• Designation - O (Oxygen);
• Latin name - Oxigenium;
• Period - II;
• Group - 16 (VIa);
• Atomic mass - 15.9994;
• Atomic number - 8;
• Radius of an atom = 60 pm;
• Covalent radius = 73 pm;
• Electron distribution - 1s 2 2s 2 2p 4 ;
• t melting = -218.4°C;
• boiling point = -182.96°C;
• Electronegativity (according to Pauling / according to Alpred and Rochov) = 3.44 / 3.50;
• Oxidation state: +2; +1; 12 ; 0; - 13 ; - 12 ; -one; -2;
• Density (n.a.) \u003d 1.42897 g / cm 3;
• Molar volume = 14.0 cm 3 / mol.

Oxygen ("generating acids") was discovered in 1774 by J. Priestley. This is the most common chemical element on Earth - the mass fraction of oxygen in earth's crust is 47.2%. In the atmospheric air, the proportion of oxygen is 21%, which is associated with the activity of green plants.

Oxygen is a constituent of many, both inorganic and organic compounds. Oxygen is necessary for the life of all highly organized living organisms: humans, animals, birds, fish. Oxygen makes up from 50 to 85% of the mass of animal and plant tissues.

Three stable isotopes of oxygen are known: 16 O, 17 O, 18 O.

In the free state, oxygen exists in two allotropic modifications: O 2 - oxygen; O 3 - ozone.

Periodic table of chemical elements of D. I. Mendeleev, stands at number "8", refers to the 16 (VIa) group (See Atoms of the 16 (VIa) group).

Rice. The structure of the oxygen atom.

The oxygen atom contains 8 electrons: 2 electrons are in the inner s-orbital and 6 more in the outer energy level - 2 (paired) in the s-sublevel and 4 (two paired and two unpaired) in the p-sublevel (see Electronic structure of atoms) .

Due to the two unpaired p-electrons of the outer level, oxygen forms two covalent bonds, accepting two electrons and showing the oxidation state -2 (H 2 O, CaO, H 2 SO 4).

In compounds with oxygen bonds O-O atom oxygen exhibits an oxidation state of -1 (H 2 O 2).

With the more electronegative fluorine, oxygen donates its valence electrons, exhibiting an oxidation state of +2 (OF 2).

O2

A diatomic oxygen molecule is formed by a double bond of two oxygen atoms. For this reason, molecular oxygen under normal conditions is a stable compound.

The dissociation energy of an oxygen molecule is about 2 times lower than in a nitrogen molecule (see Covalent bond multiplicity), therefore, oxygen has a higher reactivity than nitrogen (but much less than, for example, fluorine).

The reactivity of oxygen increases as it is heated. Oxygen reacts with all elements except inert gases. Due to its high electronegativity (see What is Electronegativity) in chemical compounds(with the exception of fluorine), oxygen acts as an oxidizing agent with a degree of -2 (only fluorine oxidizes oxygen to form oxygen difluoride OF 2).

Properties of oxygen gas:

• colorless, odorless and tasteless gas;
• in liquid or solid form, oxygen has a blue color;
• sparingly soluble in water: the mass fraction of oxygen at 20°C is 0.004%.

Chemical properties of oxygen

In all reactions, oxygen plays the role of an oxidizing agent, combining with all elements (with the exception of helium, argon and neon) by direct interaction (except for fluorine, chlorine, gold and platinum metals).

With metals and non-metals (simple substances), oxygen forms oxides:

2Cu + O 2 = 2CuO 4Li + O 2 = 2Li 2 O 2Ca + O 2 = 2CaO S + O 2 = SO 2 C + O 2 = CO 2

When the alkali metals sodium and potassium are oxidized, peroxides are formed:

2Na + O 2 \u003d Na 2 O 2

Almost all reactions involving oxygen are exothermic, but there are exceptions:

N 2 + O 2 ↔ 2NO-Q

Many substances react with oxygen to release heat and light, a process called burning.

Combustion reactions:

• combustion of ammonia in air with the formation of water and nitrogen: 4NH 3 + 3O 2 \u003d 2N 2 + 6H 2 O
• catalytic oxidation of ammonia: 4NH 3 + 5O 2 \u003d 2NO + 6H 2 O
• combustion of hydrogen sulfide in excess oxygen: 2H 2 S + 3O 2 \u003d 2SO 2 + 2H 2 O
• with a lack of oxygen, hydrogen sulfide is slowly oxidized to free sulfur: 2H 2 S + O 2 \u003d 2S + 2H 2 O
• combustion organic matter in oxygen to form water and carbon dioxide: CH 4 + 2O 2 → CO 2 + 2H 2 O C 2 H 5 OH + 3O 2 → 2CO 2 + 3H 2 O
• during the combustion of nitrogen-containing organic substances, in addition to carbon dioxide and water, free nitrogen is released: 4CH 3 NH 5 + 9O 2 → 4CO 2 + 2N 2 + 10H 2 O

Many substances (alcohols, aldehydes, acids) are obtained by the reaction of controlled oxidation of organic substances. Also, many natural processes, such as respiration or decay, are inherently oxidative reactions organic substances.

An even stronger oxidizing agent than oxygen is ozone, which can oxidize potassium iodide to a free ion - this reaction is used for the qualitative and quantitative determination of ozone: O 3 + 2KI + H 2 O \u003d I 2 ↓ + 2KOH + O 2

Obtaining and using oxygen

Oxygen is widely used in industry and medicine:

• in metallurgy, oxygen is used in the smelting of steel (cast iron);
• in the chemical industry, oxygen is needed for the production of acids (sulfuric and nitric), methanol, acetylene, aldehydes;
• in the space industry, oxygen is used as an oxidizer for rocket fuel;
• in medicine, oxygen is used in breathing apparatus;
• in nature, oxygen plays an extremely important role - in the process of oxidation of carbohydrates, fats and proteins, the energy necessary for living organisms is released.

How to get oxygen:

• industrial ways:
  • liquefaction of air with subsequent separation of the liquid mixture of gases into components;
  • water electrolysis:
    2H 2 O \u003d 2H 2 + O 2.
• laboratory methods (decomposition of salts when heated):
  • potassium permanganate:
    2KMnO 4 \u003d K 2 MnO 4 + MnO 2 + O 2;
  • Berthollet salt:
    2KClO 3 \u003d 2KCl + 3O 2.
• thermal decomposition of alkali metal nitrates:
  2NaNO 3 \u003d 2NaNO 2 + O 2
• catalytic decomposition of hydrogen peroxide (MnO 2 catalyst):
  2H 2 O 2 \u003d 2H 2 O + O 2;
• interaction of carbon dioxide peroxides with alkali metal peroxides:
  2CO 2 + 2Na 2 O 2 \u003d 2Na 2 CO 3 + O 2.

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

History 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. Oxygen addition reactions are described in scientific papers S. Gales (1731) and P. Bayen (1774). The studies of K. Scheele in 1771–1773 of the interaction of metals and phosphorus with oxygen deserve special attention. J. Priestley reported the discovery of oxygen as an element in 1774, a few months after Bayen reported on reactions with air. The name oxygenium ("oxygen") was given to this element shortly after its discovery by Priestley and comes from Greek words, denoting "giving birth to acid"; 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 natural 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 oxygen isotopes (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 the identification of certain molecules, as well as for biochemical and medical-chemical studies (a method for studying non-radioactive traces). The third non-radioactive oxygen isotope 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 accepted by the International Commission for the standard atomic mass in 1961, the weighted average atomic mass oxygen became equal to 15.9994. Until 1961, chemists considered the standard unit of atomic mass to be the atomic mass of oxygen, which was assumed to be 16,000 for a mixture of three natural oxygen isotopes. Physicists took the mass number of the oxygen isotope 16 8 O as a standard unit of atomic mass, therefore, according to 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 inner level and 6 electrons in the outer. Therefore, in chemical reactions, oxygen can accept from donors up to two electrons, completing its outer shell up 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 expended for the reverse process of molecule dissociation 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 in the formation of the nitrogen molecule N 2 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 by 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 magnetic field, being a paramagnet).

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 rather quickly. It is likely that most reactions proceed 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, most effective method 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 the liquefaction of air. With a slow rise in temperature (fractional distillation), liquid air evaporates first noble gases (the most difficult to liquefy), then nitrogen, and liquid oxygen remains. As a result, liquid oxygen contains traces of noble gases and a relatively high percentage of nitrogen. For many applications, these impurities do not interfere. However, to obtain oxygen of high 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 iron through the Bessemer process to remove C, S and P impurities quickly and efficiently. Oxygen blast produces steel faster and better 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 obtained by various chemical methods, and some of them are used to obtain small amounts of pure oxygen in laboratory practice.

Electrolysis.

One of the methods for obtaining 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 impurities of hydrogen are formed. With the help of a discharge device, traces of hydrogen in gas mixture again converted into water, the vapors of which are removed by freezing or adsorption.

Thermal dissociation.

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

Manganese dioxide, added in small amounts before calcination, makes it possible to maintain the required temperature and dissociation rate, and MnO 2 itself does not change during the process.

Methods of 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 in heating BaO in air until BaO 2 was formed, followed by thermal decomposition of the peroxide. The thermal decomposition method retains its importance for the production of hydrogen peroxide.

SOME PHYSICAL PROPERTIES OF OXYGEN
atomic number	8
Atomic mass	15,9994
Melting point, °С	–218,4
Boiling point, °C	–183,0
Density
solid, g / cm 3 (at t pl)	1,27
liquid g / cm 3 (at t kip)	1,14
gaseous, g / dm 3 (at 0 ° C)	1,429
relative to air	1,105
critical a, g / cm 3	0,430
Critical temperature a, °C	–118,8
Critical pressure a, atm	49,7
Solubility, cm 3 /100 ml of solvent
in water (0°C)	4,89
in water (100°C)	1,7
in alcohol (25°C)	2,78
Radius, Å	0,74
covalent	0,66
ionic (O 2–)	1,40
Ionization potential, V
the first	13,614
second	35,146
Electronegativity (F=4)	3,5
a The temperature and pressure at which the density of a gas and a liquid is the same.

physical properties.

Oxygen under normal conditions is a colorless, odorless and tasteless gas. Liquid oxygen has a pale blue color. Solid oxygen exists in at least three crystalline modifications. Gaseous oxygen is soluble in water and probably forms unstable compounds such as O 2 H H 2 O, and possibly O 2 H 2H 2 O.

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 a high rate 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 O 2 . Under suitable conditions, all elements, except for 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 oxides of alkali metals, it is formed predominantly ionic bond. 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 transition of electrons is incomplete, and the negative charge density on oxygen is less pronounced, so the bond is less ionic or more covalent.

During the oxidation of metals with oxygen, heat is released, the magnitude of which correlates with the strength of the M–O bond. During the oxidation of some non-metals, heat is absorbed, which indicates their weaker bonds with oxygen. Such oxides are thermally unstable (or less stable than ionically bonded oxides) 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 non-metals, elements of the A- and B-subgroups (the minus sign means heat release).

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

1. The melting points of alkali metal oxides decrease with increasing atomic radius metal; So, t pl (Cs 2 O) t pl (Na 2 O). Oxides dominated by ionic bonding 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. Heavy metal oxides in the highest oxidation state during 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 oxidizers.

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

Sr + O 2 ® SrO 2 .

4. Oxides of active metals form colorless solutions, while oxides of most transition metals are colored and practically insoluble. Aqueous solutions of metal oxides exhibit basic properties and are hydroxides containing OH groups, while non-metal oxides in aqueous solutions form acids containing an 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 the elements are also possible. In the combustion processes of compounds, oxides are typical products, for example:

2H 2 S + 3O 2 ® 2SO 2 + 2H 2 O

Carbon-containing substances and hydrocarbons are oxidized (burned) to CO 2 and H 2 O when slightly heated. 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 for the production of 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 (stone 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 slight activation of the reaction, such as a blow or a shake, is sufficient. In these reactions, oxides are also combustion products, but they are all gaseous and expand rapidly at a 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 the lowest oxidation states of an element react with oxygen to form oxides high degrees oxidation of this 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 finds an unusual use, since 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 . The production of CaO oxide and calcium hydroxide Ca(OH) 2 is a large-scale production in the technology of ceramics and cement.

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, in the direct interaction of oxygen and hydrogen under conditions of, for example, a spark discharge, an explosion and the formation of water occur, with the release of 143 kJ/(mol H 2 O).

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 for oxygen and, accordingly, positive charges for hydrogen:

Due to the high strength of the H–O bonds, hydrogen is hardly 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 gives 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 a high affinity (high reactivity) to positively charged particles like 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 the 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 a non-metal particle that has a large positive charge, resulting in a low-charged particle that is more stable, for example:

°C a dark purple solid is formed. Liquid ozone is slightly soluble in liquid oxygen, and 49 cm 3 O 3 dissolves in 100 g of water at 0 ° C. In terms of chemical properties, ozone is much more active than oxygen, and in terms of oxidizing properties it is second only to O, F 2 and OF 2 (oxygen difluoride). Normal oxidation produces an oxide and molecular oxygen O 2 . Under the action of ozone on active metals under special conditions, ozonides of the composition K + O 3 - are formed. Ozone is obtained in industry 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, accelerates the ripening of grains and fruits. AT chemical laboratory often use an ozonizer to produce the ozone needed for some methods chemical analysis and synthesis. Rubber is easily destroyed even under the influence of low concentrations of ozone. In some industrial cities, a significant concentration of ozone in the air leads to rapid deterioration of rubber products if they are not protected with antioxidants. Ozone is highly toxic. Continuous breathing of air even with very low concentrations of ozone causes headache, nausea and other unpleasant conditions.

Oxygen O It has atomic number 8, located in the main subgroup (subgroup a) VI group in the second period. In oxygen atoms, valence electrons are located at the 2nd energy level, which has only s- and p-orbitals. This excludes the possibility of the transition of O atoms to an excited state, therefore oxygen in all compounds exhibits a constant valency equal to II. Having a high electronegativity, oxygen atoms are always negatively charged in compounds (s.o. = -2 or -1). The exception is OF 2 and O 2 F 2 fluorides.

For oxygen, the oxidation states -2, -1, +1, +2 are known

General characteristics of the element

Oxygen is the most abundant element on Earth, accounting for slightly less than half, 49%, of the total mass of the earth's crust. Natural oxygen consists of 3 stable isotopes 16 O, 17 O and 18 O (16 O predominates). Oxygen is part of the atmosphere (20.9% by volume, 23.2% by mass), water and more than 1400 minerals: silica, silicates and aluminosilicates, marbles, basalts, hematite and other minerals and rocks. Oxygen makes up 50-85% of the mass of plant and animal tissues, because it is contained in proteins, fats and carbohydrates that make up living organisms. The role of oxygen for respiration and for oxidation processes is well known.

Oxygen is relatively slightly soluble in water - 5 volumes in 100 volumes of water. However, if all the oxygen dissolved in water passed into the atmosphere, then it would occupy a huge volume - 10 million km 3 (n.c.). This is equal to approximately 1% of all oxygen in the atmosphere. Education on earth oxygen atmosphere due to the process of photosynthesis.

Discovered by the Swede K. Scheele (1771 - 1772) and the Englishman J. Priestley (1774). The first used saltpeter heating, the second - mercury oxide (+2). The name was given by A. Lavoisier ("oxygenium" - "giving birth to acids").

In free form, it exists in two allotropic modifications - "ordinary" oxygen O 2 and ozone O 3.

The structure of the ozone molecule

3O 2 \u003d 2O 3 - 285 kJ
Ozone in the stratosphere forms a thin layer that absorbs most of the biologically harmful ultraviolet radiation.
During storage, ozone spontaneously converts to oxygen. Chemically, oxygen O 2 is less active than ozone. The electronegativity of oxygen is 3.5.

Physical properties of oxygen

O 2 - colorless, odorless and tasteless gas, m.p. –218.7 °С, b.p. -182.96 °C, paramagnetic.

Liquid O 2 blue, solid - of blue color. O 2 is soluble in water (better than nitrogen and hydrogen).

Obtaining oxygen

1. industrial way- distillation of liquid air and electrolysis of water:

2H 2 O → 2H 2 + O 2

2. In the laboratory, oxygen is produced by:
1.Alkaline electrolysis aqueous solutions or aqueous solutions of oxygen-containing salts (Na 2 SO 4, etc.)

2. Thermal decomposition potassium permanganate KMnO 4:
2KMnO 4 \u003d K 2 MnO4 + MnO 2 + O 2,

Berthollet salt KClO 3:
2KClO 3 \u003d 2KCl + 3O 2 (MnO 2 catalyst)

Manganese oxide (+4) MnO 2:
4MnO 2 \u003d 2Mn 2 O 3 + O 2 (700 o C),

3MnO 2 \u003d 2Mn 3 O 4 + O 2 (1000 o C),

Barium peroxide BaO 2:
2BaO 2 \u003d 2BaO + O 2

3. Decomposition of hydrogen peroxide:
2H 2 O 2 \u003d H 2 O + O 2 (MnO 2 catalyst)

4. Decomposition of nitrates:
2KNO 3 → 2KNO 2 + O 2

On the spaceships and submarines, oxygen is obtained from a mixture of K 2 O 2 and K 2 O 4:
2K 2 O 4 + 2H 2 O \u003d 4KOH + 3O 2
4KOH + 2CO 2 \u003d 2K 2 CO 3 + 2H 2 O

Total:
2K 2 O 4 + 2CO 2 \u003d 2K 2 CO 3 + 3O 2

When K 2 O 2 is used, the overall reaction looks like this:
2K 2 O 2 + 2CO 2 \u003d 2K 2 CO 3 + O 2

If you mix K 2 O 2 and K 2 O 4 in equal molar (i.e. equimolar) amounts, then one mole of O 2 will be released per 1 mole of absorbed CO 2.

Chemical properties of oxygen

Oxygen supports combustion. Burning - b a rapid process of oxidation of a substance, accompanied by the release of a large amount of heat and light. To prove that the flask contains oxygen, and not some other gas, it is necessary to lower a smoldering splinter into the flask. In oxygen, a smoldering splinter flares brightly. Combustion various substances in air is a redox process in which oxygen is the oxidizing agent. Oxidizing agents are substances that “take away” electrons from reducing substances. Good ones oxidizing properties oxygen can be easily explained by the structure of its outer electron shell.

The valence shell of oxygen is located at the 2nd level - relatively close to the nucleus. Therefore, the nucleus strongly attracts electrons to itself. On the valence shell of oxygen 2s 2 2p 4 there are 6 electrons. Therefore, before the octet, two electrons are missing, which oxygen seeks to accept with electron shells other elements, entering into reactions with them as an oxidizing agent.

Oxygen has the second (after fluorine) electronegativity on the Pauling scale. Therefore, in the vast majority of its compounds with other elements, oxygen has negative degree of oxidation. A stronger oxidizing agent than oxygen is only its neighbor in the period - fluorine. Therefore, compounds of oxygen with fluorine are the only ones where oxygen has a positive oxidation state.

So, oxygen is the second most powerful oxidizing agent among all elements. Periodic system. Most of its most important chemical properties are related to this.
All elements react with oxygen, except for Au, Pt, He, Ne and Ar; in all reactions (except for interaction with fluorine), oxygen is an oxidizing agent.

Oxygen easily reacts with alkali and alkaline earth metals:

4Li + O 2 → 2Li 2 O,

2K + O 2 → K 2 O 2,

2Ca + O 2 → 2CaO,

2Na + O 2 → Na 2 O 2,

2K + 2O 2 → K 2 O 4

Fine iron powder (the so-called pyrophoric iron) ignites spontaneously in air, forming Fe 2 O 3, and steel wire burns in oxygen if it is heated in advance:

3 Fe + 2O 2 → Fe 3 O 4

2Mg + O 2 → 2MgO

2Cu + O 2 → 2CuO

With non-metals (sulfur, graphite, hydrogen, phosphorus, etc.), oxygen reacts when heated:

S + O 2 → SO 2,

C + O 2 → CO 2,

2H 2 + O 2 → H 2 O,

4P + 5O 2 → 2P 2 O 5,

Si + O 2 → SiO 2, etc.

Almost all reactions involving oxygen O 2 are exothermic, with rare exceptions, for example:

N 2 + O 2 → 2NO-Q

This reaction takes place at a temperature above 1200 o C or in an electrical discharge.

Oxygen is able to oxidize complex substances, for example:

2H 2 S + 3O 2 → 2SO 2 + 2H 2 O (excess oxygen),

2H 2 S + O 2 → 2S + 2H 2 O (lack of oxygen),

4NH 3 + 3O 2 → 2N 2 + 6H 2 O (without catalyst),

4NH 3 + 5O 2 → 4NO + 6H 2 O (in the presence of a Pt catalyst),

CH 4 (methane) + 2O 2 → CO 2 + 2H 2 O,

4FeS 2 (pyrite) + 11O 2 → 2Fe 2 O 3 + 8SO 2.

Compounds containing the dioxygenyl cation O 2 + are known, for example, O 2 + - (the successful synthesis of this compound prompted N. Bartlett to try to obtain compounds of inert gases).

Ozone

Ozone is chemically more active than oxygen O 2 . So, ozone oxidizes iodide - ions I - in a solution of Kl:

O 3 + 2Kl + H 2 O \u003d I 2 + O 2 + 2KOH

Ozone is highly toxic, its toxic properties are stronger than, for example, hydrogen sulfide. However, in nature, ozone, contained in the high layers of the atmosphere, acts as a protector of all life on Earth from the harmful ultraviolet radiation of the sun. Thin ozone layer absorbs this radiation, and it does not reach the surface of the Earth. There are significant fluctuations in the thickness and extent of this layer over time (the so-called ozone holes), the reasons for such fluctuations have not yet been elucidated.

Application of oxygen O 2: to intensify the processes of producing iron and steel, in the smelting of non-ferrous metals, as an oxidizing agent in various chemical industries, for life support on submarines, as an oxidizer for rocket fuel (liquid oxygen), in medicine, in welding and cutting metals.

The use of ozone O 3: for disinfection drinking water, Wastewater, air, for bleaching fabrics.

Oxygen has a high chemical activity. Many substances react with oxygen at room temperature. So, for example, a fresh cut of an apple quickly acquires a brown color, this is due to chemical reactions between the organic substances contained in the apple and the oxygen contained in the air. With simple substances, oxygen, as a rule, reacts when heated. We place a piece of coal in a metal spoon for burning substances, heat it red-hot in the flame of an alcohol lamp and lower it into a vessel with oxygen. We observe the bright combustion of coal in oxygen. Coal is a simple substance made up of the element carbon. The reaction of oxygen with carbon produces carbon dioxide:

It is worth noting that many chemicals have trivial names. Carbon dioxide is a trivial name for a substance. Trivial names of substances are used in everyday life, many of them have a long history. For example, baking soda, Bertolet salt. However, each chemical also has a systematic chemical name, the compilation of which is regulated by international rules - the systematic chemical nomenclature.

Thus, carbon dioxide has a systematic name carbon monoxide (IV).

Carbon dioxide is a complex substance, a binary compound, which includes oxygen. We put sulfur in a spoon for burning substances and heat it. Sulfur melts, then ignites. In air, sulfur burns with a pale, almost imperceptible, blue flame. We introduce sulfur into a vessel with oxygen - sulfur burns with a bright blue flame. In the reaction of sulfur with oxygen, sulfur dioxide is formed:

Sulfur dioxide, like carbon dioxide, belongs to the group of oxides. It's sulfur oxide(IV) is a colorless gas with a pungent pungent odor. Now let's add ignited red phosphorus to a vessel with oxygen. Phosphorus burns with a bright, dazzling flame. The vessel is filled with white smoke. White smoke is a reaction product, fine particulate matter phosphorus (V) oxide:

4P + 5O2 = 2P2O5

Not only non-metals can burn in oxygen. Metals also interact vigorously with oxygen. For example, magnesium burns in oxygen and in air with a dazzling white flame. The reaction product is magnesium oxide:

2Mg + O2 = 2MgO

Let's try to burn iron in oxygen. We heat a steel wire in the flame of an alcohol lamp and quickly lower it into a vessel with oxygen. Iron burns in oxygen, producing many sparks. The substance resulting from the reaction is called iron oxide:

3Fe + 2O2 = Fe3O4.

Sheaves of sparks formed during the burning of a Bengal fire are explained by the combustion of iron powder, which is part of these pyrotechnic products. After the reactions considered, important conclusions can be drawn: oxygen reacts with both metals and non-metals; often these reactions are accompanied by combustion of substances. The reaction products of oxygen with simple substances are oxides. Please note that when oxygen interacts with simple substances - metals and non-metals, complex substances - oxides are formed. This type of chemical reaction is called connection reactions.

Connection reaction - a reaction in which two or more less complex substances are formed, as a result of which more complex substances are formed

The interaction of oxygen with complex substances

Oxygen can react with complex substances. As an example, consider the reaction that occurs during the combustion of household gas, which consists of methane CH4. According to the combustion of methane in the burner of the furnace, it can be concluded that the reaction proceeds with the release of energy in the form of heat and light. What are the products of this reaction?

CH4 + 2O2 = CO2 + 2H2O.

The reaction products are oxides: carbon dioxide (carbon (IV) oxide) and water (hydrogen oxide). In the reaction of oxygen with the mineral pyrite FeS2 (an important mineral of iron and sulfur), oxides of sulfur and iron are obtained. The reaction occurs when heated:

4FeS2 + 11O2 = 8SO2 + 2Fe2O3

Oxidation - combustion and slow oxidation

Combustion- this is the first chemical reaction that the person has met. Fire... Is it possible to imagine our existence without fire? He entered our life, became inseparable from it. Without fire, a person cannot cook food, steel; without it, transport is impossible. Fire has become our friend and ally, a symbol of glorious deeds, good deeds, a memory of the past.

From a chemical point of view, combustion- This is a chemical reaction, accompanied by the release of a stream of hot gases and energy in the form of heat and light. We can say that oxygen, reacting with simple substances, oxidizes them:

Simple substance + Oxygen oxidation → Oxidation products (oxides) + Energy.

Oxidation of substances may not be accompanied by combustion, that is, the release of a flame. Such processes are called slow oxidation. Slow oxidation is a process of gradual interaction of substances with oxygen, with a slow release of heat, not accompanied by combustion. So, for example, carbon dioxide is formed not only during the combustion of carbon in oxygen, but also during the slow oxidation of organic substances by atmospheric oxygen. (rotting, decay).

Summary of the article:

• In the reaction of simple substances with oxygen, oxides are formed
• Reactions of simple substances with oxygen proceed, as a rule, when heated
• Reactions of simple substances with oxygen are compound reactions
• Trivial names chemical substances do not reflect the chemical composition of substances, are used in everyday practice, many of them have developed historically
• The systematic names of chemicals reflect chemical composition substances comply with the international systematic nomenclature
• A compound reaction is a reaction in which, from two or more less complex substances, more complex substances are formed.
• Oxygen is able to react with complex substances
• Combustion is a chemical reaction accompanied by the release of energy in the form of heat and light.
• Slow oxidation - the process of gradual interaction of substances with oxygen, with a slow release of heat, not accompanied by combustion

8 O 1s 2 2s 2 2p 4 ; A r = 15.999 Isotopes: 16 O (99.759%); 17 O (0.037%); 18 O (0.204%); EO - 3.5

Clark in the earth's crust 47% by mass; in the hydrosphere 85.82% by weight; in the atmosphere 20.95% by volume.

The most common element.

Forms of finding the element: a) in free form - O 2, O 3;

b) in bound form: O 2- anions (mainly)

Oxygen is a typical non-metal, p-element. Valency = II; oxidation state -2 (except for H 2 O 2, OF 2, O 2 F 2)

Physical properties of O 2

Molecular oxygen O 2 under normal conditions is in a gaseous state, has no color, smell and taste, and is slightly soluble in water. Upon deep cooling under pressure, it condenses into a pale blue liquid (Tbp - 183 ° C), which at -219 ° C turns into blue crystals.

How to get

1. Oxygen is formed in nature in the process of photosynthesis mCO 2 + nH 2 O → mO 2 + Cm (H 2 O) n

2. Industrial production

a) rectification of liquid air (separation from N 2);

b) water electrolysis: 2H 2 O → 2H 2 + O 2

3. In the laboratory, they are obtained by thermal redox decomposition of salts:

a) 2KSlO 3 \u003d 3O 2 + 2KCI

b) 2KMnO 4 \u003d O 2 + MnO 2 + K 2 MnO 4

c) 2KNO 3 \u003d O 2 + 2KNO 2

d) 2Cu (NO 3) O 2 \u003d O 2 + 4NO 2 + 2CuO

e) 2AgNO 3 \u003d O 2 + 2NO 2 + 2Ag

4. In hermetically sealed rooms and in autonomous breathing apparatus, oxygen is obtained by the reaction:

2Na 2 O 2 + 2СO 2 \u003d O 2 + 2Na 2 CO 3

Chemical properties of oxygen

Oxygen is a strong oxidizing agent. In terms of chemical activity, it is second only to fluorine. Forms compounds with all elements except He, Ne and Ag. Reacts directly with most simple substances under normal conditions or when heated, as well as in the presence of catalysts (with the exception of Au, Pt, Hal 2, noble gases). Reactions involving O 2 are in most cases exothermic, often proceeding in the combustion mode, sometimes in an explosion. As a result of reactions, compounds are formed in which oxygen atoms, as a rule, have C.O. -2:

Alkali metal oxidation

4Li + O 2 = 2Li 2 O lithium oxide

2Na + O 2 \u003d Na 2 O 2 sodium peroxide

K + O 2 \u003d KO 2 potassium superoxide

Oxidation of all metals except Au, Pt

Me + O 2 = Me x O y oxides

Oxidation of non-metals, except halogens and noble gases

N 2 + O 2 \u003d 2NO - Q

S + O 2 \u003d SO 2;

C + O 2 \u003d CO 2;

4P + 5O 2 \u003d 2P 2 O 5

Si + O 2 \u003d SiO 2

Oxidation hydrogen compounds non-metals and metals

4HI + O 2 \u003d 2I 2 + 2H 2 O

2H 2 S + 3O 2 \u003d 2SO 2 + 2H 2 O

4NH 3 + 3O 2 \u003d 2N 2 + 6H 2 O

4NH 3 + 5O 2 \u003d 4NO + 6H 2 O

2PH 3 + 4O 2 \u003d P 2 O 5 + 3H 2 O

SiH 4 + 2O 2 \u003d SiO 2 + 2H 2 O

C x H y + O 2 = CO 2 + H 2 O

MeH x + 3O 2 \u003d Me x O y + H 2 O

Oxidation of lower oxides and hydroxides of polyvalent metals and nonmetals

4FeO + O 2 \u003d 2Fe 2 O 3

4Fe(OH) 2 + O 2 + 2H 2 O = 4Fe(OH) 3

2SO 2 + O 2 = 2SO 3

4NO 2 + O 2 + 2H 2 O \u003d 4HNO 3

Oxidation of metal sulfides

4FeS 2 + 11О 2 = 8SO 2 + 2Fe 2 О 3

Oxidation of organic substances

All organic compounds burn when oxidized by atmospheric oxygen.

Oxidation products various elements included in their molecules are:

Except reactions complete oxidation(combustion) partial oxidation reactions are also possible.

Examples of reactions of incomplete oxidation of organic substances:

1) catalytic oxidation of alkanes

2) catalytic oxidation of alkenes

3) oxidation of alcohols

2R-CH 2 OH + O 2 → 2RCOH + 2H 2 O

4) oxidation of aldehydes

Ozone

Ozone O 3 is a stronger oxidizing agent than O 2, since during the reaction its molecules decompose to form atomic oxygen.

Pure O 3 is a blue gas, very toxic.

K + O 3 \u003d KO 3 potassium ozonide, red.

PbS + 2O 3 \u003d PbSO 4 + O 2

2KI + O 3 + H 2 O \u003d I 2 + 2KOH + O 2

The latter reaction is used for the qualitative and quantitative determination of ozone.