How does oxygen react in a reaction? Oxygen – characteristics of the element, prevalence in nature, physical and chemical properties, preparation

The chemical element oxygen can exist in the form of two allotropic modifications, i.e. forms two simple substances. Both of these substances have a molecular structure. One of them has the formula O 2 and is called oxygen, i.e. the same as the name of the chemical element by which it is formed.

Another simple substance formed by oxygen is called ozone. Ozone, unlike oxygen, consists of triatomic molecules, i.e. has the formula O 3 .
Since the main and most common form of oxygen is molecular oxygen O 2, first of all we will consider its chemical properties.

The chemical element oxygen is in second place in terms of electronegativity among all elements and is second only to fluorine. In this regard, it is logical to assume the high activity of oxygen and the presence of almost only oxidizing properties. Indeed, the list of simple and complex substances with which oxygen can react is huge. However, it should be noted that since the oxygen molecule has a strong double bond, most reactions with oxygen require heating to occur. Most often, strong heating is required at the very beginning of the reaction (ignition), after which many reactions proceed further independently without the supply of heat from the outside.

Among simple substances, only noble metals (Ag, Pt, Au), halogens and inert gases are not oxidized by oxygen.

Sulfur burns in oxygen to form sulfur dioxide:

Phosphorus, depending on the excess or lack of oxygen, can form both phosphorus oxide (V) and phosphorus oxide (III):

The interaction of oxygen with nitrogen occurs under extremely harsh conditions, since the binding energies in oxygen and especially nitrogen molecules are very high. The high electronegativity of both elements also contributes to the complexity of the reaction. The reaction begins only at temperatures above 2000 o C and is reversible:

Not all simple substances react with oxygen to form oxides. For example, sodium, when burned in oxygen, forms peroxide:

and potassium is a superoxide:

Most often, when complex substances burn in oxygen, a mixture of oxides of the elements that formed the original substance is formed. For example:

However, when nitrogen-containing organic substances burn in oxygen, molecular nitrogen N2 is formed instead of nitrogen oxide. For example:

When chlorine derivatives burn in oxygen, hydrogen chloride is formed instead of chlorine oxides:

Chemical properties of sulfur

Sulfur as a chemical element can exist in several allotropic modifications. There are rhombic, monoclinic and plastic sulfur. Monoclinic sulfur can be obtained by slowly cooling a melt of orthorhombic sulfur, while plastic sulfur, on the contrary, is obtained by sharply cooling a melt of sulfur that has previously been brought to a boil. Plastic sulfur has a rare property of elasticity for inorganic substances - it is capable of reversibly stretching under the influence of external force, returning to its original shape when this influence ceases. Orthorhombic sulfur is the most stable under normal conditions, and all other allotropic modifications transform into it over time.

Orthorhombic sulfur molecules consist of eight atoms, i.e. its formula can be written as S 8. However, since the chemical properties of all modifications are similar enough to not make it difficult to write reaction equations, any sulfur is simply designated by the symbol S.

Sulfur can interact with both simple and complex substances. In chemical reactions it will exhibit both oxidizing and reducing properties.

The oxidizing properties of sulfur manifest themselves when it interacts with metals, as well as non-metals formed by atoms of a less electronegative element (hydrogen, carbon, phosphorus):

Sulfur acts as a reducing agent when interacting with nonmetals formed by more electronegative elements (oxygen, halogens), as well as complex substances with a pronounced oxidizing function, for example, sulfuric and concentrated nitric acids:

Sulfur also reacts when boiled with concentrated aqueous solutions of alkalis. The interaction proceeds according to the type of disproportionation, i.e. sulfur simultaneously lowers and increases its oxidation state.

Oxygen (lat. Oxygenium), O, chemical element of group VI of the periodic system of Mendeleev; atomic number 8, atomic mass 15.9994. Under normal conditions, oxygen is a colorless, odorless, and tasteless gas. It is difficult to name another element that would play such an important role on our planet as Oxygen.

Historical reference. The processes of combustion and respiration have long attracted the attention of scientists. The first indications that not all air, but only the “active” part of it supports combustion, were found in Chinese manuscripts of the 8th century. Much later, Leonardo da Vinci (1452-1519) considered air as a mixture of two gases, only one of which is consumed during combustion and respiration. The final discovery of the two main components of air - nitrogen and oxygen, which made an era in science, occurred only at the end of the 18th century. Oxygen was obtained almost simultaneously by K. Scheele (1769-70) by calcining saltpeter (KNO3, NaNO3), manganese dioxide MnO2 and other substances and J. Priestley (1774) by heating red lead Pb3O4 and mercuric oxide HgO. In 1772, D. Rutherford discovered nitrogen. In 1775, A. Lavoisier, having carried out a quantitative analysis of air, found that it “consists of two (gases) of a different and, so to speak, opposite nature,” that is, of Oxygen and Nitrogen. Based on extensive experimental research, Lavoisier correctly explained combustion and respiration as processes of interaction of substances with Oxygen. Since Oxygen is part of acids, Lavoisier called it oxygene, that is, “forming acids” (from the Greek oxys - sour and gennao - I give birth; hence the Russian name “oxygen”).

Oxygen distribution in nature. Oxygen is the most common chemical element on Earth. Bound Oxygen makes up about 6/7 of the mass of the Earth's water shell - the hydrosphere (85.82% by mass), almost half of the lithosphere (47% by mass), and only in the atmosphere, where Oxygen is in a free state, does it take second place (23 .15% by weight) after nitrogen.

Oxygen also ranks first in the number of minerals it forms (1364); Among the minerals containing Oxygen, silicates (feldspars, micas and others), quartz, iron oxides, carbonates and sulfates predominate. Living organisms contain on average about 70% Oxygen; it is part of most of the most important organic compounds (proteins, fats, carbohydrates, etc.) and in the composition of inorganic compounds of the skeleton. The role of free oxygen is extremely important in biochemical and physiological processes, especially in respiration. With the exception of some anaerobic microorganisms, all animals and plants obtain the energy necessary for life through the biological oxidation of various substances with the help of Oxygen.

The entire mass of free Oxygen on the Earth arose and is preserved thanks to the vital activity of green plants on land and the World Ocean, which release Oxygen in the process of photosynthesis. On the earth's surface, where photosynthesis occurs and free oxygen predominates, sharply oxidizing conditions are formed. On the contrary, in magma, as well as deep horizons of groundwater, in the silts of seas and lakes, in swamps, where free oxygen is absent, a reducing environment is formed. Redox processes involving Oxygen determine the concentration of many elements and the formation of mineral deposits - coal, oil, sulfur, iron ores, copper, etc. Changes in the oxygen cycle are also brought about by human economic activity. In some industrialized countries, the combustion of fuel consumes more oxygen than is produced by plants during photosynthesis. In total, about 9·109 tons of Oxygen are consumed annually in the world for fuel combustion.

Isotopes, atom and molecule of Oxygen. Oxygen has three stable isotopes: 16O, 17O and 18O, 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, 16O, in the mixture of isotopes is due to the fact that the nucleus of the 16O atom consists of 8 protons and 8 neutrons. And such nuclei, as follows from the theory of the atomic nucleus, are particularly stable.

In accordance with the position of Oxygen in Mendeleev’s periodic table of elements, the electrons of the Oxygen atom are located in two shells: 2 on the inner and 6 on the outer (configuration 1s22s22p4). Since the outer shell of the Oxygen atom is unfilled and the ionization potential and electron affinity are 13.61 and 1.46 eV, respectively, the Oxygen atom in chemical compounds usually acquires electrons and has a negative effective charge. On the contrary, compounds in which electrons are detached (more precisely, pulled away) from the Oxygen atom are extremely rare (such as, for example, F2O, F2O3). Previously, based solely on the position of Oxygen in the periodic table, the Oxygen atom in oxides and in most other compounds was assigned a negative charge (-2). However, as experimental data show, the O2 - ion does not exist either in the free state or in compounds, and the negative effective charge of the Oxygen atom almost never significantly exceeds unity.

Under normal conditions, the Oxygen molecule is diatomic (O2); in a quiet electrical discharge, a triatomic molecule O3 - ozone - is also formed; at high pressures O4 molecules are found in small quantities. The electronic structure of O2 is of great theoretical interest. In the ground state, the O2 molecule has two unpaired electrons; the “usual” classical structural formula O=O with two two-electron bonds is not applicable to it. A comprehensive explanation of this fact is given within the framework of the theory of molecular orbitals. The ionization energy of the Oxygen molecule (O2 - e > O2+) is 12.2 eV, and the electron affinity (O2 + e > O2-) is 0.94 eV. The dissociation of molecular Oxygen into atoms at ordinary temperature is negligible; it becomes noticeable only at 1500°C; at 5000°C, oxygen molecules are almost completely dissociated into atoms.

Physical properties of Oxygen. Oxygen is a colorless gas that condenses at -182.9°C and normal pressure into a pale blue liquid, which solidifies at -218.7°C, forming blue crystals. The density of oxygen gas (at 0°C and normal pressure) is 1.42897 g/l. The critical temperature of Oxygen is quite low (Tcrit = -118.84°C), that is, lower than that of Cl2, CO2, SO2 and some other gases; Tcrit = 4.97 Mn/m2 (49.71 at). Thermal conductivity (at 0°C) 23.86·10-3 W/(m·K). Molar heat capacity (at 0°C) in J/(mol K) Сp = 28.9, Сv = 20.5, Сp/Сv = 1.403. The dielectric constant of gaseous Oxygen is 1.000547 (0°C), liquid 1.491. Viscosity 189 ppm (0°C). Oxygen is slightly soluble in water: at 20°C and 1 atm, 0.031 m3 of water dissolves in 1 m3, and at 0°C - 0.049 m3 of oxygen. Good solid oxygen absorbers are platinum black and active charcoal.

Chemical properties of Oxygen. Oxygen forms chemical compounds with all elements except light inert gases. Being the most active (after fluorine) non-metal, Oxygen interacts directly with most elements; exceptions are heavy inert gases, halogens, gold and platinum; their connections with oxygen are obtained indirectly. Almost all reactions of Oxygen with other substances - oxidation reactions - are exothermic, that is, they are accompanied by the release of energy. Oxygen reacts extremely slowly with hydrogen at normal temperatures; above 550°C this reaction occurs with an explosion 2H2 + O2 = 2H2O.

Oxygen reacts very slowly with sulfur, carbon, nitrogen, and phosphorus under normal conditions. As the temperature rises, the reaction rate increases and at a certain ignition temperature characteristic of each element, combustion begins. The reaction of nitrogen with Oxygen, due to the special strength of the N2 molecule, is endothermic and becomes noticeable only above 1200°C or in an electric discharge: N2 + O2 = 2NO. Oxygen actively oxidizes almost all metals, especially alkali and alkaline earth metals. The activity of interaction between a metal and Oxygen depends on many factors - the state of the metal surface, the degree of grinding, and the presence of impurities.

In the process of interaction of a substance with Oxygen, the role of water is extremely important. For example, even such an active metal as potassium does not react with completely moisture-free Oxygen, but ignites in Oxygen at ordinary temperatures in the presence of even minute amounts of water vapor. It is estimated that up to 10% of all metal produced is lost annually as a result of corrosion.

Oxides of some metals, adding oxygen, form peroxide compounds containing 2 or more interconnected oxygen atoms. Thus, the peroxides Na2O2 and BaO2 include the peroxide ion O22-, the superoxides NaO2 and СО2 - the O2- ion, and the ozonides NaO3, СО3, RbO3 and CsO3 - the O3- ion. Oxygen interacts exothermically with many complex substances. So, ammonia burns in Oxygen in the absence of catalysts, the reaction proceeds according to the equation: 4NH3 + 3O2 = 2N2 + 6H2O. The oxidation of ammonia with oxygen in the presence of a catalyst produces NO (this process is used in the production of nitric acid). Of particular importance is the combustion of hydrocarbons (natural gas, gasoline, kerosene) - the most important source of heat in everyday life and industry, for example CH4 + 2O2 = CO2 + 2H2O. The interaction of hydrocarbons with Oxygen underlies many important production processes - such as, for example, the so-called methane conversion carried out to produce hydrogen: 2CH4 + O2 + 2H2O = 2CO2 + 6H2. Many organic compounds (hydrocarbons with double or triple bonds, aldehydes, phenols, as well as turpentine, drying oils, and others) vigorously add oxygen. Oxidation of nutrients in cells by oxygen serves as a source of energy for living organisms.

Obtaining Oxygen. There are 3 main ways to obtain Oxygen: chemical, electrolysis (electrolysis of water) and physical (separation of air).

The chemical method was invented earlier than others. Oxygen can be obtained, for example, from Berthollet salt KClO3, which decomposes when heated, releasing O2 in the amount of 0.27 m 3 per 1 kg of salt. Barium oxide BaO, when heated to 540°C, first absorbs Oxygen from the air, forming BaO2 peroxide, and upon subsequent heating to 870°C, BaO2 decomposes, releasing pure Oxygen. It can also be obtained from KMnO4, Ca2PbO4, K2Cr2O7 and other substances by heating and adding catalysts. The chemical method of producing Oxygen is low-productivity and expensive, has no industrial significance and is used only in laboratory practice.

The electrolysis method consists of passing a direct electric current through water, to which a solution of sodium hydroxide NaOH has been added to increase its electrical conductivity. In this case, water decomposes into Oxygen and Hydrogen. Oxygen collects near the positive electrode of the electrolyzer, and hydrogen collects near the negative electrode. In this way, Oxygen is produced as a by-product in the production of hydrogen. To obtain 2 m3 of hydrogen and 1 m3 of oxygen, 12-15 kWh of electricity is consumed.

Air separation is the main method of obtaining Oxygen in modern technology. It is very difficult to separate air in its normal gaseous state, so the air is first liquefied and then separated into its component parts. This method of obtaining Oxygen is called air separation using the deep cooling method. First, the air is compressed by a compressor, then, after passing through heat exchangers, it expands in an expander machine or throttle valve, as a result of which it is cooled to a temperature of 93 K (-180 ° C) and turns into liquid air. Further separation of liquid air, consisting mainly of liquid nitrogen and liquid oxygen, is based on the difference in boiling point of its components [bp O2 90.18 K (-182.9°C), bp N2 77.36 K (-195.8° WITH)]. With the gradual evaporation of liquid air, primarily nitrogen is evaporated first, and the remaining liquid is increasingly enriched in Oxygen. By repeating a similar process many times on the distillation trays of air separation columns, liquid Oxygen of the required purity (concentration) is obtained. The USSR produces small (several liters) and the world's largest oxygen air separation plants (35,000 m 3 /h of oxygen). These installations produce technological Oxygen with a concentration of 95-98.5%, technical Oxygen with a concentration of 99.2-99.9% and purer, medical Oxygen, producing products in liquid and gaseous form. Electrical energy consumption ranges from 0.41 to 1.6 kWh/m3.

Oxygen can also be obtained by separating air using the method of selective permeation (diffusion) through membrane partitions. Air under high pressure is passed through fluoroplastic, glass or plastic partitions, the structural lattice of which is capable of passing molecules of some components and retaining others.

Gaseous Oxygen is stored and transported in steel cylinders and receivers at a pressure of 15 and 42 Mn/m2 (150 and 420 bar, respectively, or 150 and 420 atm), liquid Oxygen in metal Dewar vessels or in special tank tanks. Special pipelines are also used to transport liquid and gaseous Oxygen. Oxygen cylinders are painted blue and have the word “oxygen” written in black.

Application of Oxygen. Technical Oxygen is used in the processes of gas-flame processing of metals, in welding, oxygen cutting, surface hardening, metallization and others, as well as in aviation, on submarines, etc. Technological Oxygen is used in the chemical industry for the production of artificial liquid fuels, lubricating oils, nitric and sulfuric acids, methanol, ammonia and ammonia fertilizers, metal peroxides and other chemical products. Liquid Oxygen is used in blasting operations, in jet engines and in laboratory practice as a coolant.

Pure Oxygen enclosed in cylinders is used for breathing at high altitudes, during space flights, during scuba diving, etc. In medicine, Oxygen is given for inhalation to seriously ill patients, used for the preparation of oxygen, water and air (in oxygen tents) baths, for intramuscular administration, etc. .P.

Oxygen is widely used in metallurgy to intensify a number of pyrometallurgical processes. The complete or partial replacement of air entering metallurgical units with oxygen changed the chemistry of the processes, their thermal parameters and technical and economic indicators. Oxygen blast made it possible to reduce heat losses with exhaust gases, a significant part of which was nitrogen during air blast. Without taking a significant part in chemical processes, nitrogen slowed down the course of reactions, reducing the concentration of active reagents in the redox environment. When purging with Oxygen, fuel consumption is reduced, the quality of the metal is improved, in metallurgical units it is possible to obtain new types of products (for example, slags and gases of an unusual composition for a given process, which find special technical application), etc.

The first experiments in the use of oxygen-enriched blast in blast furnace production for the smelting of pig iron and ferromanganese were carried out simultaneously in the USSR and Germany in 1932-33. An increased content of Oxygen in the blast furnace blast is accompanied by a large reduction in the consumption of the latter, while the content of carbon monoxide in the blast furnace gas increases and its heat of combustion increases. Enriching the blast with Oxygen makes it possible to increase the productivity of the blast furnace, and in combination with gaseous and liquid fuel supplied to the hearth, it leads to a reduction in coke consumption. In this case, for every additional percentage of Oxygen in the blast, productivity increases by approximately 2.5%, and coke consumption decreases by 1%.

Oxygen in open-hearth production in the USSR was first used to intensify fuel combustion (on an industrial scale, oxygen was first used for this purpose at the Serp and Molot and Krasnoye Sormovo plants in 1932-33). In 1933, they began to inject Oxygen directly into the liquid bath in order to oxidize impurities during the finishing period. With an increase in the intensity of melt blowing by 1 m 3 /t per 1 hour, furnace productivity increases by 5-10%, fuel consumption is reduced by 4-5%. However, when blowing, metal losses increase. When Oxygen consumption is up to 10 m 3 /t per 1 hour, the steel yield decreases slightly (up to 1%). Oxygen is becoming increasingly common in open-hearth production. So, if in 1965 52.1% of steel was smelted using oxygen in open-hearth furnaces, then in 1970 it was already 71%.

Experiments on the use of oxygen in electric furnaces in the USSR began in 1946 at the Elektrostal plant. The introduction of oxygen blast made it possible to increase the productivity of furnaces by 25-30%, reduce specific energy consumption by 20-30%, improve the quality of steel, and reduce the consumption of electrodes and some scarce alloying additives. The supply of Oxygen to electric furnaces turned out to be especially effective in the production of stainless steels with low carbon content, the smelting of which is very difficult due to the carburizing effect of the electrodes. The share of electric steel produced in the USSR using oxygen continuously grew and in 1970 amounted to 74.6% of total steel production.

In cupola melting, Oxygen-enriched blast is used mainly for high superheating of cast iron, which is necessary in the production of high-quality, in particular high-alloy, castings (silicon, chromium, etc.). Depending on the degree of oxygen enrichment of the cupola blast, fuel consumption is reduced by 30-50%, the sulfur content in the metal is reduced by 30-40%, the productivity of the cupola increases by 80-100% and the temperature of the cast iron produced from it increases significantly (up to 1500°C) .

Oxygen became widespread in non-ferrous metallurgy somewhat later than in ferrous metallurgy. Oxygen-enriched blast is used in converting mattes, in the processes of slag distillation, Waeltzing, agglomeration and in reflective smelting of copper concentrates. In lead, copper and nickel production, oxygen blast intensified the processes of shaft smelting, reduced coke consumption by 10-20%, increased penetration by 15-20% and reduced the amount of fluxes in some cases by 2-3 times. Enrichment of air blast with oxygen up to 30% during roasting of zinc sulfide concentrates increased the productivity of the process by 70% and reduced the volume of exhaust gases by 30%.

oxygen element isotope property

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Chemical properties of oxygen. Oxides

This paragraph talks about:

> about the reactions of oxygen with simple and complex substances;
> about compound reactions;
> about compounds called oxides.

The chemical properties of each substance are manifested in chemical reactions with his participation.

Oxygen is one of the most active non-metals. But under normal conditions it reacts with few substances. Its reactivity increases significantly with increasing temperature.

Reactions of oxygen with simple substances.

Oxygen reacts, as a rule, when heated, with most non-metals and almost all metals.

Reaction with coal (carbon). It is known that coal heated in air to a high temperature ignites. This indicates a chemical reaction of the substance with oxygen. The heat released during this process is used, for example, to heat houses in rural areas.

The main product of coal combustion is carbon dioxide. His chemical formula- CO 2 . Coal is a mixture of many substances. The mass fraction of carbon in it exceeds 80%. Assuming that coal consists only of carbon atoms, we write the corresponding chemical equation:

t
C + O 2 = CO 2.

Carbon forms simple substances - graphite and diamond. They have a common name - carbon - and react with oxygen when heated according to the given chemical equation 1.

Reactions in which one substance is formed from several substances are called compound reactions.

Reaction with sulfur.

This chemical transformation occurs when everyone lights a match; sulfur is part of its head. In the laboratory, the reaction of sulfur with oxygen is carried out in a fume hood. A small amount of sulfur (light yellow powder or crystals) is heated in an iron spoon. Substance first it melts, then it ignites as a result of interaction with oxygen in the air and burns with a barely noticeable blue flame (Fig. 56, b). A pungent odor of the reaction product appears - sulfur dioxide (we smell this odor at the moment a match lights up). The chemical formula of sulfur dioxide is SO 2, and the reaction equation is
t
S + O 2 = SO 2.

Rice. 56. Sulfur (a) and its combustion in air (b) and in oxygen (c)

1 In case of insufficient oxygen, another Carbon compound is formed with Oxygen- carbon monoxide
t
CO: 2C + O 2 = 2CO.

Rice. 57. Red phosphorus (a) and its combustion in air (b) and in oxygen (c)

If a spoon with burning sulfur is placed in a vessel with oxygen, then the sulfur will burn with a brighter flame than in air (Fig. 56, c). This can be explained by the fact that there are more O 2 molecules in pure oxygen than in air.

Reaction with phosphorus. Phosphorus, like sulfur, burns more intensely in oxygen than in air (Fig. 57). The product of the reaction is a white solid - phosphorus(\/) oxide (its small particles form smoke):
t
P + O 2 -> P 2 0 5 .

Convert the reaction diagram into a chemical equation.

Reaction with magnesium.

Previously this reaction was used photographers to create bright lighting (“magnesium flash”) when taking photographs. In a chemical laboratory, the corresponding experiment is carried out as follows. Using metal tweezers, take the magnesium strip and set it on fire in air. Magnesium burns with a dazzling white flame (Fig. 58, b); You can't look at him! The reaction produces a white solid. This is a compound of Magnesium with Oxygen; its name is magnesium oxide.

Rice. 58. Magnesium (a) and its combustion in air (b)

Write an equation for the reaction of magnesium with oxygen.

Reactions of oxygen with complex substances. Oxygen can interact with some oxygen-containing compounds. For example, carbon monoxide CO burns in air to form carbon dioxide:

t
2CO + O 2 = 2C0 2.

We carry out many reactions of oxygen with complex substances in everyday life, burning natural gas (methane), alcohol, wood, paper, kerosene, etc. When they burn, carbon dioxide and water vapor are formed:
t
CH 4 + 20 2 = CO 2 + 2H 2 O;
methane
t
C 2 H 5 OH + 30 2 = 2C0 2 + 3H 2 O.
alcohol

Oxides.

The products of all reactions discussed in the paragraph are binary compounds of elements with Oxygen.

A compound formed by two elements, one of which is Oxygen, is called an oxide.

The general formula of the oxides is EnOm.

Each oxide has a chemical name, and some also have traditional, or trivial 1 names (Table 4). The chemical name of the oxide consists of two words. The first word is the name of the corresponding element, and the second is the word “oxide”. If an element has a variable valency, it can form several oxides. Their names should be different. To do this, after the name of the element, indicate (without indentation) in Roman numerals in brackets the value of its valency in the oxide. An example of such a compound name is cuprum(II) oxide (pronounced cuprum-two-oxide).

Table 4

1 The term comes from the Latin word trivialis - ordinary.

conclusions

Oxygen is a chemically active substance. It interacts with most simple substances as well as complex substances. The products of such reactions are compounds of elements with Oxygen - oxides.

Reactions in which one substance is formed from several substances are called compound reactions.

?
135. How do compound and decomposition reactions differ?

136. Convert reaction schemes into chemical equations:

a) Li + O 2 -> Li 2 O;
N2 + O 2 -> NO;

b) SO 2 + O 2 -> SO 3;
CrO + O 2 -> Cr 2 O 3.

137. Select from the given formulas those that correspond to oxides:

O 2, NaOH, H 2 O, HCI, I 2 O 5, FeO.

138. Give chemical names to oxides with the following formulas:

NO, Ti 2 O 3, Cu 2 O, MnO 2, CI 2 O 7, V 2 O 5, CrO 3.

Please note that the elements that form these oxides have variable valence.

139. Write down the formulas: a) plumbum(I\/) oxide; b) chromium(III) oxide;
c) chlorine(I) oxide; d) nitrogen(I\/) oxide; e) osmium(\/III) oxide.

140. Complete the formulas of simple substances in the reaction schemes and make up chemical equations:

a) ... + ... -> CaO;

b) NO + ... -> NO 2; ... + ... -> As 2 O 3 ; Mn 2 O 3 + ... -> MnO 2.

141. Write the reaction equations with the help of which you can carry out such “chains” of transformations, i.e., get a second from the first substance, and a third from the second:

a) C -> CO -> CO 2;
b) P -> P 2 0 3 -> P 2 0 5 ;
c) Cu -> Cu 2 O -> CuO.

142.. Write down equations for the reactions that occur when acetone (CH 3) 2 CO and ether (C 2 H 5) 2 O burn in air. The products of each reaction are carbon dioxide and water.

143. The mass fraction of Oxygen in EO 2 oxide is 26%. Identify element E.

144. Two flasks are filled with oxygen. After they were sealed, excess magnesium was burned in one flask, and excess sulfur in the other. In which flask was a vacuum formed? Explain your answer.

Popel P. P., Kryklya L. S., Chemistry: Pidruch. for 7th grade zagalnosvit. navch. closing - K.: VC "Academy", 2008. - 136 p.: ill.

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.

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.

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 has a pale blue 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 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 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:

The discovery of oxygen happened twice, in the second half of the 18th century, several years apart. In 1771, oxygen was obtained by Swede Karl Scheele by heating saltpeter and sulfuric acid. The resulting gas was called "fire air". In 1774, the English chemist Joseph Priestley carried out the process of decomposing mercuric oxide in a completely closed vessel and discovered oxygen, but mistook it for an ingredient in air. Only after Priestley shared his discovery with the Frenchman Antoine Lavoisier did it become clear that a new element (calorizator) had been discovered. Priestley takes the lead in this discovery because Scheele published his scientific work describing the discovery only in 1777.

Oxygen is an element of group XVI of period II of the periodic table of chemical elements by D.I. Mendeleev, has atomic number 8 and atomic mass 15.9994. It is customary to denote oxygen by the symbol ABOUT(from Latin Oxygenium- generating acid). In Russian the name oxygen became a derivative of acids, a term that was introduced by M.V. Lomonosov.

Being in nature

Oxygen is the most common element found in the earth's crust and the World Ocean. Oxygen compounds (mainly silicates) make up at least 47% of the mass of the earth's crust; oxygen is produced during photosynthesis by forests and all green plants, most of which comes from phytoplankton in marine and fresh waters. Oxygen is an essential component of any living cells and is also found in most substances of organic origin.

Physical and chemical properties

Oxygen is a light non-metal, belongs to the group of chalcogens, and has high chemical activity. Oxygen, as a simple substance, is a colorless, odorless and tasteless gas; it has a liquid state - light blue transparent liquid and a solid state - light blue crystals. Consists of two oxygen atoms (denoted by the formula O₂).

Oxygen is involved in redox reactions. Living things 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, and gangrene. Artificial ozone enrichment is used to disinfect and deodorize air and purify drinking water.

Oxygen is the basis of the life activity of all living organisms on Earth and is the main biogenic element. It is found in the molecules of all the most important substances that are responsible for the structure and functions of cells (lipids, proteins, carbohydrates, nucleic acids). Every living organism contains much more oxygen than any element (up to 70%). For example, the body of an average adult human weighing 70 kg contains 43 kg of oxygen.

Oxygen enters living organisms (plants, animals and humans) through the respiratory system and the intake of water. Remembering that in the human body the most important respiratory organ is the skin, it becomes clear how much oxygen a person can receive, especially in the summer on the shore of a reservoir. Determining a person’s need for oxygen is quite difficult, because it depends on many factors - age, gender, body weight and surface area, nutrition system, external environment, etc.

Use of oxygen in life

Oxygen is used almost everywhere - from metallurgy to the production of rocket fuel and explosives used for road work in the mountains; from medicine to the food industry.

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