, oxygen is priceless. The element is the basis of life. Iron transports oxygen throughout the human body. A bunch of elements is called hemoglobin. Its deficiency is anemia.

The disease has serious consequences. The first of them is a decrease in immunity. Interestingly, in some animals, oxygen in the blood is not carried by iron. In horseshoe crabs, for example, copper delivers the 8th element to the organs.