In Lesson 17 " Obtaining oxygen» from the course « Chemistry for dummies» find out how oxygen is obtained in the laboratory; learn what a catalyst is and how plants affect the production of oxygen on our planet.
The most important substance for humans and other living organisms that is part of the air is oxygen. Large quantities of oxygen are used in industry, so it is important to know how to get it.
In a chemical laboratory, oxygen can be obtained by heating some complex substances, which include oxygen atoms. Among these substances is the substance KMnO 4, which is available in your home first aid kit called "potassium permanganate".
You are familiar with the simplest devices for obtaining gases. If a little KMnO 4 powder is placed in one of these devices and heated, oxygen will be released (Fig. 76):
Oxygen can also be obtained by decomposition of hydrogen peroxide H 2 O 2 . To do this, a very small amount of a special substance should be added to a test tube with H 2 O 2 - catalyst- and close the test tube with a stopper with a gas outlet tube (Fig. 77).
For this reaction, the catalyst is a substance whose formula is MnO 2. The following chemical reaction takes place:
Note that there is no catalyst formula on either the left or right side of the equation. Its formula is usually written in the reaction equation over the equal sign. Why is a catalyst added? The process of decomposition of H 2 O 2 under room conditions proceeds very slowly. Therefore, it takes a long time to obtain appreciable amounts of oxygen. However, this reaction can be drastically accelerated by the addition of a catalyst.
Catalyst A substance that speeds up a chemical reaction but is not itself consumed in it.
Precisely because the catalyst is not consumed in the reaction, we do not write down its formula in any of the parts of the reaction equation.
Another way to obtain oxygen is the decomposition of water under the action of a direct electric current. This process is called electrolysis water. You can get oxygen in the device, schematically shown in Figure 78.
The following chemical reaction takes place:
Oxygen in nature
A huge amount of gaseous oxygen is contained in the atmosphere, dissolved in the waters of the seas and oceans. Oxygen is essential for all living organisms to breathe. Without oxygen, it would be impossible to obtain energy by burning various types of fuel. Approximately 2% of atmospheric oxygen is consumed annually for these needs.
Where does oxygen come from on Earth, and why does its amount remain approximately constant despite such consumption? The only source of oxygen on our planet is green plants, which produce it under the action of sunlight through the process of photosynthesis. This is a very complex process with many steps. As a result of photosynthesis in the green parts of plants, carbon dioxide and water are converted into glucose C 6 H 12 O 6 and oxygen. Total
the equation of reactions occurring in the process of photosynthesis can be represented as follows:
It has been established that about one tenth (11%) of the oxygen produced by green plants is provided by terrestrial plants, and the remaining nine tenths (89%) is provided by aquatic plants.
Obtaining oxygen and nitrogen from the air
Huge reserves of oxygen in the atmosphere make it possible to obtain and use it in various industries. Under industrial conditions, oxygen, nitrogen and some other gases (argon, neon) are obtained from the air.
To do this, the air is first converted into a liquid (Fig. 79) by cooling to such a low temperature at which all its components pass into a liquid state of aggregation.
Then this liquid is slowly heated, as a result of which, at different temperatures, the substances contained in the air are sequentially boiled away (i.e., transferred to a gaseous state). By collecting gases boiling off at different temperatures, nitrogen, oxygen and other substances are obtained separately.
Lesson summary:
- Under laboratory conditions, oxygen is obtained by decomposition of some complex substances, which include oxygen atoms.
- A catalyst is a substance that speeds up a chemical reaction without being consumed.
- The source of oxygen on our planet is green plants in which the process of photosynthesis takes place.
- In industry, oxygen is obtained from the air.
I hope lesson 17 " Obtaining oxygen' was clear and informative. If you have any questions, write them in the comments.
Oxygen is a tasteless, odorless, and colorless gas. In terms of content in the atmosphere, it ranks second after nitrogen. Oxygen is a strong oxidizing agent and a reactive non-metal. This gas was discovered simultaneously by several scientists in the 18th century. The Swedish chemist Scheele was the first to produce oxygen in 1772. Oxygen was studied by the French chemist Lavoisier, who gave it the name "oxygène". A smoldering torch helps to detect oxygen: when it comes into contact with gas, it flares up brightly.
Importance of oxygen
This gas is involved in combustion processes. Oxygen is produced by green plants whose leaves carry out the process of photosynthesis, which enriches the atmosphere with this vital gas.
How to get oxygen? Gas is extracted from the air in an industrial way, while the air is purified and liquefied. Our planet has huge reserves of water, a component of which is oxygen. This means that gas can be obtained by decomposing water. You can do this at home.
How to get oxygen from water
To conduct the experiment, you will need the following tools and materials:
Source of power;
Plastic glasses (2 pieces);
Electrodes (2 pieces);
Galvanic bath.
Let's consider the process itself. Pour water into the galvanic bath by more than half the volume, then add 2 ml of caustic soda or dilute sulfuric acid - this will increase the electrical conductivity of the water.
We make holes in the bottom of plastic cups, we stretch electrodes through them - carbon plates. It is necessary to isolate the air gap between the glass and the plate. We place the glasses in the bath so that the electrodes are in the water and the glasses are upside down. There should be very little air between the surface of the water and the bottom of the glass.
Solder a metal wire to each electrode, connect to a power source. The electrode connected to the negative pole is called the cathode, and the electrode connected to the positive pole is called the anode.
An electric current passes through the water - electrolysis of water is carried out.
water electrolysis
A chemical reaction takes place, during which two gases are formed. Hydrogen is collected inside the glass with the cathode, oxygen is collected in the glass with the anode. The formation of gases in glasses with electrodes is determined by air bubbles rising from the water. Through the tube, we withdraw oxygen from the glass into another container.
Safety regulations
Conducting a chemical experiment to obtain oxygen from water is possible only if safety regulations are observed. The gases produced during the electrolysis of water must not be mixed. The resulting hydrogen is explosive, so it should not come into contact with air. You can find out what experiments with gases are safe to do at home.
How to get oxygen in the laboratory
Method one: pour potassium permanganate into a test tube, put the test tube on fire. Potassium permanganate is heated, oxygen is released. We catch the gas with a pneumatic bath. Bottom line: 1 liter of oxygen is released from 10 g of potassium permanganate.
Pneumatic Bath by Stephen Hales
Method two: pour 5 g of saltpeter into a test tube, close the test tube with a refractory stopper with a glass tube. We fix the test tube on the table with a tripod, put a bath of sand under it to avoid excessive heating. We turn on the gas burner and direct the fire to a test tube with saltpeter. The substance melts, oxygen is released. We collect gas through a glass tube into a balloon put on it.
Method three: pour potassium chlorate into a test tube and put the test tube on the fire of a gas burner, after closing it with a refractory stopper with a glass tube. Bertoletova salt in the process of heating releases oxygen. We collect gas through the tube by putting a balloon on it.
Method four: we fix the glass test tube on the table using a tripod, pour hydrogen peroxide into the test tube. Upon contact with air, the unstable compound decomposes into oxygen and water. To speed up the oxygen evolution reaction, add activated charcoal to the test tube. We close the test tube with a refractory stopper with a glass tube, put a balloon on the tube and collect oxygen.
PROPERTIES OF OXYGEN AND METHODS FOR ITS PRODUCTION
Oxygen O 2 is the most abundant element on earth. It is found in large quantities in the form of chemical compounds with various substances in the earth's crust (up to 50% wt.), in combination with hydrogen in water (about 86% wt.) and in a free state in atmospheric air, mixed mainly with nitrogen in the amount of 20.93% vol. (23.15% by weight).
Oxygen is of great importance in the national economy. It is widely used in metallurgy; chemical industry; for flame treatment of metals, fire drilling of hard rocks, underground coal gasification; in medicine and various breathing apparatus, for example, for high-altitude flights, and in other areas.
Under normal conditions, oxygen is a colorless, odorless and tasteless gas, non-flammable, but actively supports combustion. At very low temperatures, oxygen turns into a liquid and even a solid.
The most important physical constants of oxygen are as follows:
| Molecular weight | 32 |
| Weight 1 m 3 at 0 ° C and 760 mm Hg. Art. in kg | 1,43 |
| The same at 20 ° C and 760 mm Hg. Art. in kg | 1,33 |
| Critical temperature in °С | -118 |
| Critical pressure in kgf / m 3 | 51,35 |
| Boiling point at 760 mm Hg. Art. in °С | -182,97 |
| Weight of 1 liter of liquid oxygen at -182, 97 °C and 760 mm Hg. Art. in kg. |
1,13 |
| The amount of gaseous oxygen obtained from 1 liter of liquid at 20 ° C and 760 mm Hg. Art. in l |
850 |
| Solidification temperature at 760 mm Hg. Art. in °C | -218,4 |
Oxygen has a high chemical activity and forms compounds with all chemical elements, except for rare gases. Reactions of oxygen with organic substances have a pronounced exothermic character. So, when compressed oxygen interacts with fatty or finely dispersed solid combustible substances, they are instantly oxidized and the heat released contributes to spontaneous combustion of these substances, which can cause a fire or explosion. This property must be especially taken into account when handling oxygen equipment.
One of the important properties of oxygen is its ability to form widely explosive mixtures with combustible gases and liquid combustible vapors, which can also lead to explosions in the presence of an open flame or even a spark. Explosives are also mixtures of air with gaseous or vaporous combustibles.
Oxygen can be obtained: 1) by chemical means; 2) water electrolysis; 3) by physical means from the air.
Chemical methods, which consist in obtaining oxygen from various substances, are inefficient and currently have only laboratory significance.
The electrolysis of water, i.e., its decomposition into components - hydrogen and oxygen, is carried out in apparatuses called electrolyzers. A direct current is passed through water, into which caustic soda NaOH is added to increase the electrical conductivity; oxygen is collected at the anode and hydrogen is collected at the cathode. The disadvantage of this method is the high power consumption: 12-15 kW is consumed per 1 m 3 0 2 (in addition, 2 m 3 H 2 is obtained). h. This method is rational in the presence of cheap electricity, as well as in the production of electrolytic hydrogen, when oxygen is a waste product.
The physical method consists in the separation of air into components by deep cooling. This method makes it possible to obtain oxygen in practically unlimited quantities and is of major industrial importance. Electricity consumption per 1 m 3 O 2 is 0.4-1.6 kW. h, depending on the type of installation.
OBTAINING OXYGEN FROM AIR
Atmospheric air is basically a mechanical mixture of three gases with the following volume content: nitrogen - 78.09%, oxygen - 20.93%, argon - 0.93%. In addition, it contains about 0.03% carbon dioxide and small amounts of rare gases, hydrogen, nitrous oxide, etc.
The main task in obtaining oxygen from air is to separate the air into oxygen and nitrogen. Along the way, argon is separated, the use of which in special welding methods is constantly increasing, as well as rare gases, which play an important role in a number of industries. Nitrogen has some uses in welding as a shielding gas, in medicine and other fields.
The essence of the method lies in the deep cooling of air with its conversion to a liquid state, which at normal atmospheric pressure can be achieved in the temperature range from -191.8 ° C (the beginning of liquefaction) to -193.7 ° C (the end of liquefaction).
The separation of liquid into oxygen and nitrogen is carried out by using the difference in their boiling points, namely: T kip. o2 \u003d -182.97 ° C; Boiling point N2 = -195.8 ° C (at 760 mm Hg).
With the gradual evaporation of the liquid, nitrogen, which has a lower boiling point, will first pass into the gaseous phase, 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 rectification.
For the production of oxygen from the air, there are specialized enterprises equipped with high-performance plants. In addition, large metalworking enterprises have their own oxygen stations.
The low temperatures required to liquefy the air are obtained by means of so-called refrigeration cycles. The main refrigeration cycles used in modern installations are briefly discussed below.
The refrigeration cycle with air throttling is based on the Joule-Thomson effect, i.e., a sharp decrease in the temperature of the gas during its free expansion. The cycle diagram is shown in fig. 2.
The air is compressed in a multi-stage compressor 1 to 200 kgf/cm 2 and then passes through the cooler 2 with running water. Deep air cooling takes place in the heat exchanger 3 by a reverse flow of cold gas from the liquid collector (liquefier) 4. As a result of air expansion in the throttle valve 5, it is additionally cooled and partially liquefied.
The pressure in the collection 4 is regulated within 1-2 kgf/cm 2 . The liquid is periodically drained from the collector into special containers through valve 6. The non-liquefied part of the air is removed through the heat exchanger, cooling new portions of the incoming air.
Air is cooled down to the liquefaction temperature gradually; when the unit is turned on, there is a start-up period during which no air liquefaction is observed, but only the unit cools down. This period takes several hours.
The advantage of the cycle is its simplicity, and the disadvantage is the relatively high power consumption - up to 4.1 kW. h per 1 kg of liquefied air at a compressor pressure of 200 kgf/cm 2 ; at lower pressure, the specific power consumption increases sharply. This cycle is used in installations of small and medium capacity to produce gaseous oxygen.
Somewhat more complex is the throttling cycle with ammonia pre-cooling.
The medium-pressure refrigeration cycle with expansion in an expander is based on lowering the gas temperature during expansion with the return of external work. In addition, the Joule-Thomson effect is also used. The cycle diagram is shown in fig. 3.
The air is compressed in the compressor 1 to 20-40 kgf / cm 2, passes through the refrigerator 2 and then through the heat exchangers 3 and 4. After the heat exchanger 3, most of the air (70-80%) is sent to the piston expansion machine-expander 6, and the smaller part air (20-30%) goes to free expansion into the throttle valve 5 and then the collector 7, which has a valve 8 for draining the liquid. In expander 6
the air, already cooled in the first heat exchanger, does work - it pushes the piston of the machine, its pressure drops to 1 kgf / cm 2, due to which the temperature drops sharply. From the expander, cold air, having a temperature of about -100 ° C, is discharged outside through heat exchangers 4 and 3, cooling the incoming air. Thus, the expander provides a very efficient cooling of the plant at a relatively low pressure in the compressor. The work of the expander is used usefully and this partially compensates for the energy spent on compressing the air in the compressor.
The advantages of the cycle are: a relatively low compression pressure, which simplifies the design of the compressor and increased cooling capacity (thanks to the expander), which ensures stable operation of the unit when oxygen is taken in liquid form.
Low-pressure refrigeration cycle with expansion in a turbo-expander, developed by Acad. P. L. Kapitsa, is based on the use of low-pressure air with cold production only due to the expansion of this air in an air turbine (turbo expander) with the production of external work. The cycle diagram is shown in fig. four.
The air is compressed by the turbocharger 1 to 6-7 kgf/cm 2 , cooled with water in the cooler 2 and enters the regenerators 3 (heat exchangers), where it is cooled by a reverse flow of cold air. Up to 95% of the air after the regenerators is sent to the turbo expander 4, expands to an absolute pressure of 1 kgf / cm 2 with the performance of external work and is rapidly cooled, after which it is fed into the tube space of the condenser 5 and condenses the rest of the compressed air (5%), entering the annulus. From the condenser 5, the main air flow is directed to the regenerators and cools the incoming air, and the liquid air is passed through the throttle valve 6 to the collector 7, from which it drains through the valve 8. The diagram shows one regenerator, but in reality they are installed several and switched on in turn.
The advantages of the low-pressure cycle with a turbo-expander are: higher efficiency of turbomachines in comparison with piston-type machines, simplification of the technological scheme, increase in reliability and explosion safety of the installation. The cycle is used in installations of high productivity.
The separation of liquid air into components is carried out by means of a rectification process, the essence of which is that the vaporous mixture of nitrogen and oxygen formed during the evaporation of liquid air is passed through a liquid with a lower oxygen content. Since there is less oxygen in the liquid and more nitrogen, it has a lower temperature than the vapor passing through it, and this causes the condensation of oxygen from the vapor and the enrichment of the liquid with simultaneous evaporation of nitrogen from the liquid, i.e., the enrichment of the vapor above the liquid .
An idea of the essence of the rectification process can be given by the one shown in Fig. 5 is a simplified diagram of the process of multiple evaporation and condensation of liquid air.
We assume that air consists only of nitrogen and oxygen. Imagine that there are several vessels connected to each other (I-V), in the upper one there is liquid air with a content of 21% oxygen. Due to the stepped arrangement of the vessels, the liquid will flow down and, at the same time, will gradually be enriched with oxygen, and its temperature will increase.
Let us assume that in vessel II there is a liquid containing 30% 0 2 , in vessel III - 40%, in vessel IV - 50%, and in vessel V - 60% oxygen.
To determine the oxygen content in the vapor phase, we use a special graph - fig. 6, whose curves indicate the oxygen content in liquid and vapor at various pressures.
Let's start to evaporate the liquid in the vessel V at an absolute pressure of 1 kgf/cm 2 . As can be seen from fig. 6, above the liquid in this vessel, consisting of 60% 0 2 and 40% N 2, there can be an equilibrium vapor in composition, containing 26.5% 0 2 and 73.5% N 2, having the same temperature as the liquid . We feed this vapor into vessel IV, where the liquid contains only 50% 0 2 and 50% N 2 and therefore will be colder. From fig. 6 it can be seen that the vapor above this liquid can contain only 19% 0 2 and 81% N 2, and only in this case its temperature will be equal to the temperature of the liquid in this vessel.
Therefore, the steam supplied to vessel IV from vessel V, containing 26.5% O 2 , has a higher temperature than the liquid in vessel IV; therefore, the oxygen of the vapor condenses in the liquid of vessel IV, and part of the nitrogen from it will evaporate. As a result, the liquid in vessel IV will be enriched with oxygen, and the vapor above it with nitrogen.
Similarly, the process will take place in other vessels and, thus, when draining from the upper vessels into the lower ones, the liquid is enriched with oxygen, condensing it from the rising vapors and giving them its nitrogen.
Continuing the process up, you can get a vapor consisting of almost pure nitrogen, and in the lower part - pure liquid oxygen. In fact, the rectification process that occurs in the distillation columns of oxygen plants is much more complicated than described, but its fundamental content is the same.
Regardless of the technological scheme of the installation and the type of refrigeration cycle, the process of producing oxygen from air includes the following stages:
1) air purification from dust, water vapor and carbon dioxide. The binding of CO 2 is achieved by passing air through an aqueous solution of NaOH;
2) air compression in the compressor with subsequent cooling in refrigerators;
3) cooling of compressed air in heat exchangers;
4) expansion of compressed air in a throttle valve or expander for its cooling and liquefaction;
5) liquefaction and rectification of air to obtain oxygen and nitrogen;
6) discharge of liquid oxygen into stationary tanks and removal of gaseous oxygen into gas holders;
7) quality control of the resulting oxygen;
8) filling transport tanks with liquid oxygen and filling cylinders with gaseous oxygen.
The quality of gaseous and liquid oxygen is regulated by the relevant GOSTs.
According to GOST 5583-58, gaseous technical oxygen of three grades is produced: the highest - with a content of at least 99.5% O 2, the 1st - at least 99.2% O 2 and the 2nd - at least 98.5% O 2 , the rest is argon and nitrogen (0.5-1.5%). The moisture content should not exceed 0.07 g/l 3 . Oxygen obtained by electrolysis of water must not contain more than 0.7% hydrogen by volume.
According to GOST 6331-52, liquid oxygen of two grades is produced: grade A with a content of at least 99.2% O 2 and grade B with a content of at least 98.5% O 2. The content of acetylene in liquid oxygen should not exceed 0.3 cm 3 /l.
Used for the intensification of various processes at the enterprises of the metallurgical, chemical and other industries, technological oxygen contains 90-98% O 2 .
Quality control of gaseous, as well as liquid oxygen is carried out directly in the production process using special instruments.
Administration Overall rating of the article: Published: 2012.06.01
This lesson is devoted to the study of modern methods of obtaining oxygen. You will learn by what methods and from what substances oxygen is obtained in the laboratory and industry.
Topic: Substances and their transformations
Lesson:Obtaining oxygen
For industrial purposes, oxygen must be obtained in large volumes and as cheaply as possible. This method of obtaining oxygen was proposed by the Nobel Prize winner Peter Leonidovich Kapitsa. He invented the air liquefaction plant. As you know, about 21% by volume of oxygen is in the air. Oxygen can be separated from liquid air by distillation, because All substances in air have different boiling points. The boiling point of oxygen is -183°C, and that of nitrogen is -196°C. This means that during the distillation of liquefied air, nitrogen will boil and evaporate first, and then oxygen.
In the laboratory, oxygen is not required in such large quantities as in industry. Usually it is brought in blue steel cylinders in which it is under pressure. In some cases, it is still required to obtain oxygen chemically. For this, decomposition reactions are used.
EXPERIMENT 1. Pour a solution of hydrogen peroxide into a Petri dish. At room temperature, hydrogen peroxide decomposes slowly (we do not see signs of a reaction), but this process can be accelerated by adding a few grains of manganese (IV) oxide to the solution. Around the grains of black oxide, gas bubbles immediately begin to stand out. This is oxygen. No matter how long the reaction takes, grains of manganese(IV) oxide do not dissolve in the solution. That is, manganese(IV) oxide participates in the reaction, accelerates it, but is not itself consumed in it.
Substances that speed up a reaction but are not consumed in the reaction are called catalysts.
Reactions accelerated by catalysts are called catalytic.
The acceleration of a reaction by a catalyst is called catalysis.
Thus, manganese (IV) oxide serves as a catalyst in the decomposition of hydrogen peroxide. In the reaction equation, the catalyst formula is written above the equal sign. Let's write down the equation of the carried out reaction. When hydrogen peroxide decomposes, oxygen is released and water is formed. The release of oxygen from the solution is shown by an arrow pointing up:
2. A single collection of digital educational resources ().
3. Electronic version of the journal "Chemistry and Life" ().
Homework
With. 66-67 №№ 2 - 5 from the Workbook in chemistry: 8th grade: to the textbook by P.A. Orzhekovsky and others. “Chemistry. Grade 8” / O.V. Ushakova, P.I. Bespalov, P.A. Orzhekovsky; under. ed. prof. P.A. Orzhekovsky - M.: AST: Astrel: Profizdat, 2006.
Hello. You have already read my articles on the Tutoronline.ru blog. 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 in chemistry, sign up for my classes in the schedule. 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 part of more than 1400 different minerals and organic substances, 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 heating chromium salts of the highest oxidation state:
4K 2 Cr 2 O 7 → 4K 2 CrO 4 + 2Cr 2 O 3 + 3 O 2
bichromate chromate
potassium potassium
In industry, oxygen is obtained:
1) Electrolytic decomposition of water:
2H 2 O → 2H 2 + O 2
2) Interaction of 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:
2H 2 O \u003d 4e + 4H + O 2
The accumulated protons contribute to the synthesis of ATP:
ADP + F = ATP
In the dark phase, carbon dioxide and water are converted into glucose. And oxygen is released as a by-product:
6CO 2 + 6H 2 O \u003d C 6 H 12 O 6 + O 2
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