interaction with water form alkali; c) passive, inactive; b) when interacting with metals, they form salts; G) typical metals; 2. A metal that can be used to produce hydrogen (by reacting it with water at n.a.): a) Zn; b) Mg; c) Au; d) Hg; e) K; 3. Oxides and hydroxides that are able to react with both acids and alkalis are called: a) amphoteric b) acidic c) basic 4. From left to right in periods metallic properties: a) increase b) weaken c) remain unchanged 5. Element of a side subgroup of group VII: a) chlorine b) phosphorus c) manganese d) francium 6. The charge of the atomic nucleus is determined: a) by the period number b) by the group number c) by serial number 7. The same in the structure of atoms of elements with serial numbers 17 and 35: a) total electrons; c) quantity electronic levels; d) the number of electrons on the last energy level; b) the number of neutrons; 8. Item with electronic formula 1s22s2p63s2p4: a) carbon; b) sulfur; c) chlorine; d) sodium; 9. The carbon atom has an electronic formula: a) 1s22s22p3 b) 1s22s2 c) 1s22s22p2 10. Which element atom has the following structure of the last energy level ... 3s23p5: a) phosphorus; b) fluorine; c) chlorine; d) magnesium; 11. The number of unpaired electrons in electron shell element No. 19: a) 1; b) 2; at 3; d) 4; 12. Serial number an element whose atoms are capable of forming a higher oxide of the RO3 type: a) No. 11 (sodium); b) No. 14 (silicon); c) No. 16 (sulfur); 13. An element with the electronic formula 1s22s22p63s23p5 forms a volatile hydrogen bond type: a) RH4; b) RH3; c) H2R; d) HR; 14. The volume of 3 mol of hydrogen at normal conditions: a) 22.4 l; b) 44.8 l; c) 67.2 l; d) 89.6 l; e) 112 l; 15. Element of the fourth period, located in secondary subgroup; oxide and hydroxide exhibit amphoteric character. This element forms oxide type RO and hydroxide R(OH)2. a) magnesium b) calcium c) zinc d) carbon 16. Maximum valency of silicon: a) IV b) V c) VI d) VII 17. Minimum valency of selenium (No. 34): a) I b) II c) III d ) IV 18. Molecular mass salt obtained by the interaction of two higher oxides elements with the configuration of the atom in them, respectively, 1s22s22p63s23p64s1 and 1s22s22p3 is equal to: a) 85; b) 111; c) 63; d) 101; e) 164; 19. Product "X", which is obtained as a result of transformations: Al salt Al (OH) 3 X a) Al Cl3 b) Al H3 c) Na Al O2 d) Al e) Al2O3 20. The sum of the coefficients in the reaction equation, the scheme of which H2S + O2 → SO2 + H2O a) 5; b) 6; at 7; d) 8; e) 9; 21. Molar mass magnesium oxide (in g/mol): a) 24; b) 36; c) 40; d) 80; e) 82; 22. The number of moles of iron oxide (III) that make up 800 g this compound: a) 1; b) 2; at 3; d) 4; e) 5; 23. During the combustion of 8 g of CH4 methane, 401 kJ of heat was released. Calculate thermal effect (Q) chemical reaction CH4 (g) + 2O2 (g) = CO2 (g) + 2H2O (g) + Q: a) + 401 kJ; b) + 802 kJ; c) - 802 kJ; d) + 1604 kJ; e) - 1604 kJ; 24. Under normal conditions, 128 g of oxygen occupy the volume: a) 11.2 liters; b) 22.4 l; c) 44.8 l; d) 67.2 l; e) 89.6 l; 25. Mass fraction hydrogen in the SiH4 compound is: a) 30%; b) 12.5%; c) 40%; d) 60%; e) 65%; 26. The mass fraction of oxygen in the EO2 compound is 50%. The name of the element E in the compound: a) nitrogen; b) titanium; c) sulfur; d) selenium; e) carbon; 27. The number of moles of iron oxide (III) interacting with 44.8 liters of hydrogen (n.o.): a) 0.67 mol; b) 2 mol; c) 0.3 mol; d) 0.4 mol; e) 5 mol; 28. Weight of hydrochloric acid required to obtain 44.8 liters of hydrogen (n.o.) (Mg + 2HCl = MgCl2 + H2): a) 146 g; b) 73 g; c) 292 g; d) 219 g; e) 20 g; 29. Mass of salt contained in 400 g of 80% sodium chloride solution: a) 146 g; b) 320 g; c) 210 g; d) 32 g; e) 200 g; 30. The mass of salt, which is formed by the interaction of potassium hydroxide with 300 g of a 65% solution of orthophosphoric acid: a) 422 g; b) 196 g; c) 360 g; d) 435 g; e) 200 g;

In 1766, the English chemist G. Cavendish collected "combustible air" displaced by metals from acids and studied its properties. But only 15 years later it was proved that this "air" is part of the water, and the name "hydrogenium" was given to it, that is, "giving birth to water", "hydrogen".

The share of hydrogen on Earth, including water and air, accounts for about 1% by mass. It is very common and vital important element. It is part of all plants and animals, as well as the most common substance on Earth - water.

Hydrogen is the most abundant element in the universe. It stands at the beginning of a long and complex process synthesis of elements in stars.

Solar energy is the main source of life on Earth. And the fundamental principle of this energy - thermonuclear reaction occurring on the Sun in several stages. Its result is the formation of 4 hydrogen nuclei - protons of one helium nucleus and two positrons. At the same time, it highlights great amount energy.

Man managed to reproduce on Earth not a very accurate likeness of the main solar reaction. AT earthly conditions we can force only the heavy isotopes of hydrogen 2 H - deuterium and 3 H - tritium to enter into such a reaction. Ordinary hydrogen with an atomic mass of 1 - protium - is beyond our control in this sense. Managed thermonuclear fusion as an unlimited source of peaceful energy is not yet available to man.

AT periodic system elements hydrogen occupies special place. This is the element that starts periodic table Mendeleev. It usually stands in group I above lithium. Because the hydrogen atom has only one valence electron (and generally one electron). However, in modern editions periodic table hydrogen is also placed in VII group over fluorine, since hydrogen is found in common with halogens. In addition, hydrogen is able to form compounds with metals - hydrides. In practice, the most important of these is the combination of lithium with the heavy hydrogen deuterium.

Isotopes of all elements have basic physical and Chemical properties practically identical. But for hydrogen isotopes - protium, deuterium and tritium - they differ quite a lot. For example, the boiling points of protium, deuterium, and tritium differ by several degrees. Therefore, isotopes of hydrogen are easier to separate than isotopes of any other element.

Hydrogen is a colorless gas, odorless and tasteless. It is the lightest of all gases, 14.4 times lighter than air. Hydrogen becomes liquid at -252.6°C and solid at -259.1°C.

AT normal conditions chemical activity hydrogen is low, it reacts with fluorine, iodine and chlorine. But at elevated temperature hydrogen interacts with bromine, iodine, sulfur, selenium, tellurium, and in the presence of catalysts with nitrogen, forming ammonia NH3. A mixture of 2 volumes of H2 and 1 volume of O2 - it is called explosive gas - explodes violently when ignited. Hydrogen burns in oxygen with a non-luminous flame, forming water.

At high temperature hydrogen is able to "remove" oxygen from the molecules of many compounds, including most metal oxides. For a chemist, hydrogen is, first of all, an excellent reducing agent, although it is still quite expensive. Yes, and it is not easy to work with him. Therefore, on an industrial scale, hydrogen reduction (for example, metals from oxides) is used very limitedly.

Hydrogen is widely used in the process of hydrogenation - the transformation of liquid fats into solid ones, for example, to obtain edible margarine from vegetable oils, as well as in a number of chemical syntheses. The largest consumers of hydrogen in chemical industry still remain the production of ammonia and methyl alcohol.

Increasing interest is being shown today in hydrogen as a source of thermal energy. Indeed, the combustion of pure hydrogen releases significantly more heat than when burning the same amount of any fuel. There were even designs for hydrogen-powered vehicles. In most of them, the source of hydrogen is solid hydrides of some metals, which, under certain conditions, firmly retain the hydrogen associated with them. But it is worth changing these conditions, for example, raising the temperature above some, usually rather low, threshold, and hydrogen begins to be released into a device that replaces a carburetor in such a car. Of course, on the way to creating mass hydrogen car there are still many technical difficulties. But, apparently, they will be overcome soon enough, since such fuel is energetically beneficial. In addition, when hydrogen is burned, it does not form harmful impurities polluting the atmosphere, and only clean water is obtained.

Liquid

Hydrogen(lat. Hydrogenium; denoted by the symbol H) is the first element of the periodic system 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 analysis organic matter.

The three isotopes of hydrogen have 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. In a mixture with air or oxygen, it is combustible and explosive. Non-toxic. Soluble in ethanol and a number of metals: iron, nickel, palladium, platinum.

Story

The release of combustible gas during the interaction of acids and metals was observed in the 16th and XVII centuries at the dawn of the formation of chemistry as a science. Mikhail Vasilyevich Lomonosov also directly pointed to its isolation, but already definitely realizing that this was not phlogiston. English physicist and chemist Henry Cavendish in 1766 he investigated this gas and called it "combustible air". When burned, "combustible air" produced water, but Cavendish's adherence to the theory of phlogiston prevented him from doing so. correct conclusions. 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 red-hot iron. Thus, he established that "combustible air" is part of the water and can be obtained from it.

origin of name

Lavoisier gave the name hydrogène to hydrogen, meaning “water-bearing”. Russian name"hydrogen" was proposed by the chemist M.F. Solovyov 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 taken together is less than 0.1%). Thus, hydrogen is the main component 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

Mass fraction of hydrogen in earth's crust is 1% - this is the tenth most common 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 proportion of atoms of which is ~ 52%). Therefore, the importance of hydrogen in the 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 found in the atmosphere (0.00005% by volume).

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

Receipt

Industrial methods of obtaining simple substances depend on the form in which the corresponding element is in nature, that is, what can be the raw material for its production. So, oxygen, available in a free state, is obtained in a physical way- extraction from liquid air. Hydrogen, on the other hand, is almost all in the form of compounds, therefore, to obtain it, chemical methods. In particular, decomposition reactions can be used. One of the ways to produce hydrogen is the reaction of decomposition of water by electric current.

Basic industrial way hydrogen production - the reaction with water of methane, which is part of natural gas. It is carried out at a high temperature (it is easy to verify that when methane is passed even through boiling water, no reaction occurs):

CH 4 + 2H 2 O \u003d CO 2 + 4H 2 −165 kJ

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

Hydrogen is usually produced in the laboratory by reacting zinc with hydrochloric acid.

In industry

1. Electrolysis aqueous solutions salts:

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:

2CH4 + O2? 2CO + 4H2

4. Cracking and reforming of hydrocarbons in the process of oil refining.

In the laboratory

1.Action of dilute acids on metals. To carry out such a 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.The action of alkalis on zinc or aluminum:

2Al + 2NaOH + 6H 2 O → 2Na + 3H 2

Zn + 2KOH + 2H 2 O → K 2 + H 2

5.With the help of 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 the orthohydrogen molecule o-H 2 (mp. −259.10 ° C, bp. −252.56 ° C) nuclear spins are directed in the same way (parallel), while parahydrogen p-H 2 (mp. −259.32 ° C, bp. −252.89 ° C) - opposite to each other (anti-parallel). 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 entirely shifted towards the latter. At 80 K, the aspect ratio is approximately 1:1. Desorbed parahydrogen, when heated, transforms into orthohydrogen up to the formation of an equilibrium at room temperature mixtures (ortho-para: 75:25). Without a catalyst, the transformation occurs slowly (in the 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, 14.5 times lighter than air. It is obvious that what less mass molecules, the higher their speed at the same temperature. As the lightest, 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 about seven times higher than that of air.

The hydrogen molecule is diatomic - H 2. Under normal conditions, it is a colorless, odorless and tasteless gas. Density 0.08987 g/l (n.o.), boiling point −252.76 °C, specific heat 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). Related to the solubility of hydrogen in metals is its ability to diffuse through them; diffusion through a carbonaceous alloy (for example, steel) is sometimes accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (the 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 / cm 3) and fluid (viscosity at -253 °C 13.8 centigrade). 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-H 2 , 0.21% ortho-H 2 .

Solid hydrogen, melting point −259.2 °C, density 0.0807 g/cm3 (at −262 °C) — snow-like mass, hexagonal crystals, space group P6/mmc, cell parameters a=3,75 c=6.12. At high pressure hydrogen goes into a metallic state.

isotopes

Hydrogen occurs in the form 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 hydrogen production.

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

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

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

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

	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-D2, o-D2, p-T2, o-T 2 . Heteroisotopic hydrogen (HD, HT, DT) do not have ortho and para modifications.

Chemical properties

Fraction of dissociated hydrogen molecules

Hydrogen molecules H 2 are quite strong, and in order for hydrogen to react, a lot of energy must be expended:

H 2 \u003d 2H - 432 kJ

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

Ca + H 2 \u003d 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, such as lighting:

O 2 + 2H 2 \u003d 2H 2 O

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

CuO + H 2 \u003d Cu + H 2 O

The written equation reflects restorative properties hydrogen.

N 2 + 3H 2 → 2NH 3

Forms hydrogen halides with halogens:

F 2 + H 2 → 2HF, the reaction proceeds with an explosion in the dark and at any temperature,

Cl 2 + H 2 → 2HCl, the reaction proceeds with an explosion, only in the light.

It interacts with soot at strong heating:

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- saline, solids, 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 recovery 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, alkanes, are formed.

Geochemistry of hydrogen

Free hydrogen H 2 is relatively rare in terrestrial gases, but in the form of water it accepts exclusively important participation in geochemical processes.

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

Hydrogen is continuously produced in the atmosphere as a result of the decomposition of water. solar radiation. Having a small mass, hydrogen molecules have a high rate of diffusion motion (it is close to the second space velocity) and, getting into the upper atmosphere, can fly into outer space.

Features of circulation

Hydrogen, when mixed with air, forms an explosive mixture - the so-called explosive gas. This gas is most explosive at volume ratio hydrogen and oxygen 2:1, or hydrogen and air 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 with oxygen occur from 4% to 96% by volume. When mixed with air from 4% to 75(74)% by volume.

Economy

The cost of hydrogen in large wholesale deliveries 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 food additive E949(packing gas)

food industry

Aviation industry

Hydrogen is very light and always rises in the air. Once airships and Balloons filled with hydrogen. But in the 30s. 20th century there were several catastrophes, during which the airships exploded and burned down. 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 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"(“LW”) is a liquid state of aggregation of hydrogen, with a low specific gravity 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 explosive substances with an ignition factor range of 4-75%. The spin ratio of isomers in liquid hydrogen is: 99.79% - parahydrogen; 0.21% - orthohydrogen. Hydrogen expansion coefficient when changing state of aggregation gaseous is 848:1 at 20°C.

As with any other gas, liquefying hydrogen reduces its volume. After liquefaction, "ZHV" is stored in thermally insulated containers under pressure. Liquid hydrogen liquid hydrogen, LH2, LH 2) is widely 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 in 1756 was by the English scientist William Cullen, Gaspard Monge was the first to obtain the 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 in the US to patent the air conditioner in 1851. Werner Siemens proposed the concept of regenerative cooling in 1857, Carl Linde patented equipment for producing liquid air using a cascaded "Joule-Thomson expansion effect" and regenerative cooling in 1876. In 1885, the Polish physicist and chemist Zygmund Wroblewski published the critical temperature of hydrogen 33 K, the critical pressure 13.3 atm. and a boiling point at 23 K. Hydrogen was first liquefied by James Dewar in 1898 using regenerative refrigeration and his invention, the Dewar vessel. The first synthesis of a stable isomer of liquid hydrogen, parahydrogen, was carried out by Paul Harteck and Karl Bonhoeffer in 1929.

Spin isomers of hydrogen

Hydrogen at room temperature consists mainly of the spin isomer, orthohydrogen. After production, liquid hydrogen is in a metastable state and must be converted to the parahydrogen form in order to avoid explosive exothermic reaction, which takes place when it changes at low temperatures. The conversion to the parahydrogen phase is usually carried out using catalysts such as iron oxide, chromium oxide, Activated carbon platinum-plated asbestos, rare earth metals or by using uranium or nickel additives.

Usage

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

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

Advantages

The advantage of using hydrogen is the "zero emission" of its application. The product of its interaction with air is water.

Obstacles

One liter of "ZHV" weighs only 0.07 kg. That is, his 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 common to all cryogenic materials. It is close in this regard to liquid oxygen, but requires more caution due to fire hazard. Even in insulated containers, it is difficult to keep it at the low temperature required to keep it liquid (typically it 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 for jet acceleration of launch vehicles and spacecraft. In most liquid propellant rocket engines, hydrogen is first used to regeneratively cool the nozzle and other parts of the engine before it is mixed with an oxidizer and burned to produce thrust. Modern H 2 /O 2 powered engines in use consume a hydrogen-rich fuel mixture, which results in some unburned hydrogen in the exhaust. In addition to increasing the specific impulse of the engine by reducing the molecular weight, this also reduces the erosion of the nozzle and combustion chamber.

Such obstacles to the use of "ZHV" in other areas, such as cryogenic nature and low density, are also a deterrent to use in this case. For 2009, there is only one launch vehicle (LV "Delta-4"), 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 for the use of sludge-like hydrogen, that is, the semi-frozen form of "ZHV".

In the periodic system has its own certain place position, which reflects the properties displayed by him and speaks of his electronic structure. However, among all there is one special atom that occupies two cells at once. It is located in two groups of elements that are completely opposite in their manifested properties. This is hydrogen. These features make it unique.

Hydrogen is not just an element, but also a simple substance, as well as an integral part of many complex connections, biogenic and organogenic element. Therefore, we consider its characteristics and properties in more detail.

Hydrogen as a chemical element

Hydrogen is an element of the first group of the main subgroup, as well as the seventh group of the main subgroup in the first small period. This period consists of only two atoms: helium and the element we are considering. Let us describe the main features of the position of hydrogen in the periodic system.

1. The serial number of hydrogen is 1, the number of electrons is the same, respectively, the number of protons is the same. The atomic mass is 1.00795. There are three isotopes of this element with mass numbers 1, 2, 3. However, the properties of each of them are very different, since an increase in mass even by one for hydrogen is immediately double.
2. The fact that it contains only one electron on the outer allows it to successfully exhibit both oxidizing and reducing properties. In addition, after the release of an electron, it remains a free orbital, which takes part in the formation chemical bonds according to the donor-acceptor mechanism.
3. Hydrogen is a strong reducing agent. Therefore, the first group of the main subgroup is considered to be his main place, where he leads the most active metals- alkaline.
4. However, when interacting with strong reducing agents, such as, for example, metals, it can also be an oxidizing agent, accepting an electron. These compounds are called hydrides. On this basis, it heads the subgroup of halogens, with which it is similar.
5. Thanks to a very small atomic mass Hydrogen is considered the lightest element. In addition, its density is also very low, so it is also the benchmark for lightness.

Thus, it is obvious that the hydrogen atom is a completely unique, unlike all other elements. Consequently, its properties are also special, and the formed ones are simple and complex substances very important. Let's consider them further.

simple substance

If we talk about this element as a molecule, then we must say that it is diatomic. That is, hydrogen (a simple substance) is a gas. Its empirical formula will be written as H 2, and the graphic one - through a single sigma bond H-H. The mechanism of bond formation between atoms is covalent non-polar.

1. Steam reforming of methane.
2. Coal gasification - the process involves heating coal to 1000 0 C, resulting in the formation of hydrogen and high-carbon coal.
3. Electrolysis. This method can only be used for aqueous solutions of various salts, since melts do not lead to water discharge at the cathode.

Laboratory methods for producing hydrogen:

1. Hydrolysis of metal hydrides.
2. The action of dilute acids on active metals and medium activity.
3. The interaction of alkaline and alkaline earth metals with water.

To collect the resulting hydrogen, it is necessary to keep the test tube turned upside down. After all, this gas cannot be collected in the same way as, for example, carbon dioxide. This is hydrogen, it is much lighter than air. Dissipates quickly, and large quantities explodes when mixed with air. Therefore, the tube must be inverted. After filling it, it must be closed with a rubber stopper.

To check the purity of the collected hydrogen, you should bring a lit match to the neck. If the cotton is deaf and quiet, then the gas is clean, with minimal air impurities. If loud and whistling - dirty, with big share foreign components.

Areas of use

When hydrogen is burned, it releases a large number of energy (heat), that this gas is considered the most profitable fuel. In addition, it is environmentally friendly. However, its use in this area is currently limited. This is due to the ill-conceived and unsolved problems of synthesizing pure hydrogen, which would be suitable for use as fuel in reactors, engines and portable devices, as well as residential heating boilers.

After all, the methods for obtaining this gas are quite expensive, so first it is necessary to develop a special method of synthesis. One that will allow you to receive the product in large volume and at minimal cost.

There are several main areas in which the gas we are considering is used.

1. Chemical syntheses. Based on hydrogenation, soaps, margarines, and plastics are obtained. With the participation of hydrogen, methanol and ammonia are synthesized, as well as other compounds.
2. AT Food Industry- as an additive E949.
3. Aviation industry (rocket building, aircraft building).
4. Power industry.
5. Meteorology.
6. Fuel of an environmentally friendly type.

Obviously, hydrogen is as important as it is abundant in nature. More big role play the various compounds formed by it.

Hydrogen compounds

These are complex substances containing hydrogen atoms. There are several main types of such substances.

1. Hydrogen halides. General formula- H Hal. Of particular importance among them is hydrogen chloride. It is a gas that dissolves in water to form a hydrochloric acid solution. This acid is found wide application in almost all chemical syntheses. And both organic and inorganic. Hydrogen chloride is a compound that has the empirical formula HCL and is one of the largest in terms of annual production in our country. Hydrogen halides also include hydrogen iodide, hydrogen fluoride, and hydrogen bromide. All of them form the corresponding acids.
2. Volatile Almost all of them are quite poisonous gases. For example, hydrogen sulfide, methane, silane, phosphine and others. However, they are very flammable.
3. Hydrides are compounds with metals. They belong to the class of salts.
4. Hydroxides: bases, acids and amphoteric compounds. Their composition necessarily includes hydrogen atoms, one or more. Example: NaOH, K 2 , H 2 SO 4 and others.
5. Hydrogen hydroxide. This compound is better known as water. Another name for hydrogen oxide. The empirical formula looks like this - H 2 O.
6. Hydrogen peroxide. This is the strongest oxidizing agent, the formula of which is H 2 O 2.
7. Numerous organic compounds: hydrocarbons, proteins, fats, lipids, vitamins, hormones, essential oils and others.

Obviously, the variety of compounds of the element we are considering is very large. This once again confirms its high importance for nature and man, as well as for all living beings.

is the best solvent

As mentioned above, the common name given substance- water. Consists of two hydrogen and one oxygen atoms linked together by covalent polar bonds. The water molecule is a dipole, which explains many of its properties. In particular, the fact that it is a universal solvent.

Exactly at aquatic environment almost everything happens chemical processes. Internal reactions of plastic and energy metabolism in living organisms are also carried out using hydrogen oxide.

Water is considered to be the most important substance on the planet. It is known that no living organism can live without it. On Earth, it is able to exist in three states of aggregation:

• liquid;
• gas (steam);
• solid (ice).

Depending on the isotope of hydrogen that is part of the molecule, there are three types of water.

1. Light or protium. An isotope with a mass number of 1. The formula is H 2 O. This is the usual form that all organisms use.
2. Deuterium or heavy, its formula is D 2 O. Contains the isotope 2 H.
3. Super heavy or tritium. The formula looks like T 3 O, the isotope is 3 H.

The reserves of fresh protium water on the planet are very important. It is already lacking in many countries. Methods are being developed to treat salt water in order to obtain drinking water.

Hydrogen peroxide is a universal remedy

This compound, as mentioned above, is an excellent oxidizing agent. However, with strong representatives it can also behave as a reducer. In addition, it has a pronounced bactericidal effect.

Another name for this compound is peroxide. It is in this form that it is used in medicine. A 3% solution of the crystalline hydrate of the compound in question is a medical drug that is used to treat small wounds in order to decontaminate them. However, it has been proven that in this case, wound healing over time increases.

Hydrogen peroxide is also used in rocket fuel, in the industry for disinfection and bleaching, as a foaming agent for the production of appropriate materials (foam, for example). In addition, peroxide helps clean aquariums, bleach hair, and whiten teeth. However, at the same time it harms the tissues, therefore it is not recommended by specialists for this purpose.