Physical properties of hydrogen. Properties and applications of hydrogen. Chemical properties of hydrogen: features and application Does hydrogen react with water

Hydrogen is a gas; it is in first place in the Periodic Table. The name of this element, widespread in nature, is translated from Latin as “generating water.” So what physical and chemical properties of hydrogen do we know?

Hydrogen: general information

Under normal conditions, hydrogen has no taste, no smell, no color.

Rice. 1. Formula of hydrogen.

Since an atom has one electronic energy level, which can contain a maximum of two electrons, then for a stable state the atom can either accept one electron (oxidation state -1) or give up one electron (oxidation state +1), exhibiting a constant valence I This is why the symbol for the element hydrogen is placed not only in group IA (the main subgroup of group I) together with the alkali metals, but also in group VIIA (the main subgroup of group VII) together with the halogens. Halogen atoms also lack one electron to fill the outer level, and they, like hydrogen, are nonmetals. Hydrogen exhibits a positive oxidation state in compounds where it is associated with more electronegative nonmetal elements, and a negative oxidation state in compounds with metals.

Rice. 2. The location of hydrogen in the periodic table.

Hydrogen has three isotopes, each of which has its own name: protium, deuterium, tritium. The amount of the latter on Earth is negligible.

Chemical properties of hydrogen

In the simple substance H2, the bond between the atoms is strong (bond energy 436 kJ/mol), therefore the activity of molecular hydrogen is low. Under normal conditions, it reacts only with very reactive metals, and the only non-metal with which hydrogen reacts is fluorine:

F 2 +H 2 =2HF (hydrogen fluoride)

Hydrogen reacts with other simple (metals and non-metals) and complex (oxides, unspecified organic compounds) substances either upon irradiation and increased temperature, or in the presence of a catalyst.

Hydrogen burns in oxygen, releasing a significant amount of heat:

2H 2 +O 2 =2H 2 O

A mixture of hydrogen and oxygen (2 volumes of hydrogen and 1 volume of oxygen) explodes violently when ignited and is therefore called detonating gas. When working with hydrogen, safety regulations must be followed.

Rice. 3. Explosive gas.

In the presence of catalysts, the gas can react with nitrogen:

3H 2 +N 2 =2NH 3

– this reaction at elevated temperatures and pressures produces ammonia in industry.

At high temperatures, hydrogen is able to react with sulfur, selenium, and tellurium. and when interacting with alkali and alkaline earth metals, the formation of hydrides occurs: 4.3. Total ratings received: 152.

DEFINITION

Hydrogen– the first element of the Periodic Table of Chemical Elements D.I. Mendeleev. Symbol - N.

Atomic mass – 1 amu. The hydrogen molecule is diatomic – H2.

The electronic configuration of the hydrogen atom is 1s 1. Hydrogen belongs to the s-element family. In its compounds it exhibits oxidation states -1, 0, +1. Natural hydrogen consists of two stable isotopes - protium 1H (99.98%) and deuterium 2H (D) (0.015%) - and the radioactive isotope tritium 3H (T) (trace amounts, half-life - 12.5 years) .

Chemical properties of hydrogen

Under normal conditions, molecular hydrogen exhibits relatively low reactivity, which is explained by the high strength of bonds in the molecule. When heated, it interacts with almost all simple substances formed by elements of the main subgroups (except for noble gases, B, Si, P, Al). In chemical reactions it can act both as a reducing agent (more often) and an oxidizing agent (less often).

Hydrogen exhibits properties of the reducing agent(H 2 0 -2e → 2H +) in the following reactions:

1. Reactions of interaction with simple substances - non-metals. Hydrogen reacts with halogens, moreover, the reaction of interaction with fluorine under normal conditions, in the dark, with an explosion, with chlorine - under illumination (or UV irradiation) according to a chain mechanism, with bromine and iodine only when heated; oxygen(a mixture of oxygen and hydrogen in a volume ratio of 2:1 is called “explosive gas”), gray, nitrogen And carbon:

H 2 + Hal 2 = 2HHal;

2H 2 + O 2 = 2H 2 O + Q (t);

H 2 + S = H 2 S (t = 150 – 300C);

3H 2 + N 2 ↔ 2NH 3 (t = 500C, p, kat = Fe, Pt);

2H 2 + C ↔ CH 4 (t, p, kat).

2. Reactions of interaction with complex substances. Hydrogen reacts with oxides of low-active metals, and it is capable of reducing only metals that are in the activity series to the right of zinc:

CuO + H 2 = Cu + H 2 O (t);

Fe 2 O 3 + 3H 2 = 2Fe + 3H 2 O (t);

WO 3 + 3H 2 = W + 3H 2 O (t).

Hydrogen reacts with non-metal oxides:

H 2 + CO 2 ↔ CO + H 2 O (t);

2H 2 + CO ↔ CH 3 OH (t = 300C, p = 250 – 300 atm., kat = ZnO, Cr 2 O 3).

Hydrogen enters into hydrogenation reactions with organic compounds of the class of cycloalkanes, alkenes, arenes, aldehydes and ketones, etc. All these reactions are carried out with heating, under pressure, using platinum or nickel as catalysts:

CH 2 = CH 2 + H 2 ↔ CH 3 -CH 3 ;

C 6 H 6 + 3H 2 ↔ C 6 H 12 ;

C 3 H 6 + H 2 ↔ C 3 H 8;

CH 3 CHO + H 2 ↔ CH 3 -CH 2 -OH;

CH 3 -CO-CH 3 + H 2 ↔ CH 3 -CH(OH)-CH 3 .

Hydrogen as an oxidizing agent(H 2 +2e → 2H -) appears in reactions with alkali and alkaline earth metals. In this case, hydrides are formed - crystalline ionic compounds in which hydrogen exhibits an oxidation state of -1.

2Na +H 2 ↔ 2NaH (t, p).

Ca + H 2 ↔ CaH 2 (t, p).

Physical properties of hydrogen

Hydrogen is a light, colorless, odorless gas, density at ambient conditions. – 0.09 g/l, 14.5 times lighter than air, t boil = -252.8C, t pl = - 259.2C. Hydrogen is poorly soluble in water and organic solvents; it is highly soluble in some metals: nickel, palladium, platinum.

According to modern cosmochemistry, hydrogen is the most common element in the Universe. The main form of existence of hydrogen in outer space is individual atoms. Hydrogen is the 9th most abundant element on Earth among all elements. The main amount of hydrogen on Earth is in a bound state - in the composition of water, oil, natural gas, coal, etc. Hydrogen is rarely found in the form of a simple substance - in the composition of volcanic gases.

Hydrogen production

There are laboratory and industrial methods for producing hydrogen. Laboratory methods include the interaction of metals with acids (1), as well as the interaction of aluminum with aqueous solutions of alkalis (2). Among industrial methods for producing hydrogen, electrolysis of aqueous solutions of alkalis and salts (3) and methane conversion (4) play an important role:

Zn + 2HCl = ZnCl 2 + H 2 (1);

2Al + 2NaOH + 6H 2 O = 2Na +3 H 2 (2);

2NaCl + 2H 2 O = H 2 + Cl 2 + 2NaOH (3);

CH 4 + H 2 O ↔ CO + H 2 (4).

Examples of problem solving

EXAMPLE 1

Exercise When 23.8 g of metallic tin reacted with an excess of hydrochloric acid, hydrogen was released in an amount sufficient to obtain 12.8 g of metallic copper. Determine the oxidation state of tin in the resulting compound.
Solution Based on the electronic structure of the tin atom (...5s 2 5p 2), we can conclude that tin is characterized by two oxidation states - +2, +4. Based on this, we create equations for possible reactions:

Sn + 2HCl = H 2 + SnCl 2 (1);

Sn + 4HCl = 2H 2 + SnCl 4 (2);

CuO + H 2 = Cu + H 2 O (3).

Let's find the amount of copper substance:

v(Cu) = m(Cu)/M(Cu) = 12.8/64 = 0.2 mol.

According to equation 3, the amount of hydrogen substance:

v(H 2) = v(Cu) = 0.2 mol.

Knowing the mass of tin, we find its amount of substance:

v(Sn) = m(Sn)/M(Sn) = 23.8/119 = 0.2 mol.

Let's compare the amounts of tin and hydrogen substances according to equations 1 and 2 and according to the conditions of the problem:

v 1 (Sn): v 1 (H 2) = 1:1 (equation 1);

v 2 (Sn): v 2 (H 2) = 1:2 (equation 2);

v(Sn): v(H 2) = 0.2:0.2 = 1:1 (problem condition).

Therefore, tin reacts with hydrochloric acid according to equation 1 and the oxidation state of tin is +2.
Answer The oxidation state of tin is +2.

EXAMPLE 2

Exercise The gas released by the action of 2.0 g of zinc per 18.7 ml of 14.6% hydrochloric acid (solution density 1.07 g/ml) was passed through when heated over 4.0 g of copper (II) oxide. What is the mass of the resulting solid mixture?
Solution When zinc reacts with hydrochloric acid, hydrogen is released:

Zn + 2HCl = ZnСl 2 + H 2 (1),

which, when heated, reduces copper(II) oxide to copper(2):

CuO + H 2 = Cu + H 2 O.

Let's find the amounts of substances in the first reaction:

m(HCl solution) = 18.7. 1.07 = 20.0 g;

m(HCl) = 20.0. 0.146 = 2.92 g;

v(HCl) = 2.92/36.5 = 0.08 mol;

v(Zn) = 2.0/65 = 0.031 mol.

Zinc is in short supply, so the amount of hydrogen released is:

v(H 2) = v(Zn) = 0.031 mol.

In the second reaction, hydrogen is in short supply because:

v(СuО) = 4.0/80 = 0.05 mol.

As a result of the reaction, 0.031 mol CuO will turn into 0.031 mol Cu, and the mass loss will be:

m(СuО) – m(Сu) = 0.031×80 – 0.031×64 = 0.50 g.

The mass of the solid mixture of CuO and Cu after passing hydrogen will be:

4.0-0.5 = 3.5 g.
Answer The mass of the solid mixture of CuO and Cu is 3.5 g.

Hydrogen is a simple substance H2 (dihydrogen, diprotium, light hydrogen).

Brief hydrogen characteristic:

  • Non-metal.
  • Colorless gas, difficult to liquefy.
  • Poorly soluble in water.
  • It dissolves better in organic solvents.
  • Chemisorption by metals: iron, nickel, platinum, palladium.
  • Strong reducing agent.
  • Interacts (at high temperatures) with non-metals, metals, metal oxides.
  • Atomic hydrogen H0, obtained from the thermal decomposition of H2, has the greatest reducing ability.
  • Hydrogen isotopes:
    • 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 (no.s.) = 0.08988 g/l
  • melting temperature = -259.19°C
  • boiling point = -252.87°C
  • Volumetric hydrogen solubility coefficient:
    • (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 (when burned or exposed to 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, CuO 2 catalyst)
  • H 2 +CaC 2 = Ca+C 2 H 2 (t over 2200°C)
  • H 2 +BaH 2 = Ba(H 2) 2 (t 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 - dideuterium:

  • Heavy hydrogen.
  • Colorless gas, difficult to liquefy.
  • Dideutherium is contained in natural hydrogen at 0.012-0.016% (by weight).
  • In a gas mixture of dideuterium and protium, isotope exchange occurs at high temperatures.
  • Slightly soluble in ordinary and heavy water.
  • With ordinary water, isotope 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 temperature = -254.5°C
  • boiling point = -249.49°C

T 2 - ditritium:

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

HD - deuterium hydrogen:

  • Colorless gas.
  • Does not dissolve in water.
  • Chemical properties similar to H2.
  • Relative molecular weight = 3.022
  • Relative density of solid deuterium hydrogen (t=-257°C) = 0.146
  • Overpressure (no.s.) = 0.135 g/l
  • melting temperature = -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 impurities H 2 18 O and H 2 17 O
  • According to the hydrogen isotopic composition, water consists of 1 H 2 O with an admixture of HDO.
  • Liquid water undergoes protolysis (H 3 O + and OH -):
    • H3O+ (oxonium cation) is the strongest acid in aqueous solution;
    • OH - (hydroxide ion) is the strongest base in aqueous solution;
    • Water is the weakest conjugate protolyte.
  • With many substances, water forms crystalline hydrates.
  • Water is a chemically active substance.
  • Water is a universal 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.s.) = 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.
  • Viscosity is higher than that of water.
  • Mixes with ordinary water in unlimited quantities.
  • Isotopic exchange produces semi-heavy water HDO.
  • Solvent power is lower than that of ordinary water.
  • The chemical properties of deuterium oxide are similar to the chemical properties of water, but all reactions proceed more slowly.
  • 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 electrolyte residue.
  • 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 temperature = 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 with ordinary 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 the chemical properties of water, but all reactions proceed even more slowly than in heavy water.
  • Traces of tritium oxide are found in natural water and atmosphere.
  • Superheavy water is obtained by passing tritium over hot copper oxide CuO.
  • Relative molecular weight of superheavy water = 22.03
  • melting point = 4.5°C

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 the substance in its pure state, began studying it and described its properties.

This is the story of the discovery of hydrogen. During the experiments, the researcher determined that it is a flammable gas, the combustion of which in the air produces water. This led to the determination of the qualitative composition of 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 “water-giving.” The name refers to the combustion reaction that produces water.

Characteristics of hydrogen

Designation of hydrogen N. Mendeleev assigned the first atomic number to this chemical element, 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 H2 is 2 a. e. The molar mass is numerically equal to it.

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

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

Physical properties

Under normal conditions, the simple substance hydrogen in the form of diatomic molecules is a gas, colorless, tasteless and odorless. Slightly soluble in water and other solvents.

Crystallization temperature - 259.2 o C, boiling point - 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 necessary to purify hydrogen from gaseous impurities. When n. u. hydrogen has a density of 0.09 kg/m3.

Is it possible to transform 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.

This is interesting: there is an assumption that on the giant planets, Jupiter and Saturn, hydrogen is found in the form of a metal. It is assumed that metallic solid hydrogen is also present in 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 needs to be increased by creating appropriate conditions - increasing the temperature, using catalysts, etc.

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

If you ignite pure hydrogen at the end of a gas outlet tube in air, it will burn evenly, but barely noticeably. If you place the gas outlet tube 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:

The 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 occurs similarly to form hydrogen chloride.

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

As a result of the 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 - 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, as well as in thermonuclear power.

Hydrogen also reacts with substances from the complex category. For example, with copper (II) oxide, 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 red-brown, and droplets of water settle on the cold walls of the test tube.

Hydrogen is oxidized during the reaction, forming water, and copper is reduced from oxide to a simple substance (Cu).

Areas of use

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

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

Scientists unanimously predict that hydrogen fuel will take the lead in the energy sector.

Receipt in industry

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

The conversion of coke or methane with water vapor is used for these purposes. The decomposition of methane at elevated temperatures also produces hydrogen. Liquefaction of coke oven gas by the fractional method is also used for the industrial production of hydrogen.

Obtained in the laboratory

In the laboratory, a Kipp apparatus is used to produce hydrogen.

The reagents are hydrochloric or sulfuric acid and zinc. The reaction produces hydrogen.

Finding hydrogen in nature

Hydrogen is more common than any other element in the Universe. The bulk of stars, including the Sun, and other cosmic bodies is hydrogen.

In the earth's crust it is only 0.15%. It is present in many minerals, in all organic substances, as well as in water, which covers 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 flammable natural gases.

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

The most powerful hydrogen bomb is based on the splitting of the lightest atom.

Liquid

Hydrogen(lat. Hydrogenium; indicated by the symbol H) is the first element of the periodic table of elements. Widely distributed in nature. The cation (and nucleus) of the most common isotope of hydrogen, 1 H, is the proton. The properties of the 1 H nucleus make it possible to widely use NMR spectroscopy in the analysis of organic substances.

Three isotopes of hydrogen have their own names: 1 H - protium (H), 2 H - deuterium (D) and 3 H - tritium (radioactive) (T).

The simple substance hydrogen - H 2 - is a light colorless gas. When mixed with air or oxygen, it is flammable and explosive. Non-toxic. Soluble in ethanol and a number of metals: iron, nickel, palladium, platinum.

Story

The release of flammable gas during the interaction of acids and metals was observed in the 16th and 17th centuries at the dawn of the formation of chemistry as a science. Mikhail Vasilyevich Lomonosov also directly pointed out its isolation, but he was already definitely aware that it was not phlogiston. The English physicist and chemist Henry Cavendish examined this gas in 1766 and called it “combustible air.” When burned, the “combustible air” produced water, but Cavendish’s adherence to the phlogiston theory prevented him from drawing the correct conclusions. The French chemist Antoine Lavoisier, together with the engineer J. Meunier, using special gasometers, in 1783 carried out the synthesis of water, and then its analysis, decomposing water vapor with hot iron. Thus, he established that “combustible air” is part of water and can be obtained from it.

origin of name

Lavoisier gave hydrogen the name hydrogène - “giving birth to water.” The Russian name “hydrogen” was proposed by the chemist M. F. Soloviev in 1824 - by analogy with Slomonosov’s “oxygen”.

Prevalence

Hydrogen is the most abundant element in the Universe. It accounts for about 92% of all atoms (8% are helium atoms, the share of all other elements combined is less than 0.1%). Thus, hydrogen is the main component of stars and interstellar gas. Under conditions of stellar temperatures (for example, the surface temperature of the Sun is ~ 6000 °C), hydrogen exists in the form of plasma; in interstellar space, this element exists in the form of individual molecules, atoms and ions and can form molecular clouds that vary significantly in size, density and temperature.

Earth's crust and living organisms

The mass fraction of hydrogen in the earth's crust is 1% - it is the tenth most abundant element. However, its role in nature is determined not by mass, but by the number of atoms, the share of which among other elements is 17% (second place after oxygen, the share of atoms of which is ~ 52%). Therefore, the importance of hydrogen in chemical processes occurring on Earth is almost as great as that of oxygen. Unlike oxygen, which exists on Earth in both bound and free states, almost all hydrogen on Earth is in the form of compounds; Only a very small amount of hydrogen in the form of a simple substance is contained in the atmosphere (0.00005% by volume).

Hydrogen is part of almost all organic substances and is present in all living cells. In living cells, hydrogen accounts for almost 50% of the number of atoms.

Receipt

Industrial methods for producing simple substances depend on the form in which the corresponding element is found in nature, that is, what can be the raw material for its production. Thus, oxygen, which is available in a free state, is obtained physically - by separation from liquid air. Almost all hydrogen is in the form of compounds, so chemical methods are used to obtain it. In particular, decomposition reactions can be used. One way to produce hydrogen is through the decomposition of water by electric current.

The main industrial method for producing hydrogen is the reaction of methane, which is part of natural gas, with water. It is carried out at high temperature (it is easy to verify that when passing methane even through boiling water, no reaction occurs):

CH 4 + 2H 2 O = CO 2 + 4H 2 −165 kJ

In the laboratory, to obtain simple substances, they do not necessarily use natural raw materials, but choose those starting materials from which it is easier to isolate the required substance. For example, in the laboratory, oxygen is not obtained from the air. The same applies to the production of hydrogen. One of the laboratory methods for producing hydrogen, which is sometimes used in industry, is the decomposition of water by electric current.

Typically, hydrogen is produced in the laboratory by reacting zinc with hydrochloric acid.

In industry

1.Electrolysis of aqueous salt solutions:

2NaCl + 2H 2 O → H 2 + 2NaOH + Cl 2

2.Passing water vapor over hot coke at a temperature of about 1000 °C:

H2O+C? H2+CO

3. From natural gas.

Steam conversion:

CH 4 + H 2 O ? CO + 3H 2 (1000 °C)

Catalytic oxidation with oxygen:

2CH 4 + O 2 ? 2CO + 4H2

4. Cracking and reforming of hydrocarbons during oil refining.

In the laboratory

1.The effect of dilute acids on metals. To carry out this reaction, zinc and dilute hydrochloric acid are most often used:

Zn + 2HCl → ZnCl 2 + H 2

2.Interaction of calcium with water:

Ca + 2H 2 O → Ca(OH) 2 + H 2

3.Hydrolysis of hydrides:

NaH + H 2 O → NaOH + H 2

4.Effect of alkalis on zinc or aluminum:

2Al + 2NaOH + 6H 2 O → 2Na + 3H 2

Zn + 2KOH + 2H 2 O → K 2 + H 2

5.Using electrolysis. During the electrolysis of aqueous solutions of alkalis or acids, hydrogen is released at the cathode, for example:

2H 3 O + + 2e − → H 2 + 2H 2 O

Physical properties

Hydrogen can exist in two forms (modifications) - in the form of ortho- and para-hydrogen. In an orthohydrogen molecule o-H 2 (mp −259.10 °C, bp −252.56 °C) nuclear spins are directed identically (parallel), and for parahydrogen p-H 2 (melting point −259.32 °C, boiling point −252.89 °C) - opposite to each other (antiparallel). Equilibrium mixture o-H 2 and p-H 2 at a given temperature is called equilibrium hydrogen e-H2.

Hydrogen modifications can be separated by adsorption on active carbon at liquid nitrogen temperature. At very low temperatures, the equilibrium between orthohydrogen and parahydrogen is almost completely shifted towards the latter. At 80 K the ratio of forms is approximately 1:1. When heated, desorbed parahydrogen is converted into orthohydrogen until a mixture is formed that is equilibrium at room temperature (ortho-para: 75:25). Without a catalyst, the transformation occurs slowly (under conditions of the interstellar medium - with characteristic times up to cosmological ones), which makes it possible to study the properties of individual modifications.

Hydrogen is the lightest gas, it is 14.5 times lighter than air. Obviously, the smaller the mass of the molecules, the higher their speed at the same temperature. As the lightest molecules, hydrogen molecules move faster than the molecules of any other gas and thus can transfer heat from one body to another faster. It follows that hydrogen has the highest thermal conductivity among gaseous substances. Its thermal conductivity is approximately seven times higher than the thermal conductivity of air.

The hydrogen molecule is diatomic - H2. Under normal conditions, it is a colorless, odorless, and tasteless gas. Density 0.08987 g/l (n.s.), boiling point −252.76 °C, specific heat of combustion 120.9×10 6 J/kg, slightly soluble in water - 18.8 ml/l. Hydrogen is highly soluble in many metals (Ni, Pt, Pd, etc.), especially in palladium (850 volumes per 1 volume of Pd). The solubility of hydrogen in metals is related to its ability to diffuse through them; Diffusion through a carbon alloy (for example, steel) is sometimes accompanied by destruction of the alloy due to the interaction of hydrogen with carbon (so-called decarbonization). Practically insoluble in silver.

Liquid hydrogen exists in a very narrow temperature range from −252.76 to −259.2 °C. It is a colorless liquid, very light (density at −253 °C 0.0708 g/cm3) and fluid (viscosity at −253 °C 13.8 spuaz). The critical parameters of hydrogen are very low: temperature −240.2 °C and pressure 12.8 atm. This explains the difficulties in liquefying hydrogen. In the liquid state, equilibrium hydrogen consists of 99.79% para-H2, 0.21% ortho-H2.

Solid hydrogen, melting point −259.2 °C, density 0.0807 g/cm 3 (at −262 °C) - snow-like mass, hexagonal crystals, space group P6/mmc, cell parameters a=3,75 c=6.12. At high pressure, hydrogen transforms into a metallic state.

Isotopes

Hydrogen occurs in the form of three isotopes, which have individual names: 1 H - protium (H), 2 H - deuterium (D), 3 H - tritium (radioactive) (T).

Protium and deuterium are stable isotopes with mass numbers 1 and 2. Their content in nature is 99.9885 ± 0.0070% and 0.0115 ± 0.0070%, respectively. This ratio may vary slightly depending on the source and method of producing hydrogen.

The hydrogen isotope 3H (tritium) is unstable. Its half-life is 12.32 years. Tritium occurs naturally in very small quantities.

The literature also provides data on hydrogen isotopes with mass numbers of 4 - 7 and half-lives of 10 -22 - 10 -23 s.

Natural hydrogen consists of H 2 and HD (deuterium hydrogen) molecules in a ratio of 3200:1. The content of pure deuterium hydrogen D 2 is even less. The ratio of the concentrations of HD and D 2 is approximately 6400:1.

Of all the isotopes of chemical elements, the physical and chemical properties of hydrogen isotopes differ from each other the most. This is due to the largest relative change in atomic masses.

Temperature
melting,
K

Temperature
boiling,
K

Triple
dot,
K/kPa

Critical
dot,
K/kPa

Density
liquid/gas,
kg/m³

Deuterium and tritium also have ortho- and para-modifications: p-D 2 , o-D 2 , p-T 2, o-T 2 . Heteroisotope hydrogen (HD, HT, DT) does not have ortho- and para-modifications.

Chemical properties

Fraction of dissociated hydrogen molecules

Hydrogen molecules H2 are quite strong, and in order for hydrogen to react, a lot of energy must be expended:

H 2 = 2H − 432 kJ

Therefore, at ordinary temperatures, hydrogen reacts only with very active metals, such as calcium, forming calcium hydride:

Ca + H 2 = CaH 2

and with the only non-metal - fluorine, forming hydrogen fluoride:

Hydrogen reacts with most metals and non-metals at elevated temperatures or under other influences, for example, lighting:

O 2 + 2H 2 = 2H 2 O

It can “take away” oxygen from some oxides, for example:

CuO + H 2 = Cu + H 2 O

The written equation reflects the reducing properties of hydrogen.

N 2 + 3H 2 → 2NH 3

Forms hydrogen halides with halogens:

F 2 + H 2 → 2HF, the reaction occurs explosively in the dark and at any temperature,

Cl 2 + H 2 → 2HCl, the reaction proceeds explosively, only in the light.

It interacts with soot under high heat:

C + 2H 2 → CH 4

Interaction with alkali and alkaline earth metals

When interacting with active metals, hydrogen forms hydrides:

2Na + H 2 → 2NaH

Ca + H 2 → CaH 2

Mg + H 2 → MgH 2

Hydrides- salt-like, solid substances, easily hydrolyzed:

CaH 2 + 2H 2 O → Ca(OH) 2 + 2H 2

Interaction with metal oxides (usually d-elements)

Oxides are reduced to metals:

CuO + H 2 → Cu + H 2 O

Fe 2 O 3 + 3H 2 → 2Fe + 3H 2 O

WO 3 + 3H 2 → W + 3H 2 O

Hydrogenation of organic compounds

Molecular hydrogen is widely used in organic synthesis for the reduction of organic compounds. These processes are called hydrogenation reactions. These reactions are carried out in the presence of a catalyst at elevated pressure and temperature. The catalyst can be either homogeneous (eg Wilkinson Catalyst) or heterogeneous (eg Raney nickel, palladium on carbon).

Thus, in particular, during the catalytic hydrogenation of unsaturated compounds such as alkenes and alkynes, saturated compounds are formed - alkanes.

Geochemistry of hydrogen

Free hydrogen H2 is relatively rare in terrestrial gases, but in the form of water it takes an extremely important part in geochemical processes.

Hydrogen can be present in minerals in the form of ammonium ion, hydroxyl ion and crystalline water.

In the atmosphere, hydrogen is continuously produced as a result of the decomposition of water by solar radiation. Having a low mass, hydrogen molecules have a high speed of diffusion motion (it is close to the second cosmic speed) and, when they enter the upper layers of the atmosphere, they can fly into outer space.

Features of treatment

Hydrogen, when mixed with air, forms an explosive mixture - the so-called detonating gas. This gas is most explosive when the volume ratio of hydrogen and oxygen is 2:1, or hydrogen and air is approximately 2:5, since air contains approximately 21% oxygen. Hydrogen is also a fire hazard. Liquid hydrogen can cause severe frostbite if it comes into contact with the skin.

Explosive concentrations of hydrogen and oxygen occur from 4% to 96% by volume. When mixed with air from 4% to 75(74)% by volume.

Economy

The cost of hydrogen for large wholesale supplies ranges from $2-5 per kg.

Application

Atomic hydrogen is used for atomic hydrogen welding.

Chemical industry

  • In the production of ammonia, methanol, soap and plastics
  • In the production of margarine from liquid vegetable oils
  • Registered as a dietary supplement E949(packing gas)

Food industry

Aviation industry

Hydrogen is very light and always rises in the air. Once upon a time, airships and balloons were filled with hydrogen. But in the 30s. XX century There were several disasters during which airships exploded and burned. Nowadays, airships are filled with helium, despite its significantly higher cost.

Fuel

Hydrogen is used as rocket fuel.

Research is underway on the use of hydrogen as a fuel for cars and trucks. Hydrogen engines do not pollute the environment and emit only water vapor.

Hydrogen-oxygen fuel cells use hydrogen to directly convert the energy of a chemical reaction into electrical energy.

"Liquid Hydrogen"(“LH”) is the liquid state of hydrogen, with a low specific density of 0.07 g/cm³ and cryogenic properties with a freezing point of 14.01 K (−259.14 °C) and a boiling point of 20.28 K (−252.87 °C). It is a colorless, odorless liquid, which when mixed with air is classified as explosive with a flammability range of 4-75%. The spin ratio of isomers in liquid hydrogen is: 99.79% - parahydrogen; 0.21% - orthohydrogen. The expansion coefficient of hydrogen when changing its state of aggregation to gaseous is 848:1 at 20°C.

As with any other gas, liquefaction of hydrogen leads to a decrease in its volume. After liquefaction, liquid liquid is stored in thermally insulated containers under pressure. Liquid hydrogen Liquid hydrogen, LH2, LH 2) is actively used in industry, as a form of gas storage, and in the space industry, as rocket fuel.

Story

The first documented use of artificial refrigeration was carried out by the English scientist William Cullen in 1756, Gaspard Monge was the first to obtain a liquid state of sulfur oxide in 1784, Michael Faraday was the first to obtain liquefied ammonia, the American inventor Oliver Evans was the first to develop a refrigeration compressor in 1805, Jacob Perkins was the first to patent cooling machine in 1834 and John Gorey was the first to patent an air conditioner in the United States in 1851. Werner Siemens proposed the concept of regenerative cooling in 1857, Karl Linde patented equipment for producing liquid air using a cascade "Joule-Thomson expansion effect" and regenerative cooling in 1876. In 1885, Polish physicist and chemist Zygmunt Wroblewski published the critical temperature of hydrogen 33 K, the critical pressure 13.3 atm. and boiling point at 23 K. Hydrogen was first liquefied by James Dewar in 1898 using regenerative cooling and his invention, the Dewar flask. The first synthesis of a stable isomer of liquid hydrogen, parahydrogen, was carried out by Paul Harteck and Carl Bonhoeffer in 1929.

Spin isomers of hydrogen

Hydrogen at room temperature consists primarily of a spin isomer, orthohydrogen. After production, liquid hydrogen is in a metastable state and must be converted to the parahydrogen form in order to avoid the explosive exothermic reaction that occurs when it changes at low temperatures. Conversion to the parahydrogen phase is usually accomplished using catalysts such as iron oxide, chromium oxide, activated carbon, platinum-coated asbestos, rare earth metals, or through the use of uranium or nickel additives.

Usage

Liquid hydrogen can be used as a form of fuel storage for internal combustion engines and fuel cells. Various submarines (projects "212A" and "214", Germany) and hydrogen transport concepts have been created using this aggregate form of hydrogen (see for example "DeepC" or "BMW H2R"). Due to the proximity of the designs, the creators of LHV equipment can use or only modify systems using liquefied natural gas (LNG). However, due to the lower volumetric energy density, combustion requires a larger volume of hydrogen than natural gas. If liquid hydrogen is used instead of "CNG" in piston engines, a more bulky fuel system is usually required. With direct injection, increased losses in the intake tract reduce cylinder filling.

Liquid hydrogen is also used to cool neutrons in neutron scattering experiments. The masses of the neutron and the hydrogen nucleus are almost equal, so the exchange of energy during an elastic collision is most effective.

Advantages

The advantage of using hydrogen is the “zero emissions” of its use. The product of its interaction with air is water.

Obstacles

One liter of “ZhV” weighs only 0.07 kg. That is, its specific gravity is 70.99 g/l at 20 K. Liquid hydrogen requires cryogenic storage technology, such as special thermally insulated containers and requires special handling, which is typical for all cryogenic materials. It is close in this respect to liquid oxygen, but requires greater caution due to the fire hazard. Even with insulated containers, it is difficult to keep it at the low temperatures required to keep it liquid (it typically evaporates at a rate of 1% per day). When handling it, you also need to follow the usual safety precautions when working with hydrogen - it is cold enough to liquefy air, which is explosive.

Rocket fuel

Liquid hydrogen is a common component of rocket fuels, which is used to propel launch vehicles and spacecraft. In most liquid hydrogen rocket engines, it is first used to regeneratively cool the nozzle and other engine parts before it is mixed with an oxidizer and burned to produce thrust. Modern engines using H 2 /O 2 components consume a fuel mixture over-enriched in hydrogen, which leads to a certain amount of unburned hydrogen in the exhaust. In addition to increasing the specific impulse of the engine by reducing molecular weight, this also reduces erosion of the nozzle and combustion chamber.

Such obstacles to the use of LH in other areas, such as cryogenic nature and low density, are also a limiting factor for use in this case. As of 2009, there is only one launch vehicle (Delta-4 launch vehicle), which is entirely a hydrogen rocket. Basically, “ZhV” is used either on the upper stages of rockets or on blocks, which perform a significant part of the work of launching the payload into space in a vacuum. As one of the measures to increase the density of this type of fuel, there are proposals to use sludge-like hydrogen, that is, a semi-frozen form of “liquid hydrogen”.

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