Hydrogen is a complex substance. Hydrogen in nature (0.9% in the Earth's crust)

Hydrogen(lat. Hydrogenium), H, a chemical element, the first by serial number in Mendeleev's periodic system; atomic mass 1.0079. Under ordinary conditions Hydrogen is a gas; has no color, smell and taste.

Distribution of Hydrogen in nature. Hydrogen is widely distributed in nature, its content in the earth's crust (lithosphere and hydrosphere) is 1% by mass, and 16% by the number of atoms. Hydrogen is part of the most common substance on Earth - water (11.19% Hydrogen by mass), in the compounds that make up coal, oil, natural gases, clay, as well as animal and plant organisms (that is, in the composition of proteins, nucleic acids , fats, carbohydrates, etc.). Hydrogen is extremely rare in the free state; it is found in small amounts in volcanic and other natural gases. Negligible amounts of free Hydrogen (0.0001% by number of atoms) are present in the atmosphere. In near-Earth space, Hydrogen in the form of a stream of protons forms the internal ("proton") radiation belt of the Earth. Hydrogen is the most abundant element in space. In the form of plasma, it makes up about half the mass of the Sun and most stars, the bulk of the gases of the interstellar medium and gaseous nebulae. Hydrogen is present in the atmosphere of a number of planets and in comets in the form of free H 2 , methane CH 4 , ammonia NH 3 , water H 2 O, radicals such as CH, NH, OH, SiH, PH, etc. Hydrogen enters in the form of a proton flux in the corpuscular radiation of the Sun and cosmic rays.

Isotopes, atom and molecule of Hydrogen. Ordinary Hydrogen consists of a mixture of 2 stable isotopes: light Hydrogen, or protium (1 H), and heavy Hydrogen, or deuterium (2 H, or D). In natural hydrogen compounds, there are on average 6800 atoms of 1 H per 1 atom of 2 H. A radioactive isotope with a mass number of 3 is called superheavy Hydrogen, or tritium (3 H, or T), with soft β-radiation and a half-life T ½ = 12.262 years . In nature, tritium is formed, for example, from atmospheric nitrogen under the action of cosmic ray neutrons; it is negligible in the atmosphere (4·10 -15% of the total number of hydrogen atoms). An extremely unstable isotope 4 H was obtained. The mass numbers of the isotopes 1 H, 2 H, 3 H and 4 H, respectively 1, 2, 3 and 4, indicate that the nucleus of the protium atom contains only one proton, deuterium - one proton and one neutron, tritium - one proton and 2 neutrons, 4 H - one proton and 3 neutrons. The large difference in the masses of the isotopes of Hydrogen causes a more noticeable difference in their physical and chemical properties than in the case of isotopes of other elements.

The Hydrogen atom has the simplest structure among the atoms of all other elements: it consists of a nucleus and one electron. The binding energy of an electron with a nucleus (ionization potential) is 13.595 eV. Neutral atom Hydrogen can also attach a second electron, forming a negative ion H - in this case, the binding energy of the second electron with a neutral atom (electron affinity) is 0.78 eV. Quantum mechanics makes it possible to calculate all possible energy levels of the Hydrogen atom and, consequently, to give a complete interpretation of its atomic spectrum. The Hydrogen atom is used as a model atom in quantum mechanical calculations of the energy levels of other, more complex atoms.

The Hydrogen H 2 molecule consists of two atoms connected by a covalent chemical bond. The energy of dissociation (that is, decay into atoms) is 4.776 eV. The interatomic distance at the equilibrium position of the nuclei is 0.7414Å. At high temperatures, molecular Hydrogen dissociates into atoms (the degree of dissociation at 2000°C is 0.0013; at 5000°C it is 0.95). Atomic Hydrogen is also formed in various chemical reactions (for example, by the action of Zn on hydrochloric acid). However, the existence of Hydrogen in the atomic state lasts only a short time, the atoms recombine into H 2 molecules.

Physical properties of Hydrogen. Hydrogen is the lightest of all known substances (14.4 times lighter than air), density 0.0899 g/l at 0°C and 1 atm. Hydrogen boils (liquefies) and melts (solidifies) at -252.8°C and -259.1°C, respectively (only helium has lower melting and boiling points). The critical temperature of Hydrogen is very low (-240°C), so its liquefaction is associated with great difficulties; critical pressure 12.8 kgf / cm 2 (12.8 atm), critical density 0.0312 g / cm 3. Hydrogen has the highest thermal conductivity of all gases, equal to 0.174 W/(m·K) at 0°С and 1 atm, i.e. 4.16·10 -4 cal/(s·cm·°С). The specific heat capacity of Hydrogen at 0°C and 1 atm C is 14.208 kJ/(kg K), i.e. 3.394 cal/(g°C). Hydrogen is slightly soluble in water (0.0182 ml / g at 20 ° C and 1 atm), but well - in many metals (Ni, Pt, Pa and others), especially in palladium (850 volumes per 1 volume of Pd). The solubility of Hydrogen in metals is related to its ability to diffuse through them; diffusion through a carbon alloy (for example, steel) is sometimes accompanied by the destruction of the alloy due to the interaction of Hydrogen with carbon (the so-called decarbonization). Liquid Hydrogen is very light (density at -253°C 0.0708 g/cm3) and fluid (viscosity at -253°C 13.8 centipoise).

Chemical properties of Hydrogen. In most compounds, Hydrogen exhibits a valency (more precisely, an oxidation state) of +1, like sodium and other alkali metals; usually it is considered as an analogue of these metals, heading group I of the Mendeleev system. However, in metal hydrides, the Hydrogen ion is negatively charged (oxidation state -1), that is, the Na + H - hydride is built like Na + Cl - chloride. This and some other facts (the closeness of the physical properties of Hydrogen and halogens, the ability of halogens to replace Hydrogen in organic compounds) give grounds to include Hydrogen also in group VII of the periodic system. Under normal conditions, molecular Hydrogen is relatively inactive, combining directly with only the most active nonmetals (with fluorine, and in the light also with chlorine). However, when heated, it reacts with many elements. Atomic Hydrogen has an increased chemical activity compared to molecular hydrogen. Hydrogen combines with oxygen to form water:

H 2 + 1/2 O 2 \u003d H 2 O

with the release of 285.937 kJ / mol, that is, 68.3174 kcal / mol of heat (at 25 ° C and 1 atm). At ordinary temperatures, the reaction proceeds extremely slowly, above 550 ° C - with an explosion. The explosive limits of a hydrogen-oxygen mixture are (by volume) from 4 to 94% H 2, and a hydrogen-air mixture - from 4 to 74% H 2 (a mixture of 2 volumes of H 2 and 1 volume of O 2 is called explosive gas). Hydrogen is used to reduce many metals, as it takes away oxygen from their oxides:

CuO + H 2 \u003d Cu + H 2 O,

Fe 3 O 4 + 4H 2 \u003d 3Fe + 4H 2 O, etc.

With halogens Hydrogen forms hydrogen halides, for example:

H 2 + Cl 2 \u003d 2HCl.

Hydrogen explodes with fluorine (even in the dark and at -252°C), reacts with chlorine and bromine only when illuminated or heated, and with iodine only when heated. Hydrogen reacts with nitrogen to form ammonia:

ZN 2 + N 2 \u003d 2NH 3

only on a catalyst and at elevated temperatures and pressures. When heated, Hydrogen reacts vigorously with sulfur:

H 2 + S \u003d H 2 S (hydrogen sulfide),

much more difficult with selenium and tellurium. Hydrogen can react with pure carbon without a catalyst only at high temperatures:

2H 2 + C (amorphous) = CH 4 (methane).

Hydrogen directly reacts with some metals (alkali, alkaline earth and others), forming hydrides:

H 2 + 2Li = 2LiH.

Of great practical importance are the reactions of Hydrogen with carbon monoxide (II), in which, depending on the temperature, pressure, and catalyst, various organic compounds are formed, for example, HCHO, CH 3 OH, and others. Unsaturated hydrocarbons react with Hydrogen to become saturated, for example:

C n H 2n + H 2 \u003d C n H 2n + 2.

The role of hydrogen and its compounds in chemistry is exceptionally great. Hydrogen determines the acidic properties of the so-called protic acids. Hydrogen tends to form a so-called hydrogen bond with some elements, which has a decisive influence on the properties of many organic and inorganic compounds.

Getting Hydrogen. The main types of raw materials for the industrial production of Hydrogen are natural combustible gases, coke oven gas and oil refining gases. Hydrogen is also obtained from water by electrolysis (in places with cheap electricity). The most important methods for the production of Hydrogen from natural gas are the catalytic interaction of hydrocarbons, mainly methane, with water vapor (conversion):

CH 4 + H 2 O \u003d CO + ZH 2,

and incomplete oxidation of hydrocarbons by oxygen:

CH 4 + 1/2 O 2 \u003d CO + 2H 2

The resulting carbon monoxide (II) is also subjected to conversion:

CO + H 2 O \u003d CO 2 + H 2.

Hydrogen produced from natural gas is the cheapest.

Hydrogen is isolated from coke oven gas and refinery gases by removing the remaining components of the gas mixture, which are more easily liquefied than hydrogen, upon deep cooling. The electrolysis of water is carried out with direct current, passing it through a solution of KOH or NaOH (acids are not used to avoid corrosion of steel equipment). Hydrogen is produced in laboratories by the electrolysis of water, as well as by the reaction between zinc and hydrochloric acid. However, more often they use ready-made hydrogen in cylinders.

Application of Hydrogen. Hydrogen began to be produced on an industrial scale at the end of the 18th century for filling balloons. At present, hydrogen is widely used in the chemical industry, mainly for the production of ammonia. A large consumer of hydrogen is also the production of methyl and other alcohols, synthetic gasoline and other products obtained by synthesis from hydrogen and carbon monoxide (II). Hydrogen is used for the hydrogenation of solid and heavy liquid fuels, fats and others, for the synthesis of HCl, for the hydrotreatment of petroleum products, in welding and cutting metals with an oxygen-hydrogen flame (temperature up to 2800 ° C) and in atomic hydrogen welding (up to 4000 ° C) . Hydrogen isotopes, deuterium and tritium, have found very important applications in nuclear power engineering.

Phenols

Structure
The hydroxyl group in the molecules of organic compounds can be connected directly to the aromatic nucleus, or it can be separated from it by one or more carbon atoms. It can be expected that, depending on this, the properties of substances will differ significantly from each other due to the mutual influence of groups of atoms (remember one of the provisions of Butlerov's theory). Indeed, organic compounds containing an aromatic phenyl C 6 H 5 - radical directly bonded to a hydroxyl group exhibit special properties that differ from those of alcohols. Such compounds are called phenols.

Phenols - organic substances whose molecules contain a phenyl radical associated with one or more hydroxyl groups.
Like alcohols, phenols are classified by atomicity, i.e., by the number of hydroxyl groups. Monatomic phenols contain one hydroxyl group in the molecule:

There are other polyatomic phenols containing three or more hydroxyl groups in the benzene ring.
Let's get acquainted in more detail with the structure and properties of the simplest representative of this class - phenol C6H50H. The name of this substance formed the basis for the name of the entire class - phenols.

Physical properties
Solid colorless crystalline substance, tºpl = 43 °C, tº bp = °C, with a sharp characteristic odor. Poisonous. Phenol is slightly soluble in water at room temperature. An aqueous solution of phenol is called carbolic acid. It causes burns on contact with the skin, so phenol must be handled with care.
The structure of the phenol molecule
In the phenol molecule, the hydroxyl is directly bonded to the carbon atom of the benzene aromatic nucleus.
Let us recall the structure of the groups of atoms that form the phenol molecule.
The aromatic ring consists of six carbon atoms forming a regular hexagon due to the sp 2 hybridization of the electron orbitals of six carbon atoms. These atoms are linked by z-bonds. The p-electrons of each carbon atom not participating in the formation of st-bonds, overlapping on opposite sides of the z-bond plane, form two parts of a single six-electron P-a cloud covering the entire benzene ring (aromatic nucleus). In the C6H6 benzene molecule, the aromatic nucleus is absolutely symmetrical, a single electronic P-cloud evenly covers the ring of carbon atoms under and above the plane of the molecule (Fig. 24). The covalent bond between the oxygen and hydrogen atoms of the hydroxyl radical is strongly polar, the general electron cloud of the O-H bond is shifted towards the oxygen atom, on which a partial negative charge arises, and on the hydrogen atom, a partial positive charge. In addition, the oxygen atom in the hydroxyl group has two unshared electron pairs belonging only to it.

In a phenol molecule, the hydroxyl radical interacts with the aromatic nucleus, while the lone electron pairs of the oxygen atom interact with a single TC cloud of the benzene ring, forming a single electronic system. Such an interaction of lone electron pairs and clouds of r-bonds is called conjugation. As a result of conjugation of the lone electron pair of the oxygen atom of the hydroxy group with the electron system of the benzene ring, the electron density on the oxygen atom decreases. This decrease is compensated for by the greater polarization of the О–Н bond, which, in turn, leads to an increase in the positive charge on the hydrogen atom. Therefore, the hydrogen of the hydroxyl group in the phenol molecule has an "acidic" character.
It is logical to assume that the conjugation of the electrons of the benzene ring and the hydroxyl group affects not only its properties, but also the reactivity of the benzene ring.
In fact, as you remember, the conjugation of the lone pairs of the oxygen atom with the n-cloud of the benzene ring leads to a redistribution of the electron density in it. It decreases at the carbon atom associated with the OH group (the influence of the electron pairs of the oxygen atom affects) and increases at the carbon atoms adjacent to it (i.e., positions 2 and 6, or ortho positions). Obviously, an increase in the electron density at these carbon atoms of the benzene ring leads to the localization (concentration) of a negative charge on them. Under the influence of this charge, there is a further redistribution of electron density in the aromatic nucleus - its displacement from the 3rd and 5th atoms (.meta-position) to the 4th (ortho-position). These processes can be expressed by the scheme:

Thus, the presence of a hydroxyl radical in the phenol molecule leads to a change in the n-cloud of the benzene ring, an increase in the electron density at the 2, 4 and 6 carbon atoms (ortho-, dara-positions) and a decrease in the electron density at the 3rd and 5- th carbon atoms (meta positions).
The localization of the electron density in the ortho and para positions makes them most likely to be attacked by electrophilic particles when interacting with other substances.
Consequently, the influence of the radicals that make up the phenol molecule is mutual, and it determines its characteristic properties.
Chemical properties of phenol
Acid properties
As already mentioned, the hydrogen atom of the hydroxyl group of phenol has an acidic character. The acidic properties of phenol are more pronounced than those of water and alcohols. Unlike alcohols and water, phenol reacts not only with alkali metals, but also with alkalis to form phenolates.
However, the acidic properties of phenols are less pronounced than those of inorganic and carboxylic acids. So, for example, the acidic properties of phenol are about 3000 times less than those of carbonic acid. Therefore, by passing carbon dioxide through an aqueous solution of sodium phenolate, free phenol can be isolated:

The addition of hydrochloric or sulfuric acid to an aqueous solution of sodium phenolate also leads to the formation of phenol.
Qualitative reaction to phenol
Phenol reacts with iron(III) chloride to form an intensely violet colored complex compound.
This reaction makes it possible to detect it even in very small quantities. Other phenols containing one or more hydroxyl groups on the benzene ring also give a bright blue-violet color when reacted with iron(III) chloride.
Benzene ring reactions
The presence of a hydroxyl substituent greatly facilitates the course of electrophilic substitution reactions in the benzene ring.
1. Bromination of phenol. Unlike benzene, phenol bromination does not require the addition of a catalyst (iron(III) bromide).
In addition, the interaction with phenol proceeds selectively (selectively): bromine atoms are sent to the ortho and para positions, replacing the hydrogen atoms located there. The selectivity of the substitution is explained by the features of the electronic structure of the phenol molecule discussed above. So, when phenol reacts with bromine water, a white precipitate of 2,4,6-tribromophenol is formed.
This reaction, as well as the reaction with iron(III) chloride, serves for the qualitative detection of phenol.

2. Phenol nitration is also easier than benzene nitration. The reaction with dilute nitric acid proceeds at room temperature. As a result, a mixture of ortho- and para-isomers of nitrophenol is formed:

3. Hydrogenation of the aromatic ring of phenol in the presence of a catalyst is easy.
4. Polycondensation of phenol with aldehydes, in particular, with formaldehyde, occurs with the formation of reaction products - phenol-formaldehyde resins and solid polymers.
The interaction of phenol with formaldehyde can be described by the scheme:

You have probably noticed that “mobile” hydrogen atoms are preserved in the dimer molecule, which means that the reaction can continue further with a sufficient amount of reagents.
The polycondensation reaction, i.e., the reaction of obtaining a polymer, proceeding with the release of a low molecular weight by-product (water), can continue further (until one of the reagents is completely consumed) with the formation of huge macromolecules. The process can be described by the overall equation:

The formation of linear molecules occurs at ordinary temperature. Carrying out this reaction when heated leads to the fact that the resulting product has a branched structure, it is solid and insoluble in water. As a result of heating a linear phenol-formaldehyde resin with an excess of aldehyde, solid plastic masses with unique properties are obtained. Polymers based on phenol-formaldehyde resins are used for the manufacture of varnishes and paints, plastic products that are resistant to heating, cooling, water, alkalis and acids, they have high dielectric properties. Polymers based on phenol-formaldehyde resins are used to make the most critical and important parts of electrical appliances, power unit cases and machine parts, the polymer base of printed circuit boards for radio devices.

Adhesives based on phenol-formaldehyde resins are able to reliably connect parts of various nature, maintaining the highest bond strength in a very wide temperature range. Such glue is used to fasten the metal base of lighting lamps to a glass bulb. Now it has become clear to you why phenol and products based on it are widely used (Scheme 8).

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

Both simple and complex substances enter into chemical interaction 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 is of great importance for humans and is used in a variety of areas:

1. In the chemical industry it is raw materials, in other industries it is fuel. Do not do without hydrogen and the enterprises of petrochemistry and oil refining.
2. In the electric power industry, this simple substance acts as a cooling agent.
3. In ferrous and non-ferrous metallurgy, hydrogen plays the role of a reducing agent.
4. With this help, an inert environment is created when packaging products.
5. The pharmaceutical industry uses hydrogen as a reagent in the production of hydrogen peroxide.
6. Meteorological probes are filled with this light gas.
7. 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. The liquefaction of coke oven gas by the fractional method is also used for the industrial production of 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 stars, including the Sun, and other cosmic bodies is hydrogen.

It is only 0.15% in the earth's crust. 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.

The most powerful hydrogen bomb is based on the splitting of the lightest atom.

Chemical properties of hydrogen

Under normal conditions, molecular Hydrogen is relatively inactive, combining directly with only the most active nonmetals (with fluorine, and in the light also with chlorine). However, when heated, it reacts with many elements.

Hydrogen reacts with simple and complex substances:

At high temperature, hydrogen reacts directly with some metals(alkaline, alkaline earth and others), forming white crystalline substances - metal hydrides (Li H, Na H, KH, CaH 2, etc.):

H 2 + 2Li = 2LiH

Metal hydrides are easily decomposed by water with the formation of the corresponding alkali and hydrogen:

Sa H 2 + 2H 2 O \u003d Ca (OH) 2 + 2H 2

1). With oxygen Hydrogen forms water:

Video "Combustion of hydrogen"

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

At ordinary temperatures, the reaction proceeds extremely slowly, above 550 ° C - with an explosion (a mixture of 2 volumes of H 2 and 1 volume of O 2 is called explosive gas) .

Video "Explosion of explosive gas"

Video "Preparation and explosion of an explosive mixture"

2). With halogens Hydrogen forms hydrogen halides, for example:

H 2 + Cl 2 \u003d 2HCl

Hydrogen explodes with fluorine (even in the dark and at -252°C), reacts with chlorine and bromine only when illuminated or heated, and with iodine only when heated.

3). With nitrogen Hydrogen reacts with the formation of ammonia:

ZN 2 + N 2 \u003d 2NH 3

only on a catalyst and at elevated temperatures and pressures.

4). When heated, hydrogen reacts vigorously with sulfur:

H 2 + S \u003d H 2 S (hydrogen sulfide),

much more difficult with selenium and tellurium.

5). with pure carbon Hydrogen can react without a catalyst only at high temperatures:

2H 2 + C (amorphous) = CH 4 (methane)

- Hydrogen enters into a substitution reaction with metal oxides , while water is formed in the products and the metal is reduced. Hydrogen - exhibits the properties of a reducing agent:

Hydrogen is used for the recovery of many metals, since it takes away oxygen from their oxides:

Fe 3 O 4 + 4H 2 \u003d 3Fe + 4H 2 O, etc.

Application of hydrogen

Video "Use of hydrogen"

Currently, hydrogen is produced in huge quantities. A very large part of it is used in the synthesis of ammonia, the hydrogenation of fats and the hydrogenation of coal, oils and hydrocarbons. In addition, hydrogen is used for the synthesis of hydrochloric acid, methyl alcohol, hydrocyanic acid, in welding and forging metals, as well as in the manufacture of incandescent lamps and precious stones. Hydrogen goes on sale in cylinders under pressure over 150 atm. They are painted dark green and are supplied with a red inscription "Hydrogen".

Hydrogen is used to convert liquid fats into solid fats (hydrogenation), to produce liquid fuels by hydrogenating coal and fuel oil. In metallurgy, hydrogen is used as a reducing agent for oxides or chlorides to produce metals and non-metals (germanium, silicon, gallium, zirconium, hafnium, molybdenum, tungsten, etc.).

The practical application of hydrogen is diverse: it is usually filled with balloons, in the chemical industry it serves as a raw material for the production of many very important products (ammonia, etc.), in the food industry - for the production of solid fats from vegetable oils, etc. High temperature (up to 2600 °C), obtained by burning hydrogen in oxygen, is used to melt refractory metals, quartz, etc. Liquid hydrogen is one of the most efficient jet fuels. The annual world consumption of hydrogen exceeds 1 million tons.

SIMULATORS

No. 2. Hydrogen

TASKS FOR REINFORCEMENT

In Lesson 22 " Chemical properties of hydrogen» from the course « Chemistry for dummies» find out with what substances hydrogen reacts; find out what chemical properties hydrogen has.

Hydrogen enters into chemical reactions with simple and complex substances. However, under normal conditions, hydrogen is inactive. For its interaction with other substances, it is necessary to create conditions: increase the temperature, apply a catalyst, etc.

Reactions of hydrogen with simple substances

When heated, hydrogen enters into a combination reaction with simple substances - oxygen, chlorine, nitrogen, sulfur.

If you set fire to pure hydrogen in air, coming out of the gas outlet tube, it burns with an even, barely noticeable flame. Now let's place a tube with burning hydrogen in a jar of oxygen (Fig. 95).

The combustion of hydrogen continues, while drops of water formed as a result of the reaction are visible on the walls of the jar:

When hydrogen burns, a lot of heat is released. The temperature of the oxygen-hydrogen flame reaches more than 2000 °C.

The chemical reaction of hydrogen with oxygen refers to compound reactions. As a result of the reaction, hydrogen oxide (water) is formed. This means that hydrogen was oxidized by oxygen, i.e. we can also call this reaction an oxidation reaction.

If, however, a small amount of hydrogen is collected in a test tube turned upside down by displacing air, and then a burning match is brought to its hole, then a loud “barking” sound of a small explosion of a mixture of hydrogen and air will be heard. Such a mixture is called "explosive".

On a note: The ability of hydrogen in a mixture with air to form "explosive gas" has often been the cause of accidents in balloons filled with hydrogen. Violation of the tightness of the ball shell led to a fire and even an explosion. Nowadays, balloons are filled with helium or constantly pumped hot air.

In an atmosphere of chlorine, hydrogen burns to form a complex substance - hydrogen chloride. In this case, the reaction proceeds:

The reaction of hydrogen with nitrogen occurs at elevated temperature and pressure in the presence of a catalyst. As a result of the reaction, ammonia NH 3 is formed:

If a stream of hydrogen is directed to sulfur melted in a test tube, then the smell of rotten eggs will be felt at its hole. This is how hydrogen sulfide gas H 2 S smells - the product of the reaction of hydrogen with sulfur:

On a note: Hydrogen is able not only to dissolve in some metals, but also togyrate with them. This forms chemical compounds called hydrides (NaH - sodium hydride). Hydrides of some metals are used as fuel in solid-fuel rocket engines, as well as in the production of thermonuclear energy.

Reactions of hydrogen with complex substances

Hydrogen reacts at elevated temperatures not only with simple but also with complex substances. Consider, as an example, its reaction with copper (II) oxide CuO (Fig. 96).

Let us pass hydrogen over the heated powder of copper(II) oxide CuO. As the reaction proceeds, the color of the powder changes from black to brownish red. This is the color of the simple copper substance Cu. During the reaction, droplets of liquid appear on the cold parts of the test tube. This is another product of the reaction - water H 2 O. Note that, in contrast to the simple substance of copper, water is a complex substance.

The equation for the reaction of copper(II) oxide with hydrogen:

Hydrogen in reaction with copper(II) oxide exhibits the ability to take away oxygen from the metal oxide, thereby restoring the metal from this oxide. As a result, there copper recovery from the complex substance CuO to metallic copper (Cu).

Recovery reactions- These are reactions in which complex substances donate oxygen atoms to other substances.

A substance that removes oxygen atoms is called a reducing agent. In the reaction with copper(II) oxide, the reducing agent is hydrogen. Hydrogen also reacts with oxides of some other metals, such as PbO, HgO, MoO 3 , WO 3 and others. Oxidation and reduction are always interconnected. If one substance (H 2) is oxidized, then the other (CuO) is reduced, and vice versa.

Lesson summary:

1. When heated, hydrogen reacts with oxygen, chlorine, nitrogen, and sulfur.
2. Restoration is the giving of oxygen atoms by complex substances to other substances.
3. The processes of oxidation and reduction are interconnected.

I hope lesson 22 " Chemical properties of hydrogen' was clear and informative. If you have any questions, write them in the comments.

The hydrogen atom has the electronic formula of the outer (and only) electronic level 1 s one . On the one hand, by the presence of one electron in the outer electronic level, the hydrogen atom is similar to alkali metal atoms. However, just like halogens, it lacks only one electron to fill the external electronic level, since no more than 2 electrons can be located on the first electronic level. It turns out that hydrogen can be placed simultaneously in both the first and the penultimate (seventh) group of the periodic table, which is sometimes done in various versions of the periodic system:

From the point of view of the properties of hydrogen as a simple substance, it nevertheless has more in common with halogens. Hydrogen, as well as halogens, is a non-metal and forms diatomic molecules (H 2) similarly to them.

Under normal conditions, hydrogen is a gaseous, inactive substance. The low activity of hydrogen is explained by the high strength of the bond between the hydrogen atoms in the molecule, which requires either strong heating or the use of catalysts, or both at the same time, to break it.

Interaction of hydrogen with simple substances

with metals

Of the metals, hydrogen reacts only with alkali and alkaline earth! Alkali metals include metals of the main subgroup of group I (Li, Na, K, Rb, Cs, Fr), and alkaline earth metals are metals of the main subgroup of group II, except for beryllium and magnesium (Ca, Sr, Ba, Ra)

When interacting with active metals, hydrogen exhibits oxidizing properties, i.e. lowers its oxidation state. In this case, hydrides of alkali and alkaline earth metals are formed, which have an ionic structure. The reaction proceeds when heated:

It should be noted that interaction with active metals is the only case when molecular hydrogen H2 is an oxidizing agent.

with non-metals

Of non-metals, hydrogen reacts only with carbon, nitrogen, oxygen, sulfur, selenium and halogens!

Carbon should be understood as graphite or amorphous carbon, since diamond is an extremely inert allotropic modification of carbon.

When interacting with non-metals, hydrogen can only perform the function of a reducing agent, that is, it can only increase its oxidation state:

Interaction of hydrogen with complex substances

with metal oxides

Hydrogen does not react with metal oxides that are in the activity series of metals up to aluminum (inclusive), however, it is able to reduce many metal oxides to the right of aluminum when heated:

with non-metal oxides

Of the non-metal oxides, hydrogen reacts when heated with oxides of nitrogen, halogens, and carbon. Of all the interactions of hydrogen with non-metal oxides, its reaction with carbon monoxide CO should be especially noted.

The mixture of CO and H 2 even has its own name - “synthesis gas”, since, depending on the conditions, such demanded industrial products as methanol, formaldehyde and even synthetic hydrocarbons can be obtained from it:

with acids

Hydrogen does not react with inorganic acids!

Of the organic acids, hydrogen reacts only with unsaturated acids, as well as with acids containing functional groups capable of being reduced by hydrogen, in particular aldehyde, keto or nitro groups.

with salts

In the case of aqueous solutions of salts, their interaction with hydrogen does not occur. However, when hydrogen is passed over solid salts of some metals of medium and low activity, their partial or complete reduction is possible, for example:

Chemical properties of halogens

Halogens are the chemical elements of group VIIA (F, Cl, Br, I, At), as well as the simple substances they form. Hereinafter, unless otherwise stated, halogens will be understood as simple substances.

All halogens have a molecular structure, which leads to low melting and boiling points of these substances. Halogen molecules are diatomic, i.e. their formula can be written in general form as Hal 2 .

It should be noted such a specific physical property of iodine as its ability to sublimation or, in other words, sublimation. sublimation, they call the phenomenon in which a substance in the solid state does not melt when heated, but, bypassing the liquid phase, immediately passes into the gaseous state.

The electronic structure of the external energy level of an atom of any halogen has the form ns 2 np 5, where n is the period number of the periodic table in which the halogen is located. As you can see, only one electron is missing from the eight-electron outer shell of the halogen atoms. From this it is logical to assume the predominantly oxidizing properties of free halogens, which is also confirmed in practice. As you know, the electronegativity of non-metals decreases when moving down the subgroup, and therefore the activity of halogens decreases in the series:

F 2 > Cl 2 > Br 2 > I 2

Interaction of halogens with simple substances

All halogens are highly reactive and react with most simple substances. However, it should be noted that fluorine, due to its extremely high reactivity, can react even with those simple substances with which other halogens cannot react. Such simple substances include oxygen, carbon (diamond), nitrogen, platinum, gold, and some noble gases (xenon and krypton). Those. actually, fluorine does not react only with some noble gases.

The remaining halogens, i.e. chlorine, bromine and iodine are also active substances, but less active than fluorine. They react with almost all simple substances except oxygen, nitrogen, carbon in the form of diamond, platinum, gold and noble gases.

Interaction of halogens with non-metals

hydrogen

All halogens react with hydrogen to form hydrogen halides with the general formula HHal. At the same time, the reaction of fluorine with hydrogen begins spontaneously even in the dark and proceeds with an explosion in accordance with the equation:

The reaction of chlorine with hydrogen can be initiated by intense ultraviolet irradiation or heating. Also leaks with an explosion:

Bromine and iodine react with hydrogen only when heated, and at the same time, the reaction with iodine is reversible:

phosphorus

The interaction of fluorine with phosphorus leads to the oxidation of phosphorus to the highest oxidation state (+5). In this case, the formation of phosphorus pentafluoride occurs:

When chlorine and bromine interact with phosphorus, it is possible to obtain phosphorus halides both in the + 3 oxidation state and in the + 5 oxidation state, which depends on the proportions of the reactants:

In the case of white phosphorus in an atmosphere of fluorine, chlorine or liquid bromine, the reaction begins spontaneously.

The interaction of phosphorus with iodine can lead to the formation of only phosphorus triiodide due to the significantly lower oxidizing ability than other halogens:

gray

Fluorine oxidizes sulfur to the highest oxidation state +6, forming sulfur hexafluoride:

Chlorine and bromine react with sulfur, forming compounds containing sulfur in oxidation states that are extremely unusual for it +1 and +2. These interactions are very specific, and to pass the exam in chemistry, the ability to write down the equations of these interactions is not necessary. Therefore, the following three equations are given rather for guidance:

Interaction of halogens with metals

As mentioned above, fluorine is able to react with all metals, even such inactive ones as platinum and gold:

The remaining halogens react with all metals except platinum and gold:

Reactions of halogens with complex substances

Substitution reactions with halogens

More active halogens, i.e. whose chemical elements are located higher in the periodic table, are able to displace less active halogens from the hydrohalic acids and metal halides they form:

Similarly, bromine and iodine displace sulfur from solutions of sulfides and or hydrogen sulfide:

Chlorine is a stronger oxidizing agent and oxidizes hydrogen sulfide in its aqueous solution not to sulfur, but to sulfuric acid:

Interaction of halogens with water

Water burns in fluorine with a blue flame in accordance with the reaction equation:

Bromine and chlorine react differently with water than fluorine. If fluorine acted as an oxidizing agent, then chlorine and bromine disproportionate in water, forming a mixture of acids. In this case, the reactions are reversible:

The interaction of iodine with water proceeds to such an insignificant degree that it can be neglected and considered that the reaction does not proceed at all.

Interaction of halogens with alkali solutions

Fluorine, when interacting with an aqueous solution of alkali, again acts as an oxidizing agent:

The ability to write this equation is not required to pass the exam. It is enough to know the fact about the possibility of such an interaction and the oxidizing role of fluorine in this reaction.

Unlike fluorine, the remaining halogens disproportionate in alkali solutions, that is, they simultaneously increase and decrease their oxidation state. At the same time, in the case of chlorine and bromine, depending on the temperature, flow in two different directions is possible. In particular, in the cold, the reactions proceed as follows:

and when heated:

Iodine reacts with alkalis exclusively according to the second option, i.e. with the formation of iodate, because hypoiodite is unstable not only when heated, but also at ordinary temperatures and even in the cold.