Oxygen, properties of the atom, chemical and physical properties

Historical reference.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).

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).
2HgO →ot 2Hg + O2↑

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.

The structure of the atom.

Also on topic:

AIR

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 168O (8 protons and 8 neutrons). The content of another isotope, 188O (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, 178O (0.04%), contains 9 neutrons and has a mass number of 17. After the mass of the carbon isotope 126C was adopted by the International Commission as the standard atomic mass 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 168O as the standard unit of atomic mass, so on the physical scale the average atomic mass of oxygen was 16.0044 ( see also

ATOMIC MASS).

An oxygen atom has 8 electrons, 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 ( see also

ATOMIC STRUCTURE).

Chalcogens - oxygen-related elements

Atoms with similar properties form one group in the periodic table. Oxygen heads the chalcogen family, but differs from them in a number of properties.

The atomic mass of oxygen, the ancestor of the group, is 16 a. e.m. Chalcogens, when forming compounds with hydrogen and metals, exhibit their usual oxidation state: –2. For example, in the composition of water (H2O), the oxidation number of oxygen is –2.

The composition of typical hydrogen compounds of chalcogens corresponds to the general formula: H2R. When these substances dissolve, acids are formed. Only the hydrogen compound of oxygen—water—has special properties. Scientists have concluded that this unusual substance is both a very weak acid and a very weak base.

Sulfur, selenium and tellurium have typical positive oxidation states (+4, +6) when combined with oxygen and other highly electronegative (EO) nonmetals. The composition of chalcogen oxides is reflected by the general formulas: RO2, RO3. The corresponding acids have the composition: H2RO3, H2RO4.

The elements correspond to simple substances: oxygen, sulfur, selenium, tellurium and polonium. The first three representatives exhibit non-metallic properties. The formula of oxygen is O2. An allotropic modification of the same element is ozone (O3). Both modifications are gases. Sulfur and selenium are solid non-metals. Tellurium is a metalloid substance, a conductor of electric current, polonium is a metal.

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.)

Properties of oxygen - a chemical element

At the 2p sublevel of the atom there are two unpaired electrons, which explains the appearance of oxidation states –2 and +2. Two paired electrons cannot be separated for the oxidation state to increase to +4, as in sulfur and other chalcogens. The reason is the lack of a free sublevel. Therefore, in compounds, the chemical element oxygen does not exhibit a valence and oxidation state equal to the group number in the short version of the periodic table (6). Its usual oxidation number is –2.

Only in compounds with fluorine does oxygen exhibit an uncharacteristic positive oxidation state of +2. The EO value of two strong nonmetals is different: EO (O) = 3.5; EO (F) = 4. As a more electronegative chemical element, fluorine holds its electrons more tightly and attracts valence particles at the outer energy level of the oxygen atom. Therefore, in the reaction with fluorine, oxygen is a reducing agent and donates electrons.

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 O2. It is known that alkali (Li, Na, K) and alkaline earth (Ca, Sr, Ba) metals react with molecular oxygen to form peroxides:

Temperature of liquid oxygen in Celsius

Oxygen is the most abundant element on the planet. It is present in water, the earth's crust, air and in the organisms of living beings, actively participating in many metabolic processes. In nature it usually exists as a gas, and in industry it is often used as a liquid. How does liquid oxygen behave? What properties does it have and where is it used?

Chemical properties

Oxygen gas is an oxidizing agent. By itself, it is non-flammable, but it supports the combustion process well, and at significant concentrations and high temperatures it is explosive.

It can react with active substances (for example, alkali metals) even at room temperature and at ordinary concentrations in the air, forming oxide compounds with them. The result is clearly visible on many metals, on which it manifests itself in the form of corrosion.

Liquid oxygen also has strong oxidizing properties. Many substances impregnated with it are easily flammable and burn, releasing energy and heat. Cotton, paper, wood, coal and some other materials can explode.

Receipt

The most common and easiest source of oxygen is air. Moreover, it is inexhaustible and is present everywhere in our lives. To obtain the necessary substances from it, it is liquefied and then divided into liquid nitrogen and oxygen.

Another way to obtain liquid is by condensing it from gas. To do this, simply lower a copper coil into a container of liquid nitrogen, and then pass oxygen gas through the coil. The temperature of nitrogen is lower than that of oxygen, so as it passes through the copper tube, the gas will condense and turn into a liquid. In this case, a small layer of snow forms on the surface of the coil.

Application

The ability of liquid oxygen to oxidize other substances and enhance combustion is valued in many areas of production. At the end of the 19th - mid-20th centuries, it was used to make the explosive "Oxiliquit", which was used in the mining industry to blast rock, and also as a weapon in World War II.

Today it is more often used in medicine, pharmaceuticals, metallurgy, glass, chemical, paper and other types of industries. With its help, various useful compounds are obtained, for example titanium oxide, which is involved in the production of paints, paper and plastics.

When making glass, it is needed to maintain heat in furnaces, as well as to reduce the amount of nitrogen oxide that enters the atmosphere.

In space aviation, liquid oxygen is one of the components of rocket fuel, where it is used as an oxidizer, and hydrogen or kerosene acts as the fuel itself.

Medicine and pharmaceuticals cannot do without it either. Liquid oxygen is included in bioreactors and is also used as an additive to enzymes.

In medicine, it is necessary for anesthesia, preparing oxygen baths and cocktails, treating or alleviating intoxication, asthma and other ailments.

Here it is most often not used directly as a liquid, but is a source of gaseous oxygen.

Storage and precautions

Liquid oxygen does not ignite or explode on its own, it is not toxic to humans and is not harmful to the environment. However, the active reaction in chemical processes, as well as the cryogenic effect, make it not an entirely safe substance.

When working with it, you need to keep lubricants, combustible and flammable materials away, and always use gloves and protective clothing. Oxygen at very low temperatures easily damages the skin and can lead to frostbite, injury and death of living cells. If the fluid covers a significant part of the body, it can even end in death.

Technical and medical liquid oxygen is stored in Dewar vessels, which are made primarily of steel or aluminum. These are cylindrical containers with double walls, between the walls of which there is a vacuum cavity, as well as thermal insulation materials. They work on the principle of thermoses, keeping liquids inside well.

Receipt and application.

Due to the presence of free oxygen in the atmosphere, the most effective method of extracting it is by liquefying the air, from which impurities, CO2, 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.

Being in nature

Accumulation of O2 in the Earth's atmosphere. The green graph is the lower estimate of the oxygen level, the red graph is the upper estimate. 1
.
(3.85-2.45 billion years ago) - O2 was not produced 2
.
(2.45–1.85 Ga) O2 was produced but absorbed by the ocean and seafloor rocks 3
.
(1.85-0.85 billion years ago) O2 leaves the ocean, but is consumed during the oxidation of rocks on land and during the formation of the ozone layer 4
.
(0.85–0.54 billion years ago), all rocks on land were oxidized, and O2 began to accumulate in the atmosphere 5
. (0.54 billion years ago - present) modern period, O2 content in the atmosphere has stabilized

Oxygen is the most common element in the earth's crust; its share (in various compounds, mainly silicates) accounts for about 47% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 85.82% (by mass). More than 1,500 compounds in the earth's crust contain oxygen.

In the atmosphere, the content of free oxygen is 20.95% by volume and 23.10% by mass (about 1015 tons). However, before the appearance of the first photosynthetic microbes in the Archean 3.5 billion years ago, it was practically absent from the atmosphere. Free oxygen began to appear in large quantities in the Paleoproterozoic (3-2.3 billion years ago) as a result of a global change in the composition of the atmosphere (oxygen catastrophe). For the first billion years, almost all the oxygen was absorbed by iron dissolved in the oceans and formed deposits of jaspilite. 3-2.7 billion years ago it began to be released into the atmosphere and 1.7 billion years ago reached 10% of the current level.

The presence of large amounts of dissolved and free oxygen in the oceans and atmosphere led to the extinction of most anaerobic organisms. However, cellular respiration with oxygen allowed aerobic organisms to produce much more ATP than anaerobic organisms, making them dominant.

Since the beginning of the Cambrian 540 million years ago, oxygen content has fluctuated from 15% to 30% by volume. By the end of the Carboniferous period (about 300 million years ago), its level peaked at 35% by volume, which may have contributed to the large size of insects and amphibians at this time.

The bulk of the oxygen on Earth is produced by the phytoplankton of the World Ocean. About 60% of the oxygen used by living beings is spent on the processes of rotting and decomposition, 80% of the oxygen produced by forests is spent on rotting and decomposition of forest vegetation.

Human activity has very little effect on the amount of free oxygen in the atmosphere. At current rates of photosynthesis, it will take about 2,000 years to restore all the oxygen in the atmosphere.

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%.

In 2016, Danish scientists proved that free oxygen was part of the atmosphere already 3.8 billion years ago.

Thermal dissociation.

An important laboratory method for producing oxygen, proposed by J. Priestley, is the thermal decomposition of heavy metal oxides: 2HgO ® 2Hg + O2. 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 MnO2 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:

2BaO2® 2BaO + O2

The latter method was at one time widely used to extract oxygen from the atmosphere and consisted of heating BaO in air to form BaO2, followed by thermal decomposition of the peroxide.
The thermal decomposition method remains important for the production of hydrogen peroxide. SOME PHYSICAL PROPERTIES OF OXYGEN

Boiling point of oxygen at different pressures

Liquid oxygen is a state of aggregation of oxygen in which it is a pale blue liquid.

It belongs to the category of substances that were among the first to be used in various fields of industry. Liquid O2 is used for two purposes: to enhance combustion processes and to oxidize chemical processes.

It is the need to solve these problems that has led to the popularity of air separation equipment.

Physical properties of liquid oxygen

In its liquid state, oxygen has a pale blue tint. When liquid oxygen is poured from one container to another, it releases water vapor, absorbing heat from the surrounding air. At the same time, the air temperature drops sharply, which leads to the formation of fog.

This type of oxygen can boil at a temperature of 183°C. If at this time you place it in an environment in which the air temperature is about 30-40°C, then the boiling will only intensify. At room temperature, the liquid evaporates quickly.

In order to reduce the rate of evaporation of liquid oxygen, it is placed in special cylinders. The O2 storage cylinder is a two-layer vessel.

The inner wall of the cylinder is covered with a layer of silver, and between it and the outer wall all the air is completely pumped out. The silver layer is necessary to reflect heat.

Oxygen can be stored in such a cylinder for several days.

Other physical properties of liquid oxygen include the following:

• boiling point – -183°С,
• critical pressure – 497 atmospheres,
• melting point – -219°С,
• solidification temperature – -220°C.

How is liquid oxygen produced?

The oxygen we breathe is a kind of “mix” of nitrogen, oxygen and argon. The mixture also contains carbon dioxide (0.03%), hydrogen, nitrous oxide and other rare gases.

In order to convert oxygen into a liquid state, it is necessary to cool the air.

At a pressure of 50 atmospheres and an air temperature from -191.8 to -193.7, deep cooling of the air is achieved and its transition to a liquid state.

After this, rectification is carried out, that is, the separation of nitrogen from oxygen. This is achieved by repeatedly heating the liquid, during which the nitrogen first evaporates, and the remaining liquid is enriched with O2.

In what areas is liquid oxygen used?

Currently, liquid oxygen is used in various fields of industry:

• chemical,
• glass,
• metallurgical,
• pharmaceutical,
• pulp and paper.

Liquid O2 serves as a raw material for the production of other chemical compounds, such as titanium dioxide or ethylene oxide. It can also be used to increase the productivity of most oxidative processes.

In the glass industry, oxygen is used to intensify combustion processes necessary to maintain the operation of glass melting furnaces. In addition, it helps reduce nitrogen oxide emissions and increase efficiency in glass production.

For the same purpose, liquid O2 is used in metallurgy, where it enriches the air and increases the efficiency of the combustion process.

Liquid oxygen is associated with acceleration of cell growth processes, so in pharmaceuticals it is added to fermenters and bioreactors.

In the pulp and paper industry, this type of oxygen is used for oxidative extraction, wastewater treatment and delignification (the process of producing cellulose).

In addition, liquid oxygen is used in the automotive and mechanical engineering industries, where it is used as an auxiliary gas during laser cutting. It is also added to protective gas mixtures.

Safety precautions when working with liquid oxygen

When working with liquid oxygen there is no threat of poisoning, but still some safety requirements must be strictly observed:

• wear special clothing to protect parts of the body from frostbite,
• avoid contact with open flames during and 20-30 minutes after working with O2,
• carry out welding and repair work only 2-3 hours after finishing manipulations with this type of gas,
• Before pumping O2, it is necessary to slightly cool the system by using a small amount of product.

Advantages of cooperation with NPK Grasys

Research and Production supplies equipment that will allow you to independently obtain gaseous oxygen from atmospheric air.

Our company has been developing and manufacturing gas and air separation equipment for more than 10 years, as well as engineering, design and implementation of complex turnkey work. We will help you solve any problems related to gas and air separation, associated petroleum gas utilization and natural gas treatment.

In the equipment production process, we use nanotechnology and high-quality components, which improve the technical and operational properties of the product. Contact representatives to receive detailed information about the installation you are interested in!

Source

Temperature - boiling - liquid oxygen

The boiling point of liquid oxygen is 182 9 C, argon - 186 1 C. Due to the proximity of these temperatures, it is quite difficult to separate them, however, using multiple rectification, a gas is obtained containing 45 - 50% argon, 45 - 50% oxygen and about 5% nitrogen.

To free argon from oxygen, zeolite is also used - a synthetic silicate of aluminum and sodium, which is a molecular sieve. Oxygen molecules pass through the zeolite pores ( d - 2 8 A), and argon molecules are retained. Argon is also obtained from waste from nitrogen fertilizer plants.

Ag is used for illuminated advertising as a protective medium. [1]

Hydrogen peroxide.

Another compound consisting only of hydrogen and oxygen is hydrogen peroxide H2O2. The name “peroxide” is adopted for compounds containing an –O–O– bond. Hydrogen peroxide has the structure of an asymmetrically bent chain:

Hydrogen peroxide is produced by the reaction of metal peroxide with acid

BaO2 + H2SO4® BaSO4 + H2O2

or by the decomposition of peroxodisulfuric acid H2S2O8, which is obtained electrolytically:

A concentrated solution of H2O2 can be obtained by special distillation methods. Hydrogen peroxide is used as an oxidizer in rocket engines. Dilute peroxide solutions serve as antiseptics, bleaches and mild oxidizing agents. H2O2 is added to many acids and oxides to produce compounds similar to hydrates. In the presence of a strong oxidizing agent (such as MnO2 or MnO4–), H2O2 oxidizes, releasing oxygen and water.

origin of name

The word oxygen

(also called “acid solution” at the beginning of the 19th century) its appearance in the Russian language is to some extent due 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 oxygene), proposed by A. Lavoisier (from the ancient Greek ὀξύς - “sour” and γεννάω - “I give 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.

Oxoanions and oxocations

– oxygen-containing particles having a residual negative (oxoanions) or residual positive (oxocations) charge. The O2– 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– rather than O2– is formed:

2Na + 2H2O ® 2Na+ + 2OH– + H2

or

Na2O + H2O ® 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:

Obtaining oxygen in the laboratory

When oxygen-containing substances, such as potassium permanganate, are heated, a colorless gas is released, which can be collected in a flask or test tube. If you introduce a lit splinter into pure oxygen, it burns more brightly than in air. Two other laboratory methods for producing oxygen are the decomposition of hydrogen peroxide and potassium chlorate (Berthollet salt). Let's consider the diagram of a device that is used for thermal decomposition.

Pour a little Berthollet salt into a test tube or round-bottomed flask and close it with a stopper with a gas outlet tube. Its opposite end should be directed (under water) into the flask turned upside down. The neck should be lowered into a wide glass or crystallizer filled with water. When a test tube containing Berthollet salt is heated, oxygen is released. It enters the flask through the gas outlet tube, displacing water from it. When the flask is filled with gas, it is closed under water with a stopper and turned over. The oxygen obtained in this laboratory experiment can be used to study the chemical properties of a simple substance.

Ozone.

In addition to atomic oxygen O and the diatomic molecule O2, there is a third form of oxygen - ozone O3, containing three oxygen atoms. All three forms are allotropic modifications. Ozone is formed by passing a quiet electrical discharge through dry oxygen: 3O2 2O3.

In this case, several percent of ozone is formed. The reaction is catalyzed by metal ions. Ozone has a sharp, pungent odor that can be detected near operating electrical machines or in the vicinity of atmospheric electrical discharge. The gas is bluish in color and condenses at –112°C into a dark blue liquid, and at –193°C a dark purple solid phase is formed. Liquid ozone is slightly soluble in liquid oxygen, and 49 cm3 of O3 dissolves in 100 g of water at 0° C. In terms of chemical properties, ozone is much more active than oxygen and is second only to O, F2 and OF2 (oxygen difluoride) in oxidizing properties. Conventional oxidation produces oxide and molecular oxygen O2. When ozone acts on active metals under special conditions, ozonides of the composition K+O3– are formed. Ozone is produced industrially for special purposes; it is a good disinfectant and is used to purify water and as a bleach, improves the condition of the atmosphere in closed systems, disinfects objects and food, and accelerates the ripening of grains and fruits. In a chemistry laboratory, an ozonizer is often used to produce ozone, which is necessary for some methods of chemical analysis and synthesis. Rubber is easily destroyed even when exposed to low concentrations of ozone. In some industrial cities, significant concentrations of ozone in the air lead to rapid deterioration of rubber products if they are not protected by antioxidants. Ozone is very toxic. Constant inhalation of air, even with very low concentrations of ozone, causes headaches, nausea and other unpleasant conditions.

Physical properties

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

Liquid oxygen
Under normal conditions, oxygen is a colorless, tasteless, and odorless gas.

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 O2 in 1 volume of Ag at +961 °C). It is highly soluble in perfluorinated hydrocarbons (20-40 v/v%).

The interatomic distance is 0.12074 nm. Is paramagnetic. In liquid form it is attracted by a magnet.

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-O2 - 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-O2 - 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-O2 - 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-O2—temperature range 20–240 K and pressure 6–8 GPa, orange crystals;
• ε-phase, contains O4 or O8 molecules, exists at pressures from 10 to 96 GPa, crystal color from dark red to black, monoclinic system;
• ζ-On - pressure over 96 GPa, metallic state with a characteristic metallic luster, at low temperatures it transforms into a superconducting state.

Element in the environment

The Earth's crust is composed primarily of silicon-oxygen minerals, and many other elements are present as their oxides. Oxygen gas makes up one fifth of the atmosphere. O2 in the Earth's atmosphere is produced by photosynthesis by plants , and accumulated over long periods of time as they used the abundant supplies of carbon dioxide in the early atmosphere and released oxygen.

The element is highly soluble in water, which makes life possible in rivers, lakes and oceans. The water in these bodies of water must be regularly supplied with oxygen because when its supply of O2 is depleted, it can no longer support fish and other aquatic organisms.

Almost all chemicals, except noble gases, combine with oxygen to form compounds. Water, H2O, and silica, SiO2, the main component of sand, are among the most common double oxygen compounds. Among compounds that contain more than two elements, the most common are silicates, which form most rocks and soils. Other compounds that occur in abundance in nature are calcium carbonate (limestone and marble), calcium sulfate (gypsum), aluminum oxide (bauxite) and various iron oxides, which are used as a metal source.

The element is found in all types of minerals. Some common examples include oxides, carbonates, nitrates, sulfates and phosphates. Oxides are chemical compounds that contain oxygen and another element. Carbonates are compounds that contain oxygen, carbon and one other element. An example is sodium carbonate or soda, soda ash or salt soda (Na2CO3), which is often found in detergents and cleaning products.

Nitrates, sulfates and phosphates also contain oxygen. Other elements in these compounds are nitrogen, sulfur or phosphorus plus one other element. Examples of these compounds are potassium nitrate or saltpeter (KNO3), magnesium sulfate or Epsom salts (MgSO4) and calcium phosphate (Ca3(PO4)2).

Production of oxygen on an industrial scale

The cheapest process, which produces air-free O2 molecules, does not involve chemical reactions. In industry, say, at metallurgical plants, air is liquefied at low temperature and high pressure. The most important components of the atmosphere, such as nitrogen and oxygen, boil at different temperatures. The air mixture is separated by gradually heating to normal temperature. Nitrogen molecules are released first, then oxygen molecules. The separation method is based on the different physical properties of simple substances. The formula of the simple substance oxygen is the same as it was before cooling and liquefaction of air - O2.

As a result of some electrolysis reactions, oxygen is also released, which is collected over the appropriate electrode. Industrial and construction enterprises need gas in large volumes. The demand for oxygen is constantly growing, and the chemical industry especially needs it. The resulting gas is stored for industrial and medical purposes in marked steel cylinders. Oxygen containers are painted blue or blue to distinguish them from other liquefied gases - nitrogen, methane, ammonia.

Video

And finally, an educational video about oxygen.

Author: Pavel Chaika, editor-in-chief of Poznavaika magazine

When writing the article, I tried to make it as interesting, useful and high-quality as possible. I would be grateful for any feedback and constructive criticism in the form of comments on the article. You can also write your wish/question/suggestion to my email [email protected] or Facebook, with respect, the author.

Author page

This article is available in English - Oxygen.

Chemical calculations using the formula and equations of reactions involving O2 molecules

The numerical value of the molar mass of oxygen coincides with another value - the relative molecular mass. Only in the first case are units of measurement present. Briefly, the formula of the oxygen substance and its molar mass should be written as follows: M(O2) = 32 g/mol. Under normal conditions, a mole of any gas corresponds to a volume of 22.4 liters. This means that 1 mole of O2 is 22.4 liters of substance, 2 mol of O2 is 44.8 liters. According to the reaction equation between oxygen and hydrogen, you can see that 2 moles of hydrogen and 1 mole of oxygen interact:

If 1 mole of hydrogen is involved in the reaction, then the volume of oxygen will be 0.5 mol • 22.4 l/mol = 11.2 l.

Health effects

Oxygen is essential to all life forms as it is a constituent of DNA and almost all other biologically important compounds. In the lungs, this element is absorbed by the iron atom in the center of hemoglobin in the blood and is thus transported to where it is needed.

Every person needs this element to breathe, but, as with many things, too much of it is harmful. If a person is exposed to large amounts of O2 for a long time, lung damage can occur. Inhaling 50-100% oxygen at normal pressure over an extended period causes lung damage. People who work with frequent or potentially high exposure to pure elements should undergo pulmonary function tests before starting work and upon completion.