Hydrogen was discovered in the second half of the 18th century by the English scientist in the field of physics and chemistry G. Cavendish. He managed to isolate a substance in a pure state, began to study it and described its properties.
Such is the history of the discovery of hydrogen. During the experiments, the researcher determined that it is a combustible gas, the combustion of which in air gives water. This led to the determination of the qualitative composition of water.
What is hydrogen
Hydrogen, as a simple substance, was first declared by the French chemist A. Lavoisier in 1784, since he determined that its molecule contains atoms of the same type.
The name of the chemical element in Latin sounds like hydrogenium (read "hydrogenium"), which means "giving birth to water." The name refers to the combustion reaction that produces water.
Characterization of hydrogen
The designation of hydrogen N. Mendeleev assigned the first serial number to this chemical element, placing it in the main subgroup of the first group and the first period and conditionally in the main subgroup of the seventh group.
The atomic weight (atomic mass) of hydrogen is 1.00797. The molecular weight of H 2 is 2 a. e. The molar mass is numerically equal to it.
It is represented by three isotopes with a special name: the most common protium (H), heavy deuterium (D), and radioactive tritium (T).
It is the first element that can be completely separated into isotopes. in a simple way. It is based on the high mass difference of isotopes. The process was first carried out in 1933. This is explained by the fact that only in 1932 was an isotope with a mass of 2 discovered.
Physical Properties
Under normal conditions, a simple substance hydrogen in the form of diatomic molecules is a gas, without color, which has no taste and smell. Slightly soluble in water and other solvents.
Crystallization temperature - 259.2 o C, boiling point - 252.8 o C. The diameter of hydrogen molecules is so small that they have the ability to slowly diffuse through a number of materials (rubber, glass, metals). This property is used when it is required to purify hydrogen from gaseous impurities. At n. y. hydrogen has a density of 0.09 kg/m3.
Is it possible to convert hydrogen into a metal by analogy with the elements located in the first group? Scientists have found that hydrogen, under conditions when the pressure approaches 2 million atmospheres, begins to absorb infrared rays, which indicates the polarization of the molecules of the substance. Perhaps at even higher pressures, hydrogen will become a metal.
It is interesting: there is an assumption that on the giant planets, Jupiter and Saturn, hydrogen is in the form of a metal. It is assumed that metallic solid hydrogen is also present in the composition of the earth's core, due to the ultra-high pressure created by the earth's mantle.
Chemical properties
AT chemical interaction both simple and complex substances enter with hydrogen. But the low activity of hydrogen needs to be increased by creating appropriate conditions - raising the temperature, using catalysts, etc.
When heated, simple substances such as oxygen (O 2), chlorine (Cl 2), nitrogen (N 2), sulfur (S) react with hydrogen.
If you set fire to pure hydrogen at the end of the gas tube in the air, it will burn evenly, but barely noticeable. If, however, the gas outlet tube is placed in an atmosphere of pure oxygen, then combustion will continue with the formation of water drops on the walls of the vessel, as a result of the reaction:
The combustion of water is accompanied by the release of a large amount of heat. This is an exothermic compound reaction in which hydrogen is oxidized by oxygen to form the oxide H 2 O. It is also a redox reaction in which hydrogen is oxidized and oxygen is reduced.
Similarly, the reaction with Cl 2 occurs with the formation of hydrogen chloride.
The interaction of nitrogen with hydrogen requires high temperature and high pressure, as well as the presence of a catalyst. The result is ammonia.
As a result of the reaction with sulfur, hydrogen sulfide is formed, the recognition of which facilitates the characteristic smell of rotten eggs.
The oxidation state of hydrogen in these reactions is +1, and in the hydrides described below, it is 1.
When reacting with some metals, hydrides are formed, for example, sodium hydride - NaH. Some of these complex compounds are used as fuel for rockets, as well as in fusion power.
Hydrogen also reacts with substances from the complex category. For example, with copper (II) oxide, the formula CuO. To carry out the reaction, copper hydrogen is passed over heated powdered copper (II) oxide. In the course of interaction, the reagent changes its color and becomes red-brown, and droplets of water settle on the cold walls of the test tube.
During the reaction, hydrogen is oxidized to form water, and copper is reduced from oxide to a simple substance (Cu).
Areas of use
Hydrogen has great importance for humans and finds application in various fields:
- AT chemical production- this is a raw material, in other industries - fuel. Do not do without hydrogen and the enterprises of petrochemistry and oil refining.
- In the electric power industry, this simple substance acts as a cooling agent.
- In ferrous and non-ferrous metallurgy, hydrogen plays the role of a reducing agent.
- With this help, an inert environment is created when packaging products.
- The pharmaceutical industry uses hydrogen as a reagent in the production of hydrogen peroxide.
- Meteorological probes are filled with this light gas.
- This element is also known as a fuel reducing agent for rocket engines.
Scientists unanimously predict that hydrogen fuel will be the leader in the energy sector.
Receipt in industry
In industry, hydrogen is produced by electrolysis, which is subjected to chlorides or hydroxides of alkali metals dissolved in water. It is also possible to obtain hydrogen in this way directly from water.
For this purpose, the conversion of coke or methane with steam is used. The decomposition of methane at elevated temperature also produces hydrogen. Liquefaction of coke oven gas by the fractional method is also used for industrial production hydrogen.
Obtaining in the laboratory
In the laboratory, a Kipp apparatus is used to produce hydrogen.
Hydrochloric or sulfuric acid and zinc act as reagents. As a result of the reaction, hydrogen is formed.
Finding hydrogen in nature
Hydrogen is the most common element in the universe. The bulk of the stars, including the Sun, and other space bodies makes up hydrogen.
AT earth's crust it is only 0.15%. It is present in many minerals, in all organic substances, as well as in water that covers 3/4 of the surface of our planet.
In the upper atmosphere, traces of pure hydrogen can be found. It is also found in a number of combustible natural gases.
Gaseous hydrogen is the thinnest, and liquid hydrogen is the densest substance on our planet. With the help of hydrogen, you can change the timbre of the voice, if you inhale it, and speak as you exhale.
At the heart of the action of the most powerful hydrogen bomb lies the splitting of the lightest atom.
In the periodic system, hydrogen is located in two groups of elements that are absolutely opposite in their properties. This feature makes it completely unique. Hydrogen is not only an element or substance, but also a integral part many complex compounds, organogenic and biogenic elements. Therefore, we consider its properties and characteristics in more detail.
The release of combustible gas during the interaction of metals and acids was observed as early as the 16th century, that is, during the formation of chemistry as a science. The famous English scientist Henry Cavendish studied the substance starting in 1766 and gave it the name "combustible air". When burned, this gas produced water. Unfortunately, the scientist's adherence to the theory of phlogiston (hypothetical "hyperfine matter") prevented him from coming to correct conclusions.
The French chemist and naturalist A. Lavoisier, together with the engineer J. Meunier and with the help of special gasometers, in 1783 carried out the synthesis of water, and then its analysis by decomposing water vapor with red-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 suggested that the gas under study is a simple substance and, accordingly, is one of the primary chemical elements. He called it hydrogene (from Greek words hydor - water + gennao - I give birth), that is, "giving birth to water."
The Russian name "hydrogen" was proposed in 1824 by the chemist M. Solovyov. The determination of the composition of water marked the end of the "phlogiston theory". At the turn of the 18th and 19th centuries, it was found that the hydrogen atom is very light (compared to the atoms of other elements) and its mass was taken as the main unit for comparing atomic masses, obtaining a value equal to 1.
Physical Properties
Hydrogen is the lightest of all substances known to science (it is 14.4 times lighter than air), its density is 0.0899 g/l (1 atm, 0 °C). This material melts (solidifies) and boils (liquefies), respectively, at -259.1 ° C and -252.8 ° C (only helium has lower boiling and melting t °).
The critical temperature of hydrogen is extremely low (-240 °C). For this reason, its liquefaction is a rather complicated and costly process. The critical pressure of a substance is 12.8 kgf / cm², and the critical density is 0.0312 g / cm³. Among all gases, hydrogen has the highest thermal conductivity: at 1 atm and 0 ° C, it is equal to 0.174 W / (mxK).
The specific heat capacity of a substance under the same conditions is 14.208 kJ / (kgxK) or 3.394 cal / (gh ° C). This element is slightly 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 (about 850 volumes per volume of Pd ).
The latter property is associated with its ability to diffuse, while diffusion through a carbon alloy (for example, steel) may be accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (this process is called decarbonization). In the liquid state, the substance is very light (density - 0.0708 g / cm³ at t ° \u003d -253 ° C) and fluid (viscosity - 13.8 centigrade under the same conditions).
In many compounds, this element exhibits a +1 valency (oxidation state), similar to sodium and other alkali metals. It is usually considered as an analogue of these metals. Accordingly, he heads the I group of the Mendeleev system. In metal hydrides, the hydrogen ion exhibits a negative charge (the oxidation state is -1), that is, Na + H- has a structure similar to Na + Cl- chloride. In accordance with this and some other facts (the closeness of the physical properties of the element "H" and halogens, the ability to replace it with halogens in organic compounds), Hydrogene is assigned to group VII of the Mendeleev system.
Under normal conditions, molecular hydrogen has low activity, directly combining only with the most active of 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 an increased chemical activity (compared to molecular hydrogen). With oxygen, it forms water according to the formula:
Н₂ + ½О₂ = Н₂О,
releasing 285.937 kJ/mol of heat or 68.3174 kcal/mol (25°C, 1 atm). Under normal temperature conditions, the reaction proceeds rather slowly, and at t ° >= 550 ° С, it is uncontrolled. The explosive limits of a mixture of hydrogen + oxygen by volume are 4–94% H₂, and mixtures of hydrogen + air are 4–74% H₂ (a mixture of two volumes of H₂ and one volume of O₂ is called explosive gas).
This element is used to reduce most metals, since it takes oxygen from oxides:
Fe₃O₄ + 4H₂ = 3Fe + 4Н₂О,
CuO + H₂ = Cu + H₂O etc.
With different halogens, hydrogen forms hydrogen halides, for example:
H₂ + Cl₂ = 2HCl.
However, when reacting with fluorine, hydrogen explodes (this also happens in the dark, at -252 ° C), reacts with bromine and chlorine only when heated or illuminated, and with iodine only when heated. When interacting with nitrogen, ammonia is formed, but only on a catalyst, at elevated pressures and temperatures:
ZN₂ + N₂ = 2NH₃.
When heated, hydrogen actively reacts with sulfur:
H₂ + S = H₂S (hydrogen sulfide),
and much more difficult - with tellurium or selenium. Hydrogen reacts with pure carbon without a catalyst, but at high temperatures:
2H₂ + C (amorphous) = CH₄ (methane).
This substance directly reacts with some of the metals (alkali, alkaline earth and others), forming hydrides, for example:
Н₂ + 2Li = 2LiH.
Of no small practical importance are the interactions of hydrogen and carbon monoxide (II). In this case, depending on the pressure, temperature and catalyst, various organic compounds are formed: HCHO, CH₃OH, etc. Unsaturated hydrocarbons turn into saturated ones during the reaction, for example:
С n Н₂ n + Н₂ = С n Н₂ n ₊₂.
Hydrogen and its compounds play an exceptional role in chemistry. It conditions acid properties so-called. protic acids, tends to form a hydrogen bond with different elements, which has a significant effect on the properties of many inorganic and organic compounds.
Getting hydrogen
The main types of raw materials for industrial production of this element are petroleum refining gases, natural combustible and coke oven gases. It is also obtained from water through electrolysis (in places with affordable electricity). One of essential methods The production of material from natural gas is considered to be the catalytic interaction of hydrocarbons, mainly methane, with water vapor (the so-called conversion). For example:
CH₄ + H₂O = CO + ZH₂.
Incomplete oxidation of hydrocarbons with oxygen:
CH₄ + ½O₂ \u003d CO + 2H₂.
Synthesized carbon monoxide (II) undergoes conversion:
CO + H₂O = CO₂ + H₂.
Hydrogen produced from natural gas is the cheapest.
For electrolysis of water, direct current is used, which is passed through a solution of NaOH or KOH (acids are not used to avoid corrosion of the equipment). Under laboratory conditions, the material is obtained by electrolysis of water or as a result of the reaction between hydrochloric acid oh and zinc. However, more often used ready-made factory material in cylinders.
From the gases of oil refining and coke oven gas, this element is isolated by removing all other components gas mixture, as they liquefy more easily when deep cooled.
Industrially, this material began to be obtained back in late XVIII century. Then it was used to fill balloons. At the moment, hydrogen is widely used in industry, mainly in the chemical industry, 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 from carbon monoxide (II) and hydrogen. Hydrogene is used for the hydrogenation of heavy and solid liquid fuels, fats, etc., for the synthesis of HCl, hydrotreating of petroleum products, as well as in cutting / welding of metals. Essential elements for nuclear energy are its isotopes - tritium and deuterium.
The biological role of hydrogen
About 10% of the mass of living organisms (on average) falls on this element. It is part of water and the most important groups of natural compounds, including proteins, nucleic acids, lipids, carbohydrates. What does it serve?
This stuff plays decisive role: while maintaining the spatial structure of proteins (quaternary), in the implementation of the principle of complementarity nucleic acids(i.e., in the implementation and storage of genetic information), in general, in "recognition" at the molecular level.
The hydrogen ion H+ takes part in important dynamic reactions/processes in the body. Including: in biological oxidation, which provides living cells with energy, in biosynthesis reactions, in photosynthesis in plants, in bacterial photosynthesis and nitrogen fixation, in maintaining acid-base balance and homeostasis, in membrane transport processes. Along with carbon and oxygen, it forms the functional and structural basis of the phenomena of life.
Lecture 29
Hydrogen. Water
Lecture plan:
Water. Chemical and physical properties
The role of hydrogen and water in nature
Hydrogen as a chemical element
Hydrogen is the only element periodic system D. I. Mendeleev, whose location is ambiguous. His chemical symbol in the periodic table is recorded twice: in both IA and VIIA groups. This is explained by the fact that hydrogen has a number of properties that combine it with both alkali metals and halogens (Table 14).
Table 14
Comparison of the properties of hydrogen with the properties of alkali metals and halogens
| Similarity to alkali metals | Similarity to halogens |
| At the outer energy level, hydrogen atoms contain one electron. Hydrogen belongs to the s-elements | To complete the outer and only level, hydrogen atoms, like halogen atoms, lack one electron |
| Hydrogen exhibits reducing properties. As a result of oxidation, hydrogen receives the most common oxidation state in its compounds +1 | Hydrogen, like halogens, in compounds with alkali and alkaline earth metals has an oxidation state of -1, which confirms its oxidizing properties. |
| The presence in space of solid hydrogen with a metallic crystal lattice is assumed. | Like fluorine and chlorine, hydrogen is a gas under normal conditions. Its molecules, like the molecules of halogens, are diatomic and are formed by a covalent non-polar bond |
In nature, hydrogen exists in the form of three isotopes with mass numbers 1, 2 and 3: protium 1 1 H, deuterium 2 1 D and tritium 3 1 T. The first two are stable isotopes, and the third is radioactive. The natural mixture of isotopes is dominated by protium. The quantitative ratios between the isotopes H: D: T are 1: 1.46 10 -5: 4.00 10 -15 .
Compounds of hydrogen isotopes differ in properties from each other. So, for example, the boiling and freezing points of light protium water (H 2 O), respectively, are equal to - 100 o C and 0 o C, and deuterium (D 2 O) - 101.4 o C and 3.8 o C. The reaction rate with the participation of light water is higher than heavy water.
Hydrogen is the most abundant element in the universe, accounting for about 75% of the mass of the universe or over 90% of all its atoms. Hydrogen is a part of water in its most important geological shell of the Earth - the hydrosphere.
Hydrogen forms, along with carbon, all organic substances, that is, it is part of the living shell of the Earth - the biosphere. In the earth's crust - the lithosphere - the mass content of hydrogen is only 0.88%, i.e., it occupies the 9th place among all elements. The air shell of the Earth - the atmosphere contains less than a millionth of the total volume attributable to molecular hydrogen. It is found only in the upper atmosphere.
Obtaining and using hydrogen
Hydrogen was first obtained in the 16th century by the medieval physician and alchemist Paracelsus, when an iron plate was immersed in sulfuric acid, and in 1766, the English chemist Henry Cavendish proved that hydrogen is obtained not only by the interaction of iron with sulfuric acid, but also of other metals with other acids. Cavendish also described for the first time the properties of hydrogen.
AT laboratory hydrogen conditions are obtained:
1. Interaction of metals with acid:
Zn + 2HCl → ZnCl 2 + H 2
2. Interaction of alkali and alkaline earth metals with water
2Na + 2H 2 O → 2NaOH + H 2
Ca + 2H 2 O → Ca (OH) 2 + H 2
AT industry hydrogen is produced in the following ways:
1. Electrolysis of aqueous solutions of salts, acids and alkalis. The most commonly used salt solution is:
2NaCl + 2H 2 O →el. current H 2 + Cl 2 + NaOH
2. Recovery of water vapor by red-hot coke:
C + H 2 O → t CO + H 2
The resulting mixture of carbon monoxide and hydrogen is called water gas (synthesis gas), and is widely used for the synthesis of various chemical products (ammonia, methanol, etc.). To extract hydrogen from water gas carbon monoxide converted to carbon dioxide when heated with water vapor:
CO + H 2 → t CO 2 + H 2
3. Methane heating in the presence of water vapor and oxygen. This method is currently the main one:
2CH 4 + O 2 + 2H 2 O → t 2CO 2 + 6H 2
Hydrogen is widely used for:
1. industrial synthesis of ammonia and hydrogen chloride;
2. obtaining methanol and synthetic liquid fuel as part of synthesis gas (2 volumes of hydrogen and 1 volume of CO);
3. hydrotreating and hydrocracking of oil fractions;
4. hydrogenation of liquid fats;
5. cutting and welding of metals;
6. obtaining tungsten, molybdenum and rhenium from their oxides;
7. space engines as fuel.
8. Thermonuclear reactors use hydrogen isotopes as fuel.
Physical and Chemical properties hydrogen
Hydrogen is a colorless, tasteless and odorless gas. Density at n.o. 0.09 g/l (14 times lighter than air). Hydrogen is poorly soluble in water (only 2 volumes of gas per 100 volumes of water), but it is well absorbed by d-metals - nickel, platinum, palladium (up to 900 volumes of hydrogen are dissolved in one volume of palladium).
In chemical reactions, hydrogen exhibits both reducing and oxidizing properties. Most often, hydrogen acts as a reducing agent.
1. Interaction with non-metals. Hydrogen with non-metals forms volatile hydrogen compounds(see lecture 25).
With halogens the reaction rate and flow conditions change from fluorine to iodine: hydrogen reacts with fluorine with an explosion even in the dark, with chlorine the reaction proceeds quite calmly with little light exposure, with bromine and iodine the reactions are reversible and proceed only when heated:
H 2 + F 2 → 2HF
H 2 + Cl 2 → hν 2HCl
H 2 + I 2 → t 2HI
With oxygen and sulfuric hydrogen reacts with slight heating. A 1:2 mixture of oxygen and hydrogen is called explosive gas:
H 2 + O 2 → t H 2 O
H 2 + S → t H 2 S
With nitrogen, phosphorus and carbon reaction occurs when heated high blood pressure and in the presence of a catalyst. Reactions are reversible:
3H 2 + N 2 → cat., p, t2NH 3
2H 2 + 3P → cat., p, t3PH 3
H 2 + C → cat., p, t CH 4
2. Interaction with complex substances. At high temperatures, hydrogen reduces metals from their oxides:
CuO + H 2 → t Cu + H 2 O
3. At interaction with alkali and alkaline earth metals hydrogen exhibits oxidizing properties:
2Na + H 2 → 2NaH
Ca + H 2 → CaH 2
4. Interaction with organic substances. Hydrogen actively interacts with many organic substances, such reactions are called hydrogenation reactions. Similar reactions will be considered in more detail in Part III of the collection "Organic Chemistry".
The most abundant element in the universe is hydrogen. In the matter of stars, it has the form of nuclei - protons - and is the material for thermonuclear processes. Almost half of the mass of the Sun also consists of H 2 molecules. Its content in the earth's crust reaches 0.15%, and atoms are present in the composition of oil, natural gas, and water. Together with oxygen, nitrogen and carbon, it is an organogenic element that is part of all living organisms on Earth. In our article, we will study the physical and chemical properties of hydrogen, determine the main areas of its application in industry and its importance in nature.
Position in the periodic system of chemical elements of Mendeleev
The first element to open the periodic table is hydrogen. Its atomic mass is 1.0079. It has two stable (protium and deuterium) and one radioactive isotope (tritium). Physical Properties are determined by the place of the non-metal in the table of chemical elements. Under normal conditions, hydrogen (its formula is H 2) is a gas that is almost 15 times lighter than air. The structure of an element's atom is unique: it consists of only a nucleus and one electron. The molecule of a substance is diatomic, the particles in it are connected using a covalent non-polar bond. Its energy intensity is quite high - 431 kJ. This explains the low chemical activity of the compound under normal conditions. The electronic formula of hydrogen is: H:H.
The substance also has a number of properties that have no analogues among other non-metals. Let's consider some of them.
Solubility and thermal conductivity
Metals conduct heat best, but hydrogen approaches them in terms of thermal conductivity. The explanation for the phenomenon lies in the very high speed thermal motion light molecules of a substance, therefore, in a hydrogen atmosphere, a heated object cools down 6 times faster than in air. The compound can dissolve well in metals, for example, almost 900 volumes of hydrogen can be absorbed by one volume of palladium. Metals can enter into chemical reactions with H 2 in which the oxidizing properties of hydrogen are manifested. In this case, hydrides are formed:
2Na + H 2 \u003d 2 NaH.
In this reaction, the atoms of an element accept electrons from metal particles, turning into anions with a unit negative charge. Simple substance H 2 in this case is an oxidizing agent, which is usually not typical for it.
Hydrogen as a reducing agent
What unites metals and hydrogen is not only high thermal conductivity, but also the ability of their atoms to chemical processes donate their own electrons, that is, oxidize. For example, basic oxides react with hydrogen. The redox reaction ends with the release of pure metal and the formation of water molecules:
CuO + H 2 \u003d Cu + H 2 O.
The interaction of a substance with oxygen during heating also leads to the production of water molecules. The process is exothermic and is accompanied by the release of a large amount of thermal energy. If a gas mixture of H 2 and O 2 reacts in a ratio of 2: 1, then it is called because it explodes when ignited:
2H 2 + O 2 \u003d 2H 2 O.
Water is and plays an important role in the formation of the Earth's hydrosphere, climate, and weather. It provides the circulation of elements in nature, supports all the life processes of organisms - the inhabitants of our planet.
Interaction with non-metals
The most important chemical properties of hydrogen are its reactions with non-metallic elements. Under normal conditions, they are quite chemically inert, so the substance can only react with halogens, for example, with fluorine or chlorine, which are the most active among all non-metals. So, a mixture of fluorine and hydrogen explodes in the dark or in the cold, and with chlorine - when heated or in the light. The reaction products will be hydrogen halides, the aqueous solutions of which are known as fluoride and chloride acids. C interacts at a temperature of 450-500 degrees, a pressure of 30-100 MPa and in the presence of a catalyst:
N₂ + 3H₂ ⇔ p, t, kat ⇔ 2NH₃.
The considered chemical properties of hydrogen are of great importance for industry. For example, you can get a valuable chemical product - ammonia. It is the main raw material for the production of nitrate acid and nitrogen fertilizers: urea, ammonium nitrate.
organic matter
Between carbon and hydrogen leads to the production of the simplest hydrocarbon - methane:
C + 2H 2 = CH 4.
The substance is the most important component of the natural substance and is used as a valuable type of fuel and raw material for the industry of organic synthesis.
In the chemistry of carbon compounds, an element is included in a huge number of substances: alkanes, alkenes, carbohydrates, alcohols, etc. Many reactions of organic compounds with H 2 molecules are known. They are collectively known as hydrogenation or hydrogenation. So, aldehydes can be reduced with hydrogen to alcohols, unsaturated hydrocarbons - to alkanes. For example, ethylene is converted to ethane:
C 2 H 4 + H 2 \u003d C 2 H 6.
Of great practical importance are such chemical properties of hydrogen as, for example, the hydrogenation of liquid oils: sunflower, corn, and rapeseed. It leads to the production of solid fat - lard, which is used in the production of glycerin, soap, stearin, hard margarine. To improve appearance and taste food product milk, animal fats, sugar, vitamins are added to it.
In our article, we studied the properties of hydrogen and found out its role in nature and human life.
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. Distinctive feature hydrogen is also the fact that it is the first element in the periodic system of chemical elements of D. I. Mendeleev.
Discovery and exploration
The first references to hydrogen in the writings of Paracelsus date back to the sixteenth century. But its isolation from the gas mixture of air and the study of combustible properties were already made in the seventeenth century by the scientist Lemery. Hydrogen was thoroughly studied by an English chemist, physicist and naturalist who experimentally proved that the mass of hydrogen is the smallest in comparison with other gases. In the subsequent stages of the development of science, many scientists worked with him, in particular Lavoisier, who called him "giving birth to water."
Characteristic according to the position in the PSCE
The element that opens the periodic table of 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 up a single electron in the process chemical reaction, and to the seventh - in the case of complete filling of the valence shell, that is, the reception of a negative particle, which characterizes it as similar to halogens.
Features of the electronic structure of the element
Properties complex substances, in which it is included, and the simplest substance H 2 are primarily determined by the electronic configuration of the hydrogen. The particle has one electron with Z= (-1), which rotates in its orbit around the nucleus, containing one proton with unit mass and positive charge (+1). Its electronic configuration is written as 1s 1, which means the presence of one negative particle in the very first and only s-orbital for the hydrogen.
When an electron is detached or given away, and an atom of this element has such a property that it is related to metals, a cation is obtained. In fact, the hydrogen ion is a positive elementary particle. Therefore, a hydrogen devoid of an electron is simply called a proton.
Physical Properties
Briefly describing hydrogen, it is a colorless, slightly soluble gas with a relative atomic mass equal to 2, 14.5 times lighter than air, with a liquefaction temperature of -252.8 degrees Celsius.
It can be easily seen from experience that H2 is the lightest. To do this, it is enough to fill three balls with various substances - hydrogen, carbon dioxide, ordinary air - and simultaneously release them from your hand. The one that is filled with CO 2 will reach the ground faster than anyone, after which it will fall inflated with an air mixture, and the one containing H 2 will rise to the ceiling.
The small mass and size of hydrogen particles justify its ability to penetrate through various substances. On the example of the same ball, this is easy to verify, in a couple of days it will deflate itself, since the gas will simply pass through the rubber. Also, hydrogen can accumulate in the structure of some metals (palladium or platinum), and evaporate from it when the temperature rises.
The property of low solubility of hydrogen is used in laboratory practice to isolate it by the method of hydrogen displacement (the table below contains the main parameters) determine the scope of its application and methods of production.
| Parameter of an atom or molecule of a simple substance | Meaning |
| 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 at n. y. | 0.08987 g/l |
| Boiling temperature | -252.76°C |
| Specific heat of 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 a different number of neutrons - particles with zero charge and unit mass. Examples of atoms that have a similar property are oxygen, carbon, chlorine, bromine and others, including radioactive ones.
The physical properties of hydrogen 1 H, the most common of the representatives of this group, differ significantly from the same characteristics of its counterparts. In particular, the characteristics of the substances in which they are included differ. So, there is ordinary and deuterated water, which contains in its composition, instead of a hydrogen atom with a single proton, deuterium 2 H - its isotope with two elementary particles: positive and uncharged. This isotope is twice as heavy as ordinary hydrogen, which explains the fundamental difference in the properties of the compounds they make up. In nature, deuterium is 3200 times rarer than hydrogen. The third representative is tritium 3 H, in the nucleus it has two neutrons and one proton.
Methods for obtaining and isolating
Laboratory and industrial methods are very different. So, in small quantities, gas is obtained mainly through reactions in which minerals are involved, and large-scale production uses organic synthesis to a greater extent.
The following chemical interactions are used in the laboratory:
In industrial interests, gas is obtained by such methods as:
- Thermal decomposition of methane in the presence of a catalyst to its constituents simple substances(350 degrees reaches the value of such an indicator as temperature) - hydrogen H 2 and carbon C.
- Passing vaporous water through coke at 1000 degrees Celsius to form 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 in the electrolysis of aqueous solutions of potassium or sodium chlorides.
Chemical interactions: general provisions
The physical properties of hydrogen largely explain its behavior in reaction processes with one or another compound. The valency of the hydrogen is 1, since it is located in the first group in the periodic table, and the degree of oxidation shows a different one. In all compounds, except for hydrides, hydrogen in s.o. = (1+), in molecules like XH, XH 2, XH 3 - (1-).
The hydrogen gas molecule, formed by creating a generalized electron pair, consists of two atoms and is quite stable energetically, which is why under normal conditions it is somewhat inert and enters into reactions when normal conditions change. Depending on the degree of oxidation of hydrogen in the composition of other substances, it can act both as an oxidizing agent and a reducing agent.
Substances with which hydrogen reacts and forms
Elemental interactions to form complex substances (often at elevated temperatures):
- Alkaline and alkaline earth metal+ hydrogen = hydride.
- Halogen + H 2 = hydrogen halide.
- Sulfur + hydrogen = hydrogen sulfide.
- Oxygen + H 2 = water.
- Carbon + hydrogen = methane.
- Nitrogen + H 2 = ammonia.
Interaction with complex substances:
- Obtaining synthesis gas from carbon monoxide and hydrogen.
- Recovery of metals from their oxides with H 2 .
- Hydrogen saturation of unsaturated aliphatic hydrocarbons.
hydrogen bond
The physical properties of hydrogen are such that, when combined with an electronegative element, it allows it to form a special type of bond with the same atom from neighboring molecules that have unshared electron pairs (for example, oxygen, nitrogen and fluorine). The clearest example on which it is better to consider such a phenomenon is water. It can be said that it is stitched with hydrogen bonds, which are weaker than covalent or ionic ones, but due to the fact that there are many of them, they have a significant effect on the properties of the substance. Essentially, hydrogen bonding is an electrostatic interaction that binds water molecules into dimers and polymers, giving rise to its high boiling point.
Hydrogen in the composition of mineral compounds
All contain a proton - a cation of an atom such as hydrogen. A substance whose acid residue has an oxidation state greater than (-1) is called a polybasic compound. It contains several hydrogen atoms, which makes dissociation into aqueous solutions multistage. Each subsequent proton breaks away from the rest of the acid more and more difficult. According to the quantitative content of hydrogens in the medium, its acidity is determined.
Application in human activities
Cylinders with a substance, as well as containers with other liquefied gases, such as oxygen, have a specific appearance. They are painted dark green with a bright red "Hydrogen" lettering. Gas is pumped into a cylinder under a pressure of about 150 atmospheres. Physical properties of hydrogen, in particular the ease of gaseous state of aggregation, used to fill balloons, balloons, etc. mixed with helium.
Hydrogen, the physical and chemical properties of which people learned to use many years ago, is currently used in many industries. Most of it goes to the production of ammonia. Hydrogen also participates in (hafnium, germanium, gallium, silicon, molybdenum, tungsten, zirconium and others) from oxides, acting in the reaction as a reducing agent, hydrocyanic and hydrochloric acids, as well as artificial liquid fuel. food industry uses it to turn vegetable oils into solid fats.
We determined the chemical properties and use of hydrogen in various processes of hydrogenation and hydrogenation of fats, coals, hydrocarbons, oils and fuel oil. With it, they produce gems, incandescent lamps, carry out forging and welding of metal products under the influence of an oxygen-hydrogen flame.
