Where is hydrogen found and what is it for? What kind of substance is hydrogen? Chemical and physical properties of hydrogen

• Designation - H (Hydrogen);
• Latin name - Hydrogenium;
• Period - I;
• Group - 1 (Ia);
• Atomic mass - 1.00794;
• Atomic number - 1;
• Atom radius = 53 pm;
• Covalent radius = 32 pm;
• Distribution of electrons - 1s 1;
• melting point = -259.14 ° C;
• boiling point = -252.87 ° C;
• Electronegativity (Pauling / Alpred and Rohov) = 2.02 / -;
• Oxidation state: +1; 0; -one;
• Density (n. At.) = 0.0000899 g / cm 3;
• Molar volume = 14.1 cm 3 / mol.

Binary compounds of hydrogen with oxygen:

Hydrogen ("giving birth to water") was discovered by the English scientist G. Cavendish in 1766. It is the simplest element in nature - a hydrogen atom has a nucleus and one electron, which is probably why hydrogen is the most abundant element in the Universe (it makes up more than half the mass of most stars).

About hydrogen we can say that "the spool is small, but expensive." Despite its "simplicity", hydrogen gives energy to all living things on Earth - there is a continuous thermonuclear reaction on the Sun, during which one helium atom is formed from four hydrogen atoms, this process is accompanied by the release of a colossal amount of energy (for more details, see Nuclear Fusion).

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

In compounds with non-metals (HCl, H 2 O, CH 4 ...), hydrogen gives up its only electron to more electronegative elements, exhibiting an oxidation state of +1 (more often), forming only covalent bonds(see Covalent bond).

In compounds with metals (NaH, CaH 2 ...), hydrogen, on the contrary, takes another electron into its only s-orbital, thus trying to complete its electronic layer, exhibiting an oxidation state of -1 (less often), more often forming an ionic bond (see Ionic bond), since the difference in the electronegativity of a hydrogen atom and a metal atom can be quite large.

H 2

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

Hydrogen molecules possess:

• great mobility;
• great durability;
• low polarizability;
• small size and weight.

Hydrogen gas properties:

• the lightest gas in nature, colorless and odorless;
• poorly soluble in water and organic solvents;
• in small amounts it dissolves in liquid and solid metals (especially in platinum and palladium);
• difficult to liquefy (due to its low polarizability);
• has the highest thermal conductivity of all known gases;
• when heated, it reacts with many non-metals, showing the properties of a reducing agent;
• at room temperature reacts with fluorine (explosion occurs): H 2 + F 2 = 2HF;
• reacts with metals to form hydrides, showing oxidizing properties: H 2 + Ca = CaH 2;

In compounds, hydrogen manifests its reducing properties much more strongly than oxidizing ones. Hydrogen is the strongest reducing agent after coal, aluminum and calcium. The reducing properties of hydrogen are widely used in industry for the production of metals and non-metals (simple substances) from oxides and gallides.

Fe 2 O 3 + 3H 2 = 2Fe + 3H 2 O

Reactions of hydrogen with simple substances

Hydrogen takes on an electron, playing a role reductant, in reactions:

• With oxygen(when ignited or in the presence of a catalyst), in a 2: 1 ratio (hydrogen: oxygen), an explosive oxyhydrogen gas is formed: 2H 2 0 + O 2 = 2H 2 +1 O + 572 kJ
• With gray(when heated to 150 ° C-300 ° C): H 2 0 + S ↔ H 2 +1 S
• With chlorine(when ignited or irradiated with UV rays): H 2 0 + Cl 2 = 2H +1 Cl
• With fluorine: H 2 0 + F 2 = 2H +1 F
• With nitrogen(when heated in the presence of catalysts or at high pressure): 3H 2 0 + N 2 ↔ 2NH 3 +1

Hydrogen donates an electron, playing a role oxidizer, in reactions with alkaline and alkaline earth metals with the formation of metal hydrides - salt-like ionic compounds containing hydride ions H - are unstable crystalline substances of white color.

Ca + H 2 = CaH 2 -1 2Na + H 2 0 = 2NaH -1

It is unusual for hydrogen to exhibit an oxidation state of -1. Reacting with water, hydrides decompose, reducing water to hydrogen. The reaction of calcium hydride with water is as follows:

CaH 2 -1 + 2H 2 +1 0 = 2H 2 0 + Ca (OH) 2

Reactions of hydrogen with complex substances

• at high temperatures, hydrogen reduces many metal oxides: ZnO + H 2 = Zn + H 2 O
• methyl alcohol is obtained as a result of the reaction of hydrogen with carbon monoxide (II): 2H 2 + CO → CH 3 OH
• in hydrogenation reactions, hydrogen reacts with many organic substances.

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

Application of hydrogen

• v nuclear power isotopes of hydrogen are used - deuterium and tritium;
• in the chemical industry, hydrogen is used for the synthesis of many organic matter, ammonia, hydrogen chloride;
• v Food Industry hydrogen is used in the production of solid fats by hydrogenating vegetable oils;
• high temperature of combustion of hydrogen in oxygen (2600 ° C) is used for welding and cutting metals;
• in the production of some metals, hydrogen is used as a reducing agent (see above);
• since hydrogen is a light gas, it is used in aeronautics as a filler for balloons, balloons, airships;
• as a fuel, hydrogen is used in a mixture with CO.

Recently, scientists have been paying a lot of attention to finding alternative sources of renewable energy. One of the promising areas is "hydrogen" power engineering, in which hydrogen is used as a fuel, the combustion product of which is ordinary water.

Methods for producing hydrogen

Industrial methods for producing hydrogen:

• conversion of methane (catalytic reduction of water vapor) with water vapor at high temperature (800 ° C) on a nickel catalyst: CH 4 + 2H 2 O = 4H 2 + CO 2;
• conversion of carbon monoxide with steam (t = 500 ° C) on the catalyst Fe 2 O 3: CO + H 2 O = CO 2 + H 2;
• thermal decomposition of methane: CH 4 = C + 2H 2;
• gasification of solid fuels (t = 1000 ° C): C + H 2 O = 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:

• the action on metals (usually zinc) with hydrochloric or dilute sulfuric acid: Zn + 2HCl = ZCl 2 + H 2; Zn + H 2 SO 4 = ZnSO 4 + H 2;
• interaction of water vapor with hot iron shavings: 4H 2 O + 3Fe = Fe 3 O 4 + 4H 2.

Hydrogen (Hydrogenium) was discovered in the first half of the 16th century by the German physician and naturalist Paracelsus. In 1776 G. Cavendish (England) established its properties and indicated differences from other gases. Lavoisier was the first to obtain hydrogen from water and proved that water is a chemical compound of hydrogen with oxygen (1783).

Hydrogen has three isotopes: protium, deuterium or D and tritium or T. Their mass numbers are 1, 2 and 3. Protium and deuterium are stable, tritium is radioactive (half-life 12.5 years). In natural compounds, deuterium and protium are on average contained in a ratio of 1: 6800 (by the number of atoms). Tritium is found in nature in negligible amounts.

The nucleus of a hydrogen atom contains one proton. The nuclei of deuterium and tritium include, in addition to the proton, one and two neutrons, respectively.

A hydrogen molecule consists of two atoms. Here are some properties that characterize the hydrogen atom and molecule:

Ionization energy of an atom, eV 13.60

Affinity of an atom for an electron, eV 0.75

Relative electronegativity 2.1

Atom radius, nm 0.046

Internuclear distance in a molecule, nm 0.0741

Standard eithalpy of dissociation of molecules at 436.1

115. Hydrogen in nature. Getting hydrogen.

Free hydrogen is found on Earth only in small quantities. Sometimes it is released along with other gases during volcanic eruptions, as well as from boreholes during oil production. But hydrogen is very common in the form of compounds. This can be seen already from the fact that it makes up one-ninth of the mass of water. Hydrogen is a part of all plant and animal organisms, oil, coal and brown coal, natural gases and a number of minerals. The share of hydrogen from the entire mass crust, counting water and air, accounts for about 1%. However, when recalculated as a percentage of the total number of atoms, the hydrogen content in the earth's crust is 17%.

Hydrogen is the most abundant element in the cosmos. It accounts for about half the mass of the Sun and most other stars. It is found in gaseous nebulae, in interstellar gas, and in stars. In the bowels of stars, the nuclei of hydrogen atoms are transformed into the nuclei of helium atoms. This process proceeds with the release of energy; for many stars, including the Sun, it serves as the main source of energy. The rate of the process, that is, the number of hydrogen nuclei converting into helium nuclei in one cubic meter per second, is low. Therefore, the amount of energy released per unit of time per unit of volume is small. However, due to the enormous mass of the Sun, the total amount of energy generated and emitted by the Sun is very large. It corresponds to a decrease in the mass of the Sun by about a second.

In industry, hydrogen is obtained mainly from natural gas. This gas, consisting mainly of methane, is mixed with steam and oxygen. When a mixture of gases is heated to in the presence of a catalyst, a reaction occurs, which can be schematically depicted by the equation:

The resulting gas mixture is separated. Hydrogen is purified and libro is used at the production site, or transported in steel cylinders under high pressure.

An important industrial method for producing hydrogen is also its separation from coke oven gas or from petroleum refining gases. It is carried out by deep cooling, in which all gases, except hydrogen, are liquefied.

In laboratories, hydrogen is obtained mostly by electrolysis of aqueous solutions. The concentration of these solutions is chosen such that it corresponds to their maximum electrical conductivity. The electrodes are usually made from sheet nickel. This metal does not corrode in alkali solutions, even as an anode. If necessary, the resulting hydrogen is purified from water vapor and traces of oxygen. Among other laboratory methods, the most widespread method is the extraction of hydrogen from solutions of sulfuric or hydrochloric acids by the action of zinc on them. The reaction is usually carried out in a Kipp apparatus (Fig. 105).

The most abundant chemical element in the Universe is hydrogen. This is a kind of starting point, because in the periodic table, its atomic number is equal to one. Humanity hopes to be able to learn more about it as one of the most possible vehicles in the future. Hydrogen is the simplest, lightest, most widespread element, there is a lot of it everywhere - seventy-five percent of the total mass of matter. It is found in any star, especially a lot of hydrogen in gas giants. Its role in stellar fusion reactions is key. Without hydrogen, there is no water, which means there is no life. Everyone remembers that a water molecule contains one oxygen atom, and two atoms in it - hydrogen. This is the well-known formula H 2 O.

How we use it

Discovered hydrogen in 1766 by Henry Cavendish when he was analyzing the oxidation reaction of a metal. After several years of observation, he realized that in the process of burning hydrogen, water is formed. Previously, scientists isolated this element, but did not consider it independent. In 1783, hydrogen received the name hydrogen (translated from the Greek "hydro" - water, and "gene" - to give birth). The element that generates water is hydrogen. It is a gas whose molecular formula is H 2. If the temperature is close to room temperature, and the pressure is normal, this element is imperceptible. Hydrogen may not even be caught by human senses - it is tasteless, colorless, odorless. But under pressure and at a temperature of -252.87 C (very cold!), This gas liquefies. This is how it is stored, since it takes up much more space in the form of gas. It is liquid hydrogen that is used as propellant.

Hydrogen can become solid, metallic, but this requires ultra-high pressure, and this is what the most prominent scientists - physicists and chemists - are doing now. Already, this element serves as an alternative fuel for transport. Its use is similar to how an internal combustion engine works: when hydrogen is burned, a lot of its chemical energy is released. A method for creating a fuel cell based on it has also been practically developed: when combined with oxygen, a reaction occurs, and through this, water and electricity are formed. Perhaps, soon transport will "switch" instead of gasoline to hydrogen - a lot of car manufacturers are interested in the creation of alternative combustible materials, there are also successes. But a purely hydrogen engine is still in the future, there are many difficulties here. However, the advantages are such that the creation of a fuel tank with solid hydrogen is in full swing, and scientists and engineers are not going to retreat.

Basic information

Hydrogenium (lat.) - hydrogen, the first serial number in the periodic table, denoted by H. The hydrogen atom has a mass of 1.0079, it is a gas that under normal conditions has neither taste, nor smell, nor color. Chemists since the sixteenth century have described a certain combustible gas with different names. But it turned out for everyone under the same conditions - when an acid acts on the metal. For many years, hydrogen was simply called "combustible air" by the Cavendish himself. Only in 1783 Lavoisier proved that water has a complex composition, through synthesis and analysis, and four years later he also gave "combustible air" its modern name. The root of this complex word is widely used when it is necessary to name the compounds of hydrogen and any processes in which it participates. For example, hydrogenation, hydride, and the like. And the Russian name was proposed in 1824 by M. Solovyov.

In nature, the distribution of this element is unmatched. In the lithosphere and hydrosphere of the earth's crust, its mass is one percent, but hydrogen atoms are as much as sixteen percent. The most widespread on Earth is water, and 11.19% by mass in it is hydrogen. It is also invariably present in almost all compounds of which oil, coal, all natural gases, and clay are composed. There is hydrogen in all organisms of plants and animals - in the composition of proteins, fats, nucleic acids, carbohydrates, and so on. The free state for hydrogen is not typical and almost never occurs - there is very little of it in natural and volcanic gases. An absolutely insignificant amount of hydrogen in the atmosphere - 0.0001%, by the number of atoms. On the other hand, whole streams of protons represent hydrogen in near-earth space, it consists of the inner radiation belt of our planet.

Space

In space, no element occurs as often as hydrogen. The volume of hydrogen in the composition of the elements of the Sun is more than half of its mass. Most stars form hydrogen, which is in the form of plasma. The bulk of the various gases in nebulae and in the interstellar medium also consist of hydrogen. It is present in comets, in the atmosphere of a number of planets. Naturally, not in pure form, either as free H 2, then as methane CH 4, then as ammonia NH 3, even as water H 2 O. Radicals CH, NH, SiN, OH, PH and the like are very common. As a flux of protons, hydrogen is part of the corpuscular solar radiation and cosmic rays.

In ordinary hydrogen, a mixture of two stable isotopes is light hydrogen (or protium 1 H) and heavy hydrogen (or deuterium - 2 H or D). There are other isotopes: radioactive tritium - 3 H or T, otherwise - superheavy hydrogen. And also very unstable 4 N. In nature, a hydrogen compound contains isotopes in the following proportions: there are 6800 protium atoms per deuterium atom. Tritium is formed in the atmosphere from nitrogen, which is influenced by cosmic ray neutrons, but is negligible. What do isotope mass numbers stand for? The figure indicates that the protium nucleus has only one proton, while deuterium has not only a proton in the atomic nucleus, but also a neutron. Tritium in the nucleus has two neutrons to one proton. But 4 N contains three neutrons per proton. So physical properties and chemical isotopes of hydrogen are very different in comparison with the isotopes of all other elements - too great a difference in mass.

Structure and physical properties

The structure of the hydrogen atom is the simplest in comparison with all other elements: one nucleus - one electron. Ionization potential - the binding energy of a nucleus with an electron - 13.595 electron volts (eV). It is because of the simplicity of this structure that the hydrogen atom is convenient as a model in quantum mechanics when it is necessary to calculate the energy levels of more complex atoms. In the H2 molecule there are two atoms that are linked by a chemical covalent bond. The decay energy is very high. Atomic hydrogen can be formed in chemical reactions such as zinc and hydrochloric acid. However, there is practically no interaction with hydrogen - the atomic state of hydrogen is very short, the atoms immediately recombine into H2 molecules.

From a physical point of view, hydrogen is lighter than all known substances - more than fourteen times lighter than air (remember the balloons flying away at the holidays - they have just hydrogen inside them). However, it can boil, liquefy, melt, solidify, and only helium boils and melts at lower temperatures. It is difficult to liquefy it, you need a temperature below -240 degrees Celsius. But it has a very high thermal conductivity. It almost does not dissolve in water, but the interaction with the hydrogen of metals is excellent - it dissolves in almost all, best of all in palladium (one volume of hydrogen takes eight hundred and fifty volumes). Liquid hydrogen is light and fluid, and when it dissolves in metals, it often destroys alloys due to interaction with carbon (steel, for example), diffusion and decarbonization occurs.

Chemical properties

In compounds, for the most part, hydrogen shows an oxidation state (valence) of +1, like sodium and other alkali metals. He is considered as their analogue, standing at the head of the first group of the Mendeleev system. But the hydrogen ion in metal hydrides is negatively charged, with an oxidation state of -1. Also, this element is close to halogens, which are even capable of replacing it in organic compounds. This means that hydrogen can be attributed to the seventh group of the Mendeleev system. Under normal conditions, hydrogen molecules do not differ in activity, combining only with the most active non-metals: good with fluorine, and if light - with chlorine. But when heated, hydrogen becomes different - it reacts with many elements. Compared to molecular hydrogen, atomic hydrogen is very active chemically, because in connection with oxygen, water is formed, and energy and heat are released along the way. At room temperature, this reaction is very slow, but when heated above five hundred and fifty degrees, an explosion occurs.

Hydrogen is used to reduce metals, because it takes oxygen away from their oxides. With fluorine, hydrogen forms an explosion even in the dark and at minus two hundred and fifty-two degrees Celsius. Chlorine and bromine excite hydrogen only when heated or illuminated, and iodine only when heated. Hydrogen with nitrogen forms ammonia (this is how most fertilizers are produced). When heated, it very actively interacts with sulfur, and hydrogen sulfide is obtained. With tellurium and selenium, it is difficult to cause a reaction of hydrogen, and with pure carbon, the reaction occurs at a very high temperatures, and methane is obtained. With carbon monoxide, hydrogen forms various organic compounds, here pressure, temperature, catalysts affect, and all this is of great practical importance. And in general, the role of hydrogen, as well as of its compounds, is exceptionally great, since it gives acidic properties to protic acids. A hydrogen bond is formed with many elements, which affects the properties of both inorganic and organic compounds.

Receiving and using

Hydrogen is obtained on an industrial scale from natural gases - combustible, coke oven, petroleum refining gases. It can also be obtained by electrolysis where electricity is not too expensive. However, the most important method of hydrogen production is the catalytic interaction of hydrocarbons, mostly methane, with steam when conversion is obtained. The method of oxidation of hydrocarbons with oxygen is also widely used. Extraction of hydrogen from natural gas is the cheapest method. The other two are the use of coke oven gas and refinery gas - hydrogen is released when the remaining components are liquefied. They lend themselves more easily to liquefaction, and for hydrogen, as we remember, you need -252 degrees.

Hydrogen peroxide is very popular in use. Treatment with this solution is used very often. The molecular formula H 2 O 2 is unlikely to be named by all those millions of people who want to be blondes and lighten their hair, as well as those who love cleanliness in the kitchen. Even those who treat scratches from playing with a kitten often do not realize that they are using hydrogen treatment. But everyone knows the story: since 1852, hydrogen has been used for a long time in aeronautics. The airship, invented by Henry Giffard, was based on hydrogen. They were called zeppelins. Pushed the zeppelins out of the heavens rapid development aircraft construction. In 1937, there was a major accident when the Hindenburg airship burned down. After this incident, zeppelins were never used again. But at the end of the eighteenth century, the spread of balloons filled with hydrogen was widespread. In addition to the production of ammonia, today hydrogen is required for the manufacture of methyl alcohol and other alcohols, gasoline, hydrogenated heavy fuel oils and solid fuels. You cannot do without hydrogen when welding, when cutting metals - it can be oxygen-hydrogen and atomic-hydrogen. And tritium and deuterium give life to nuclear power. These are, as we remember, isotopes of hydrogen.

Neumyvakin

Hydrogen as a chemical element is so good that it could not help but have its own fans. Ivan Pavlovich Neumyvakin is a doctor of medical sciences, professor, laureate of the State Prize and he has many more titles and awards, among them. As a traditional medicine doctor, he was named the best folk healer in Russia. It was he who developed many methods and principles of providing medical assistance to astronauts in flight. It was he who created a unique hospital - a hospital on board a spacecraft. At the same time, he was the state coordinator for the field of cosmetic medicine. Space and cosmetics. His passion for hydrogen is not aimed at making big money, as is now the case in domestic medicine, but on the contrary - to teach people to cure anything from literally a penny means, without additional visits to pharmacies.

He promotes treatment with a drug that is present in literally every home. This is hydrogen peroxide. You can criticize Neumyvakin as much as you like, he will still insist on his own: yes, indeed, literally everything can be cured with hydrogen peroxide, because it saturates the internal cells of the body with oxygen, destroys toxins, normalizes acid and alkaline balance, and from here tissues are regenerated, the whole organism. So far, no one has seen the cured with hydrogen peroxide, much less examined, however, Neumyvakin claims that using this remedy, you can completely get rid of viral, bacterial and fungal diseases, prevent the development of tumors and atherosclerosis, defeat depression, rejuvenate the body and never get sick SARS and colds.

Panacea

Ivan Pavlovich is sure that with the correct use of this simplest drug and observing all the simple instructions, you can defeat many diseases, including very serious ones. Their list is huge: from periodontal disease and tonsillitis to myocardial infarction, strokes and diabetes mellitus. Such trifles as sinusitis or osteochondrosis fly away from the first treatment sessions. Even cancerous tumors get scared and flee from hydrogen peroxide, because immunity is stimulated, the life of the body and its defenses are activated.

Even children can be treated in this way, except that it is better for pregnant women to refrain from using hydrogen peroxide for now. Also, this method is not recommended for people with transplanted organs due to possible tissue incompatibility. The dosage should be strictly observed: from one drop to ten, adding one every day. Three times a day (thirty drops of a three percent hydrogen peroxide solution per day, wow!) Half an hour before meals. The solution can be administered intravenously and under medical supervision. Sometimes hydrogen peroxide is combined for a more powerful effect with other drugs. Inside, the solution is used only in a diluted form - with clean water.

Outwardly

Compresses and rinses, even before Professor Neumyvakin created his methods, were very popular. Everyone knows that, just like alcohol compresses, hydrogen peroxide cannot be used in its pure form, because it will burn tissues, but warts or fungal lesions are lubricated locally and with a strong solution - up to fifteen percent.

For skin rashes, for headaches, procedures are also performed in which hydrogen peroxide is involved. The compress should be done with a cotton cloth dipped in a solution of two teaspoons of three percent hydrogen peroxide and fifty milligrams of pure water. Cover the fabric with foil and wrap with wool or a towel. The time of action of the compress is from a quarter of an hour to an hour and a half in the morning and in the evening until recovery.

Opinion of doctors

Opinions are divided, not everyone is amazed by the properties of hydrogen peroxide, moreover, they are not only not believed, they are laughed at. Among the doctors are also those who supported Neumyvakin and even picked up the development of his theory, but they are in the minority. Most doctors consider such a treatment plan not only ineffective, but also often destructive.

Indeed, there is not yet a single officially proven case when a patient would have been cured with hydrogen peroxide. At the same time, there is no information about the deterioration of health in connection with the use of this method. But precious time is lost, and a person who has received one of the serious illnesses and has completely relied on Neumyvakin's panacea runs the risk of being late for the start of his real traditional treatment.

Hydrogen together with nitrogen, oxygen and carbon belongs to the group of so-called organogenic elements.

It is from these elements that the human body basically consists. The proportion of hydrogen in it by weight reaches 10%, and by the number of atoms 50% ( every second atom in the body is hydrogen).

Hydrogen and the most abundant element in our universe - its share is about 75% by mass and 92% by the number of atoms. Unlike oxygen, which exists both in nature and in the body in a free form, hydrogen is almost entirely in the form of its compounds (the main compound hydrogen - water).

The biological role of hydrogen

Hydrogen as a separate element has no biological value. The compounds in which it is included are important for the body, namely water, proteins, fats, carbohydrates, vitamins, biologically active substances (excluding minerals), etc. The greatest value, of course, is the combination of hydrogen with oxygen - water, which is actually the medium for the existence of all cells in the body. Acids are another group of important hydrogen compounds - their ability to release a hydrogen ion makes it possible to form the pH of the medium. An important function of hydrogen is also its ability to form hydrogen bonds, which, for example, form active forms of proteins and the double-stranded structure of DNA in space.

Major food sources of hydrogen

Hydrogen is found in almost all nutrients, but most of it enters the body in the form of water.

Hydrogen deficiency reasons

There is no hydrogen deficiency as such, a deficiency of its compounds is observed, for example, water with its insufficient intake into the body or uncompensated accelerated excretion.

Consequences of hydrogen deficiency

As in the case of the causes, the consequences of the deficiency of its compounds, most often water, are observed. In this case, observe: dehydration, thirst, decreased tissue turgor, dry skin and mucous membranes, increased blood concentration, arterial hypotension.

Excess hydrogen

An excess of hydrogen as such also does not exist; an excess of the supply of its compounds is possible. In this case, a pattern characteristic of a particular compound is observed. For example, in the case of excess water (overhydration), swelling.

Daily requirement for hydrogen: not standardized

Hydrogen is a chemical element with the symbol H and atomic number 1. With a standard atomic weight of about 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical in the universe, accounting for approximately 75% of the baryon's total mass. Stars are mostly made of hydrogen in a plasma state. The most common isotope of hydrogen, called protium (this name is rarely used, the symbol 1H), has one proton and no neutrons. The ubiquitous appearance of atomic hydrogen first occurred in the era of recombination. At standard temperatures and pressures, hydrogen is a colorless, odorless, tasteless, non-toxic, non-metallic, flammable diatomic gas with the molecular formula H2. Because hydrogen readily forms covalent bonds with most non-metallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays a particularly important role in acid-base reactions because most acid-based reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion), in which it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H +. The hydrogen cation is described as consisting of a simple proton, but in reality, the hydrogen cations in ionic compounds are always more complex. Being the only neutral atom for which the Schrödinger equation can be solved analytically, hydrogen (namely, the study of energy and the bonding of its atom) played a key role in the development of quantum mechanics. Hydrogen gas was first produced artificially in the early 16th century by the reaction of acids with metals. In 1766-81. Henry Cavendish was the first to recognize that hydrogen gas is a discrete substance and that it produces water when burned, which is why it was named so: in Greek, hydrogen means "water producer." Industrial hydrogen production is mainly associated with the steam conversion of natural gas and, less commonly, more energy intensive methods such as water electrolysis. Most hydrogen is used close to where it is produced, with the two most common uses being fossil fuel processing (eg hydrocracking) and ammonia production, mainly for the fertilizer market. Hydrogen is a concern in metallurgy because it can brittle many metals, making it difficult to design pipelines and storage tanks.

Properties

Combustion

Hydrogen gas (dihydrogen or molecular hydrogen) is a flammable gas that will burn in air over a very wide concentration range from 4% to 75% by volume. The enthalpy of combustion is 286 kJ / mol:

2 H2 (g) + O2 (g) → 2 H2O (l) + 572 kJ (286 kJ / mol)

Hydrogen gas forms explosive mixtures with air in concentrations from 4-74% and with chlorine in concentrations up to 5.95%. Explosive reactions can be caused by sparks, heat or sunlight... The autoignition temperature of hydrogen, the spontaneous ignition temperature in air, is 500 ° C (932 ° F). Pure hydrogen-oxygen flames emit ultraviolet radiation and with a high oxygen mixture are almost invisible to the naked eye, as evidenced by the faint plume of the space shuttle's main engine compared to the highly visible plume of the space shuttle solid rocket amplifier that uses an ammonium perchlorate composite. A flame detector may be required to detect burning hydrogen leaks; such leaks can be very dangerous. The hydrogen flame is blue under other conditions, and resembles the blue flame of natural gas. The sinking of the Hindenburg airship is a notorious example of the burning of hydrogen, and the case is still under debate. The visible orange flame in this incident was caused by exposure to a mixture of hydrogen and oxygen combined with carbon compounds from the airship's skin. H2 reacts with every oxidizing element. Hydrogen can react spontaneously at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially hazardous acids.

Electron energy levels

The energy level of the ground state of an electron in a hydrogen atom is -13.6 eV, which is equivalent to an ultraviolet photon with a wavelength of about 91 nm. The energy levels of hydrogen can be calculated fairly accurately using Bohr's model of the atom, which conceptualizes the electron as an "orbiting" proton, similar to the Earth's orbit of the Sun. However, an atomic electron and a proton are held together by electromagnetic force, while planets and celestial objects are held together by gravity. Due to the discretization of angular momentum postulated in early quantum mechanics by Bohr, an electron in Bohr's model can only occupy certain allowable distances from the proton and therefore only certain allowable energies. A more accurate description of the hydrogen atom comes from purely quantum mechanical processing that uses the Schrödinger equation, Dirac's equation, or even the Feynman integrated circuit to calculate the probability density of an electron around a proton. The most sophisticated processing techniques produce small effects. special theory relativity and vacuum polarization. In quantum machining, an electron in a ground state hydrogen atom has no torque at all, which illustrates how a "planetary orbit" differs from the motion of an electron.

Elementary molecular forms

There are two different spin isomers of diatomic hydrogen molecules, which differ in the relative spin of their nuclei. In orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (1/2 + 1/2); in the form of parahydrogen, the spins are antiparallel and form a singlet with the molecular spin quantum number 0 (1/2 1/2). At standard temperature and pressure, hydrogen gas contains about 25% para-form and 75% ortho-form, also known as "normal form". The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but since the ortho-form is an excited state and has a higher energy than the para-form, it is unstable and cannot be purified. At very low temperatures, the state of equilibrium consists almost exclusively of the para-form. Thermal properties The liquid and gas phases of pure parahydrogen differ significantly from the properties of the normal form due to differences in the rotational heat capacities, which is discussed in more detail in the spin isomers of hydrogen. The ortho / pair difference also occurs in other hydrogen-containing molecules or functional groups such as water and methylene, but this is of little consequence to their thermal properties. The uncatalyzed interconversion between vapor and ortho H2 increases with increasing temperature; thus, the rapidly condensed H2 contains large amounts of the high energy orthogonal form, which is very slowly converted to the para form. The ortho / vapor ratio in condensed H2 is important factor in the preparation and storage of liquid hydrogen: the transformation from ortho to vapor is exothermic and provides enough heat to vaporize part of the hydrogen liquid, resulting in the loss of liquefied material. Ortho-para conversion catalysts such as iron oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromium oxide or some nickel compounds are used for cooling with hydrogen.

Phases

Hydrogen gas

Liquid hydrogen

Slime hydrogen

Solid hydrogen

Metallic hydrogen

Connections

Covalent and organic compounds

While H2 is not very reactive under standard conditions, it forms compounds with most elements. Hydrogen can form compounds with elements that are more electronegative, such as halogens (eg F, Cl, Br, I) or oxygen; in these compounds, hydrogen takes on a partial positive charge. When bonded with fluorine, oxygen, or nitrogen, hydrogen can participate in the form of a medium-strength non-covalent bond with other similar molecules, a phenomenon called hydrogen bonding that is critical to the stability of many biological molecules. Hydrogen also forms compounds with less electronegative elements such as metals and metalloids, where it takes on a partial negative charge. These compounds are often known as hydrides. Hydrogen forms a vast array of compounds with carbon, called hydrocarbons, and an even greater variety of compounds with heteroatoms, which, because of their common bond with living things, are called organic compounds. Their properties are studied in organic chemistry, and their study in the context of living organisms is known as biochemistry. According to some definitions, "organic" compounds must contain only carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond that gives this class of compounds most of their specific chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known and are usually formed by complex synthetic pathways that rarely involve elemental hydrogen.

Hydrides

Hydrogen compounds are often referred to as hydrides. The term "hydride" implies that the H atom has acquired a negative or anionic character, designated H-, and is used when hydrogen forms a compound with a more electropositive element. The existence of the hydride anion, proposed by Gilbert N. Lewis in 1916 for salt-containing hydrides of groups 1 and 2, was demonstrated by Moers in 1920 by electrolysis of molten lithium hydride (LiH), producing a stoichiometric amount of hydrogen per anode. For hydrides other than Group 1 and 2 metals, this term is misleading given the low electronegativity of hydrogen. An exception in Group 2 hydrides is BeH2, which is polymeric. In lithium aluminum hydride, the AlH-4 anion carries hydride centers firmly attached to Al (III). Although hydrides can be formed in almost all elements of the basic group, the number and combination of possible compounds vary greatly; for example, more than 100 binary borane hydrides and only one binary aluminum hydride are known. Binary indium hydride has not yet been identified, although large complexes exist. In inorganic chemistry, hydrides can also serve as bridging ligands that bind two metal centers in a coordination complex. This function is especially characteristic for elements of group 13, especially in boranes (boron hydrides) and aluminum complexes, as well as in clustered carboranes.

Protons and acids

Oxidation of hydrogen removes its electron and gives H +, which does not contain electrons and a nucleus, which usually consists of one proton. This is why H + is often referred to as a proton. This view is central to the discussion of acids. According to the Bronsted-Lowry theory, acids are proton donors, and bases are proton acceptors. A naked proton, H +, cannot exist in solution or in ionic crystals due to its irresistible attraction to other atoms or molecules with electrons. Except for the high temperatures associated with plasma, such protons cannot be removed from the electron clouds of atoms and molecules and will remain attached to them. However, the term "proton" is sometimes used metaphorically to refer to positively charged or cationic hydrogen attached to other species in this way, and as such, is referred to as “H +” without any meaning that any individual protons exist freely as a species. To avoid the appearance of a naked "solvated proton" in solution, acidic aqueous solutions are sometimes thought to contain a less unlikely fictitious species called "hydronium ion" (H 3 O +). However, even in this case, such solvated hydrogen cations are more realistically perceived as organized clusters that form species close to H 9O + 4. Other oxonium ions are found when water is in acidic solution with other solvents. Although exotic on Earth, one of the most abundant ions in the Universe is H + 3, known as protonated molecular hydrogen or trihydrogen cation.

Isotopes

Hydrogen has three naturally occurring isotopes, designated 1H, 2H, and 3H. Other highly unstable nuclei (from 4H to 7H) have been synthesized in the laboratory, but have not been observed in nature. 1H is the most abundant hydrogen isotope with a prevalence of over 99.98%. Since the nucleus of this isotope consists of only one proton, it is given a descriptive but rarely used formal name protium. 2H, another stable isotope of hydrogen, is known as deuterium and contains one proton and one neutron in its nucleus. It is believed that all the deuterium in the universe was produced during Big bang and has existed since that time until now. Deuterium is not a radioactive element and does not pose a significant toxicity hazard. Water enriched with molecules that include deuterium instead of normal hydrogen is called heavy water. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy. Heavy water is used as a neutron moderator and as a coolant for nuclear reactors. Deuterium is also a potential fuel for commercial nuclear fusion. 3H is known as tritium and contains one proton and two neutrons in its nucleus. It is radioactive, decays into helium-3 through beta decay with a half-life of 12.32 years. It is so radioactive that it can be used in luminous paint, which makes it useful in making watches with a luminous dial, for example. The glass prevents a small amount of radiation from escaping. A small amount of tritium is formed naturally by the interaction of cosmic rays with atmospheric gases; tritium was also released during testing nuclear weapons... It is used in nuclear fusion reactions as an indicator of isotope geochemistry and in specialized lighting devices self-powered. Tritium has also been used in chemical and biological labeling experiments as a radioactive label. Hydrogen is the only element that has different names for its isotopes, which are widely used today. During the early study of radioactivity, various heavy radioactive isotopes were given their own names, but such names are no longer used, with the exception of deuterium and tritium. The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the corresponding symbol for protium P is already used for phosphorus and is therefore not available for protium. In its nomenclature guidelines, the International Union of Pure and Applied Chemistry allows the use of any characters from D, T, 2H, and 3H, although 2H and 3H are preferred. The exotic muonium atom (symbol Mu), composed of an anti-muon and an electron, is also sometimes regarded as a light radioisotope of hydrogen due to the mass difference between the anti-muon and an electron, which was discovered in 1960. During the lifetime of a muon, 2.2 μs, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu), similarly to hydrogen chloride and sodium hydride, respectively.

Story

Discovery and use

In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which leads to the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, calling this gas "flammable air" due to its metal-acid reaction. He suggested that "flammable air" was virtually identical to a hypothetical substance called "phlogiston" and again discovered in 1781 that gas produces water when burned. It is believed that it was he who discovered hydrogen as an element. In 1783, Antoine Lavoisier named this element hydrogen (from the Greek ὑδρο-hydro meaning water and -γενής genes, meaning creator), when he and Laplace reproduced Cavendish's data that burning hydrogen produces water. Lavoisier produced hydrogen for his mass conservation experiments by reacting a stream of steam with metallic iron through an incandescent lamp heated in a fire. Anaerobic oxidation of iron by protons of water at high temperatures can be schematically represented by a set of the following reactions:

Fe + H2O → FeO + H2

2 Fe + 3 H2O → Fe2O3 + 3 H2

3 Fe + 4 H2O → Fe3O4 + 4 H2

Many metals, such as zirconium, undergo a similar reaction with water to produce hydrogen. The hydrogen was first liquefied by James Dewar in 1898 using regenerative refrigeration and his invention, the vacuum flask. The following year, he produced solid hydrogen. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium instead of ordinary hydrogen, was discovered by Yurey's group in 1932. François Isaac de Rivaz built the first Rivaz engine, an internal combustion engine powered by hydrogen and oxygen, in 1806. Edward Daniel Clarke invented the hydrogen gas tube in 1819. The Doebereiner Flame (the first full-fledged lighter) was invented in 1823. The first hydrogen cylinder was invented by Jacques Charles in 1783. Hydrogen provided the rise of the first reliable form of air traffic after the invention of Henri Giffard's first hydrogen-powered airship in 1852. The German Count Ferdinand von Zeppelin promoted the idea of ​​rigid airships lifted into the air by hydrogen, which were later called the Zeppelin; the first of these took off for the first time in 1900. Regularly scheduled flights began in 1910 and by the outbreak of World War I in August 1914, they had carried 35,000 passengers without major incident. During the war, hydrogen airships were used as observation platforms and bombers. The first non-stop transatlantic flight was made by the British R34 airship in 1919. Regular passenger service resumed in the 1920s and the discovery of stocks of helium in the United States was supposed to improve flight safety, but the US government refused to sell gas for this purpose, so H2 was used in the Hindenburg airship, which was destroyed in a fire in Milan in New Jersey May 6, 1937 The incident was broadcast live on radio and filmed. It has been widely speculated that the ignition was due to a hydrogen leak, but subsequent research indicates that the aluminized fabric covering could ignite with static electricity. But by this time, hydrogen's reputation as a lift gas had already been damaged. In the same year, the first hydrogen-cooled turbine generator with hydrogen gas as a refrigerant in the rotor and stator entered service in 1937 in Dayton, Ohio, by Dayton Power & Light Co; Due to the thermal conductivity of hydrogen gas, it is the most common gas for use in this field today. The nickel-hydrogen battery was first used in 1977 aboard the US Navigation Technology Satellite 2 (NTS-2). The ISS, Mars Odyssey and Mars Global Surveyor are all powered by nickel-hydrogen batteries. In the dark part of its orbit, the Hubble Space Telescope is also powered by nickel-hydrogen batteries that were finally replaced in May 2009, more than 19 years after launch and 13 years after their design.

Role in quantum theory

Because of its simple atomic structure, consisting only of a proton and an electron, the hydrogen atom, together with the spectrum of light created from or absorbed by it, has been central to the development of the theory of atomic structure. In addition, the study of the corresponding simplicity of the hydrogen molecule and the corresponding H + 2 cation led to an understanding of the nature of the chemical bond, which soon followed the physical treatment of the hydrogen atom in quantum mechanics in mid-2020.One of the first quantum effects that were clearly observed (but were not understood at the time), there was Maxwell's observation of hydrogen half a century before the full quantum mechanical theory emerged. Maxwell noted that specific heat H2 irreversibly departs from a diatomic gas below room temperature and begins to increasingly resemble the specific heat of a monatomic gas at cryogenic temperatures. According to quantum theory, this behavior arises from the distance of the (quantized) levels of rotational energy, which are especially widely spaced in H2 due to its low mass. These widely spaced levels prevent an equal division of thermal energy into rotational motion in hydrogen at low temperatures. Diatom gases, which are made up of heavier atoms, do not have such widely spaced levels and do not exhibit the same effect. Antihydrogen is an antimaterial analogue of hydrogen. It consists of an antiproton with a positron. Antihydrogen is the only type of antimatter atom that has been produced as of 2015.

Being in nature

Hydrogen is the most abundant chemical element in the Universe, accounting for 75% of normal matter by mass and over 90% by the number of atoms. (Most of the mass of the universe, however, is not in the form of this chemical element, but it is believed to have as yet undiscovered forms of mass, such as dark matter and dark energy.) This element is found in great abundance in stars and gas giants. Molecular H2 clouds are associated with star formation. Hydrogen plays a vital role in turning stars on through the proton-proton reaction and nuclear fusion of the CNO cycle. All over the world, hydrogen is found mainly in atomic and plasma states with properties quite different from those of molecular hydrogen. As a plasma, the electron and proton of hydrogen are not bonded to each other, resulting in very high electrical conductivity and high emissivity (generating light from the sun and other stars). Charged particles are strongly influenced by magnetic and electric fields. For example, in solar wind they interact with the Earth's magnetosphere, creating the Birkeland currents and the aurora. Hydrogen is in a neutral atomic state in the interstellar medium. It is believed that large amounts of neutral hydrogen found in damped Lyman-alpha systems dominate the cosmological baryon density of the Universe up to redshift z = 4. Under normal conditions on Earth, elemental hydrogen exists as a diatomic gas, H2. However, hydrogen gas is very rare in the earth's atmosphere (1 ppm by volume) due to its light weight, which makes it easier to overcome Earth's gravity than heavier gases. However, hydrogen is the third most abundant element on the Earth's surface, existing mainly in the form chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flute, just like methane, which is an increasingly important source of hydrogen. A molecular form called protonated molecular hydrogen (H + 3) is found in the interstellar medium, where it is generated by ionizing molecular hydrogen from cosmic rays. This charged ion has also been observed in the upper atmosphere of the planet Jupiter. Ion is relatively stable in environment due to low temperature and density. H + 3 is one of the most abundant ions in the Universe and plays a prominent role in the chemistry of the interstellar medium. Neutral triatomic hydrogen H3 can exist only in an excited form and is unstable. In contrast, the positive molecular ion of hydrogen (H + 2) is a rare molecule in the universe.

Hydrogen production

H2 is produced in chemical and biological laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of displacing reducing equivalents in biochemical reactions.

Steam reforming

Hydrogen can be produced in several ways, but the economically most important processes involve the removal of hydrogen from hydrocarbons, since about 95% of hydrogen production in 2000 came from steam reforming. Commercially, large volumes of hydrogen are typically produced by steam reforming of natural gas. At high temperatures (1000-1400 K, 700-1100 ° C, or 1300-2000 ° F), steam (water vapor) reacts with methane to produce carbon monoxide and H2.

CH4 + H2O → CO + 3 H2

This reaction works best at low pressures, but nevertheless, it can be carried out at high pressures (2.0 MPa, 20 atm or 600 inches of mercury). This is because high pressure H2 is the most popular product and pressure superheat cleaning systems perform better at higher pressures. The product mixture is known as "syngas" because it is often used directly to produce methanol and related compounds. Hydrocarbons other than methane can be used to produce synthesis gas with different product ratios. One of the many complications of this highly optimized technology is the formation of coke or carbon:

CH4 → C + 2 H2

Consequently, steam reforming typically uses excess H2O. Additional hydrogen can be recovered from the steam using carbon monoxide through a water gas displacement reaction, especially using an iron oxide catalyst. This reaction is also a common industrial source of carbon dioxide:

CO + H2O → CO2 + H2

Other important methods for H2 include partial oxidation of hydrocarbons:

2 CH4 + O2 → 2 CO + 4 H2

And the reaction of coal, which may serve as a prelude to the shear reaction described above:

C + H2O → CO + H2

Sometimes hydrogen is produced and consumed in the same industrial process, without separation. In the Haber process for the production of ammonia, hydrogen is generated from natural gas. Brine electrolysis to produce chlorine also produces hydrogen as a by-product.

Metallic acid

In the laboratory, H2 is usually produced by reacting dilute non-oxidizing acids with some reactive metals such as zinc with a Kipp apparatus.

Zn + 2 H + → Zn2 + + H2

Aluminum can also produce H2 when treated with bases:

2 Al + 6 H2O + 2 OH- → 2 Al (OH) -4 + 3 H2

Water electrolysis is an easy way to produce hydrogen. A low voltage current flows through the water and oxygen gas is generated at the anode, while hydrogen gas is generated at the cathode. Typically, the cathode is made from platinum or another inert metal in the production of hydrogen for storage. If, however, the gas is to be burnt in situ, the presence of oxygen is desirable to promote combustion, and therefore both electrodes will be made of inert metals. (For example, iron is oxidized and therefore reduces the amount of oxygen released.) The theoretical maximum efficiency (electricity used in relation to the energy value of hydrogen produced) is in the range of 80-94%.

2 H2O (L) → 2 H2 (g) + O2 (g)

An alloy of aluminum and gallium in the form of granules added to water can be used to produce hydrogen. This process also produces aluminum oxide, but the expensive gallium, which prevents the formation of oxide skin on the granules, can be reused. This has important potential implications for the hydrogen economy, as hydrogen can be produced locally and does not need to be transported.

Thermochemical properties

There are over 200 thermochemical cycles that can be used to separate water, about a dozen of these cycles, such as the iron oxide cycle, cerium (IV) oxide cycle, cerium (III) oxide, zinc oxide zinc, sulfur iodine cycle, copper cycle, etc. chlorine and the hybrid sulfur cycle are in the research and testing stages to produce hydrogen and oxygen from water and heat without the use of electricity. A number of laboratories (including those in France, Germany, Greece, Japan and the USA) are developing thermochemical methods for producing hydrogen from solar energy and water.

Anaerobic corrosion

Under anaerobic conditions, iron and steel alloys are slowly oxidized by the protons of water, while being reduced in molecular hydrogen (H2). Anaerobic corrosion of iron leads first to the formation of iron hydroxide (green rust) and can be described by the following reaction: Fe + 2 H2O → Fe (OH) 2 + H2. In turn, under anaerobic conditions, iron hydroxide (Fe (OH) 2) can be oxidized by water protons to form magnetite and molecular hydrogen. This process is described by the Shikorr reaction: 3 Fe (OH) 2 → Fe3O4 + 2 H2O + H2 iron hydroxide → magnesium + water + hydrogen. Well-crystallized magnetite (Fe3O4) is thermodynamically more stable than iron hydroxide (Fe (OH) 2). This process takes place during the anaerobic corrosion of iron and steel in anoxic groundwater and during the restoration of soils below the water table.

Geological origin: serpentinization reaction

In the absence of oxygen (O2) in deep geological conditions prevailing far from the Earth's atmosphere, hydrogen (H2) is formed in the process of serpentinization by anaerobic oxidation of iron silicate (Fe2 +) by protons of water (H +) present in the crystal lattice of fayalite (Fe2SiO4, minal olivine -gland). The corresponding reaction leading to the formation of magnetite (Fe3O4), quartz (SiO2) and hydrogen (H2): 3Fe2SiO4 + 2 H2O → 2 Fe3O4 + 3 SiO2 + 3 H2 fayalite + water → magnetite + quartz + hydrogen. This reaction is very similar to the Schikorr reaction observed during the anaerobic oxidation of iron hydroxide in contact with water.

Formation in transformers

Of all the hazardous gases produced in power transformers, hydrogen is the most abundant and generated in most fault conditions; thus, the formation of hydrogen is an early sign of serious problems in the life cycle of a transformer.

Applications

Consumption in various processes

Large amounts of H2 are required in the petroleum and chemical industries. Mostly, H2 is used for the processing ("modernization") of fossil fuels and for the production of ammonia. In petrochemical plants, H2 is used in hydrodealkylation, hydrodesulfurization, and hydrocracking. H2 has several other important uses. H2 is used as a hydrogenating agent, in particular to increase the saturation level of unsaturated fats and oils (found in items such as margarine) and in the production of methanol. It is also a source of hydrogen in the production of hydrochloric acid. H2 is also used as a reducing agent for metal ores. Hydrogen is highly soluble in many rare earth and transition metals and is soluble in both nanocrystalline and amorphous metals. The solubility of hydrogen in metals depends on local distortions or impurities in the crystal lattice. This can be useful when hydrogen is purified by passing through hot palladium discs, but the high solubility of the gas is a metallurgical problem, contributing to the embrittlement of many metals, complicating the design of pipelines and storage tanks. In addition to being used as a reagent, H2 has a wide range of applications in physics and technology. It is used as a shielding gas in welding methods such as hydrogen atomic welding. H2 is used as a rotor coolant in electric generators in power plants because it has the highest thermal conductivity of all gases. Liquid H2 is used in cryogenic research, including superconductivity research. Since H2 is lighter than air, at just over 1/14 of the density of air, it was once widely used as a lift gas in balloons and airships. In newer applications, hydrogen is used neat or mixed with nitrogen (sometimes called forming gas) as an indicator gas for instantaneous leak detection. Hydrogen is used in the automotive, chemical, energy, aerospace and telecommunications industries. Hydrogen is an approved food additive (E 949) that allows leak testing of foodstuffs, in addition to other antioxidant properties. Rare isotopes of hydrogen also have specific uses. Deuterium (hydrogen-2) is used in nuclear fission applications as a slow neutron moderator and in nuclear fusion reactions. Deuterium compounds are used in the field of chemistry and biology to study the isotope effects of a reaction. Tritium (hydrogen-3) produced in nuclear reactors is used in the production of hydrogen bombs, as an isotopic label in the biological sciences, and as a radiation source in glowing paints. The triple point of equilibrium hydrogen is the defining fixed point in the ITS-90 temperature scale at 13.8033 Kelvin.

Cooling medium

Hydrogen is commonly used in power plants as a refrigerant in generators due to a number of beneficial properties that are a direct result of its light diatomic molecules. These include low density, low viscosity and the highest specific heat and thermal conductivity of all gases.

Energy carrier

Hydrogen is not an energy resource, except in the hypothetical context of commercial fusion power plants using deuterium or tritium, and this technology is currently far from being developed. The energy of the Sun comes from the nuclear fusion of hydrogen, but this process is difficult to achieve on Earth. Elemental hydrogen from solar, biological, or electrical sources requires more energy to produce it than is consumed when burning it, so in these cases hydrogen functions as an energy carrier, by analogy with a battery. Hydrogen can be obtained from fossil sources (such as methane), but these sources are depleted. The energy density per unit volume of both liquid hydrogen and compressed hydrogen gas at any practically achievable pressure is significantly less than that of traditional energy sources, although the energy density per unit mass of fuel is higher. However, elemental hydrogen has been widely discussed in the energy context as a possible future energy carrier for the entire economy. For example, CO2 sequestration followed by carbon capture and storage can be carried out at the point of production of H2 from fossil fuels. The hydrogen used in transportation will burn relatively cleanly, with some NOx emissions, but no carbon emissions. However, the infrastructure cost associated with a full conversion to a hydrogen economy will be substantial. Fuel cells can convert hydrogen and oxygen directly into electricity more efficiently than internal combustion engines.

Semiconductor industry

Hydrogen is used to saturate the dangling bonds of amorphous silicon and amorphous carbon, which helps stabilize material properties. It is also a potential electron donor in various oxide materials, including ZnO, SnO2, CdO, MgO, ZrO2, HfO2, La2O3, Y2O3, TiO2, SrTiO3, LaAlO3, SiO2, Al2O3, ZrSiO4, HfSiO4, and SrZrO3.

Biological reactions

H2 is a product of certain types of anaerobic metabolism and is produced by several microorganisms, usually through reactions catalyzed by iron or nickel-containing enzymes called hydrogenases. These enzymes catalyze a reversible redox reaction between H2 and its components, two protons and two electrons. The creation of hydrogen gas occurs by transferring the reducing equivalents formed during the fermentation of pyruvate into water. The natural cycle of production and consumption of hydrogen by organisms is called the hydrogen cycle. Water splitting, the process by which water breaks down into its constituent protons, electrons and oxygen, occurs in light reactions in all photosynthetic organisms. Several such organisms, including the algae Chlamydomonas Reinhardtii and cyanobacteria, have developed a second stage in dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast. Attempts have been made to genetically modify cyanobacterial hydrases to efficiently synthesize H2 gas even in the presence of oxygen. Efforts have also been made using genetically modified algae in a bioreactor.