Hydrogen physical and chemical properties obtaining application. Physical and chemical properties of hydrogen. Methods for obtaining and isolating

The history of the discovery of hydrogen

If it is the most abundant chemical element on Earth, then hydrogen is the most abundant element in the entire universe. Our (and other stars) are about half hydrogen, and as for interstellar gas, it is 90% hydrogen atoms. This is not a small place chemical element occupies on Earth, because together with oxygen it is part of water, and its very name "hydrogen" comes from two ancient Greek words: "water" and "give birth." In addition to water, hydrogen is present in most organic substances and cells, without it, as well as without oxygen, Life itself would be unthinkable.

The history of the discovery of hydrogen

The first scientist to notice hydrogen was the great alchemist and healer of the Middle Ages, Theophrastus Paracelsus. In his alchemical experiments, in the hope of finding the "philosopher's stone" mixing with acids Paracelsus received a previously unknown combustible gas. True, it was not possible to separate this gas from the air.

Only a century and a half after Paracelsus, the French chemist Lemery managed to separate hydrogen from air and prove its flammability. True, Lemery did not understand that the gas he received was pure hydrogen. In parallel, the Russian scientist Lomonosov was engaged in similar chemical experiments, but the real breakthrough in the study of hydrogen was made by the English chemist Henry Cavendish, who is rightfully considered the discoverer of hydrogen.

In 1766, Cavendish managed to obtain pure hydrogen, which he called "combustible air." After another 20 years, the talented French chemist Antoine Lavoisier was able to synthesize water and extract from it this very "combustible air" - hydrogen. And by the way, it was Lavoisier who offered hydrogen its name - "Hydrogenium", aka "hydrogen".

Antoine Lavoisier with his wife, who helped him conduct chemical experiments, including the synthesis of hydrogen.

The arrangement of chemical elements in the periodic system of Mendeleev is based on their atomic weight, calculated relative to the atomic weight of hydrogen. That is, in other words, hydrogen and its atomic weight is the cornerstone of the periodic table, the fulcrum on the basis of which the great chemist created his system. Therefore, it is not surprising that hydrogen occupies the honorable first place in the periodic table.

In addition, hydrogen has the following characteristics:

• The atomic mass of hydrogen is 1.00795.
• Hydrogen has three isotopes, each of which has individual properties.
• Hydrogen is a light element with low density.
• Hydrogen has reducing and oxidizing properties.
• Entering with metals, hydrogen takes their electron and becomes an oxidizing agent. These compounds are called hydrates.

Hydrogen is a gas, its molecule consists of two atoms.

This is how a hydrogen molecule looks schematically.

Molecular hydrogen formed from such diatomic molecules explodes when a burning match is brought up. The hydrogen molecule in the explosion breaks down into atoms, which turn into helium nuclei. This is exactly how it happens on the Sun and other stars - due to the constant disintegration of hydrogen molecules, our star burns and warms us with its heat.

Physical properties of hydrogen

Hydrogen has the following physical properties:

• The boiling point of hydrogen is 252.76 ° C;
• And at a temperature of 259.14 ° C, it already begins to melt.
• Hydrogen dissolves slightly in water.
• Pure hydrogen is a highly dangerous explosive and flammable substance.
• Hydrogen is 14.5 times lighter than air.

Chemical properties of hydrogen

Since hydrogen can be in different situations both an oxidizing agent and a reducing agent, it is used to carry out reactions and syntheses.

The oxidizing properties of hydrogen interact with active (usually alkali and alkaline earth) metals, the result of these interactions is the formation of hydrides - salt-like compounds. However, hydrides are also formed during the reactions of hydrogen with low-activity metals.

The reducing properties of hydrogen have the ability to reduce metals to simple substances from their oxides, in industry this is called hydrogenothermy.

How to get hydrogen?

Among the industrial means for producing hydrogen are:

• coal gasification,
• steam reforming of methane,
• electrolysis.

In the laboratory, hydrogen can be obtained:

• during hydrolysis of metal hydrides,
• when reacting with water of alkali and alkaline earth metals,
• when diluted acids interact with active metals.

Application of hydrogen

Since hydrogen is 14 times lighter than air, in the old days it was stuffed with balloons and airships. But after a series of disasters that occurred with airships, the designers had to look for a replacement for hydrogen (recall that pure hydrogen is an explosive substance, and the slightest spark was enough to cause an explosion).

The explosion of the Hindenburg airship in 1937, the cause of the explosion was the ignition of hydrogen (due to a short circuit), on which this huge airship flew.

Therefore, for the likes of aircraft instead of hydrogen, they began to use helium, which is also lighter than air, the production of helium is more laborious, but it is not as explosive as hydrogen.

Also, hydrogen is used for cleaning different types fuels, especially based on oil and petroleum products.

Hydrogen video

And in conclusion, an educational video on the topic of our article.

Hydrogen is a simple substance H 2 (dihydrogen, diprotium, light hydrogen).

Brief characteristic of hydrogen:

• Non-metal.
• A colorless gas that is difficult to liquefy.
• Poorly soluble in water.
• It dissolves better in organic solvents.
• Chemisorbed by metals: iron, nickel, platinum, palladium.
• Strong reducing agent.
• Interacts (with high temperatures) with non-metals, metals, metal oxides.
• Atomic hydrogen H 0, obtained by thermal decomposition of H 2, has the highest reducing ability.
• Isotopes of hydrogen:
  • 1 H - protium
  • 2 H - deuterium (D)
  • 3 H - tritium (T)
• Relative molecular weight = 2.016
• Relative density of solid hydrogen (t = -260 ° C) = 0.08667
• Relative density of liquid hydrogen (t = -253 ° C) = 0.07108
• Overpressure (n.o.) = 0.08988 g / l
• melting point = -259.19 ° C
• boiling point = -252.87 ° C
• Volumetric coefficient of solubility of hydrogen:
  • (t = 0 ° C) = 2.15;
  • (t = 20 ° C) = 1.82;
  • (t = 60 ° C) = 1.60;

1. Thermal decomposition of hydrogen(t = 2000-3500 ° C):
H 2 ↔ 2H 0

2. Interaction of hydrogen with non-metals:

• H 2 + F 2 = 2HF (t = -250 .. + 20 ° C)
• H 2 + Cl 2 = 2HCl (on combustion or in the light at room temperature):
  • Cl 2 = 2Cl 0
  • Cl 0 + H 2 = HCl + H 0
  • H 0 + Cl 2 = HCl + Cl 0
• H 2 + Br 2 = 2HBr (t = 350-500 ° C, platinum catalyst)
• H 2 + I 2 = 2HI (t = 350-500 ° C, platinum catalyst)
• H 2 + O 2 = 2H 2 O:
  • H 2 + O 2 = 2OH 0
  • OH 0 + H 2 = H 2 O + H 0
  • H 0 + O 2 = OH 0 + O 0
  • O 0 + H 2 = OH 0 + H 0
• H 2 + S = H 2 S (t = 150..200 ° C)
• 3H 2 + N 2 = 2NH 3 (t = 500 ° C, iron catalyst)
• 2H 2 + C (coke) = CH 4 (t = 600 ° C, platinum catalyst)
• H 2 + 2C (coke) = C 2 H 2 (t = 1500..2000 ° C)
• H 2 + 2C (coke) + N 2 = 2HCN (t more than 1800 ° C)

3. Interaction of hydrogen with complex substances :

• 4H 2 + (Fe II Fe 2 III) O 4 = 3Fe + 4H 2 O (t more than 570 ° C)
• H 2 + Ag 2 SO 4 = 2Ag + H 2 SO 4 (t more than 200 ° C)
• 4H 2 + 2Na 2 SO 4 = Na 2 S + 4H 2 O (t = 550-600 ° C, catalyst Fe 2 O 3)
• 3H 2 + 2BCl 3 = 2B + 6HCl (t = 800-1200 ° C)
• H 2 + 2EuCl 3 = 2EuCl 2 + 2HCl (t = 270 ° C)
• 4H 2 + CO 2 = CH 4 + 2H 2 O (t = 200 ° C, catalyst CuO 2)
• H 2 + CaC 2 = Ca + C 2 H 2 (t more than 2200 ° C)
• H 2 + BaH 2 = Ba (H 2) 2 (t up to 0 ° C, solution)

4. Participation of hydrogen in redox reactions:

• 2H 0 (Zn, dil. HCl) + KNO 3 = KNO 2 + H 2 O
• 8H 0 (Al, conc. KOH) + KNO 3 = NH 3 + KOH + 2H 2 O
• 2H 0 (Zn, dil. HCl) + EuCl 3 = 2EuCl 2 + 2HCl
• 2H 0 (Al) + NaOH (conc.) + Ag 2 S = 2Ag ↓ + H 2 O + NaHS
• 2H 0 (Zn, dil. H 2 SO 4) + C 2 N 2 = 2HCN

Hydrogen compounds

D 2 - diduterium:

• Heavy hydrogen.
• A colorless gas that is difficult to liquefy.
• Dideuterium is contained in natural hydrogen 0.012-0.016% (by weight).
• In a gas mixture of dideuterium and protium, isotope exchange occurs at high temperatures.
• Poorly soluble in ordinary and heavy water.
• With ordinary water, isotopic exchange is negligible.
• Chemical properties are similar to light hydrogen, but dideuterium is less reactive.
• Relative molecular weight = 4.028
• Relative density of liquid dideuterium (t = -253 ° C) = 0.17
• melting point = -254.5 ° C
• boiling point = -249.49 ° C

T 2 - dithritium:

• Superheavy hydrogen.
• Colorless radioactive gas.
• The half-life is 12.34 years.
• In nature, dithritium is formed as a result of the bombardment of 14 N nuclei with cosmic radiation by neutrons; traces of dithritium are found in natural waters.
• Ditritium is obtained in a nuclear reactor by bombarding lithium with slow neutrons.
• Relative molecular weight = 6.032
• melting point = -252.52 ° C
• boiling point = -248.12 ° C

HD - deuterium hydrogen:

• Colorless gas.
• Does not dissolve in water.
• Chemical properties are similar to H 2.
• Relative molecular weight = 3.022
• Relative density of solid hydrogen deuteride (t = -257 ° C) = 0.146
• Overpressure (n.a.) = 0.135 g / L
• melting point = -256.5 ° C
• boiling point = -251.02 ° C

Hydrogen oxides

H 2 O - water:

• Colorless liquid.
• According to the isotopic composition of oxygen, water consists of H 2 16 O with admixtures of H 2 18 O and H 2 17 O
• According to the isotopic composition of hydrogen, water consists of 1 H 2 O with an admixture of HDO.
• Liquid water undergoes protolysis (H 3 O + and OH -):
  • H 3 O + (oxonium cation) is the most strong acid in aqueous solution;
  • OH - (hydroxide ion) is the strongest base in aqueous solution;
  • Water is the weakest conjugate protolith.
• With many substances, water forms crystalline hydrates.
• Water is a chemically active substance.
• Water is a versatile liquid solvent for inorganic compounds.
• Relative molecular weight of water = 18.02
• Relative density of solid water (ice) (t = 0 ° C) = 0.917
• Relative density of liquid water:
  • (t = 0 ° C) = 0.999841
  • (t = 20 ° C) = 0.998203
  • (t = 25 ° C) = 0.997044
  • (t = 50 ° C) = 0.97180
  • (t = 100 ° C) = 0.95835
• density (n.o.) = 0.8652 g / l
• melting point = 0 ° C
• boiling point = 100 ° C
• Ionic product of water (25 ° C) = 1.008 10 -14

1. Thermal decomposition of water:
2H 2 O ↔ 2H 2 + O 2 (above 1000 ° C)

D 2 O - deuterium oxide:

• Heavy water.
• Colorless hygroscopic liquid.
• The viscosity is higher than that of water.
• Mixes up with ordinary water in unlimited quantities.
• Semi-heavy water HDO is formed during isotope exchange.
• The dissolving power is lower than that of ordinary water.
• The chemical properties of deuterium oxide are similar to those of water, but all reactions are slower.
• Heavy water is present in natural water (mass ratio to ordinary water 1: 5500).
• Deuterium oxide is obtained by repeated electrolysis of natural water, in which heavy water accumulates in the remainder of the electrolyte.
• Relative molecular weight of heavy water = 20.03
• Relative density of liquid heavy water (t = 11.6 ° C) = 1.1071
• Relative density of liquid heavy water (t = 25 ° C) = 1.1042
• melting point = 3.813 ° C
• boiling point = 101.43 ° C

T 2 O - tritium oxide:

• Super heavy water.
• Colorless liquid.
• The viscosity is higher and the dissolving power is lower than that of ordinary and heavy water.
• Mixes up with regular and heavy water in unlimited quantities.
• Isotopic exchange with ordinary and heavy water leads to the formation of HTO, DTO.
• The chemical properties of superheavy water are similar to those of water, but all reactions proceed even more slowly than in heavy water.
• Traces of tritium oxide are found in natural water and the atmosphere.
• Superheavy water is obtained by passing tritium over red-hot copper oxide CuO.
• Superheavy Water Relative Molecular Weight = 22.03
• melting point = 4.5 ° C

Hydrogen is the very first element in the Periodic Table of Chemical Elements, has an atomic number of 1 and a relative atomic mass of 1.0079. What are the physical properties of hydrogen?

Physical properties of hydrogen

Translated from Latin, hydrogen means "giving birth to water." Back in 1766, the English scientist G. Cavendish collected "combustible air" released by the action of acids on metals and began to study its properties. In 1787 A. Lavoisier defined this "combustible air" as a new chemical element that is part of water.

Rice. 1. A. Lavoisier.

Hydrogen has 2 stable isotopes - protium and deuterium, as well as radioactive - tritium, the amount of which on our planet is very small.

Hydrogen is the most abundant element in space. The sun and most stars have hydrogen as their primary element. Also, this gas is part of water, oil, natural gas. The total hydrogen content on Earth is 1%.

Rice. 2. Formula of hydrogen.

The atom of this substance includes a nucleus and one electron. When an electron is lost from hydrogen, it forms a positively charged ion, that is, it exhibits metallic properties. But also a hydrogen atom is capable of not only losing but also attaching an electron. In this it is very similar to halogens. Therefore, hydrogen in the Periodic Table belongs to both I and VII groups. The non-metallic properties of hydrogen are more pronounced in it.

A hydrogen molecule consists of two atoms linked by a covalent bond

Under normal conditions, hydrogen is a colorless gaseous element that is odorless and tasteless. It is 14 times lighter than air, and its boiling point is -252.8 degrees Celsius.

Table "Physical properties of hydrogen"

In addition to its physical properties, hydrogen also possesses a number of chemical properties. When heated or under the action of catalysts, hydrogen reacts with metals and non-metals, sulfur, selenium, tellurium, and can also reduce oxides of many metals.

Hydrogen production

From industrial methods of producing hydrogen (except for electrolysis aqueous solutions salts) the following should be noted:

• passing water vapor through hot coal at a temperature of 1000 degrees:

• conversion of methane with water vapor at a temperature of 900 degrees:

CH 4 + 2H 2 O = CO 2 + 4H 2

Hydrogen was discovered in the second half of the 18th century by the English scientist in the field of physics and chemistry G. Cavendish. He managed to isolate a substance in a pure state, began to study it and described its properties.

This is the story of the discovery of hydrogen. In the course of experiments, the researcher determined that it is a combustible gas, the combustion of which in air gives water. This led to the determination of the qualitative composition of the water.

What is hydrogen

The French chemist A. Lavoisier first announced hydrogen as a simple substance in 1784, since he determined that its molecule contains atoms of the same type.

The name of the chemical element in Latin sounds like hydrogenium (read "hydrogenium"), which means "giving birth to water". The name refers to the combustion reaction that produces water.

Characterization of hydrogen

N. Mendeleev assigned the designation hydrogen to this chemical element the first serial number, placing it in the main subgroup of the first group and the first period, and conditionally in the main subgroup of the seventh group.

The atomic weight (atomic mass) of hydrogen is 1.00797. The molecular weight of H 2 is 2 amu. e. Molar mass numerically equal to it.

It is represented by three isotopes with a special name: the most common protium (H), heavy deuterium (D), radioactive tritium (T).

This is the first element that can be completely separated into isotopes. in a simple way... It is based on the high difference in the masses of the isotopes. The process was first carried out in 1933. This is explained by the fact that only in 1932 an isotope with a mass of 2 was identified.

Physical properties

Under normal conditions, a simple substance hydrogen in the form of diatomic molecules is a gas, colorless, tasteless and odorless. Let's slightly dissolve in water and other solvents.

The crystallization temperature is 259.2 o C, the boiling point is 252.8 o C. The diameter of hydrogen molecules is so small that they have the ability to slowly diffuse through a number of materials (rubber, glass, metals). This property is used when it is required to purify hydrogen from gaseous impurities. Under n. at. hydrogen has a density equal to 0.09 kg / m3.

Is it possible to convert hydrogen into a metal by analogy with the elements located in the first group? Scientists have found that hydrogen, under conditions when the pressure approaches 2 million atmospheres, begins to absorb infrared rays, which indicates the polarization of the molecules of the substance. Perhaps at even higher pressures, hydrogen will become a metal.

It is interesting: there is an assumption that on the giant planets, Jupiter and Saturn, hydrogen is in the form of metal. It is assumed that metallic solid hydrogen is also present in the composition of the earth's core, due to the ultra-high pressure created by the earth's mantle.

Chemical properties

Both simple and complex substances enter into chemical interaction with hydrogen. But the low activity of hydrogen must be increased by creating appropriate conditions - by raising the temperature, using catalysts, etc.

When heated, such simple substances as oxygen (O 2), chlorine (Cl 2), nitrogen (N 2), sulfur (S) react with hydrogen.

If you ignite pure hydrogen at the end of the gas outlet tube in the air, it will burn evenly, but barely noticeable. If the gas outlet tube is placed in an atmosphere of pure oxygen, then combustion will continue with the formation of water droplets on the walls of the vessel, as a result of the reaction:

Combustion of water is accompanied by the release of a large amount of heat. It is an exothermic compound reaction in which hydrogen is oxidized by oxygen to form the oxide H 2 O. It is also a redox reaction in which hydrogen is oxidized and oxygen is reduced.

The reaction with Cl 2 proceeds in a similar way with the formation of hydrogen chloride.

The interaction of nitrogen with hydrogen requires a high temperature and increased pressure, as well as the presence of a catalyst. The result is ammonia.

As a result of reaction with sulfur, hydrogen sulfide is formed, the recognition of which is facilitated by the characteristic smell of rotten eggs.

The oxidation state of hydrogen in these reactions is +1, and in the hydrides described below, it is 1.

When reacting with some metals, hydrides are formed, for example, sodium hydride - NaH. Some of these complex compounds are used as fuel for rockets and also in thermonuclear power.

Hydrogen also reacts with complex substances. For example, with copper (II) oxide, the formula CuO. To carry out the reaction, copper hydrogen is passed over heated powdered copper (II) oxide. During the interaction, the reagent changes its color and becomes reddish-brown, and droplets of water settle on the cold walls of the test tube.

During the reaction, hydrogen is oxidized to form water, and copper is reduced from oxide to a simple substance (Cu).

Areas of use

Hydrogen has great importance for humans and is used in a variety of areas:

1. In the chemical industry, these are raw materials, in other industries, it is fuel. Petrochemical and oil refining enterprises cannot do without hydrogen.
2. In the power industry, this simple substance acts as a cooling agent.
3. In ferrous and nonferrous metallurgy, hydrogen is assigned the role of a reducing agent.
4. With this, an inert environment is created when packaging products.
5. Pharmaceutical industry - uses hydrogen as a reagent in the production of hydrogen peroxide.
6. Meteorological probes are filled with this light gas.
7. This element is also known as a fuel reducer for rocket engines.

Scientists unanimously prophesy the palm in the energy sector for hydrogen fuel.

Getting in industry

In industry, hydrogen is obtained by electrolysis, which is subjected to chlorides or hydroxides of alkali metals dissolved in water. It is also possible to obtain hydrogen in this way directly from water.

Used for this purpose is the conversion of coke or methane with steam. Decomposition of methane at elevated temperatures also produces hydrogen. Liquefaction of coke oven gas by the fractional method is also used for industrial production of hydrogen.

Getting in the laboratory

The laboratory uses the Kipp apparatus to produce hydrogen.

The reagents are saline or sulphuric acid and zinc. The reaction produces hydrogen.

Finding hydrogen in nature

Hydrogen is the most common element in the universe. The bulk of stars, including the Sun, and other cosmic bodies is hydrogen.

V earth crust its only 0.15%. It is present in many minerals, in all organic matter and also in water covering 3/4 of the surface of our planet.

Traces of pure hydrogen can be found in the upper atmosphere. It is also found in a number of combustible natural gases.

Gaseous hydrogen is the least dense and liquid hydrogen is the most dense substance on our planet. With the help of hydrogen, you can change the timbre of the voice, if you inhale it, and on the exhale speak.

At the heart of the action is the most powerful hydrogen bomb lies the splitting of the lightest atom.

Structure and physical properties of hydrogen Hydrogen is a diatomic gas H2. It is colorless and odorless. It is the lightest gas. Due to this property, it was used in balloons, airships and similar devices, however, the widespread use of hydrogen for these purposes is hindered by its explosiveness in a mixture with air.

Hydrogen molecules are non-polar and very small, so there is little interaction between them. In this regard, it has very low melting (-259 ° C) and boiling points (-253 ° C). Hydrogen is practically insoluble in water.

Hydrogen has 3 isotopes: ordinary 1H, deuterium 2H or D, and radioactive tritium 3H or T. Heavy isotopes of hydrogen are unique in that they are 2 or even 3 times heavier than ordinary hydrogen! That is why replacing ordinary hydrogen with deuterium or tritium noticeably affects the properties of the substance (for example, the boiling points of ordinary hydrogen H2 and deuterium D2 differ by 3.2 degrees). Interaction of hydrogen with simple substances Hydrogen is a non-metal of medium electronegativity. Therefore, both oxidizing and reducing properties are inherent in it.

The oxidizing properties of hydrogen are manifested in reactions with typical metals - elements of the main subgroups of groups I-II of the periodic table. The most active metals (alkali and alkaline earth) when heated with hydrogen give hydrides - solid salt-like substances containing a hydride ion H- in the crystal lattice. 2Na + H2 = 2NaH ; Ca + H2 = CaH2 The reducing properties of hydrogen appear in reactions with more typical non-metals than hydrogen: 1) Interaction with halogens H2 + F2 = 2HF

The interaction with fluorine analogs - chlorine, bromine, iodine - proceeds in a similar way. As the activity of the halogen decreases, the intensity of the reaction decreases. The reaction with fluorine occurs explosively under normal conditions, illumination or heating is required for the reaction with chlorine, and the reaction with iodine proceeds only with strong heating and is reversible. 2) Interaction with oxygen 2H2 + O2 = 2H2O The reaction proceeds with a large release of heat, sometimes with an explosion. 3) Interaction with sulfur H2 + S = H2S Sulfur is a much less active non-metal than oxygen, and the interaction with hydrogen proceeds calmly. 4) Interaction with nitrogen 3H2 + N2↔ 2NH3 The reaction is reversible, proceeds to a noticeable extent only in the presence of a catalyst, under heating and under pressure. The product is called ammonia. 5) Interaction with carbonС + 2Н2↔ СН4 The reaction takes place in an electric arc or at very high temperatures. Other hydrocarbons are also formed as by-products. 3. Interaction of hydrogen with complex substances Hydrogen also exhibits reducing properties in reactions with complex substances: 1) Reduction of metal oxides located in the electrochemical series of voltages to the right of aluminum, as well as nonmetal oxides: Fe2O3 + 2H2 2Fe + 3H2O ; CuO + H2 Cu + H2O Hydrogen is used as a reducing agent for the extraction of metals from oxide ores. Reactions proceed when heated. 2) Attachment to organic unsaturated substances; С2Н4 + Н2 (t; p) → С2Н6 The reactions proceed in the presence of a catalyst and under pressure. We will not touch on other hydrogen reactions for now. 4. Obtaining hydrogen In industry, hydrogen is produced by processing hydrocarbon raw materials - natural and associated gas, coke, etc. Laboratory methods for producing hydrogen:

1) Interaction of metals standing in the electrochemical series of metal voltages to the left of hydrogen with acids. Li K Ba Sr Ca Na Mg Al Mn Zn Cr Fe Cd Co Ni Sn Pb (H2) Cu Hg Ag Pt Mg + 2HCl = MgCl2 + H22) Interaction of metals in the electrochemical series of metal voltages to the left of magnesium with cold water. This also produces alkali.

2Na + 2H2O = 2NaOH + H2 A metal located in the electrochemical series of metal voltages to the left of manganese is capable of displacing hydrogen from water at certain conditions(magnesium - from hot water, aluminum - provided that the oxide film is removed from the surface).

Mg + 2H2O Mg (OH) 2 + H2

A metal located in the electrochemical series of metal voltages to the left of cobalt is capable of displacing hydrogen from water vapor. This also produces an oxide.

3Fe + 4H2O vapor Fe3O4 + 4H23) Interaction of metals, hydroxides of which are amphoteric, with alkali solutions.

Metals, hydroxides of which are amphoteric, displace hydrogen from alkali solutions. You need to know 2 such metals - aluminum and zinc:

2Al + 2NaOH + 6H2O = 2Na + + 3H2

Zn + 2KOH + 2H2O = K2 + H2

In this case, complex salts are formed - hydroxoaluminates and hydroxyzincates.

All the methods listed so far are based on the same process - the oxidation of a metal with a hydrogen atom in the +1 oxidation state:

М0 + nН + = Мn + + n / 2 H2

4) Interaction of hydrides of active metals with water:

CaH2 + 2H2O = Ca (OH) 2 + 2H2

This process is based on the interaction of hydrogen in the -1 oxidation state with hydrogen in the +1 oxidation state:

5) Electrolysis of aqueous solutions of alkalis, acids, some salts:

2H2O 2H2 + O2

5. Hydrogen compounds In this table, on the left, a light shadow highlights the cells of elements that form ionic compounds with hydrogen - hydrides. These substances contain a hydride ion H-. They are solid, colorless, salt-like substances and react with water to produce hydrogen.

Elements of the main subgroups IV-VII groups form compounds of molecular structure with hydrogen. They are sometimes also called hydrides, but this is incorrect. They do not contain a hydride ion, they consist of molecules. As a rule, the simplest hydrogen compounds of these elements are colorless gases. Exceptions are water, which is a liquid, and hydrogen fluoride, which is gaseous at room temperature, but liquid under normal conditions.

Dark cells mark elements that form compounds with hydrogen, exhibiting acidic properties.

Dark cells with a cross indicate elements that form compounds with hydrogen and exhibit basic properties.

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29). general characteristics properties of the elements of the main subgroup 7gr. Chlorine. Lore properties. Hydrochloric acid. The subgroup of halogens includes fluorine, chlorine, bromine, iodine and astatine (astatine is a radioactive element, little studied). These are p-elements of group VII periodic system D.I. Mendeleev. At the external energy level, their atoms each have 7 electrons ns2np5. This explains the commonality of their properties.

They easily attach one electron at a time, exhibiting an oxidation state of -1. Halogens have this oxidation state in compounds with hydrogen and metals.

However, halogen atoms, in addition to fluorine, can also exhibit positive oxidation states: +1, +3, +5, +7. Possible values ​​of the oxidation degrees are explained by the electronic structure, which for fluorine atoms can be represented by the diagram

Being the most electronegative element, fluorine can only accept one electron per 2p sublevel. It has one unpaired electron, so fluorine is only monovalent and the oxidation state is always -1.

Electronic structure the chlorine atom is expressed by the scheme In the chlorine atom, one unpaired electron on the 3p-sublevel and in the usual (unexcited) state, chlorine is univalent. But since chlorine is in the third period, it has five more orbitals of the 3d-sublevel, in which 10 electrons can be accommodated.

Fluorine has no free orbitals, which means that at chemical reactions there is no separation of paired electrons in the atom. Therefore, when considering the properties of halogens, it is always necessary to take into account the characteristics of fluorine and compounds.

Aqueous solutions of hydrogen compounds of halogens are acids: HF - hydrofluoric (hydrofluoric), HCl - hydrochloric (hydrochloric), HBr - hydrogen bromide, HI - hydriodic.

Chlorine (Latin Chlorum), Cl, chemical element of group VII of Mendeleev's periodic system, atomic number 17, atomic mass 35.453; belongs to the halogen family. Under normal conditions (0 ° C, 0.1 MN / m2, or 1 kgf / cm2) yellow-green gas with a sharp irritating odor. Natural Chlorine consists of two stable isotopes: 35Cl (75.77%) and 37Cl (24.23%).

Chlorine chemical properties. The outer electronic configuration of the Cl atom is 3s23p5. In accordance with this, Chlorine in compounds exhibits oxidation states -1, + 1, +3, +4, +5, +6 and +7. The covalent radius of the atom is 0.99 Å, the ionic radius of Cl is 1.82 Å, the affinity of the Chlorine atom to the electron is 3.65 eV, and the ionization energy is 12.97 eV.

Chemically, chlorine is very active, it combines directly with almost all metals (with some only in the presence of moisture or when heated) and with non-metals (except carbon, nitrogen, oxygen, inert gases), forming the corresponding chlorides, reacts with many compounds, replaces hydrogen in saturated hydrocarbons and joins unsaturated compounds. Chlorine displaces bromine and iodine from their compounds with hydrogen and metals; it is displaced by fluorine from chlorine compounds with these elements. Alkali metals in the presence of traces of moisture, they interact with Chlorine with ignition, most metals react with dry Chlorine only when heated Phosphorus ignites in an atmosphere of Chlorine, forming РCl3, and with further chlorination - РСl5; sulfur with Chlorine when heated gives S2Cl2, SCl2 and other SnClm. Arsenic, antimony, bismuth, strontium, tellurium interact vigorously with Chlorine. A mixture of Chlorine with hydrogen burns with a colorless or yellow-green flame with the formation of hydrogen chloride (this is a chain reaction). Chlorine forms oxides with oxygen: Cl2O, ClO2, Cl2O6, Cl2O7, Cl2O8, as well as hypochlorites (hypochlorous acid salts), chlorites, chlorates and perchlorates. Everything oxygen compounds chlorine form explosive mixtures with easily oxidizable substances. Chlorine in water is hydrolyzed, forming hypochlorous and hydrochloric acids: Cl2 + Н2О = НClО + НCl. When chlorinating aqueous solutions of alkalis in cold conditions, hypochlorites and chlorides are formed: 2NaOH + Cl2 = NaClO + NaCl + H2O, and when heated, chlorates. Chlorinating dry calcium hydroxide produces bleach. When ammonia interacts with Chlorine, nitrogen trichloride is formed. In the chlorination of organic compounds, Chlorine either replaces hydrogen or binds at multiple bonds, forming various chlorine-containing organic compounds... Chlorine forms interhalogen compounds with other halogens. Fluorides ClF, ClF3, ClF3 are very reactive; for example, glass wool ignites spontaneously in a ClF3 atmosphere. Known compounds of chlorine with oxygen and fluorine - Chlorine oxyfluorides: ClO3F, ClO2F3, ClOF, ClOF3 and fluorine perchlorate FClO4. Hydrochloric acid (hydrochloric acid, hydrochloric acid, hydrogen chloride) - HCl, a solution of hydrogen chloride in water; strong monobasic acid. Colorless (technical hydrochloric acid is yellowish due to impurities of Fe, Cl2, etc.), "fuming" in the air, caustic liquid. The maximum concentration at 20 ° C is 38% by weight. Salts of hydrochloric acid are called chlorides.

Interaction with strong oxidants (potassium permanganate, manganese dioxide) with the release of chlorine gas:

Interaction with ammonia with the formation of thick white smoke, consisting of the smallest crystals of ammonium chloride:

A qualitative reaction to hydrochloric acid and its salt is its interaction with silver nitrate, in which a ferrous precipitate of silver chloride is formed, insoluble in nitric acid:

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