Obtaining the chemical properties of oxygen. Oxygen gas

Oxygen supports the processes of respiration and combustion. Many nonmetals burn in oxygen. For example, coal burns in air, interacting with oxygen. As a result of this reaction, carbon dioxide and heat is released. It is known that heat is denoted by the letter “Q”. If heat is released as a result of a reaction, then “Q” is written in the equation; if it is absorbed, then “-Q”.

The heat that is released or absorbed during a chemical reaction is called thermal effect chemical reaction.

Reactions that occur with the release of heat are called exothermic.

Reactions that occur with the absorption of heat are called endothermic.

Interaction of oxygen with nonmetals

Reaction equation for coal combustion in air:

CO 2 = CO 2 Q

If you burn coal in a vessel with oxygen, then the coal will burn faster than in air. That is, the combustion rate of coal in oxygen is higher than in air.

Sulfur also burns in air, and heat is also released. This means that the reaction between sulfur and oxygen can be called exothermic. In pure oxygen, sulfur burns faster than in air.

Equation for the combustion of sulfur in oxygen, if this results in the formation of sulfur oxide (IV) :

S O 2 = SO 2 Q

Similarly, it is possible to carry out the combustion reaction of phosphorus in air or oxygen. This reaction is also exothermic. Its equation, if phosphorus (V) oxide is formed as a result:

4P 5O 2 = 2P 2 O 5 Q

Interaction of oxygen with metals

Some metals can burn in an oxygen atmosphere. For example, iron burns in oxygen to form iron scale:

3Fe 2O 2 = Fe 3 O 4 Q

But copper does not burn in oxygen, but is oxidized by oxygen when heated. In this case, copper (II) oxide is formed:

2CuO2 = 2CuO

Interaction of oxygen with complex substances

Oxygen is capable of reacting not only with simple substances, but also with complex substances.

Natural gas methane burns in oxygen to form carbon monoxide (IV) and water:

CH 4 2O 2 = CO 2 2H 2 O Q

With incomplete combustion of methane (in conditions of insufficient oxygen), not carbon dioxide is formed, but carbon monoxide CO. Carbon monoxide – poisonous substance, extremely dangerous for humans, because the person does not feel its toxic effect, but slowly falls asleep with loss of consciousness.

Reactions of simple and complex substances with oxygen are called oxidation. When simple and complex substances interact with oxygen, as a rule, complex substances are formed consisting of two elements, one of which is oxygen. These substances are called oxides.

1. Collection of problems and exercises in chemistry: 8th grade: for textbooks. P.A. Orzhekovsky and others. “Chemistry. 8th grade” / P.A. Orzhekovsky, N.A. Titov, F.F. Hegel. – M.: AST: Astrel, 2006. (p.70-74)

2. Ushakova O.V. Workbook in chemistry: 8th grade: to the textbook by P.A. Orzhekovsky and others. “Chemistry. 8th grade” / O.V. Ushakova, P.I. Bespalov, P.A. Orzhekovsky; under. ed. prof. P.A. Orzhekovsky - M.: AST: Astrel: Profizdat, 2006. (p.68-70)

3. Chemistry. 8th grade. Textbook for general education institutions / P.A. Orzhekovsky, L.M. Meshcheryakova, M.M. Shalashova. – M.:Astrel, 2012. (§21)

4. Chemistry: 8th grade: textbook. for general education institutions / P.A. Orzhekovsky, L.M. Meshcheryakova, L.S. Pontak. M.: AST: Astrel, 2005. (§28)

5. Chemistry: inorganic. chemistry: textbook. for 8th grade general education establishment /G.E. Rudzitis, F.G. Feldman. – M.: Education, OJSC “Moscow Textbooks”, 2009. (§20)

6. Encyclopedia for children. Volume 17. Chemistry / Chapter. ed.V.A. Volodin, Ved. scientific ed. I. Leenson. – M.: Avanta, 2003.

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Chemical properties oxygen. Oxides

In this paragraph we're talking 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. His 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 high temperature, lights up. 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. Mass fraction Carbon content 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 common name- carbon - and interact 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 everyone does when he 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. Small quantity 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 smell when a match lights up). Chemical formula 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 white solid- phosphorus(\/) oxide (its fine particles produce 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 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 valence 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 Latin word trivialis - ordinary.

Conclusions

Oxygen - 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 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.

Oxygen – chemical element, the properties of which will be discussed in the next few paragraphs. Let us turn to the Periodic Table of Chemical Elements by D.I. Mendeleev. The element oxygen is located in period 2, group VI, the main subgroup.

It also states that relative atomic mass oxygen is 16.

By serial number oxygen in the Periodic Table, you can easily determine the number of electrons contained in its atom, the charge of the nucleus of the oxygen atom, and the number of protons.

The valence of oxygen in most compounds is II. An oxygen atom can gain two electrons and become an ion: O0 + 2ē = O−2.

It is worth noting that oxygen is the most common element on our planet. Oxygen is part of water. Marine and fresh waters 89% by weight consist of oxygen. Oxygen is found in many minerals and rocks. The mass fraction of oxygen in the earth's crust is about 47%. Air contains about 23% oxygen by weight.

Physical properties of oxygen

When two oxygen atoms interact, a stable molecule of the simple substance oxygen O2 is formed. This simple substance, like the element, is called oxygen. Do not confuse oxygen as an element and oxygen as a simple substance!

By physical properties oxygen– a colorless, odorless and tasteless gas. Practically insoluble in water (at room temperature and normal atmospheric pressure The solubility of oxygen is about 8 mg per liter of water).

Oxygen is soluble in water - 31 ml of oxygen (0.004% by weight) dissolves in 1 liter of water at a temperature of 20°C. However, this amount is sufficient for the breathing of fish living in reservoirs. Oxygen gas is slightly heavier than air: 1 liter of air at a temperature of 0°C and normal pressure weighs 1.29 g, and 1 liter of oxygen weighs 1.43 g.

Oxygen exhibits interesting properties with strong cooling. So, at a temperature –183°С oxygen condenses into a clear mobile liquid pale blue colors.

If liquid oxygen is cooled even further, then at a temperature –218°С oxygen “freezes” in the form blue crystals. If the temperature is gradually increased, then –218°С, solid oxygen will begin to melt, and when –183°С- will boil. Consequently, the boiling and condensation points, as well as the freezing and melting points for substances are the same.

So-called Dewar flasks are used for storing and transporting liquid oxygen.. Dewar flasks are used for storing and transporting liquids whose temperature must be long time remain constant. The Dewar flask is named after its inventor, Scottish physicist and chemist James Dewar.

The simplest Dewar vessel is a household thermos. The structure of the vessel is quite simple: it is a flask placed in a large flask. Air is pumped out from the sealed space between the flasks. Due to the absence of air between the walls of the flasks, the liquid poured into the inner flask for a long time does not cool down or heat up.

Oxygen is a paramagnetic substance, that is, in liquid and solid states it is attracted by a magnet

In nature, there is another simple substance consisting of oxygen atoms. This is ozone. The chemical formula of ozone is O3. Ozone, like oxygen, is a gas under normal conditions. Ozone is formed in the atmosphere during lightning strikes. The characteristic smell of freshness after a thunderstorm is the smell of ozone.

If ozone is obtained in the laboratory and collected significant amount it, then in high concentrations ozone will have a sharp, unpleasant odor. Ozone is obtained in the laboratory using special devices - ozonizers. Ozonator- a glass tube into which a current of oxygen is supplied and an electrical discharge is created. Electric discharge converts oxygen into ozone:

Unlike colorless oxygen, ozone is a gas blue color. The solubility of ozone in water is about 0.5 liters of gas per 1 liter of water, which is significantly more than that of oxygen. Taking into account this property, ozone is used for disinfection drinking water, as it has a detrimental effect on pathogenic microorganisms.

At low temperatures, ozone behaves similarly to oxygen. At a temperature of –112°C it condenses into liquid purple, and at a temperature of –197°C crystallizes in the form of dark purple, almost black crystals

Thus, we can conclude that atoms of the same chemical element can form different simple substances.

The phenomenon of the existence of a chemical element in the form of several simple substances is called allotropy.

Simple substances formed by the same element are called allotropic modifications

Means, oxygen and ozone – allotropic modifications chemical element oxygen. There is evidence that at ultra-low temperatures, in a liquid or solid state, oxygen can exist in the form of O4 and O8 molecules.

Oxygen cycle in nature

The amount of oxygen in the atmosphere is constant. Consequently, the consumed oxygen is constantly replenished with new oxygen.

The most important sources of oxygen in nature are carbon dioxide and water. Oxygen enters the atmosphere mainly as a result of the process of photosynthesis occurring in plants, according to the reaction scheme:

CO2 + H2O → C6H12O6 + O2.

Oxygen can also be formed in upper layers Earth's atmosphere: due to exposure solar radiation, water vapor partially decomposes to form oxygen.

Oxygen is consumed during respiration, fuel combustion, oxidation various substances in living organisms, oxidation inorganic substances contained in nature. A large amount of oxygen is consumed in technological processes, such as steelmaking.

The oxygen cycle in nature can be represented as a diagram:

• Oxygen– element of group VI, main subgroup, 2 periods of the Periodic System D.I. Mendeleev
• The element oxygen forms two allotropic modifications in nature: oxygen O2 and ozone O3
• The phenomenon of the existence of a chemical element in the form of several simple substances is called allotropy
• Simple substances are called allotropic modifications
• Oxygen and ozone have different physical properties
• Oxygen– a colorless gas, odorless, tasteless, practically insoluble in water, at a temperature of –183°C it condenses into a pale blue liquid. At a temperature of –218°C crystallizes in the form of crystals blue
• Ozone– a blue gas with a pungent unpleasant odor. Let's dissolve well in water. At a temperature of –112°С it condenses into a violet liquid, crystallizes in the form of dark purple, almost black crystals, at a temperature of –197°С
• Liquid oxygen, ozone and other gases are stored in Dewar flasks

When cutting metal, it is carried out with a high-temperature gas flame obtained by burning flammable gas or liquid vapor mixed with technically pure oxygen.

Oxygen is the most abundant element on earth, occurring in the form chemical compounds with various substances: in the ground - up to 50% by weight, in combination with hydrogen in water - about 86% by weight and in the air - up to 21% by volume and 23% by weight.

Oxygen at normal conditions(temperature 20°C, pressure 0.1 MPa) is a colorless, non-flammable gas, slightly heavier than air, odorless, but actively supporting combustion. At normal atmospheric pressure and a temperature of 0°C, the mass of 1 m 3 of oxygen is 1.43 kg, and at a temperature of 20°C and normal atmospheric pressure - 1.33 kg.

Oxygen has high chemical activity, forming compounds with all chemical elements except (argon, helium, xenon, krypton and neon). Reactions of the compound with oxygen proceed with the release of large quantity heat, i.e. they are exothermic in nature.

Upon contact of compressed oxygen gas With organic substances, oils, fats, coal dust, flammable plastics, their spontaneous ignition may occur as a result of the release of heat during rapid compression of oxygen, friction and impact of solid particles on metal, as well as electrostatic spark discharge. Therefore, when using oxygen, care must be taken to ensure that it does not come into contact with flammable or combustible substances.

All oxygen equipment, oxygen lines and cylinders must be thoroughly degreased. capable of forming explosive mixtures with flammable gases or liquid flammable vapors over a wide range, which can also lead to explosions if present open fire or even sparks.

The noted features of oxygen should always be kept in mind when using it in gas-flame processing processes.

Atmospheric air is mainly a mechanical mixture of three gases with the following volume content: nitrogen - 78.08%, oxygen - 20.95%, argon - 0.94%, the rest is carbon dioxide, nitrous oxide, etc. Oxygen is obtained by separating air to oxygen and by the method of deep cooling (liquefaction), along with the separation of argon, the use of which is continuously increasing. Nitrogen is used as a shielding gas when welding copper.

Oxygen can be obtained chemically or by electrolysis of water. Chemical methods inefficient and uneconomical. At electrolysis of water DC Oxygen is produced as a by-product in the production of pure hydrogen.

Oxygen is produced in industry from atmospheric air by deep cooling and rectification. In installations for obtaining oxygen and nitrogen from air, the latter is purified from harmful impurities, compressed in a compressor to the corresponding refrigeration cycle pressure of 0.6-20 MPa and cooled in heat exchangers to the liquefaction temperature, the difference in the liquefaction temperatures of oxygen and nitrogen is 13°C, which is sufficient for their complete separation in the liquid phase.

Liquid pure oxygen accumulates in the air separation apparatus, evaporates and collects in a gas holder, from where it is pumped into cylinders by a compressor under a pressure of up to 20 MPa.

Technical oxygen is also transported via pipeline. The pressure of oxygen transported through the pipeline must be agreed upon between the manufacturer and the consumer. Oxygen is delivered to the site in oxygen cylinders, and in liquid form in special vessels with good thermal insulation.

To convert liquid oxygen into gas, gasifiers or pumps with liquid oxygen evaporators are used. At normal atmospheric pressure and a temperature of 20°C, 1 dm 3 of liquid oxygen upon evaporation gives 860 dm 3 of gaseous oxygen. Therefore, it is advisable to deliver oxygen to the welding site in a liquid state, since this reduces the weight of the container by 10 times, which saves metal for the manufacture of cylinders and reduces the cost of transporting and storing cylinders.

For welding and cutting According to -78, technical oxygen is produced in three grades:

• 1st - purity of at least 99.7%
• 2nd - no less than 99.5%
• 3rd - no less than 99.2% by volume

The purity of oxygen has great value for oxygen cutting. The less gas impurities it contains, the higher the cutting speed, cleaner and less consumption oxygen.

Oxygen

OXYGEN-A; m. A chemical element (O), a colorless and odorless gas that is part of the air, necessary for breathing and combustion and forms water in combination with hydrogen.

◊ Shut off oxygen to someone. Create unbearable living and working conditions.

◁ Oxygen, oh, oh. Kth Wednesday. K connections. Kth cutting(gas cutting). Kth welding(gas welding). Kth fasting; some insufficiency (honey.; decreased oxygen content in body tissues; hypoxia).

◊ Oxygen cushion (see cushion).

(lat. Oxygenium), chemical element of group VI periodic table. In free form, it is found in the form of two modifications - O 2 (“ordinary” oxygen) and O 3 (ozone). O 2 - colorless and odorless gas, density 1.42897 g/l, t pl –218.6ºC, t kip –182.96ºC. Chemically the most active (after fluorine) non-metal. It interacts directly with most other elements (hydrogen, halogens, sulfur, many metals, etc.) (oxidation) and, as a rule, releases energy. As the temperature increases, the rate of oxidation increases and combustion may begin. Animals and plants receive the energy necessary for life due to the biological oxidation of various substances with oxygen entering the organisms during respiration. The most common element on Earth; in the form of compounds is about 1/2 of the mass earth's crust; is part of water (88.8% by weight) and many tissues of living organisms (about 70% by weight). Free atmospheric oxygen (20.95% by volume) is formed and preserved through photosynthesis. Oxygen (or air enriched with it) is used in metallurgy, chemical industry, in medicine, oxygen breathing apparatus. Liquid oxygen is a component of rocket fuel.

Encyclopedic Dictionary. 2009 .

See what “oxygen” is in other dictionaries:

- (Oxygenum). A colorless, odorless and tasteless gas. Slightly soluble in water (approximately 1:43). Oxygen inhalation is widely used for various diseases accompanied by hypoxia: with respiratory diseases (pneumonia, pulmonary edema... Dictionary of medicines