Physical properties and use of hydrogen. Physical properties of hydrogen
Getting Started with the consideration of the chemical and physical properties of hydrogen, it should be noted that in the usual state, this chemical element is in a gaseous form. Colorless hydrogen gas has no smell, he is tasteless. For the first time, this chemical element was called hydrogen after a scientist A. Lavoisie was carried out experiments with water, based on the results of which, world Science He learned that water is a multicomponent liquid, which includes hydrogen. The event was happening in 1787, but long before this date hydrogen was known as a scientist called "combustible gas".
Hydrogen in nature
According to scientists, hydrogen is contained in the earth's crust and in water (approximately 11.2% in the total volume of water). This gas is part of many minerals that humanity over the centuries extracts from the bowels of the earth. Partially properties of hydrogen are characteristic of oil, natural gases and clay, for animal organisms and plants. But in its pure form, that is, not connected to other chemical elements of the Mendeleev table, this gas is extremely rare in nature. This gas can go to the surface of the Earth when eruption of volcanoes. Free hydrogen in insignificant quantities is present in the atmosphere.
Chemical properties of hydrogen
Since the chemical properties of hydrogen are inseparable, this chemical element refers to the I group of the Mendeleev system and to the VII system group. As a representative of the first group, hydrogen is, in fact, an alkaline metal, which has an oxidation degree of +1 in most of the compounds in which it enters. The same valence is characteristic of sodium and others. alkali metals. In view of such chemical properties, hydrogen is considered as an element similar to these metals.
If we are talking About hydrides of metals, the hydrogen ion has a negative valence - its degree of oxidation is -1. Na + H- is based on the same scheme as Na + Cl- chloride. This fact is the reason for the hydrogen to the VII group of the Mendeleev system. Hydrogen, being able to a molecule, provided that it resides in a normal medium, is sedimed, and can be connected exclusively with non-metals, more active for it. Such metals include fluorine, if there is light, hydrogen is connected to chlorine. If hydrogen is heated, then it becomes more active, entering into reactions with many elements of the periodic Mendeleev system.
Atomic hydrogen exhibits more active chemical properties than molecular. Oxygen molecules C form water - H2 + 1 / 2O2 \u003d H2O. When hydrogen interacts with halogens, the H2 + CL2 \u003d 2NCL halogen hydrogen are formed, and in this reaction, hydrogen enters in the absence of light and at sufficiently large negative temperatures - up to - 252 ° C. The chemical properties of hydrogen allow it to be used to restore many metals, since reacting, hydrogen absorbs oxygen oxygen, for example, Cuo + H2 \u003d Cu + H2O. Hydrogen is involved in the formation of ammonia, interacting with nitrogen in the reaction of ZN2 + N2 \u003d 2NN3, but provided that the catalyst will be used, and the temperature and pressure are increased.
The energetic reaction occurs when hydrogen interacts with sulfur in the reaction H2 + S \u003d H2S, the result of hydrogen sulfide. Slightly less active in the interaction of hydrogen with tellurium and selenium. If there is no catalyst, it reacts with pure carbon, hydrogen only under the condition that high temperatures will be created. 2N2 + C (amorphous) \u003d CH4 (methane). In the process of hydrogen activity with some alkaline and other metals, hydrides are obtained, for example, H2 + 2Li \u003d 2LIH.
Physical properties of hydrogen
Hydrogen is very easy chemical substance. At least scientists argue that this momentNo lighter substance than hydrogen. Its mass is 14.4 times easier for air, the density is 0.0899 g / l at 0 ° C. At temperatures in -259.1 ° C hydrogen, it is capable of melting - this is a very critical temperature that is not typical for the conversion of most chemical compounds From one state to another. Only such an element as helium exceeds the physical properties of hydrogen in this regard. The liquefaction of hydrogen is difficult, since its critical temperature is equal to (-240 ° C). Hydrogen is the largest gas of all known to humanity. All the properties described above are the most significant physical properties of hydrogen, which are used by a person for specific purposes. Also these properties are the most relevant for modern science.
Hydrogen H is a chemical element, one of the most common in our universe. The mass of hydrogen as an element in the composition of substances is 75% of the total content of atoms of another type. It is included in the most important and vital connection on the planet - water. A distinctive feature hydrogen is also the fact that it is the first element in the periodic system chemical elements D. I. Mendeleev.
Opening and research
The first mentions of hydrogen in the writings of Paracels are dated by the sixteenth century. But its release from the gas mixture of air and the study of combustible properties was produced already in the seventeenth century by scientist leverage. An English chemist, a physicist and a naturalist, who was experiencing a thoroughly, was proved thoroughly thoroughly studied that the mass of hydrogen is smallest in comparison with other gases. In subsequent stages of development of science, many scientists worked with him, in particular the Lavoisier, who called it "born water".
Characteristic by position in PSHE
An element that opens a periodic table D. I. Mendeleev is hydrogen. The physical and chemical properties of the atom show some duality, since the hydrogen is simultaneously referred to the first group, the main subgroup, if it behaves like a metal and gives the only electron in the process chemical reaction, and to the seventh - in the case of full filling of the valence shell, that is, the reception of the negative particle, which characterizes it as similar to halogens.
Features electronic structure element
The properties of complex substances whose composition is included, and simple substance H 2 is primarily determined by electronic configuration of hydrogen. The particle has one electron with z \u003d (-1), which rotates in its orbit around the kernel containing one proton with a single mass and a positive charge (+1). His electronic configuration It is written as 1s 1, which means the presence of one negative particle on the very first and only s-orbital hydrogen.
If the electron is separated or the return, and the atom of this element has such a property that it relates it to metals, the cation is obtained. In essence, hydrogen ion is a positive elementary particle. Therefore, the devoid of electron hydrogen is called simply proton.
Physical properties
If hydrogen is described briefly, it is a colorless, low-soluble gas with a relative atomic weight of equal to 2, 14.5 times lighter than air, with a liquefaction temperature, component -252.8 degrees Celsius.
On experience you can easily make sure that H 2 is the easiest. To do this, it is enough to fill three balls with various substances - hydrogen, carbon dioxide, ordinary air - and at the same time release them out of hand. The faster of all will reach the Earth, which is filled with 2, after it drops the inflated air mixture, and H 2 contains at all at all rises to the ceiling.
The small mass and size of hydrogen particles justify its ability to penetrate various substances. Using the example of the same ball in this easy to make sure, after a couple of days it will be blown out, as the gas will simply pass through the rubber. Also, hydrogen can accumulate in the structure of some metals (palladium or platinum), and when the temperature is raised to evaporate from it.
The hydrogen low solubility property is used in laboratory practice for its release by the hydrogen displacement method (the table shown below contains the basic parameters) determine the spheres of its use and methods of obtaining.
| The parameter of the atom or molecule of a simple substance | Value |
| Atomic mass (molar mass) | 1,008 g / mol |
| Electronic configuration | 1s 1. |
| Crystal cell | Hexagonal |
| Thermal conductivity | (300 K) 0.1815 W / (M · K) |
| Density with n. y | 0,08987 g / l |
| Boiling temperature | -252,76 ° C. |
| Specific heat combustion | 120.9 · 10 6 J / kg |
| Melting temperature | -259.2 ° C. |
| Solubility in water | 18.8 ml / l |
Isotopic composition
Like many other representatives of the periodic system of chemical elements, hydrogen has several natural isotopes, that is, atoms with the same number of protons in the nucleus, but by different numbers of neutrons - particles with a zero charge and a single mass. Examples of atoms with a similar property - oxygen, carbon, chlorine, bromine, and other, including radioactive.
Physical properties Hydrogen 1 H, most common from representatives of this group, is significantly different from the same characteristics of its fellow. In particular, the peculiarities of the substances are based on which they enter. Thus, there is ordinary and deuterated water containing in its composition instead of a hydrogen atom with a single proton of deuterium 2 H is its isotope with two elementary particles: positive and uncharged. This isotope is twice as much as possible hydrogen, which explains the cardinal difference in the properties of the compounds that they constitute. In nature, deuterium meets 3200 times less often than hydrogen. The third representative - tritium 3 N, in the core he has two neutrons and one proton.
Methods for obtaining and highlighting
Laboratory and industrial methods are very different. Thus, in small quantities, the gas is mainly obtained by reactions in which minerals are involved, and large-scale production is largely used by organic synthesis.
The laboratory uses the following chemical interactions:
In the industrial interests of the gas receive such methods as:
- Thermal decomposition of methane in the presence of a catalyst to the components of its simple substances (350 degrees reaches the value of such an indicator as temperature) - hydrogen H 2 and carbon S.
- Purchase of vapor water through Cox at 1000 degrees Celsius with the formation of carbon dioxide CO 2 and H 2 (the most common method).
- Conversion of gaseous methane on a nickel catalyst at a temperature reaching 800 degrees.
- Hydrogen is a by-product with electrolysis aqueous solutions Potassium chlorides or sodium.
Chemical interactions: General
The physical properties of hydrogen largely explain its behavior in response processes with one or another compound. The hydrogen valence is 1, as it is located in the Mendeleev table in the first group, and the degree of oxidation shows different. In all compounds, except hydrides, hydrogen in C.O. \u003d (1+), in the HN type molecules, XN 2, HN 3 - (1-).
The hydrogen gas molecule, formed by creating a generalized electronic pair, consists of two atoms and is rather stable energy, that is, under normal conditions, somewhat inert and in the reaction enters the normal conditions. Depending on the degree of hydrogen oxidation in other substances, it can act as an oxidizing agent and a reducing agent.
Substances that react and which forms hydrogen
Elemental interactions with the formation of complex substances (often at elevated temperatures):
- Alkaline and alkaline earth metal + hydrogen \u003d hydride.
- Halogen + H 2 \u003d halogen hydrogen.
- Sulfur + hydrogen \u003d hydrogen sulfide.
- Oxygen + H 2 \u003d water.
- Carbon + hydrogen \u003d methane.
- Nitrogen + H 2 \u003d ammonia.
Interaction with compound substances:
- Preparation of synthesis gas from carbon monoxide and hydrogen.
- Restoration of metals from their oxides with H 2.
- Saturation by hydrogen of unsaturated aliphatic hydrocarbons.
Hydrogen communications
The physical properties of hydrogen are such that allow it being in a compound with an electroneary element to form a special type of communication with the same atom from neighboring molecules having meaningless electronic pairs (for example, oxygen, nitrogen and fluorine). The brightest example on which it is better to consider a similar phenomenon is water. It can be said to be stitched by hydrogen bonds that are weaker than covalent or ionic, but due to the fact that there are many of them, there is a significant impact on the properties of the substance. In fact, the hydrogen bond is an electrostatic interaction that binds water molecules into dimers and polymers, justifying its high boiling point.
Hydrogen in mineral compounds
All includes a proton - a cation of such an atom like hydrogen. The substance, the acid residue of which has a degree of oxidation (-1), is called a multi-stronger connection. It contains several hydrogen atoms, which makes dissociation in aqueous solutions of multistage. Each subsequent proton takes off from the residue of the acid is increasingly. According to the quantitative content of hydrogen in the medium, its acidity is determined.
Application in human activity
Cylinders with substance, as well as tanks with other liquefied gases, such as oxygen, have a specific appearance. They painted in a dark-green color with a bright red inscription "Hydrogen". Gas are pumped into a cylinder under pressure of about 150 atmospheres. The physical properties of hydrogen, in particular the ease of gaseous aggregate stateused to fill it in a mixture with helium of balloons, balls-probes, etc.
Hydrogen, the physical and chemical properties of which people learned to use many years ago, to date are involved in many industries. The main mass of his mass is on the production of ammonia. Also, hydrogen is also involved in (Hafnia, Germany, Gallium, silicon, molybdenum, tungsten, zirconium and other) from oxides, acting in the reaction as a reducing agent, blue and hydrochloric acids, as well as artificial liquid fuel. The food industry uses it to convert vegetable oils into solid fats.
The chemical properties and the use of hydrogen in various processes of hydrogenation and hydrogenation of fats, coal, hydrocarbons, oils and fuel oil are determined. With the help of it, precious stones are produced, incandescent lamps, carry a forging and welding of metal products under the influence of an oxygen-hydrogen flame.
In the periodic system, hydrogen is located in two absolutely opposite in their properties of groups of elements. This feature make it completely unique. Hydrogen is not simply an element or substance, but also is an integral part of many complex compounds, organogenic and biogenic element. Therefore, we consider its properties and characteristics in more detail.
The separation of fuel gas in the process of interaction between metals and acids was observed in the XVI century, that is, during the formation of chemistry as science. The famous English scientist Henry Cavendish explored the substance since 1766, and gave him the name "combustible air". When burning, this gas gave water. Unfortunately, the commitment of the scientist theory of phlogiston (hypothetical "hypothone of matter") prevented him to come to the right conclusions.
The French chemist and the naturalist A. Lavoisier, together with the engineer J. More and with the help of special gasometers in 1783, conducted a synthesis of water, and after and its analysis by decomposing water vapor hot iron. Thus, scientists were able to come to the right conclusions. They found that "combustible air" is not only part of the water, but can also be obtained from it.
In 1787, Lavoisier put forward the assumption that the gas under study is a simple substance and, accordingly, refers to the number of primary chemical elements. He called him Hydrogene (from the Greek Words of Hydor - Water + Gennao - God), i.e. "Horing Water".
The Russian name "Hydrogen" in 1824 proposed a Chemist M. Solovyov. The determination of the composition of water marked the end of the "Flogiston theory". At the junction of the XVIII and XIX centuries, it was found that the hydrogen atom is very light (compared to atoms of other elements) and its mass was adopted for the main unit of comparison of atomic masses, obtaining a value equal to 1.
Physical properties
Hydrogen is the easiest of all known science of substances (it is 14.4 times lighter than air), its density is 0.0899 g / l (1 atm, 0 ° C). This material melts (hardens) and boils (liquefied), respectively, at -259.1 ° C and -252.8 ° C (only helium has lower boiling and melting t °).
Critical temperature of hydrogen is extremely low (-240 ° C). For this reason, his liquefaction is a rather complicated and cost process. The critical pressure of the substance is 12.8 kgf / cm², and the critical density is 0.0312 g / cm³. Among all gases, hydrogen has the greatest thermal conductivity: at 1 atm and 0 ° C, it equals 0.174 W / (MHC).
Specific heat capacity of the substance under the same conditions - 14.208 KJ / (CGKK) or 3,394 Cal / (GC ° C). This element is weakly soluble in water (about 0.0182 ml / g at 1 atm and 20 ° C), but well - in most metals (Ni, Pt, PA and others), especially in palladium (approximately 850 volumes per one PD ).
With the latest property, its diffusion ability is associated, while the diffusion through a carbon alloy (for example, steel) can be accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (this process is called decarbonization). In a liquid state, the substance is very easy (density - 0.0708 g / cm³ at t ° \u003d -253 ° C) and fluid (viscosity - 13.8 scholasis under the same conditions).
In many compounds, this element exhibits valence +1 (degree of oxidation), like sodium and other alkaline metals. It is usually considered as analogue of these metals. Accordingly, he heads the I group of the Mendeleev system. In the hydrides of metals, hydrogen ion shows a negative charge (the degree of oxidation at the same time -1), that is, Na + H- has a structure similar to Na + Cl- chloride. In accordance with this and some other facts (the proximity of the physical properties of the element "H" and halogen, the ability to replace it with halogens in organic compounds) Hydrogene belongs to the VII group of the Mendeleev system.
Under normal conditions, molecular hydrogen has low activity, directly connecting only with the most active non-metals (with fluorine and chlorine, with the latter - in the light). In turn, when heated, it interacts with many chemical elements.
Atomic hydrogen has increased chemical activity (if compared with molecular). With oxygen, it forms water by the formula:
N₂ + ½₂ \u003d N₂O,
highlighting 285.937 KJ / Mol heat or 68,3174 kcal / mol (25 ° C, 1 atm). In conventional temperature conditions, the reaction proceeds quite slowly, and at t °\u003e \u003d 550 ° C - uncontrollable. The explosion limits of the mixture of hydrogen + oxygen in volume are 4-94% H₂, and the mixtures of hydrogen + air - 4-74% H₂ (a mixture of two volumes of H₂ and one volume of O₂ is called rat gas.
This element is used to restore most metals, as it takes oxygen by oxides:
Fe₃O₄ + 4H₂ \u003d 3FE + 4N₂O,
Cuo + H₂ \u003d Cu + H₂o, etc.
With different halogens, hydrogen forms halogen hydrogen sodes, for example:
N₂ + CL₂ \u003d 2NSL.
However, when reactions with fluorine, hydrogen explodes (this occurs in the dark, at -252 ° C), with bromine and chlorine reacts only when heated or illumination, and with iodine - exclusively when heated. When interacting with nitrogen, ammonia is formed, but only on the catalyst, increased pressures and temperature:
ZN₂ + N₂ \u003d 2NN₃.
When heated, hydrogen actively reacts with sulfur:
N₂ + S \u003d H₂S (hydrogen sulfide)
and it is much more difficult - with tellurium or selenium. With pure carbon, hydrogen reacts without a catalyst, but at high temperatures:
2N₂ + C (amorphous) \u003d CH₄ (methane).
This substance directly reacts with some of the metals (alkaline, alkaline earth and other), forming hydrides, for example:
H₂ + 2Li \u003d 2LIH.
Essential practical value There are reacts of hydrogen and carbon oxide (II). In this case, depending on the pressure, temperature and catalyst, different organic compounds are formed: NSNO, CN₃on, etc. Unsaturated hydrocarbons in the reaction process are moving into saturated, for example:
With N ₂ n + H₂ \u003d C n ₂ n ₊₂.
Hydrogen and its compounds play an exceptional role in chemistry. It causes the acid properties of the T. N. proton acids, inclined to form with different elements hydrogen communicationsproviding a significant impact on the properties of many inorganic and organic compounds.
Obtaining hydrogen
The main types of raw materials for the industrial production of this element are gases of refining, natural combustible and coke gases. It is also obtained from water through electrolysis (in places with affordable electricity). One of the most important methods for the production of natural gas material is the catalytic interaction of hydrocarbons, mainly methane, with water vapor (T.N. Conversion). For example:
CH₄ + H₂O \u003d CO + ZN₂.
Incomplete oxidation of hydrocarbons with oxygen:
CH₄ + ½O₂ \u003d CO + 2N₂.
Synthesized carbon oxide (II) conversion:
CO + N₂O \u003d SO + H₂.
Hydrogen produced from natural gas is the cheapest.
For electrolysis of water, a constant current is used, which is passed through a solution of NaOH or con (acids are not used to avoid corrosion of instruments). In the laboratory, the material is obtained by electrolysis of water or as a result of the reaction between hydrochloric acid and zinc. However, more often use ready-made factory material in cylinders.
From the gas of oil refining and coke gas, this element is isolated by removing all other components of the gas mixture, since they are easier to liquefy with deep cooling.
Industrially, this material began to receive even at the end of the XVIII century. Then it was used to fill balloons. At the moment, hydrogen is widely used in industry, mainly in the chemical, for the production of ammonia.
Mass consumers of the substance are manufacturers of methyl and other alcohols, synthetic gasoline and many other products. They are obtained by synthesis of carbon oxide (II) and hydrogen. Hydrogene is used to hydrogenize heavy and solid liquid fuels, fats, etc., for the synthesis of HCl, hydrotreating of petroleum products, as well as in cutting / welding of metals. The most important elements for nuclear energy are its isotopes - tritium and deuterium.
Biological role of hydrogen
About 10% of the mass of living organisms (on average) falls on this element. It is part of the water and the most important groups. natural connections, including proteins, nucleic acids, lipids, carbohydrates. Why does it serve?
This material plays a decisive role: when maintaining the spatial structure of proteins (quaternary), in the implementation of the principle of complimentaryness nucleic acids (i.e. in the implementation and storage genetic information), in general in "recognition" at the molecular level.
The hydrogen ion H + takes part in important dynamic reactions / processes in the body. Including: in biological oxidation, which provides living cells by energy, in biosynthesis reactions, in photosynthesis in plants, in bacterial photosynthesis and nitrogenation, in maintaining acid-alkaline balance and homeostasis, in the membrane transport processes. Along with carbon and oxygen, it forms a functional and structural basis of life phenomena.
Industrial methods of obtaining simple substances depend on what form the corresponding element is in nature, that is, that may be raw materials for its preparation. Thus, oxygen existing in free state is obtained by a physical method - separation from liquid air. Hydrogen is almost entirely in the form of compounds, therefore, chemical methods are used to obtain it. In particular, decomposition reactions can be used. One of the methods of obtaining hydrogen is the reaction of water decomposition by electric shock.
The main industrial method of obtaining hydrogen is a reaction with water of methane, which is part of natural gas. It is carried out at high temperatures (it is easy to make sure that when methane passes, even through boiling water, no reaction occurs):
CH 4 + 2N 2 0 \u003d CO 2 + 4N 2 - 165 kJ
In the laboratory, not necessarily natural raw materials are used to obtain simple substances, but choose the source substances, of which it is easier to select the necessary substance. For example, in the laboratory oxygen is not obtained from the air. The same applies to the preparation of hydrogen. One of the laboratory methods for producing hydrogen, which is sometimes used in the industry - expansion of water with electric stroke.
Usually, hydrogen laboratories are obtained by the interaction of zinc with hydrochloric acid.
In industry
1.Electrolysis of aqueous salts:
2NACL + 2H 2 O → H 2 + 2NAOH + CL 2
2.Transmission of water vapor over hot coke at a temperature of about 1000 ° C:
H 2 O + C ⇄ H 2 + CO
3.From natural gas.
Conversion by water steam: CH 4 + H 2 O ⇄ CO + 3H 2 (1000 ° C) Catalytic oxidation with oxygen: 2CH 4 + O 2 ⇄ 2CO + 4H 2
4. Crequen and reforming hydrocarbons in the process of oil refining.
In the laboratory
1.The effect of diluted acids to metals. To carry out such a reaction, zinc and hydrochloric acid are most often used:
Zn + 2hcl → ZnCl 2 + H 2
2.Calcium interaction with water:
CA + 2H 2 O → Ca (OH) 2 + H 2
3.Hydrolysis hydrides:
NAH + H 2 O → NaOH + H 2
4.Action alkalis for 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. With the electrolysis of the aqueous solutions of alkali or acids on the cathode, hydrogen is released, for example:
2H 3 O + + 2e - → H 2 + 2H 2 O
- Bioreactor for hydrogen production
Physical properties
Gaseous hydrogen can exist in two forms (modifications) - in the form of ortho and para-hydrogen.
In the orthodorod molecule (so pl. -259.10 ° C, t. Kip. -252.56 ° C) nuclear spins are directed equally (parallel), and at Paravodorod (m. Pl. -259,32 ° C, t . Kip. -252,89 ° C) - opposite to each other (anti-parallel).
It is possible to split alto hydrogen altropy forms at an active angle at liquid nitrogen temperature. At very low temperatures, the equilibrium between the orthopomy and the waterproof is almost aimed towards the latter. At 80 to the form ratio of approximately 1: 1. The desorbed paralodine under heating turns into an orthodoxide up to the formation of equilibrium at room temperature of the mixture (ortho-steam: 75:25). Without a catalyst, the transformation occurs slowly, which makes it possible to study the properties of individual allotropic forms. Hydrogen molecule Dvkhatomna - H₂. Under normal conditions, it is gas without color, smell and taste. Hydrogen is the easiest gas, its density is many times less than air density. Obviously, the less weight of molecules, the higher their speed at the same temperature. As the easiest, hydrogen molecules are moving faster than molecules of any other gas and thus faster can transmit heat from one body to another. It follows that hydrogen has the highest thermal conductivity among gaseous substances. Its thermal conductivity is approximately seven times higher than thermal conductivity of air.
Chemical properties
Hydrogen molecules H₂ are quite durable, and in order for hydrogen to enter into the reaction, a large energy should be spent: H 2 \u003d 2N - 432 kJ so, at normal temperatures, hydrogen reacts with very active metals, for example with calcium, forming calcium hydride: CA + H 2 \u003d SAN 2 and with a single non-metallol - fluorine, forming fluorine hydrogen: F 2 + H 2 \u003d 2HF with most metals and non-metals hydrogen reacts at elevated temperatures or with a different effect, for example when lighting. It can "take away" oxygen from some oxides, for example: Cuo + H 2 \u003d Cu + H 2 0 The recorded equation reflects the recovery reaction. Recovery reactions are called processes, as a result of which oxygen is taken from the compound; Oxygen consistent substances are called reducing agents (at the same time they themselves are oxidized). Next, another definition of the concepts of "oxidation" and "recovery" will be given. And this definition, historically first, retains the meaning and now, especially in organic chemistry. Recovery response is the opposite of the oxidation reaction. Both of these reactions always proceed at the same time as one process: when oxidizing (recovery) of a single substance, it is defined simultaneously recovery (oxidation) of another.
N 2 + 3H 2 → 2 NH 3
With halogens forms halogen breeding:
F 2 + H 2 → 2 HF, the reaction proceeds with an explosion in the dark and at any temperature, CL 2 + H 2 → 2 HCl, the reaction proceeds with an explosion, only in the light.
With soot interact with strong heating:
C + 2H 2 → CH 4
Interaction with alkaline and lump-earth metals
Hydrogen forms with active metals hydrides:
Na + H 2 → 2 NAH 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 metals oxides (usually D-elements)
Oxides are restored to metals:
Cuo + H 2 → Cu + H 2 O FE 2 O 3 + 3H 2 → 2 Fe + 3H 2 O WO 3 + 3H 2 → W + 3H 2 O
Hydrogenation of organic compounds
Under the action of hydrogen on unsaturated hydrocarbons in the presence of a nickel catalyst and an elevated temperature, a reaction occurs hydrogenation:
CH 2 \u003d CH 2 + H 2 → CH 3 -CH 3
Hydrogen restores aldehydes to alcohols:
CH 3 CHO + H 2 → C 2 H 5 OH.
Geochemistry of hydrogen
Hydrogen is the main building material of the universe. This is the most common element, and all the elements are formed from it as a result of thermonuclear and nuclear reactions.
The free hydrogen H 2 is relatively rarely found in the earth's gases, but in the form of water it takes extremely important participation in geochemical processes.
The hydrogen minerals can be included in the form of ammonium ion, hydroxyl ion and crystalline water.
In the atmosphere, hydrogen is continuously formed as a result of water decomposition by solar radiation. It migrates to the upper layers of the atmosphere and disappears into space.
Application
- Hydrogen energy
Atomic hydrogen is used for atomic hydrogen welding.
IN food Industry hydrogen is registered as a food additive E949.like packaging gas.
Features of circulation
Hydrogen at a mixture with air forms an explosive mixture - the so-called rat gas. This gas has the greatest explosiveness with a volume of hydrogen and oxygen 2: 1, or hydrogen and air approximately 2: 5, since in the air of oxygen contains approximately 21%. Also hydrogen is fire hazardous. Liquid hydrogen when popping on the skin can cause severe frostbite.
Explosive concentrations of hydrogen with oxygen arise from 4% to 96% of volumetric. With a mixture with air from 4% to 75 (74)% of volumetric.
Using hydrogen
In the chemical industry, hydrogen is used in the production of ammonia, soap and plastics. In the food industry with hydrogen from liquid vegetable oils make margarine. Hydrogen is very lung and in the air always rises up. Sometime airships and balloons filled with hydrogen. But in the 30s. XX century There were several terrible catastrophes when the airships exploded and burned. Nowadays, the airships are filled with gas helium. Hydrogen is also used as rocket fuel. Someday hydrogen may be widely used as fuel for passenger and trucks. Hydrogen engines do not pollute ambient and allocate only water vapor (though, the very obtaining hydrogen leads to some environmental pollution). Our sun mainly consists of hydrogen. Solar heat and light is the result of nuclear energy release during the merger of hydrogen nuclei.
Using hydrogen as fuel (economic efficiency)
The most important characteristic of the substances used as fuel is their heat of combustion. From the course general Chemistry It is known that the reaction of the interaction of hydrogen with oxygen occurs with heat release. If you take 1 mol H 2 (2 g) and 0.5 mol O 2 (16 g) under standard conditions and excite the reaction, then according to the equation
H 2 + 0.5 o 2 \u003d H 2 o
after completion of the reaction, 1 mol h 2 o (18 g) is formed with an energy release of 285.8 kJ / mol (for comparison: the heat of the combustion of acetylene is 1300 kJ / mol, propane - 2200 kJ / mol). 1 m³ of hydrogen weighs 89.8 g (44.9 mol). Therefore, 12832.4 kJ of energy will be spent to obtain 1 m³ of hydrogen. Taking into account the fact that 1 kW · h \u003d 3600 kJ, we get 3.56 kWh of electricity. Knowing the tariff for 1 kW of electricity and the cost of 1 m³ of gas, it is possible to conclude about the feasibility of the transition to hydrogen fuel.
For example, the experimental model of Honda FCX 3 generations with a hydrogen tank 156 l (contains 3.12 kg of hydrogen under pressure of 25 MPa) 355 km drives. Accordingly, 123.8 kWh is obtained from 3.12 kg H2. At 100 km, energy consumption will be 36.97 kWh. Knowing the cost of electricity, the cost of gas or gasoline, their consumption for a car per 100 km is easy to calculate the negative economic effect of car transition to hydrogen fuel. Let's say (Russia 2008), 10 cents per kWh of electricity lead to the fact that 1 m³ of hydrogen leads to the price of 35.6 cents, and taking into account the efficiency of water decomposition of 40-45 cents, the same number of kWh · h from gasoline burning 12832,4kg / 42000kj / 0.7kg / l * 80tesunts / l \u003d 34 cents at retail prices, whereas for hydrogen, we calculated the perfect option, without taking into account the transportation, depreciation of equipment, etc. For methane with the combustion energy of about 39 MJ On m³ the result will be below two to four times due to the difference in price (1m³ for Ukraine costs $ 179, and for Europe $ 350). That is, an equivalent amount of methane will cost 10-20 cents.
However, we should not forget that when burning hydrogen, we get clean waterfrom which it was mined. That is, we have renewable pplash Energy without harm to the environment, in contrast to gas or gasoline, which are primary energy sources.
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Hydrogen. Properties, receipt, application.Historical reference
Hydrogen - the first element of PSHE D.I. Mendeleeva.
The Russian name of hydrogen indicates that he "gives rise to water"; Latin " hydrogenium » means the same.
For the first time, the separation of combustible gas in the interaction of some metals with acids was observed by Robert Boyle and its contemporaries in the first half of the XVI century.
But hydrogen was opened only in 1766 by the English chemist Henry Cavendis, who found that, with the interaction of metals with dilute acids, some "combustible air" stands out. Observing the burning of hydrogen in air, Cavendish found that the result is water. It was in 1782.
In 1783, the French chemist Antoine Laurent Lavauzier allocated hydrogen by decomposing the water with hot iron. In 1789, hydrogen was isolated during the decomposition of water under the action of electric current.
Prevalence in nature
Hydrogen is the main element of space. For example, the sun is 70% of its mass consists of hydrogen. Hydrogen atoms in the universe of several tens of thousands of times more than all atoms of all metals combined.In the earth's atmosphere, there is also some hydrogen in the form of a simple substance - gas composition H 2. Hydrogen is much easier than air, and therefore is found in the upper layers of the atmosphere.
But much more on the land of the associated hydrogen: after all, it is part of the water, the complex substance itself common on our planet. Hydrogen associated with molecules contain and oil and natural gas, many minerals and rocks. Hydrogen is part of all organic matter.
Characteristics of hydrogen element.
Hydrogen has a dual nature, for this reason, in some cases, hydrogen is placed in a subgroup of alkali metals, and in others - in the subgroup of halogen.
Electronic configuration 1s. 1 . The hydrogen atom consists of one proton and one electron.
The hydrogen atom is able to lose the electron and turn into the H + cation, and in this it is similar to alkaline metals.
A hydrogen atom can also attach an electron, forming an anion H -, in this regard, hydrogen is similar to halogens.
Connections are always monovalent
CO: +1 and -1.
Physical properties of hydrogen
Hydrogen is gas, without color, taste and smell. 14.5 times lighter than air. Little soluble in water. It has high thermal conductivity. At t \u003d -253 ° C - liquefied, at T \u003d -259 ° C - hardens. Hydrogen molecules are so small that they are able to slowly diffuse through many materials - rubber, glass, metals, which is used when cleaning hydrogen from other gases.3 hydrogen isotop are known: - Ftia, - deuterium, - tritium. The main part of natural hydrogen is due. The deuterium is part of the heavy water, which is enriched by surface waters of the ocean. Trithium - radioactive isotope.
Chemical properties of hydrogen
Hydrogen - nonmetall, has a molecular structure. The hydrogen molecule consists of two atoms, interconnected by a covalent non-polar bond. The binding energy in the hydrogen molecule is 436 kJ / mol, which explains the low chemical activity of molecular hydrogen.
Interaction with halogens. At normal temperature, hydrogen reacts only with fluorine:
With chlorine - only in the light, forming chloride, the reaction is less vigorously with the bromine, it does not go to the end with iodine even at high temperatures.
Oxygen interaction - when heated, during the ignition, the reaction proceeds with an explosion: 2H 2 + O 2 \u003d 2H 2 O.
A mixture of 1 part of oxygen and 2 parts of hydrogen - "Hardening mixture", is most explosive.
Interaction with gray - when heated H 2 + S \u003d H 2 S.
Interaction with nitrogen. When heated, high pressure and in the presence of a catalyst:
Interaction with nitrogen oxide (II). Used in cleansing systems in production nitric acid: 2no + 2H 2 \u003d N 2 + 2H 2 O.
Interaction with metals oxides. Hydrogen is a good reducing agent, it restores many metals from their oxides: Cuo + H 2 \u003d Cu + H 2 O.
A strong reducing agent is atomic hydrogen. It is formed from molecular in electrical discharge under low pressure conditions. High reducing activity has hydrogen at the time of allocationForming with acid reduction with acid.
Metal interaction . At high temperature, it is combined with alkaline and alkaline-land metals and forming white crystalline substances - metal hydrides, showing the properties of the oxidant: 2NA + H 2 \u003d 2NAh;
Obtaining hydrogen
In the laboratory:
Metal interaction with diluted solutions of sulfur and hydrochloric acids,
The interaction of aluminum or silicon with aqueous solutions alkalis:
Si + 2NAOH + H 2 O \u003d Na 2 SiO 3 + 2H 2.
In industry:
Electrolysis of aqueous solutions of sodium chlorides and potassium or electrolysis of water during the presence of hydroxides:
2N 2 O \u003d 2N 2 + O 2.
Conversion method. Initially, water gas is obtained, passing water pairs through hot coke at 1000 ° C:
The carbon oxide (II) is then oxidized in carbon oxide (IV), passing a water gas mixture with an excess of water vapor over heated to 400-450 ° C with FE 2 O 3 catalyst:
CO + H 2 O \u003d CO 2 + H 2.
The resulting carbon oxide (IV) is absorbed by water, this method is obtained by 50% of industrial hydrogen.
Methane conversion: CH 4 + H 2 O \u003d CO + 3H 2.
Thermal decomposition of methane at 1200 ° C: CH 4 \u003d C + 2H 2.
Deep cooling (up to -196 ° C) coke gas. At this temperature, all gaseous substances are condensed, except hydrogen.
The use of hydrogen is based on its physical and chemical properties:
like light gas, it is used to fill the balloon (in a mixture with helium);
oxygen-hydrogen flame is used to obtain high temperatures when welding metals;
as the reducing agent is used to obtain metals (molybdenum, tungsten, etc.) from their oxides;
to obtain ammonia and artificial liquid fuel, for hydrogenation of fats.
