The color of hydrogen in the gaseous state. Liquid hydrogen: properties and application

• Designation - H (Hydrogen);
• Latin name - Hydrogenium;
• Period - I;
• Group - 1 (Ia);
• Atomic mass - 1,00794;
• Atomic number - 1;
• Radius of atom \u003d 53 PM;
• Covalent radius \u003d 32 PM;
• Electron distribution - 1s 1;
• t melting \u003d -259,14 ° C;
• t boiling \u003d -252,87 ° C;
• Electricity (by Paulonga / by Alpreda and Rokhov) \u003d 2.02 / -;
• The degree of oxidation: +1; 0; -one;
• Density (n. Y.) \u003d 0.0000899 g / cm 3;
• Molar volume \u003d 14.1 cm 3 / mol.

Binary compounds of hydrogen with oxygen:

Hydrogen ("referring water") was opened by the English scientist. Cavendish in 1766. This is the easiest element in nature - a hydrogen atom has a kernel and one electron, probably, for this reason, hydrogen is the most common element in the universe (it is more than half the mass of most stars).

We can say about hydrogen that "a small spool, yes roads." Despite its "simplicity", hydrogen gives energy to all living beings on Earth - a continuous thermonuclear reaction is underway in the Sun during which one atom of helium is formed from four hydrogen atoms, this process is accompanied by the release of a colossal amount of energy (see nuclear synthesis).

In the earth's crust, the mass fraction of hydrogen is only 0.15%. Meanwhile, the overwhelming number (95%) of all chemicals known on Earth contain one or more hydrogen atoms.

In connections with non-metals (HCl, H 2 O, CH 4 ...), hydrogen gives its own only electron electronegative elements, showing the degree of oxidation +1 (more often), forming only covalent bonds (see covalent bond).

In compounds with metals (NAH, CAH 2 ...) hydrogen, on the contrary, takes on its only S-orbital another electron, thus trying to complete its electronic layer, showing the degree of oxidation -1 (less often), forming more often ion Communication (see ion connection), because, the difference in the electronegativity of the hydrogen atom and the metal atom can be quite large.

H 2.

In a gaseous state, hydrogen is in the form of two-heed molecules, forming a non-polar covalent bond.

Hydrogen molecules possess:

• big mobility;
• great strength;
• low polarizability;
• small sizes and mass.

Hydrogen gas properties:

• the easiest gas in nature, without color and smell;
• poorly dissolved in water and organic solvents;
• in minor counts, dissolves in liquid and solid metals (especially in platinum and palladium);
• it is difficult to liquefy (due to their small polarizability);
• has the highest thermal conductivity of all known gases;
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For hydrogen, it is uncharacteristic to show the degree of oxidation -1. Reacting with water, hydrides decompose, restoring water to hydrogen. Calcium hydride reaction with water is as follows:

CAH 2 -1 + 2H 2 +1 0 \u003d 2H 2 0 + CA (OH) 2

Hydrogen reactions with complex substances

• at high temperatures, hydrogen restores many metal oxides: Zno + H 2 \u003d Zn + H 2 O
• methyl alcohol is obtained as a result of hydrogen reaction with carbon oxide (II): 2H 2 + Co → CH 3 OH
• in hydrogenation reactions, hydrogen reacts with many organic substances.

In more detail, the equation of chemical reactions of hydrogen and its compounds are considered on the page "Hydrogen and its compounds - the equations of chemical reactions involving hydrogen".

The use of hydrogen

• in nuclear power, hydrogen isotopes are used - deuterium and tritium;
• in the chemical industry, hydrogen is used to synthesize many organic substances, ammonia, chloride;
• in the food industry, hydrogen is used in the production of solid fats through hydrogenation of vegetable oils;
• for welding and cutting of metals, a high temperature of hydrogen burning in oxygen (2600 ° C) is used;
• when obtaining some metals, hydrogen is used as a reducing agent (see above);
• since hydrogen is light gas, it is used in aeronautics as a filler of balloons, balloons, airship;
• as the hydrogen fuel is used in the mixture with CO.

Recently, scientists pay a lot of attention to the search alternative sources renewable energy. One of the promising areas is the "hydrogen" energy in which hydrogen is used as fuel, whose combustion product is ordinary water.

Methods for producing hydrogen

Industrial methods for producing hydrogen:

• methane conversion (catalytic reduction of water vapor) water vapor at high temperature (800 ° C) on a nickel catalyst: CH 4 + 2H 2 O \u003d 4H 2 + CO 2;
• the conversion of carbon oxide with water vapor (T \u003d 500 ° C) on the FE 2 O 3 catalyst: CO + H 2 O \u003d CO 2 + H 2;
• thermal decomposition of methane: CH 4 \u003d C + 2H 2;
• gasification solid fuels (T \u003d 1000 ° C): C + H 2 O \u003d CO + H 2;
• electrolysis of water (a very expensive method in which very pure hydrogen is obtained): 2H 2 O → 2H 2 + O 2.

Laboratory methods for producing hydrogen:

• action on metals (more often zinc) hydrochloric or diluted with sulfuric acid: zn + 2hcl \u003d ZCl 2 + H 2; Zn + H 2 SO 4 \u003d ZNSO 4 + H 2;
• the interaction of water vapor with hot iron chips: 4H 2 O + 3Fe \u003d Fe 3 O 4 + 4H 2.

The purpose of today's publication is to submit comprehensive information about the unprepared reader what is hydrogenWhat is its physical and chemical properties, scope of application, value and methods of obtaining.

Hydrogen is present in the overwhelming majority of organic substances and cells in which it accounts for almost two thirds of atoms.

Photo 1. Hydrogen is considered one of the most common elements in nature

IN periodic system Mendeleev elements Hydrogen occupies an honorable first position with atomic weight equal to one.

The name "Hydrogen" (in the Latin version - Hydrogenium.It is originated from two ancient Greek words: ὕΔωρ - "" and γεννάω - "God" (literally - "referring) and was first suggested in 1824 by the Russian chemist Mikhail Solovyov.

Hydrogen is one of the water-forming (along with oxygen) elements (the chemical formula of water H 2 O).

According to physical properties, hydrogen is characterized as colorless gas (lighter air). When mixed with oxygen or air is extremely and fuel.

It is capable of dissolved in some metals (titanium, gland, platinum, palladium, nickel) and in ethanol, but very poorly soluble in silver.

The hydrogen molecule consists of two atoms and is denoted by H 2. Hydrogen has several isotopes: diet (H), deuterium (D) and tritium (t).

History of discovery of hydrogen

Even in the first half of the XVI century, when conducting alchemical experiments, mixing metals with acids, Paracelles noticed the unknown combustible gas, which he could not separate from the air.

After almost one and a half century - at the end of the XVII century - the French scientist Lemerie managed to separate the hydrogen (not yet knowing that it is hydrogen) from the air and prove its flammability.

Photo 2. Henry Cavendish - hydrogen discoverer

Chemical experiments in the middle of the XVIII century allowed Mikhail Lomonosov to identify the process of separating some gas as a result of some chemical reactions that are not, however, phlogiston.

A real breakthrough in a combustible gas study was managed to make English chemist Henry Cavendishuwhich is attributed to the discovery of hydrogen (1766).

This gas Cavendish called "flammable air". It also carried out the burning reaction of this substance, as a result of which water was obtained.

In 1783, the french chemicals led by Antoine Lavoisier was carried out by the synthesis of water, and later the decomposition of water with the allocation of "fuel air".

These studies finally proved the presence of hydrogen as part of the water. It was Lavoisier who suggested that the new gas Hydrogenium (1801) was called.

Useful properties of hydrogen

Hydrogen is easier air to fourteen and a half times.

It also distinguishes the highest thermal conductivity among other gases (white than seven times the thermal conductivity of air).

In the former balloons and airships were filled with hydrogen. After a series of disasters in the mid-1930s ending with the explosions of airship, designers had to look for hydrogen to replace.

Now helium is used for such aircraft, which is much more expensive than hydrogen, but it is not so explosive.

Photo 3. Hydrogen is used for the manufacture of rocket fuel

In many countries, research is underway to create economical engines for passenger and cargo vehicles based on hydrogen.

Cars on hydrogen fuel are much more environmentally friendly of their gasoline and diesel fellow.

Under normal conditions (room temperature and natural pressure), hydrogen is reluctant to react.

When the mixture of hydrogen and oxygen is heated to 600 ° C, the reaction begins to form the formation of water molecules.

The same reaction can be provoked by an electrical spark.

The reactions with the fate of hydrogen are completed only when the components participating in the reaction will be consumed entirely.

The temperature of the burning hydrogen reaches 2500-2800 ° C.

With the help of hydrogen, clean the various types of fuel based on oil and petroleum products produce.

In the wildlife of hydrogen to replace with nothing, as it is present in any organic matter (including oil) and in all protein compounds.

Without the participation of hydrogen, it would be impossible.

Aggregate states of hydrogen

Hydrogen is capable of abiding in three main aggregate states:

• gaseous;
• liquid;
• solid.

The usual state of hydrogen is gas. His temperature to -252.8 ° C, hydrogen turns into a liquid, and after the temperature threshold -262 ° C, hydrogen becomes solid.

Photo 4. Already several decades instead of a cheaper hydrogen for filling balloons are used by dear helium.

Scientists suggest that hydrogen is capable of being in an additional (fourth) aggregate state - metallic.

For this you just need to create a pressure of two and a half million atmospheres.

So far, alas, it is just a scientific hypothesis, since it has not been able to get "metal hydrogen" yet.

Liquid hydrogen - due to its temperature - when a person gets into contact, cause severe frostbite.

Hydrogen in Mendeleev Table

The distribution of chemical elements in the periodic table of Mendeleeva lies their atomic weight, calculated relative to the atomic weight of hydrogen.

Photo 5. In the Mendeleev table, a cell with sequence number is assigned hydrogen 1

No one could refute this approach for many years nor confirm.

With the emergence at the beginning of the 20th century and, in particular, the appearance of famous postulates of Niels Bora, explaining the structure of an atom from the standpoint of quantum mechanics, managed to prove the justice of the hypothesis of Mendeleev.

The opposite is true: it is the correspondence of the postulates of Niels Bor a periodic law, which is based on the Mendeleev table, and has become the most pleasant argument in favor of recognizing their truth.

Hydrogen participation in thermonuclear reaction

The isotopes of hydrogen deuterium and tritium are the sources of incredibly powerful energy released in the process of thermonuclear reaction.

Photo 6. Thermonuclear explosion without hydrogen would be impossible

Such a reaction is possible at a temperature not lower than 1060 ° C and proceed very quickly - within a few seconds.

In the Sun, thermonuclear reactions proceed slowly.

The task of scientists is to understand why this happens to use the knowledge gained to create new - practically inexhaustible - energy sources.

What is hydrogen (video):

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Hydrogen has their own names: H - diet (H), H - deuterium (D) and H - tritium (radioactive) (T).

Simple substance hydrogen - H 2 - light colorless gas. In a mixture with air or oxygen, fuel and explosive. Non-toxic. Soluble in ethanol and a number of metals: gland, nickel, palladium, platinum.

History

Another medieval scientist Paracels noticed that under the action of acids on iron, bubbles of some "air" are distinguished. But what it is, he could not explain. Now it is known that it was hydrogen. "Hydrogen presents an example of a gas," wrote D.I. REMEELEEV, - at first glance, not different from the air ... Paracels, which discovered that under the action of some metals on sulfuric acid, the air-shaped substance was obtained, did not determine its differences from the air. Indeed, hydrogen is blunt and there is no smell, as well as air; But, under the near future with its properties, this gas is completely different from the air. "

English Chemists are 18 in., Henry Cavendish and Joseph are attracted, re-opened hydrogen, the first studied its properties. They found that this is an unusually light gas - it is 14 times lighter than air. If you inflate them a rubber ball, he takes off the swell. This property of hydrogen was used earlier to fill balloons and airships. True, the first balloon built by the Mongolfier brothers was not filled with hydrogen, and smoke from burning wool and straw. Such a strange way of obtaining hot air is associated with the fact that the brothers apparently were not familiar with the laws of physics; They naively believed that this mixture forms "electric smoke" capable of raising their light ball. Physicist Charles, who knew the law of Archimedes, decided to fill the ball with hydrogen; Unlike Mongolphiers, filled with hot air, the balls with hydrogen are called Charles. The first such a ball (he did not carry any cargo) rose from Marsov fields in Paris on August 27, 1783 and in 45 minutes flew 20 km.

In December 1783, Charles, accompanied by Francois Robert Physics in the presence of 400 thousand spectators, was taken first flight in a balloon filled with hydrogen. Gay Louce (also with physicist Jean Batist Bio) put in 1804 a record of height, rising by 7000 meters.

But hydrogen is a fuel. Moreover, its mixtures with air exploded, and a mixture of hydrogen with oxygen is called even "rattle gas". In May 1937, a fire for a few minutes destroyed the giant German airship "Hindenburg" - it had 190,000 cubic meters of hydrogen. Then 35 people died. After many accidents, hydrogen in aeronautics are no longer used, it is replaced with helium or hot air.

With the burning of hydrogen, water is formed - a compound of hydrogen and oxygen. This proved in the late 18 French chemist Lavoisier. Hence the name of the gas - "referring water". Lavoisier also managed to get hydrogen from the water. He missed water vapors through a hot-hot iron tube with iron sawdust. Oxygen from the water is firmly connected to the hardware, and hydrogen was highlighted in free form. Now hydrogen is also obtained from water, but in another way - with the help of electrolysis (see Electrolytic dissociation. Electrolytes)

Hydrogen properties

Hydrogen is the most common chemical element in the universe. It is approximately half the mass of the Sun and most stars, is the main element in the interstellar space and in gas nebula. Western hydrogen and on Earth. Here it is in the associated state - in the form of connections. Thus, water contains 11% hydrogen by weight, clay - 1.5%. In the form of compounds with carbon, hydrogen is part of oil, natural gases, all living organisms. A little free hydrogen is contained in the air, but it is completely small there - only 0.00005%. It enters the atmosphere from volcanoes.

Many other "records" belongs to hydrogen.
Liquid hydrogen - the easiest liquid (density of 0.067 g / cm 3 at a temperature of -250 ° C),
Solid hydrogen - the easiest solid (Density of 0.076 g / cm 3).
Atoms of hydrogen - the smallest of all atoms. However, when the energy of the electromagnetic radiation is absorbed, the outer electron of the atom can be removed from the nucleus further and further. Therefore, an excited hydrogen atom theoretically can have any dimensions. And practically? In the book, global records in chemistry says that in interstellar clouds allegedly detected by their spectra atoms of hydrogen with a diameter of 0.4 mm (they are fixed on the spectral transition from the 253rd to the 252nd orbital). Atoms of such sizes can be seen with the naked eye! It gives a reference to an article published in 1991 in the world's most famous journal dedicated to chemical education - Journal of Chemical Education (it is published in the USA). However, the author of the article was wrong - he overestimated all sizes exactly 100 times (this was announced by the same magazine a year later). So, the detected hydrogen atoms have the diameter of "only" 0.004 mm, and such atoms, even if they were "solid", to see the naked eye - only in the microscope. Of course, according to atomic standards and 0.004 mm - the value is huge, tens of thousand times the diameter of an unexcited hydrogen atom.

Hydrogen molecules are also very small. Therefore, this gas easily passes through the thinnest gaps. The rubber ball, inflated by hydrogen, "losing weight" is much faster than the ball, inflounted by air: hydrogen molecules gradually seep through the smallest pores in rubber.

If you breathe hydrogen and start talking, the frequency of the published sounds will be three times higher than usual. This is enough for the sound of even a low male voice to be unnaturally high, resembling the voice of Pinocchio. This is because the height of the sound, published by a whistle, organ pipe or a person's voice apparatus, depends not only on their size and wall material, but also from the gas to which they are filled. The greater the speed of sound in the gas, the higher its tone. The speed of the sound depends on the mass of the gas molecules. Hyrogen molecules are much easier than nitrogen and oxygen molecules, of which air consists, and the sound in hydrogen spreads almost four times faster than in the air. However, inhaling hydrogen risky: in the lungs, it is inevitably mixed with air residues and forms a rat mixture. And if there will be a fire in the exhalation nearby ... That's what the story happened to the French chemist, director of the Paris Museum of Science Pilatre De Rosier (1756-1785). Somehow he decided to check what would be if inhaling hydrogen; Before him, no one has conducted such an experiment. Without noticing no effect, the scientist decided to make sure whether hydrogen penetrates into the lungs. He once again inspired this gas, and then exhaled him on the candle fire, waiting to see the flame outbreak. However, hydrogen in the lungs of a bold experimenter was mixed with air and a strong explosion occurred. "I thought I flew all my teeth with roots," he wrote later, very contented experience, who almost cost him his life.

History of receipt of deuterium and tritium

Deuterium

In addition to the "ordinary" hydrogen (Passion, from Greek protos. - the first), in nature there is also its heavy isotope - deuterium (from Latin deuteros - second) and in insignificant quantities super heavy hydrogen - tritium. The long and dramatic search for these isotopes first did not give the result due to insufficient sensitivity of the instruments. At the end of 1931, a group of American physicists - Yuri with their students, F. Lubricvedda and J. Maerfi, took 4 liters of liquid hydrogen and subjected it with fractional distillation, receiving only 1 ml in the remainder, i.e. By reducing the volume of 4 thousand times. This last milliliter of fluids after its evaporation and was investigated by a spectroscopic method. An experimental spectroscopist of ovary noticed on the spectrogram of enriched hydrogen, new very weak lines, absent from ordinary hydrogen. At the same time, the position of the lines in the spectrum exactly corresponded to the quantum-mechanical calculation of the nuclide 2H (see chemical elements).

After spectroscopic detection of deuterium, it was proposed to separate hydrogen isotopes by electrolysis. Experiments have shown that with electrolysis of water, light hydrogen is really highlighted faster than heavy. This discovery was key to obtaining heavy hydrogen. The article in which the opening of the deuterium was reported was published in the spring of 1932, and in July the results were published on the electrolytic separation of isotopes. In 1934, for the opening of heavy hydrogen, Harold Clayton Yuri received the Nobel Prize in Chemistry.

Tritium

March 17, 1934 In England, the magazine "Nature" ("Nature") was published a small note, signed by M.L. Alifantt, P. Cark and Rutherford (the last name Lord Rostford did not require the initials in the publication!). Despite the modest name of the note: the transmutation effect obtained with severe hydrogen, it reported to the world about the outstanding result - artificial production of the third isotope of hydrogen - tritium. In 1946, a well-known authority in the field of nuclear physics, the Nobel Prize winner, U. F. Libby suggested that tritium is continuously formed as a result of nuclear reactions in the atmosphere. However, in nature, tritium is so little (1 atom 1H per 1018 3H atoms), which it was possible to detect it only on weak radioactivity (half-life of 12.3 years).

Hydrides

Hydrogen forms connections - hydrides with many elements. Depending on the second element, the hydrides differ very much by properties. The most electropositive elements (alkaline and heavy alkaline earth metals) form the so-called saline hydrides of an ionic nature. They are obtained as a result of a direct metal reaction with hydrogen under pressure and at elevated temperatures (300-700 ° C) when the metal is in the molten state. Their crystal lattice contains metal cations and hydride anions H- and built similarly to NaCl grille. When heated to the melting point, the saline hydrides begin to carry out an electric current, while, unlike the electrolysis of the aqueous solutions of salts, hydrogen is highlighted not on the cathode, but on a positively charged anode. Shaft hydrides react with water with hydrogen is released and the formation of alkali solutions are easily oxidized and oxygen and used as strong reducing agents.

A number of elements form covalent hydrides, among which the hydrides of the IV-VI elements are the most known, for example, methane CH 4, ammonia NH 3, hydrogen sulfide H 2 S, etc. Covalent hydrides have a high reactivity and are reducing agents. Some of these hydrides are small and decomposed when heated or hydrolyzed with water. An example is SIH 4, GEH 4, SNH 4. From the point of view of the structure, the hydrides of the boron are interesting, for example, in 2 H 6, in 6 H 10, in 10 H 14, and others, in which the pair of electrons does not associate two, as usual, and the three atoms inn. Covalent and some mixed hydrides are also attributed, for example, Li-Aluminum Hydride LiAlh 4, which was widely used in organic chemistry as a reducing agent. Hydrides Germany, silicon, arsenic are used to obtain high-purity semiconductor materials.

The hydrides of transition metals are very diverse by properties and structure. Often these are compounds of nonstociometric composition, for example, metal-like TIH 1.7, Lah 2.87, etc. In the formation of such hydrides, hydrogen is first adsorbed on the surface of the metal, then it dissociation to atoms, which diffuse the injection of the crystal metal lattice, forming the implementation of the introduction. The hydrides of intermetallic compounds are the greatest interest, for example, containing titanium, nickel, rare-earth elements. The number of hydrogen atoms in a unit of volume of such a hydride can be five times more than even in pure liquid hydrogen! Already at room temperature, the alloys of the mentioned metals are able to quickly absorb significant amounts of hydrogen, and when heated is to highlight it. Thus, reversible "chemical batteries" of hydrogen are obtained, which, in principle, can be used to create engines operating in hydrogen fuel. Of the other hydrides of transition metals, the uranium hydride of the UH 3 is interesting, which serves as a source of other uranium compounds of high purity.

Application

Hydrogen is used mainly to obtain ammonia, which is needed for the production of fertilizers and many other substances. From liquid vegetable oils with hydrogen, solid fats are obtained, similar to butter and other animal fats. They are used in the food industry. In the production of quartz glass products, a very high temperature is required. And here hydrogen is used: the burner with a hydrogen-oxygen flame gives a temperature above 2000 degrees at which the quartz is easily melted.

In the laboratories and in the industry, the reaction of the addition of hydrogen to various connections is widely used. The most common reactions of hydrogenation of multiple carbon-carbon ties are the most common. So, from acetylene, it is possible to obtain ethylene or (with full hydrogenation) ethane, from benzene - cyclohexane, from liquid unsteady oleic acid - solid limit stearic acid, etc. Other classes of organic compounds are subjected to hydrogenation, while recovering them. Thus, when hydrogenating carbonyl compounds (aldehydes, ketones, esters), appropriate alcohols are formed; For example, an isopropyl alcohol is obtained from acetone. When hydrogenation of nitrogenations, appropriate amines are formed.

Hydrogenation with molecular hydrogen is often carried out in the presence of catalysts. In industry, as a rule, use heterogeneous catalysts, to which metals of the VIII group of the periodic system of elements - nickel, platinum, rhodium, palladium. The most active of these catalysts - platinum; With it, it can be hydrogenated at room temperature without pressure even aromatic compounds. The activity of cheaper catalysts can be increased by conducting a pressure hydrogenation reaction at elevated temperatures in special devices - autoclaves. Thus, for hydrogenation of aromatic compounds, pressure is required up to 200 atm and the temperature above 150 ° C.

In laboratory practice, various methods of noncatalithic hydrogenation are also widely used. One of them is the action of hydrogen at the time of isolation. Such "active hydrogen" can be obtained in the reaction of metallic sodium with alcohol or amalgamed zinc with hydrochloric acid. Significant propagation in organic synthesis was hydrogenated by complex hydrides - sodium sodium borohydride NABH 4 and lithium alumohydride LiAlh 4. The reaction is carried out in anhydrous media, since complex hydrides are instantly hydrolyzed.

Hydrogen is used in many chemical laboratories. It is stored under pressure in steel cylinders, which for safety with the help of special clamps are attached to the wall or even endure into the courtyard, and the gas enters the laboratory by a thin tube.

Chemical elements and materials

Hydrogen, n (lat. Hydrogenium; a. Hydrogen; N. Wasserstoff; F. Hydrogene; and. Hidrogeno), - the chemical element of the periodic system of Mendeleev elements, which is attributed simultaneously to I and VII groups, atomic number 1, atomic weight 1, 0079. Natural hydrogen has stable isotopes - diet (1 H), deuterium (2 H, or d) and radioactive - tritium (3 N, or T). For natural compounds, the average ratio D / H \u003d (158 ± 2) .10 -6 is an equilibrium content of 3 H on Earth ~ 5.10 27 atoms.

Physical properties of hydrogen

Hydrogen first described in 1766 English scientist. Cavendish. Under normal conditions, hydrogen - gas without color, odor and taste. In nature in a free state is in the form of molecules H 2. The dissociation energy of the H 2 molecule is 4.776 eV; The potential for ionization of hydrogen atom 13.595 eV. Hydrogen is the easiest substance from all known, at 0 ° C and 0.1 MPa 0.0899 kg / m 3; T boiling - 252.6 ° C, T melting - 259.1 ° C; Critical parameters: T - 240 ° C, pressure 1.28 MPa, density 31.2 kg / m 3. Thermal conductory of all gases is 0.174 W / (mk) at 0 ° C and 1 MPa, the specific heat 14,208.10 3 J (kg.k).

Chemical properties of hydrogen

Liquid hydrogen is very lung (density at -253 ° C 70.8 kg / m 3) and teaching (at -253 ° C is 13.8 SP). In most compounds, hydrogen shows the degree of oxidation +1 (similar to alkali metals), less often -1 (similar to the hydrides of metals). Under normal conditions, molecular hydrogen is low-effective; water solubility at 20 ° C and 1 MPa 0.0182 ml / g; It is well soluble in metals - Ni, pt, pd and other with oxygen forms water with heat release of 143.3 MJ / kg (at 25 ° C and 0.1 MPa); At 550 ° C and above the reaction is accompanied by an explosion. When interacting with fluorine and chlorine, the reaction also goes with an explosion. Main hydrogen compounds: H 2 O, Ammonia NH 3, hydrogen sulfide H 2 S, CH 4, hydrides of metals and halogens CAH 2, HBr, HL, and organic compounds with 2 H 4, HCHO, CH 3 OH, etc.

Hydrogen in nature

Hydrogen is a widespread element in nature, its content in 1% (by weight). The main tank of hydrogen on Earth is water (11.19%, by weight). Hydrogen is one of the main components of all natural organic compounds. In the free state is present in volcanic and other natural gases, in (0.0001%, according to atoms). It is the main part of the mass of the Sun, stars, inter-storage gas, gas nebulae. In the atmospheres, the planets are present in the form H 2, CH 4, NH 3, H 2 O, CH, NHOH, and others. It is included in the composition of the corpuscular radiation of the Sun (protons) and cosmic rays (electrons flows).

Obtaining and use of hydrogen

Raw materials for industrial hydrogen production - gas-refining gases, gasification products, etc. Basic methods for producing hydrogen: hydrocarbon reaction with water vapor, incomplete oxidation of hydrocarbons, oxide conversion, water electrolysis. Hydrogen is used for the production of ammonia, alcohols, synthetic gasoline, hydrochloric acid, hydrotreating of petroleum products, metal cutting by hydrogen-oxygen flame.

Hydrogen is a perspective gaseous fuel. Deuterium and tritium found use in nuclear power.

In the periodic system, hydrogen is located in two absolutely opposite in their properties of groups of elements. This feature make it completely unique. Hydrogen is not simply an element or substance, but also is an integral part of many complex compounds, organogenic and biogenic element. Therefore, we consider its properties and characteristics in more detail.

The separation of fuel gas in the process of interaction between metals and acids was observed in the XVI century, that is, during the formation of chemistry as science. The famous English scientist Henry Cavendish explored the substance since 1766, and gave him the name "combustible air". When burning, this gas gave water. Unfortunately, the commitment of the scientist theory of phlogiston (hypothetical "hypothone of matter") prevented him to come to the right conclusions.

The French chemist and the naturalist A. Lavoisier, together with the engineer J. More and with the help of special gasometers in 1783, conducted a synthesis of water, and after and its analysis by decomposing water vapor hot iron. Thus, scientists were able to come to the right conclusions. They found that "combustible air" is not only part of the water, but can also be obtained from it.

In 1787, Lavoisier put forward the assumption that the gas under study is simple substance And, accordingly, refers to the number of primary chemical elements. He called him Hydrogene (from the Greek Words of Hydor - Water + Gennao - God), i.e. "Horing Water".

The Russian name "Hydrogen" in 1824 proposed a Chemist M. Solovyov. The determination of the composition of water marked the end of the "Flogiston theory". At the junction of the XVIII and XIX centuries, it was found that the hydrogen atom is very light (compared to atoms of other elements) and its mass was adopted for the main unit of comparison of atomic masses, obtaining a value equal to 1.

Physical properties

Hydrogen is the easiest of all known science of substances (it is 14.4 times lighter than air), its density is 0.0899 g / l (1 atm, 0 ° C). This material melts (hardens) and boils (liquefied), respectively, at -259.1 ° C and -252.8 ° C (only helium has lower boiling and melting t °).

Critical temperature of hydrogen is extremely low (-240 ° C). For this reason, his liquefaction is a rather complicated and cost process. The critical pressure of the substance is 12.8 kgf / cm², and the critical density is 0.0312 g / cm³. Among all gases, hydrogen has the greatest thermal conductivity: at 1 atm and 0 ° C, it equals 0.174 W / (MHC).

Specific heat capacity of the substance under the same conditions - 14.208 KJ / (CGKK) or 3,394 Cal / (GC ° C). This element is weakly soluble in water (about 0.0182 ml / g at 1 atm and 20 ° C), but well - in most metals (Ni, Pt, PA and others), especially in palladium (approximately 850 volumes per one PD ).

With the latest property, its diffusion ability is associated, while the diffusion through a carbon alloy (for example, steel) can be accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (this process is called decarbonization). In a liquid state, the substance is very easy (density - 0.0708 g / cm³ at t ° \u003d -253 ° C) and fluid (viscosity - 13.8 scholasis under the same conditions).

In many compounds, this element exhibits valence +1 (degree of oxidation), like sodium and other alkaline metals. It is usually considered as analogue of these metals. Accordingly, he heads the I group of the Mendeleev system. In the hydrides of metals, hydrogen ion shows a negative charge (the degree of oxidation at the same time -1), that is, Na + H- has a structure similar to Na + Cl- chloride. In accordance with this and some other facts (the proximity of the physical properties of the element "H" and halogen, the ability to replace it with halogens in organic compounds) Hydrogene belongs to the VII group of the Mendeleev system.

Under normal conditions, molecular hydrogen has low activity, directly connecting only with the most active non-metals (with fluorine and chlorine, with the latter - in the light). In turn, when heated, it interacts with many chemical elements.

Atomic hydrogen has increased chemical activity (if compared with molecular). With oxygen, it forms water by the formula:

N₂ + ½₂ \u003d N₂O,

highlighting 285.937 KJ / Mol heat or 68,3174 kcal / mol (25 ° C, 1 atm). In conventional temperature conditions, the reaction proceeds quite slowly, and at t °\u003e \u003d 550 ° C - uncontrollable. The explosion limits of the mixture of hydrogen + oxygen in volume are 4-94% H₂, and the mixtures of hydrogen + air - 4-74% H₂ (a mixture of two volumes of H₂ and one volume of O₂ is called rat gas.

This element is used to restore most metals, as it takes oxygen by oxides:

Fe₃O₄ + 4H₂ \u003d 3FE + 4N₂O,

Cuo + H₂ \u003d Cu + H₂o, etc.

With different halogens, hydrogen forms halogen hydrogen sodes, for example:

N₂ + CL₂ \u003d 2NSL.

However, when reactions with fluorine, hydrogen explodes (this occurs in the dark, at -252 ° C), with bromine and chlorine reacts only when heated or illumination, and with iodine - exclusively when heated. When interacting with nitrogen, ammonia is formed, but only on the catalyst, at elevated pressures and temperatures:

ZN₂ + N₂ \u003d 2NN₃.

When heated, hydrogen actively reacts with sulfur:

N₂ + S \u003d H₂S (hydrogen sulfide)

and it is much more difficult - with tellurium or selenium. With pure carbon, hydrogen reacts without a catalyst, but at high temperatures:

2N₂ + C (amorphous) \u003d CH₄ (methane).

This substance directly reacts with some of the metals (alkaline, alkaline earth and other), forming hydrides, for example:

H₂ + 2Li \u003d 2LIH.

Evaliable practical importance has the interactions of hydrogen and carbon oxide (II). In this case, depending on the pressure, temperature and catalyst, different organic compounds are formed: NSNO, CN₃on, etc. Unsaturated hydrocarbons in the reaction process are moving into saturated, for example:

With N ₂ n + H₂ \u003d C n ₂ n ₊₂.

Hydrogen and its compounds play an exceptional role in chemistry. It causes the acid properties of the T. N. Protonic acids are inclined to form a hydrogen bond with different elements that have a significant impact on the properties of many inorganic and organic compounds.

Obtaining hydrogen

The main types of raw materials for the industrial production of this element are gases of refining, natural combustible and coke gases. It is also obtained from water through electrolysis (in places with affordable electricity). One of the most important methods for the production of natural gas material is the catalytic interaction of hydrocarbons, mainly methane, with water vapor (T.N. Conversion). For example:

CH₄ + H₂O \u003d CO + ZN₂.

Incomplete oxidation of hydrocarbons with oxygen:

CH₄ + ½O₂ \u003d CO + 2N₂.

Synthesized carbon oxide (II) conversion:

CO + N₂O \u003d SO + H₂.

Hydrogen produced from natural gas is the cheapest.

For electrolysis of water, a constant current is used, which is passed through a solution of NaOH or con (acids are not used to avoid corrosion of instruments). In the laboratory, the material is obtained by electrolysis of water or as a result of the reaction between hydrochloric acid and zinc. However, more often use ready-made factory material in cylinders.

From the gas of oil refining and coke gas, this element is isolated by removing all other components of the gas mixture, since they are easier to liquefy with deep cooling.

Industrially, this material began to receive even at the end of the XVIII century. Then it was used to fill balloons. At the moment, hydrogen is widely used in industry, mainly in the chemical, for the production of ammonia.

Mass consumers of the substance are manufacturers of methyl and other alcohols, synthetic gasoline and many other products. They are obtained by synthesis of carbon oxide (II) and hydrogen. Hydrogene is used to hydrogenize heavy and solid liquid fuels, fats, etc., for the synthesis of HCl, hydrotreating of petroleum products, as well as in cutting / welding of metals. The most important elements for nuclear energy are its isotopes - tritium and deuterium.

Biological role of hydrogen

About 10% of the mass of living organisms (on average) falls on this element. It is part of the water and essential groups of natural compounds, including proteins, nucleic acids, lipids, carbohydrates. Why does it serve?

This material plays a decisive role: when maintaining the spatial structure of proteins (quaternary), in the implementation of the principle of nucleic acid complimentaryness (i.e., in the implementation and storage of genetic information), in general in "recognition" at the molecular level.

The hydrogen ion H + takes part in important dynamic reactions / processes in the body. Including: in biological oxidation, which provides living cells by energy, in biosynthesis reactions, in photosynthesis in plants, in bacterial photosynthesis and nitrogenation, in maintaining acid-alkaline balance and homeostasis, in the membrane transport processes. Along with carbon and oxygen, it forms a functional and structural basis of life phenomena.