Methods for producing oxygen reactions. Industrial production of oxygen. Being in nature

Oxygen appeared in the earth's atmosphere with the emergence of green plants and photosynthetic bacteria. Thanks to oxygen, aerobic organisms carry out respiration or oxidation. It is important to obtain oxygen in industry - it is used in metallurgy, medicine, aviation, national economy and other industries.

Properties

Oxygen is the eighth element periodic table Mendeleev. It is a gas that supports combustion and oxidizes substances.

Rice. 1. Oxygen in the periodic table.

Oxygen was officially discovered in 1774. The English chemist Joseph Priestley isolated the element from mercury oxide:

2HgO → 2Hg + O 2 .

What Priestley did not know, however, was that oxygen was part of the air. The properties and presence of oxygen in the atmosphere were later pointed out by Priestley's colleague, the French chemist Antoine Lavoisier.

General characteristics of oxygen:

colorless gas;
has no smell and taste;
heavier than air;
the molecule consists of two oxygen atoms (O 2);
in the liquid state it has a pale blue color;
poorly soluble in water;
is a strong oxidizing agent.

Rice. 2. Liquid oxygen.

The presence of oxygen can be easily checked by lowering a smoldering torch into a vessel with gas. In the presence of oxygen, the torch flares up.

How to receive

There are several ways to obtain oxygen from various compounds in industrial and laboratory conditions. In industry, oxygen is obtained from air by liquefying it under pressure and at a temperature of -183°C. Liquid air is subjected to evaporation, i.e. gradually warm up. At -196°C, nitrogen begins to volatilize, while oxygen retains its liquid state.

In the laboratory, oxygen is formed from salts, hydrogen peroxide, and electrolysis. The decomposition of salts occurs when heated. For example, potassium chlorate or Bertolet salt is heated to 500 ° C, and potassium permanganate or potassium permanganate is heated to 240 ° C:

2KClO 3 → 2KCl + 3O 2;
2KMnO 4 → K 2 MnO 4 + MnO 2 + O 2.

Rice. 3. Heating Berthollet salt.

You can also get oxygen by heating saltpeter or potassium nitrate:

2KNO 3 → 2KNO 2 + O 2 .

The decomposition of hydrogen peroxide uses manganese (IV) oxide - MnO 2 , carbon or iron powder as a catalyst. General Equation as follows:

2H 2 O 2 → 2H 2 O + O 2.

The sodium hydroxide solution is subjected to electrolysis. As a result, water and oxygen are formed:

4NaOH → (electrolysis) 4Na + 2H 2 O + O 2.

Oxygen is also isolated from water by electrolysis, decomposing it into hydrogen and oxygen:

2H 2 O → 2H 2 + O 2 .

On nuclear submarines, oxygen was obtained from sodium peroxide - 2Na 2 O 2 + 2CO 2 → 2Na 2 CO 3 + O 2. The method is interesting in that carbon dioxide is absorbed along with the release of oxygen.

How to apply

Collection and recognition is necessary to release pure oxygen, which is used in industry for the oxidation of substances, as well as to maintain breathing in space, under water, in smoky rooms (oxygen is necessary for firefighters). In medicine, oxygen tanks help patients with breathing difficulties breathe. Oxygen is also used to treat respiratory diseases.

Oxygen is used to burn fuel - coal, oil, natural gas. Oxygen is widely used in metallurgy and engineering, for example, for melting, cutting and welding metal.

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Air is an inexhaustible source of oxygen. To obtain oxygen from it, this gas must be separated from nitrogen and other gases. An industrial method for producing oxygen is based on this idea. It is implemented using special, rather bulky equipment. First, the air is strongly cooled until it turns into a liquid. Then the temperature of the liquefied air is gradually increased. Nitrogen gas is the first to be released from it (the boiling point of liquid nitrogen is -196 ° C), and the liquid is enriched with oxygen.

Obtaining oxygen in the laboratory. Laboratory methods for obtaining oxygen are based on chemical reactions.

J. Priestley obtained this gas from a compound whose name is mercury (II) oxide. The scientist used a glass lens to focus sunlight on matter.

In the modern version, this experience is shown in Figure 54. When heated, mercury (||) oxide (powder yellow color) is converted into mercury and oxygen. Mercury is released into gaseous state and condenses on the walls of the test tube in the form of silvery drops. Oxygen is collected over water in the second test tube.

Now the Priestley method is not used because mercury vapor is toxic. Oxygen is produced by other reactions similar to the one discussed. They usually occur when heated.

Reactions in which several other substances are formed from one substance are called decomposition reactions.

To obtain oxygen in the laboratory, the following oxygen-containing compounds are used:

Potassium permanganate KMnO4 (common name potassium permanganate; the substance is a common disinfectant)

Potassium chlorate KClO3 (trivial name - Berthollet salt, in honor of the French chemist late XVIII - early XIX in. K.-L. Berthollet)

A small amount of catalyst - manganese (IV) oxide MnO2 - is added to potassium chlorate so that the decomposition of the compound occurs with the release of oxygen1.

Molecular structure of chalcogen hydrides H2E can be analyzed using the molecular orbital (MO) method. As an example, consider the scheme of molecular orbitals of a water molecule (Fig. 3)

For construction (For details, see G. Gray "Electrons and chemical bond", M., publishing house "Mir", 1967, pp. 155-62 and GLMiessier, DATarr, "Inorganic Chemistry", Prantice Hall Int. Inc. ., 1991, p.153-57) of the MO scheme of the H2O molecule, the origin of coordinates is compatible with the oxygen atom, and the hydrogen atoms are located in the xz plane (Fig. 3). The overlap of the 2s- and 2p-AO of oxygen with the 1s-AO of hydrogen is shown in Fig. 4. Hydrogen and oxygen AOs, which have the same symmetry and similar energies, take part in the formation of the MO. However, the contribution of AO to the formation of MOs is different, which is reflected in different values of the coefficients in the corresponding linear combinations of AOs. Interaction (overlapping) of 1s-AO of hydrogen, 2s- and 2pz-AO of oxygen leads to the formation of 2a1-bonding and 4a1-loosening MO.

Four elements - "chalcogen" (i.e. "giving birth to copper") head the main subgroup of group VI (according to the new classification - the 16th group) periodic system. In addition to sulfur, tellurium and selenium, they also include oxygen. Let's take a closer look at the properties of this most common element on Earth, as well as the use and production of oxygen.

Element abundance

In bound form, oxygen enters chemical composition water - its percentage is about 89%, as well as in the composition of the cells of all living beings - plants and animals.

In the air, oxygen is in a free state in the form of O2, occupying a fifth of its composition, and in the form of ozone - O3.

Physical Properties

Oxygen O2 is a colorless, tasteless and odorless gas. It is slightly soluble in water. The boiling point is 183 degrees below zero Celsius. In liquid form, oxygen has a blue color, and in solid form it forms blue crystals. The melting point of oxygen crystals is 218.7 degrees below zero Celsius.

Chemical properties

When heated, this element reacts with many simple substances, both metals and non-metals, while forming the so-called oxides - compounds of elements with oxygen. in which elements enter with oxygen is called oxidation.

For example,

4Na + O2= 2Na2O

2. Through the decomposition of hydrogen peroxide when it is heated in the presence of manganese oxide, which acts as a catalyst.

3. Through the decomposition of potassium permanganate.

The production of oxygen in industry is carried out in the following ways:

1. For technical purposes, oxygen is obtained from air, in which its usual content is about 20%, i.e. fifth part. To do this, the air is first burned, obtaining a mixture with a liquid oxygen content of about 54%, liquid nitrogen - 44% and liquid argon - 2%. These gases are then separated by a distillation process using a relatively small interval between the boiling points of liquid oxygen and liquid nitrogen - minus 183 and minus 198.5 degrees, respectively. It turns out that nitrogen evaporates before oxygen.

Modern equipment ensures the production of oxygen of any degree of purity. Nitrogen, which is obtained during separation, is used as a raw material in the synthesis of its derivatives.

2. also gives oxygen to a very pure degree. This method has become widespread in countries with rich resources and cheap electricity.

Application of oxygen

Oxygen is the most important element in the life of our entire planet. This gas, which is contained in the atmosphere, is consumed in the process by animals and humans.

Obtaining oxygen is very important for such areas of human activity as medicine, welding and cutting of metals, blasting, aviation (for breathing people and for the operation of engines), metallurgy.

In progress economic activity human oxygen is consumed in large quantities - for example, when burning various types of fuel: natural gas, methane, coal, wood. In all these processes, it is formed. At the same time, nature has provided for the process of natural binding of this compound through photosynthesis, which takes place in green plants under the influence of sunlight. As a result of this process, glucose is formed, which the plant then uses to build its tissues.

History of the discovery of oxygen The discovery of oxygen marked new period in the development of chemistry. Since ancient times, it has been known that air is needed for combustion. The process of combustion of substances remained incomprehensible for a long time. In the era of alchemy, the phlogiston theory became widespread, according to which substances burn due to their interaction with fiery matter, that is, with the phlogiston contained in the flame. Oxygen was obtained by the English chemist Joseph Priestley in the 70s of the 18th century. The chemist heated the red powder of mercury (II) oxide, as a result, the substance decomposed, with the formation of metallic mercury and a colorless gas:

2HgO t° → 2Hg + O2

oxides binary compounds containing oxygen When a smoldering torch was introduced into a vessel with gas, it flared up brightly. The scientist believed that a smoldering torch introduces phlogiston into the gas, and it lights up. D. Priestley I tried to breathe the resulting gas, and was delighted with how easily and freely it breathes. Then the scientist did not even imagine that the pleasure of breathing this gas is provided to everyone. D. Priestley shared the results of his experiments with the French chemist Antoine Laurent Lavoisier. Having a well-equipped laboratory at that time, A. Lavoisier repeated and improved the experiments of D. Priestley. A. Lavoisier measured the amount of gas released during the decomposition of a certain mass of mercury oxide. The chemist then heated metallic mercury in an airtight vessel until it turned into mercury(II) oxide. He found that the amount of gas released in the first experiment was equal to the gas absorbed in the second experiment. Therefore, mercury reacts with some substance in the air. And the same substance is released during the decomposition of the oxide. Lavoisier was the first to conclude that phlogiston had absolutely nothing to do with it, and it was precisely an unknown gas that caused the burning of a smoldering torch, which was later called oxygen. The discovery of oxygen marked the collapse of the phlogiston theory!

Methods for obtaining and collecting oxygen in the laboratory

Laboratory methods for obtaining oxygen are very diverse. There are many substances from which oxygen can be obtained. Consider the most common methods.

1) Decomposition of mercury oxide (II)

One of the ways to obtain oxygen in the laboratory is to obtain it by the oxide decomposition reaction described above mercury(II). Due to the high toxicity of mercury compounds and mercury vapor itself, this method is used extremely rarely.

2) Decomposition of potassium permanganate

Potassium permanganate(in everyday life we call it potassium permanganate) - crystalline substance dark purple. When potassium permanganate is heated, oxygen is released. Pour a little potassium permanganate powder into a test tube and fix it horizontally in the foot of a tripod. Place a piece of cotton wool near the opening of the test tube. We close the test tube with a stopper, into which a gas outlet tube is inserted, the end of which we lower into the receiver vessel. The vent tube must reach the bottom of the receiving vessel. A cotton wool located near the opening of the test tube is needed to prevent particles of potassium permanganate from entering the receiving vessel (during decomposition, the released oxygen carries along particles of permanganate). When the device is assembled, we start heating the test tube. The release of oxygen begins. The reaction equation for the decomposition of potassium permanganate:

2KMnO4 t° → K2MnO4 + MnO2 + O2

How to detect the presence of oxygen? Let's use Priestley's method. Let's set fire to a wooden torch, let it burn a little, then extinguish it, so that it barely smolders. We lower the smoldering torch into a vessel with oxygen. The beam is blazing bright! Gas tube was not accidentally lowered to the bottom of the receiver vessel. Oxygen is heavier than air, so it will collect at the bottom of the receiver, forcing air out of it. Oxygen can also be collected by water displacement. To do this, the gas outlet tube must be lowered into a test tube filled with water and lowered into the crystallizer with water down the hole. When oxygen is supplied, the gas displaces water from the test tube.

Decomposition of hydrogen peroxide

Hydrogen peroxide- a substance known to all. In the pharmacy it is sold under the name "hydrogen peroxide". This name is obsolete, it is more correct to use the term "peroxide". Chemical formula hydrogen peroxide H2O2 Hydrogen peroxide slowly decomposes into water and oxygen during storage. To speed up the decomposition process, you can heat or apply catalyst.

Catalyst- a substance that speeds up the rate of a chemical reaction

Pour hydrogen peroxide into the flask, add a catalyst to the liquid. Black powder, manganese oxide, can serve as a catalyst. MnO2. Immediately, the mixture will begin to foam due to the release a large number oxygen. Let's put a smoldering torch into the flask - it flares up brightly. The reaction equation for the decomposition of hydrogen peroxide:

2H2O2 MnO2 → 2H2O + O2

Please note: the catalyst that accelerates the reaction is written above the arrow, or sign «=», because it is not consumed during the reaction, but only speeds it up.

Decomposition of potassium chlorate

potassium chlorate- crystalline substance white color. It is used in the manufacture of fireworks and various other pyrotechnic products. There is a trivial name for this substance - "Bertolet's salt". This name was given to the substance in honor of the French chemist who first synthesized it, Claude Louis Berthollet. The chemical formula of potassium chlorate is KClO3. When potassium chlorate is heated in the presence of a catalyst - manganese oxide MnO2, Bertolet's salt decomposes according to the following scheme:

2KClO3 t°, MnO2 → 2KCl + 3O2.

Decomposition of nitrates

Nitrates- substances containing ions in their composition NO3⎺. Connections this class are used as mineral fertilizers, are part of pyrotechnic products. Nitrates- compounds are thermally unstable, and when heated, they decompose with the release of oxygen: Please note that all the considered methods for obtaining oxygen are similar. In all cases, oxygen is released during the decomposition of more complex substances. decomposition reaction- a reaction that complex substances decompose into simpler general view The decomposition reaction can be described by a letter scheme:

AB → A + B.

Decomposition reactions can proceed under the action of various factors. It can be heating, action electric current, catalyst application. There are reactions in which substances decompose spontaneously.

Obtaining oxygen in industry

In industry, oxygen is obtained by separating it from the air. Air- a mixture of gases, the main components of which are presented in the table. The essence of this method lies in the deep cooling of the air with its transformation into a liquid, which, under normal atmospheric pressure can be reached at a temperature of approx. -192°С. The separation of liquid into oxygen and nitrogen is carried out by using the difference in their boiling points, namely: Тbp. O2 = -183°C; Boiling point N2 = -196°С(at normal atmospheric pressure). With the gradual evaporation of the liquid into the gaseous phase, nitrogen, which has more low temperature boiling, and, as it is released, the liquid will be enriched with oxygen. Repeating this process many times makes it possible to obtain oxygen and nitrogen of the required purity. This method of separating liquids into their component parts is called distillation of liquid air.

In the laboratory, oxygen is produced by decomposition reactions
decomposition reaction a reaction in which complex substances are broken down into simpler ones
Oxygen can be collected by air displacement method or water displacement method.
A smoldering torch is used to detect oxygen, it flashes brightly in it
Catalyst- a substance that accelerates chemical reaction, but not consumed in it

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Hello .. Today I will tell you about oxygen and how to get it. I remind you, if you have questions for me, you can write them in the comments to the article. If you need any help with chemistry, . I will be glad to help you.

Oxygen is distributed in nature in the form of isotopes 16 O, 17 O, 18 O, which have the following percentage on Earth - 99.76%, 0.048%, 0.192%, respectively.

In the free state, oxygen is in the form of three allotropic modifications : atomic oxygen - O o, dioxygen - O 2 and ozone - O 3. Moreover, atomic oxygen can be obtained as follows:

KClO 3 \u003d KCl + 3O 0

KNO 3 = KNO 2 + O 0

Oxygen is found in over 1400 different minerals and organic matter, in the atmosphere its content is 21% by volume. The human body contains up to 65% oxygen. Oxygen is a colorless and odorless gas, slightly soluble in water (3 volumes of oxygen dissolve in 100 volumes of water at 20 ° C).

In the laboratory, oxygen is obtained by moderate heating of certain substances:

1) When decomposing manganese compounds (+7) and (+4):

2KMnO 4 → K 2 MnO 4 + MnO 2 + O 2
permanganate manganate
potassium potassium

2MnO 2 → 2MnO + O 2

2) When perchlorates are decomposed:

2KClO 4 → KClO 2 + KCl + 3O 2
perchlorate
potassium

3) When decomposing berthollet salt (potassium chlorate).
In this case, atomic oxygen is formed:

2KClO 3 → 2KCl + 6O 0
chlorate
potassium

4) When the salts of hypochlorous acid decompose in the light- hypochlorites:

2NaClO → 2NaCl + O 2

Ca(ClO) 2 → CaCl 2 + O 2

5) When heating nitrates.
This produces atomic oxygen. Depending on what position the nitrate metal occupies in the activity series, various reaction products are formed:

2NaNO 3 → 2NaNO 2 + O 2

Ca(NO 3) 2 → CaO + 2NO 2 + O 2

2AgNO 3 → 2 Ag + 2NO 2 + O 2

6) When decomposing peroxides:

2H 2 O 2 ↔ 2H 2 O + O 2

7) When heating oxides of inactive metals:

2Ag 2 O ↔ 4Ag + O 2

This process is relevant in everyday life. The fact is that dishes made of copper or silver, having a natural layer of an oxide film, form active oxygen when heated, which is an antibacterial effect. The dissolution of salts of inactive metals, especially nitrates, also leads to the formation of oxygen. For example, the overall process of dissolving silver nitrate can be represented in stages:

AgNO 3 + H 2 O → AgOH + HNO 3

2AgOH → Ag 2 O + O 2

2Ag 2 O → 4Ag + O 2

or in summary form:

4AgNO 3 + 2H 2 O → 4Ag + 4HNO 3 + 7O 2

8) When heated chromium salts the highest degree oxidation:

4K 2 Cr 2 O 7 → 4K 2 CrO 4 + 2Cr 2 O 3 + 3 O 2
dichromate chromate
potassium potassium

In industry, oxygen is obtained:

1) Electrolytic decomposition of water:

2H 2 O → 2H 2 + O 2

2) Interaction carbon dioxide with peroxides:

CO 2 + K 2 O 2 → K 2 CO 3 + O 2

This method is an indispensable technical solution to the problem of breathing in isolated systems: submarines, mines, spacecraft.

3) When ozone interacts with reducing agents:

O 3 + 2KJ + H 2 O → J 2 + 2KOH + O 2

Of particular importance is the production of oxygen in the process of photosynthesis. occurring in plants. All life on Earth depends fundamentally on this process. Photosynthesis is a complex multi-step process. The beginning gives him light. Photosynthesis itself consists of two phases: light and dark. In the light phase, the pigment chlorophyll contained in the leaves of plants forms the so-called “light-absorbing” complex, which takes electrons from water, and thereby splits it into hydrogen ions and oxygen: