How carbon is mined. Technical carbon, its production

Work plan:

Introduction

The structure of the carbon atom.

distribution in nature.

Getting carbon.

Physical and chemical properties.

national economic importance.

carbon in the body.

Bibliography.

Introduction

Carbon (lat. Carboneum), C - a chemical element of group IV of the periodic
Mendeleev's systems. Two stable isotopes 12С (98.892%) and 13С are known
(1,108 %).

Carbon has been known since ancient times. Charcoal served for
recovery of metals from ores, diamond - like a precious stone.
Much later, graphite began to be used for the manufacture of crucibles and
pencils.

In 1778, K. Scheele, heating graphite with saltpeter, discovered that at the same time,
as with heating coal with saltpeter, carbon dioxide is released.
The chemical composition of the diamond was established as a result of the experiments of A. Lavoisier
(1772) on the study of the combustion of diamond in air and the research of S. Tennant
(1797), who proved that the same amount of diamond and coal give at
oxidation equal amounts of carbon dioxide. Carbon as a chemical
the element was recognized only in 1789 by A. Lavoisier. Latin name
carboneum received carbon from carbon - coal.

The structure of the carbon atom.

The nucleus of the most stable carbon isotope of mass 12 (the abundance
98.9%) has 6 protons and 6 neutrons (12 nucleons) arranged in three
quartets, each containing 2 protons and two neutrons, similar to a nucleus
helium. Another stable isotope of carbon is 13C (approx. 1.1%), and in trace
quantities, there exists in nature an unstable isotope 14C with a period
half-life 5730 years, possessing?-radiation. In normal carbon
The cycle of living matter involves all three isotopes in the form of CO2. After death
living organism, carbon consumption stops and can be dated
C-containing objects by measuring the level of 14C radioactivity. decline
?-radiation of 14CO2 is proportional to the time elapsed since death.
In 1960, W. Libby was awarded for research with radioactive carbon
Nobel Prize.

In the ground state, 6 electrons of carbon form an electron
configuration 1s22s22px12py12pz0. Four electrons of the second level
are valence, which corresponds to the position of carbon in the IVA group
periodic system. Since for the detachment of an electron from an atom in a gas
phase requires a lot of energy (about 1070 kJ/mol), carbon does not form
ionic bonds with other elements, since this would require
detachment of an electron to form a positive ion. Having
electronegativity equal to 2.5, carbon does not show a strong
electron affinity, respectively, not being an active acceptor
electrons. Therefore, it is not prone to the formation of a particle with a negative
charge. But with a partially ionic nature of the bond, some compounds
carbon exist, for example, carbides. In compounds, carbon exhibits
oxidation state 4. So that four electrons can participate in
formation of bonds, it is necessary to depair 2s electrons and jump
one of these electrons into the 2pz orbital; in this case, 4
tetrahedral bonds with an angle between them of 109°. In compounds, valence
the electrons of carbon are only partially drawn away from it, so carbon
forms strong covalent bonds between neighboring C–C atoms with
using a shared electron pair. The energy of breaking such a bond is 335
kJ/mol, while for the Si–Si bond it is only 210 kJ/mol,
therefore long –Si–Si– chains are unstable. Covalent nature of the bond
persists even in compounds of highly reactive halogens with
carbon, CF4 and CCl4. Carbon atoms are able to provide
bonding more than one electron from each carbon atom; So
double С=С and triple С?С bonds are formed. Other elements also
form bonds between their atoms, but only carbon is capable of
form long chains. Therefore, thousands are known for carbon
compounds called hydrocarbons in which the carbon is bonded to
hydrogen and other carbon atoms, forming long chains or
ring structures.

In these compounds, it is possible to replace hydrogen with other atoms, most
often on oxygen, nitrogen and halogens with the formation of many organic
connections. Importance among them are fluorocarbons -
hydrocarbons in which hydrogen has been replaced by fluorine. Such connections
extremely inert, and they are used as plastic and lubricating
materials (fluorocarbons, i.e. hydrocarbons in which all hydrogen atoms
replaced by fluorine atoms) and as low-temperature refrigerants (freons,
or freons, - fluorochlorohydrocarbons).

Distribution in nature:

A carbon atom has four electrons on its outer four AOs.
Therefore, all four AOs take part in the formation of chemical bonds.
This explains the diversity and abundance of carbon compounds.

The vast majority of carbon compounds are classified as so-called
organic substances. In this section, we will look at the properties
inorganic substances formed by carbon - simple substances, its
oxides, carbonic acid and some of its salts.

Carbon forms several simple substances. Among them, the most important
diamond and graphite are considered. These allotropic modifications have atomic
crystal lattices that differ in their structures. From here
difference between their physical and chemical properties.

In a diamond, each carbon atom is bonded to four other atoms. IN
space, these atoms are located in the center and corners of the tetrahedra,
connected by their peaks. It is a very symmetrical and strong lattice.
Diamond is the hardest substance on earth.

In graphite, each atom is connected to three others in the same
planes. The formation of these bonds takes three AO with three
electrons. The fourth orbital of the 2p-AO with one electron is located
perpendicular to the plane. These remaining atomic orbitals of the entire grid
overlap each other, forming a zone of molecular orbitals. This zone
is not fully occupied, but half, which provides a metal
electrical conductivity of graphite (unlike diamond).

In addition to electrical conductivity, graphite has three more practically important
properties.

First, toughness. The melting point of graphite is above 3500? WITH -
it is the most refractory simple substance on Earth.

Secondly, the absence of any products on its surface
interactions with environment(on metals these are oxides),
increasing electrical resistance.

Thirdly, the ability to provide a lubricating effect on rubbing
surfaces. In a graphite crystal, carbon atoms are tightly bound between
itself in flat grids, and the connection between the grids is weak, it has
intermolecular nature, as in substances with molecular lattices.
Therefore, already small mechanical forces cause a displacement of the grids
relative to each other, which determines the action of graphite as a lubricant.

The binding energy between carbon atoms in simple and complex substances, in
including diamond and graphite. Very large. About the hardness of diamond
spoke. The bond between the atoms and in the graphite network is strong. So,
the tensile strength of graphite fiber far exceeds that of
iron and technical steel.

So-called composite materials are made on the basis of graphite.
in particular, carbon fiber reinforced plastics, in which graphite fibers are located on a matrix
from epoxy resin. Composite materials are increasingly used in
aviation and space technology (after all, in addition to strength, they are light;
compare the density of graphite, p=2.3 g/cm3, with the density of "light" aluminum,
p=2.7g/cm3, and especially iron, p=7.9g/cm3), as well as in shipbuilding, where
corrosion resistance is especially valuable.

Carbon Compounds of carbon

Carbon monoxide (IV) Carbonic acid

It has allotropic modifications: diamond, graphite, carbine, fullerene, etc.

Shows restorative properties

Burns in oxygen: С+О2=СО2+Q

Interacts with carbon monoxide (1U): С+СО2=2СО

Restores metals from their oxides: 3С+Fe2O3=3CO2+4Fe

Receipt

Incomplete combustion of methane: CH4 + O2 \u003d C + 2H2O odorless gas, color and taste,
heavier than air

acid oxide

When dissolved, it interacts with water: CO2 + H2O \u003d H2CO3

Reacts with bases:

CO2+Ca(OH)2=CaCO3+H2O

5. Reacts with basic oxides:

6. Formed in reactions

A) combustion of carbon in oxygen:

B) oxidation of carbon monoxide (II):

C) combustion of methane:

CH4+O2=CO2+2H2O

D) interaction of acids with carbonates:

CaCO3+2HCI=CaCI2+CO2+H2O

E) thermal decomposition of carbonates, hydrocarbonates:

2NaHCO3=Na2CO3+CO2+H2O

E) oxidation of biochemical processes of respiration, decay.

1. Weak molecule. Weak dibasic acid. in aqueous solution
there are equilibria.

2. Interacts with alkali solutions as a solution of carbon dioxide in
water with the formation of acid salts (hydrocarbonates) and medium
(carbonates):

CO2+NaOH=NaHCO3

CO2+2NaOH=Na2CO3+

3. Displaced from salts by stronger acids

CaCO3+2HCI=CaCI2+CO2+H2O

4. Salts of carbonic acid undergo hydrolysis

Carbon is chemically inert only when relatively low temperatures, A
at high levels, it is one of the strongest reducing agents. Main chemical
the use of carbon - the reduction of metals, primarily iron,
from ores.

Oxides of carbon.

With four electrons in its outer energy level, carbon in
compounds with oxygen, depending on the conditions, exhibits valencies
+2 and +4.

When burning carbonaceous substances (wood, coal, natural gas
methane, alcohol, etc.) at the temperature of an ordinary flame, the following reaction takes place:

C + O2 = CO2

But if you create conditions for increasing the temperature (for example, reduce
heat removal, which can occur inside a thick layer of burning coal, in
including in a blast furnace), then the reactions proceed:

C + O2 = 2CO

CO2 + C = 2CO

The product of complete combustion of carbon and its substances is
carbon monoxide (1U) CO2 - carbon dioxide. It is also formed during respiration.
living organisms and the decay of their remains. At the same time carbon dioxide
(together with water) is the main substance consumed by plants in
the process of their growth.

With increasing pressure, already at room temperature, carbon dioxide
liquefies. Some types of fire extinguishers are filled with liquid CO2.

When the pressure is reduced, liquid carbon monoxide boils. At the same time, his
the temperature drops sharply, since, as is known, pore formation
From physics, a large amount of heat is expended. As a result, CO2
hardens. In solid form (called "dry ice"), it is used
as a coolant. At atmospheric pressure"dry ice"
melts, and like iodine, phosphorus, carbon sublimates, only when
significantly lower temperature (-75? C).

The average carbon content in the earth's crust is 2.3 * 10-2% by weight (1 * 10 -2 in
ultrabasic, 1 * 10 -2 in basic, 2 * 10 -2 in medium, 3 * 10 -2 in acidic
rocks). Carbon builds up at the top of the earth's crust
(biosphere): in living matter 18% carbon, in wood 50%, in stone
coal 80%, oil 85%, anthracite 96%. So part of the carbon
The lithosphere is concentrated in limestones and dolomites.

The number of own carbon minerals - 112; an exceptionally large number
organic compounds carbon - hydrocarbons and their derivatives.

With the accumulation of carbon in the earth's crust, the accumulation of many other
elements sorbed by organic matter and deposited in the form
insoluble carbonates, etc.

Compared with the average content in the earth's crust, humanity in
exclusively large quantities extracts carbon from the bowels (coal,
oil, natural gas), because these fossils are the main sources of energy.

Carbon is also widely distributed in space; on the Sun it ranks 4th
place after hydrogen, helium and oxygen.

Getting carbon

Dry distillation

wood
hard coal

Charcoal
coke

Activated carbon

The purest carbon is soot

Chemical properties

Inactive, in the cold - only with F2 (CF4

Reducing agent (Weakly expressed (Oxidative

1) O2 + C (CO2 below 500(C (

(lights up

CO2 + C (CO above 900(C(

2) H2O + C (CO + H2 above 1200(C

2H2O + C (CO2 + CO2 + H2 above 1000(C

3) CuO + C (Cu + CO at (t

Cu + 2 + 2e (Cu0 is an oxidizing agent, is reduced

C0 -2e (C + 2 - reducing agent, oxidized

4) HNO3 + 3C (3 CO2 + 4 NO + 2 H2O

With H2SO4 dilute

Cu + 2 + 2e (Cu0 is an oxidizing agent, is reduced

C0 -2e (C + 2 - reducing agent, oxidized

1) Ca + 2C (Ca (((calcium carbide

C + Si (CSi carborundum

Another way:

CaO + C (CaC2 + CO

2) 2H2 + C (C-4H+4

Consider from the point of view of ox-red:

4H0 -4e (4H+ - reducing agent, oxidized

C0 +4e (C-4 is an oxidizing agent, is reduced

Carbon can be both an oxidizing agent and a reducing agent.

Carbon monoxide (IV)

Colorless and odorless, soluble in water; -76(C - dry ice; Obtaining: in
limestone calcination industry

CaCO3 (CaO + CO2(

In the laboratory, strong acid displacement CaCO3 + 2HCl (CaCl2+

Oxidizing properties are weakly expressed: only at high temperatures,
with metals, affinity for oxygen, which is greater than that of C (Mg, K)

2Mg + CO2 (2MgO + C

Acid oxide when dissolved in water, a small amount is formed
carbonic acid

1. 2NaOH + CO2 (

Na2CO3 + H2O + CO2 (

This method can be obtained salts of carbonic acid. Another way:

2. Exchange reaction

BaCl2 + Na2CO3 (

(BaCO3(+ 2NaCl

Salts: 1) carbonates, soluble in water - only alkaline and NH + 4 strong
hydrolysis.

When Ca(HCO3)2 (CaCO3 +

CaCO3 (CO2 + CaO

Alkali metal carbonates melt without decomposition.

Qualitative reaction

effervescence is a strong acid

CaCO3 + 2HCl (CaCl2+

CO2 causes lime and barite water to become cloudy Ca(OH)2 +

CO2 (CaCO3 + H2O

Dissolution leading to the destruction of old calcareous mountains.

CaCO3 + H2O + CO2 ((Ca(HCO3)2 Carbon monoxide (II)

CO (carbon monoxide)

Colorless gas, odorless, poisonous, because binds to hemoglobin
blood. Poorly soluble in water. Obtaining: burning with a lack of O2

2CH4 + 3O2 (2CO(+

In the laboratory: the action is concentrated. H2SO4

HCOOH (CO(+ H2O

Oxalic acid H2C2O4 (CO(+ CO2(+

Reducing agent Fe2O3 +

3CO (2Fe + 3CO2(

O2 + 2CO (2CO2(

Non-salt-forming, but at t = 200 (C, 20 atm

O - Na Organic compounds CH4 carbides - are obtained
in direct contact with metals.

2 groups.

I. Metallic carbides. Transitional Me + C. Electronic
conductivity, metallic luster.

II. Ionic carbides are more electropositive, colorless, transparent,
do not conduct electricity.

1) Al4C3 + 12H2O (

(4Al(OH)3 + 3CH4(

C Be2C - the same reaction

2) CaC2 + 2H2O (

(Ca(OH)2 + C2H2(

Na2C2; K2C2; SrC2; BaC2; Cu2C2

During hydrolysis - acetylene and unsaturated hydrocarbons from Mg2C2; Fe3C,
lanthanides.

Physical and chemical properties:

Four crystalline modifications of carbon are known: graphite, diamond,
carbine and lonsdaleite. Graphite - gray-black, opaque, greasy on
touch, scaly, very soft mass with a metallic sheen. At
room temperature and normal pressure (0.1 MN/m2, or 1kgf/cm2)
graphite is thermodynamically stable. Diamond - very hard, crystalline
substance. Crystals have a cubic face-centered lattice:
a \u003d 3.560 (. At room temperature and normal pressure, diamond
metastable. A noticeable transformation of diamond into graphite is observed at
temperatures above 1400 (C in vacuum or in an inert atmosphere. At
atmospheric pressure and a temperature of about 3700 (C) graphite sublimates.
Liquid carbon can be obtained at pressures above 10.5 MN/m2 (1051
kgf / cm2) and temperatures above 3700 (C. For solid carbon (coke, soot,
charcoal) is also characterized by a state with a disordered structure
"amorphous" carbon, which does not represent an independent
modifications; its structure is based on the structure of fine-crystalline
graphite. Heating some varieties of "amorphous" carbon is higher
1500-1600 (Without air access causes them to turn into graphite.
The physical properties of “amorphous” carbon depend very strongly on
dispersion of particles and the presence of impurities. Density, heat capacity,
thermal conductivity and electrical conductivity of "amorphous" carbon is always higher,
than graphite. Carbin obtained artificially. He is
fine-crystalline powder of black color (density 1.9 - 2 g/cm3).
It is built from long chains of C atoms stacked parallel to each other.
Lonsdaleite is found in meteorites and obtained artificially; its structure and
properties have not been finalized.

The configuration of the outer shell of the carbon atom is 2s22p2. For carbon
characterized by the formation of four covalent bonds due to
excitation of the outer electron shell to the 2sp3 state. That's why
carbon is equally capable of both attracting and giving
electrons. The chemical bond can be carried out due to sp3-, sp2- and
sp-hybrid orbitals, which correspond to the coordination numbers 4.3
and 2. The number of valence electrons of carbon and the number of valence orbitals
equally; this is one of the reasons for the stability of the bond between carbon atoms.

The unique ability of carbon atoms to combine with each other with
the formation of strong and long chains and cycles led to the emergence
a huge number of various carbon compounds studied
organic chemistry.

In compounds, carbon exhibits oxidation states -4; +2; +4. Atomic
radius 0.77(, covalent radii 0.77(, 0.67(, 0.60(respectively in
single, double and triple bonds; ionic radius С4- 2.60(, С4+ 0.20(.
Under normal conditions, carbon is chemically inert, at high temperatures
it combines with many elements, showing strong restorative
properties.

All forms of carbon are resistant to alkalis and acids and slowly oxidize.
only with very strong oxidizing agents (chromium mixture, concentrated
HNO3 and KCIO3, etc.). “Amorphous” carbon reacts with fluorine at room temperature.
temperature, graphite and diamond - when heated. Direct connection
carbon with chlorine occurs in an electric arc; with bromine and iodine
carbon does not react, so numerous carbon halides
synthesized indirectly. Of the oxyhalides of the general formula COX2 (where
X - halogen) the most famous chloroxide COCI2 (phosgene).

At temperatures above 1000(C), carbon interacts with many
metals, giving carbides. All forms of carbon when heated
reduce metal oxides with the formation of free metals (Zn,
Cd, Cu, Pb, etc.) or carbides (CaC2, Mo2C, WC, TaC, etc.). Carbon
reacts at temperatures above 600 - 800 (C) with water vapor and carbon dioxide
gas.

All forms of carbon are insoluble in common inorganic and organic
solvents, but dissolve in some molten metals
(eg Fe, Ni, Co).

National economic value:

Carbon is determined by the fact that over 90% of all primary sources
the world's energy consumption comes from fossil fuels,
whose dominant role will continue in the coming decades,
despite the intensive development nuclear power. Only about 10%
extracted fuel is used as raw material for the main
organic synthesis and petrochemical synthesis, to obtain
plastic masses, etc.

Carbon in the body:

Carbon is the most important biogenic element that forms the basis of life on
Earth, the structural unit of a huge number of organic compounds,
participating in the construction of organisms and ensuring their vital activity
(biopolymers, as well as numerous low molecular weight biologically
active substances - vitamins, hormones, mediators, etc.). Significant
part of the energy needed by organisms is produced in cells due to
carbon oxidation. The emergence of life on Earth is considered in
modern science as a complex process of evolution of carbon compounds.

The unique role of carbon in wildlife is due to its properties,
which, in the aggregate, no other element of the periodic
systems. Between carbon atoms, and between carbon and other
elements form strong chemical bonds, which, however, can
be broken under comparatively mild physiological conditions (these connections
may be single, double or triple). Ability of carbon
form 4 equivalent valence bonds with other atoms. Carbon
makes it possible to build carbon skeletons various types -
linear, branched, cyclic. Significantly, there are only three
elements - C, O, H - make up 98% of the total mass of living organisms. This
a certain economy is achieved in wildlife: with practically
limitless structural diversity of carbon compounds, a small
the number of types of chemical bonds can greatly reduce the number
enzymes necessary for the breakdown and synthesis of organic substances.
Features of the structure of the carbon atom underlies various kinds
isomerism of organic compounds (ability for optical isomerism
proved to be decisive in the biochemical evolution of amino acids, carbohydrates and
some alkaloids).

According to the hypothesis of A. I. Oparin, the first organic compounds on Earth
were of abiogenic origin. The sources of carbon were (CH4) and
hydrogen cyanide (HCN) contained in the Earth's primary atmosphere. WITH
the emergence of life as the only source of inorganic carbon,
through which everything is formed organic matter biosphere is
carbon dioxide (CO2) in the atmosphere and also dissolved in
natural waters in the form of HCO3. The most powerful absorption mechanism
(assimilation) of carbon (in the form of CO2) - photosynthesis - is carried out
ubiquitous green plants. On Earth, there is also evolutionarily more
an ancient way of assimilation of CO2 by chemosynthesis; in this case
Microorganisms - chemosynthetics do not use the radiant energy of the Sun, but
oxidation energy inorganic compounds. Most animals
consume carbon with food in the form of ready-made organic compounds. IN
depending on the method of assimilation of organic compounds, it is accepted
distinguish between autotrophic organisms and heterotrophic organisms. Application
for the biosynthesis of protein and other microbial nutrients,
using hydrocarbons as the only source of carbon
oil is one of the important modern scientific and technical problems.

In addition to stable isotopes of carbon, it is common in nature
radioactive 14C (in the human body it contains about 0.1 microcurie).
Using carbon isotopes in biological and medical
research has linked many major advances in the study of metabolism
substances and the carbon cycle in nature. So, with the help of radiocarbon
labels, the possibility of H14CO3 fixation by plants and tissues was proved
animals, the sequence of the reaction of photosynthesis was established, studied
amino acid metabolism, the biosynthesis pathways of many biologically
active compounds, etc. The use of 14C contributed to the success
molecular biology in the study of the mechanisms of protein biosynthesis and transmission
hereditary information. Determination of the specific activity of 14C in
carbon-containing organic residues allows us to judge their age,
which is used in paleontology and archaeology.

Bibliography.

1. Akhmetov N.S. Inorganic chemistry. Proc. allowance for students in grades 8–9.
school with deep the study of chemistry. In 2 parts - part 1, part 2, - 2nd ed. -
M.: Enlightenment, 1990 - 208 p.

2. Akhmetov N.S. General and inorganic chemistry. Proc. allowance for universities,
M.: graduate School, 1988 - 470 p.

3. Babich L.V., Balezin S.A., Glikina F.B., Zak E.G. Workshop on
inorganic chemistry. Proc. allowance for universities, M .: Higher school, 1989 -
300 s.

4. Bashlak A.T. "What Can Ignite Carbon Dioxide", w. "Chemistry at school"
1991, no. 5, p. 58.

Carbon black (GOST 7885-86) is a type of industrial carbon products used mainly in the production of rubber as a filler that enhances its useful performance properties. Unlike coke and pitch, it consists of almost one carbon, it looks like soot.

Application area

Approximately 70% of the produced carbon black is used for the manufacture of tires, 20% - for the production of rubber products. Also, technical carbon is used in paint and varnish production and in the production of printing inks, where it acts as a black pigment.

Another area of ​​application is the production of plastics and cable sheaths. Here the product is added as a filler and giving products special properties. Carbon black is also used in small volumes in other industries.

Characteristic

Carbon black is a product of a process that incorporates the latest engineering technologies and, due to its purity and well-defined set of physical and chemical properties, it has nothing to do with soot, which forms as a polluted by-product from burning coal and fuel oil, or from the operation of unregulated internal combustion engines. . According to the generally accepted international classification carbon black is designated Carbon Black (black carbon translated from in English), soot in English - soot. That is, these concepts are currently in no way mixed.

The effect of amplification due to the filling of rubbers with carbon black was no less important for the development of the rubber industry than the discovery of the phenomenon of sulfur. In rubber compounds, carbon from a large number of ingredients used by weight takes the second place after rubber. The influence of the quality indicators of carbon black on the properties of rubber products is much greater than the quality indicators of the main ingredient - rubber.

Reinforcing properties

Improvement physical properties material due to the introduction of a filler is called reinforcement (reinforcement), and such fillers are called amplifiers (carbon black, precipitated silicon oxide). Among all amplifiers, technical carbon has truly unique characteristics. Even before vulcanization, it binds to rubber, and this mixture cannot be completely separated into carbon black and rubber with solvents.

The strength of rubbers obtained on the basis of the most important elastomers:

The table shows the properties of vulcanizates obtained from various types of rubber without filling and filled with carbon black. From the data presented, it can be seen how significantly the filling with -carbon affects the tensile strength of rubbers. By the way, other dispersed powders used in rubber compounds to give the desired color or reduce the cost of the mixture - chalk, kaolin, talc, iron oxide and others do not have reinforcing properties.

Structure

Pure natural carbons are diamonds and graphite. They have a crystalline structure that is significantly different from one another. The similarity in the structure of natural graphite and artificial material carbon black was established by X-ray diffraction. Carbon atoms in graphite form large layers of condensed aromatic ring-like systems, with an interatomic distance of 0.142 nm. These graphite layers of condensed aromatic systems are commonly called basal planes. The distance between the planes is strictly defined and is 0.335 nm. All layers are located parallel to each other. The density of graphite is 2.26 g/cm 3 .

Unlike graphite, which has a three-dimensional order, technical carbon is characterized only by a two-dimensional order. It consists of well-developed graphite planes, located approximately parallel to each other, but offset with respect to adjacent layers - that is, the planes are arbitrarily oriented with respect to the normal.

Figuratively, the structure of graphite is compared with a neatly folded deck of cards, and the structure of carbon black with a deck of cards in which the cards are shifted. In it, the interplanar distance is greater than that of graphite and is 0.350-0.365 nm. Therefore, the density of carbon black is lower and is in the range of 1.76-1.9 g / cm 3, depending on the brand (most often 1.8 g / cm 3).

Coloring

Pigment (coloring) stamps carbon black are used in the manufacture of printing inks, coatings, plastics, fibers, paper and building materials. They are classified into:

• highly coloring carbon black (HC);
• medium color (MS);
• normal staining (RC);
• low color (LC).

The third letter indicates the production method - furnace (F) or channel (C). Designation example: HCF - high color furnace black (Hiqh Color Furnace).

The coloring power of a product is related to its particle size. Depending on their size, technical carbon is divided into groups:

Classification

According to the degree of reinforcing effect, technical carbon for rubber is divided into:

• Highly reinforcing (tread, hard). It is allocated with the increased durability and resilience to attrition. The particle size is small (18-30 nm). Used in conveyor belts, tire treads.
• Semi-reinforcing (frame, soft). The particle size is average (40-60 nm). They are used in diverse rubber products, tire carcasses.
• Low gain. The particle size is large (over 60 nm). Limited use in the tire industry. Provides the necessary strength while maintaining high elasticity in rubber products.

A complete classification of carbon black is given in the ASTM D1765-03 standard, adopted by all global product manufacturers and users. In it, the classification, in particular, is carried out according to the range of the specific surface area of ​​particles:

Production of carbon black

There are three technologies for producing industrial carbon black that use a cycle of incomplete combustion of hydrocarbons:

• furnace;
• channel;
• lamp;
• plasma.

There is also a thermal method, in which at high temperatures decomposition of acetylene or natural gas.

Numerous grades, obtained through various technologies, have a variety of characteristics.

Manufacturing technology

Theoretically, it is possible to obtain carbon black by all of the above methods, however, more than 96% of the product produced is obtained by the furnace method from liquid raw materials. The method makes it possible to obtain various grades of carbon black with a certain set of properties. For example, more than 20 grades of carbon black are produced using this technology for carbon black.

The general technology is this. The reactor, lined with highly refractory materials, is also supplied with air heated to 800 °C. Due to the combustion of natural gas, products of complete combustion are formed with a temperature of 1820-1900 ° C, containing a certain amount of free oxygen. Liquid hydrocarbon raw materials are injected into the high-temperature products of complete combustion, thoroughly mixed beforehand and heated to 200-300 °C. The pyrolysis of raw materials takes place at a strictly controlled temperature, which, depending on the grade of produced carbon black, has different values ​​from 1400 to 1750 °C.

At a certain distance from the place of supply of raw materials, the thermal-oxidative reaction is stopped by the injection of water. The carbon black and reaction gases formed as a result of pyrolysis enter the air heater, in which they give off part of their heat to the air used in the process, while the temperature of the carbon-gas mixture decreases from 950-1000 ° C to 500-600 ° C.

After cooling to 260-280 °C due to additional water injection, the mixture of carbon black and gases is sent to a bag filter, where carbon black is separated from gases and enters the filter hopper. The separated carbon black from the filter hopper is fed through a gas pipeline by a fan (turbo blower) to the granulation section.

Producers of carbon black

World production of carbon black exceeds 10 million tons. Such a great need for the product is primarily due to its unique reinforcing properties. The locomotives of the industry are:

• Aditya Birla Group (India) - about 15% of the market.
• Cabot Corporation (USA) - 14% of the market.
• Orion Engineered Carbons (Luxembourg) - 9%.

The largest Russian producers of carbon:

• Omsktehuglerod LLC - 40% Russian market. Factories in Omsk, Volgograd, Mogilev.
• OAO Yaroslavl Technical Carbon - 32%.
• OAO Nizhnekamsktehuglerod - 17%.

§ 4.1. General characteristics of the elements of the carbon subgroup

The chemical elements of the main subgroup of group IV include carbon c, silicon Si, germanium Ge, tin sn and lead Pb. In the series C - Si - Ge - Sn - Pb, due to the different chemical nature of the elements, they are divided into two subgroups: carbon and silicon make up subgroup of carbon, germanium, tin, lead - subgroup germanium.

Electronic configurations of the outer layer of atoms of elements ns 2 np 2, in compounds they can exhibit oxidation states from –4 to +4. As in the main subgroup of group V, a change in the chemical properties of elements is observed: carbon and silicon exhibit the properties of typical non-metals, germanium is characterized by transitional properties, and tin and lead are typical metals. With an increase in the atomic number in a subgroup, the electronegativity of the elements decreases. Covalent compounds are characteristic of carbon and silicon, while ionic compounds are characteristic of tin and lead.

Some properties of the elements of the main subgroup of group IV are presented in Table. 4.1.

Table 4.1

Element Properties
subgroups of carbon and simple substances

Table data. 4.1 confirm that in the series C - Si - Ge - Sn - Pb, a monotonous change in properties from non-metallic to metallic is observed. This is manifested in a decrease in the stability of compounds of elements in the highest oxidation state +4 and an increase in the stability of compounds of elements in a low oxidation state of +2. For C, Si and Ge, the formation of free cations is not typical, Sn and Pb easily form Sn 2+ and Pb 2+ cations.

The increase in metallic properties is evidenced by the change in the acid-base properties of oxides and hydroxides of elements in the +4 oxidation state when moving from carbon to lead:

The acidic properties of the corresponding hydroxides change similarly.

In the series from carbon to lead, the stability of element oxides in the +2 oxidation state increases.

Carbon exists in nature in the form of two stable isotopes: 12 C (98.9%) and 13 C (1.1%).

The b-radioactive carbon isotope 14 C is of great importance. radiocarbon The method for determining the age of carbonaceous rocks is the calculation of the ratio of the proportions of stable and radioactive isotopes of carbon.

Carbon ranks 11th in abundance on Earth. It is found in the atmosphere in the form of CO 2, many minerals and rocks are formed from it, for example, chalk, limestone, marble (the chemical formula of which is CaCO 3), dolomite (MgCO 3 CaCO 3), malachite (CuCO 3 Cu (OH) 2). Carbon is a part of proteins, nucleic acids, carbohydrates - substances without which life is impossible.

In almost all compounds (except CO and SiO), carbon and silicon are tetravalent. Carbon atoms in many compounds form –C–C– chains. Silicon compounds are also characterized by a polymeric structure, but unlike carbon atoms, silicon atoms form branched chains, connecting not with each other, but through oxygen –Si–O–Si–.

Carbon forms several simple substances: diamond, graphite, carbine, fullerene and amorphous carbon.

DIAMONDis a colorless transparent, highly refracting crystals with a density of 3.52 g/cm 3 . The structure of the external energy level carbon atom in the unexcited state describes the electronic configuration 2 s 2 2p 2. When chemical bonds are formed in a carbon atom, the electrons located on the s-sublevel, and it acquires configuration 2 s 1 2p 3 . The orbitals of the four unpaired electrons undergo sp 3-hybridization, leading to the formation of four equivalent hybrid orbitals, the angle between which is equal to the tetrahedral one. The atoms that are in sp 3-hybrid state, and form a diamond structure. Diamond is a high-strength substance with a unique hardness and excellent refractive power, which is important for creating abrasive materials, cutting tools and jewelry.

GRAPHITEis a gray opaque greasy to the touch mass with a density of 2.27 g/cm 3 . In graphite, the carbon atoms are in sp 2-hybrid state, which causes a layered structure of graphite, consisting of flat hexagons. The distances between carbon atoms located in different layers exceed the distances between atoms within the layer. The layered structure of graphite explains its electrical and thermal conductivity, as well as the ability to leave a mark on a solid surface. For the transformation of diamond into graphite, heating to 1800–1850 ° C without air is necessary. The reverse process takes place at a temperature of 3000 ° C and a pressure of 10 6 -10 7 kPa.

Graphite is widely used as an electrode material in electrochemistry; it is part of the lubricants, is used as a neutron moderator in nuclear reactors.

CARBINis a black crystalline powder with a density of 1.9 g/cm 3 . To obtain it, the reaction of acetylene dehydrogenation at 1000 ° C is used, as a result of which from n C 2 H 2 molecules, a polymer with a linear structure –C º C–C º C–C º C– is obtained. In this modification, the carbon atoms are in sp- hybrid state.

FULLERENESwere found in the condensation products of graphite vapors. The C 60 fullerene molecule represents interconnected five and six-membered cycles containing carbon in the sp 2 and sp 3 hybrid state. In addition to C 60, fullerenes of composition C 70 and C 76 are separated.

AMORPHOUS CARBON - the most common allotropic modification of carbon . Most often it is obtained by the decomposition of various organic substances. This form is sometimes referred to as charcoal or activated charcoal.

SILICON- the most common element after oxygen in the earth's crust (27.6% by weight). It has three stable isotopes: 28Si (92.27%), 29Si (4.68%), and 30Si (3.05%). Silicon occurs naturally in the form silica- silicon oxide (IV) SiO 2 (sometimes called quartz or sand), silicates And aluminosilicates, for example mica KAl 3 (OH, F) 2, asbestos (Mg, Fe) 6 (OH) 6, talc Mg 3 (OH) 2. Depending on the particle size and impurity content in SiO 2 during its reduction, various modifications of silicon can be obtained.

Amorphous silicon is a brown powder crystal- light gray hard brittle crystals metallic look. In the crystal lattice, each silicon atom is in the state sp 3 hybridization and is surrounded by four other atoms with which it is covalently bonded - crystalline silicon is similar to diamond.

Silicon is widely used in microelectronics as a semiconductor material for microchips and in metallurgy to obtain pure metals.

§ 4.2. Chemical properties of carbon and silicon

1. In reactions with simple substances formed by more electronegative elements (oxygen, halogens, nitrogen, sulfur), carbon and silicon exhibit properties reducing agents. When graphite and silicon are heated with an excess of oxygen, higher oxides are formed, and with a lack of oxygen, CO and SiO monoxides are formed:

E + O 2 \u003d EO 2 (excess oxygen);

2E + O 2 \u003d 2EO (lack of oxygen).

Carbon and silicon react with fluorine under normal conditions to form tetrafluorides CF 4 and SiF 4 , to obtain tetrachlorides CCl 4 and SiCl 4 heating of the reactants is necessary. Sulfur and nitrogen react with carbon and silicon only when heated strongly:

C + 2S CS 2 ;

2C + N 2 C 2 N 2 ;

Si + 2S SiS 2 .

When the mixture is heated quartz sand and coke at a temperature of about 2000 ° C, silicon carbide is formed, or carborundum- a refractory substance, close to diamond in hardness:

SiO 2 + 3C \u003d SiC + 2CO.

Carbon is often used to reduce low-activity metals from their oxides and to convert metal sulfates to sulfides:

CuO + C Cu + CO

BaSO4 + 4C BaS + 4CO.

2. Reactions with acids. Carbon and silicon are resistant to the action of ordinary acids. Carbon is oxidized with concentrated sulfuric and nitric acids:

C + 2H 2 SO 4 \u003d CO 2 + 2SO 2 + 2H 2 O;

3C + 4HNO 3 \u003d 3CO 2 + 4NO + 2H 2 O.

Silicon in concentrated sulfuric and nitric acids is passivated and dissolved in mixtures of concentrated nitric and hydrofluoric acids and: concentrated nitric and hydrochloric acids

3Si + 4HNO 3 + 18HF = 3H 2 SiF 6 + 4NO + 8H 2 O.

In this reaction, nitric acid plays the role of an oxidizing agent, and hydrofluoric or hydrochloric acid plays the role of a complexing agent.

3. Reactions with alkalis. Silicon dissolves in aqueous solutions of alkalis with the release of hydrogen:

Si + 2NaOH + H 2 O \u003d Na 2 SiO 3 + 2 H 2.

4. Interaction with water. Under normal conditions, silicon does not interact with water, but under high temperature it reacts with water vapor:

Si + \u003d H 2 SiO 3 + 2H 2.

5. Oxidative properties carbon and silicon are manifested in reactions with active metals, with the formation carbides And silicides:

Ca + 2C \u003d CaC 2;

2Mg + Si = Mg 2 Si.

6. Carbon and silicon capable disproportionate when heated with oxides of active metals, forming oxides, carbides and silicides:

CaO + 3C \u003d CaC 2 + CO;

2Al 2 O 3 + 9C \u003d Al 4 C 3 + 6CO;

2MgO + 3Si = Mg 2 Si + 2SiO.

§ 4.3. Oxygen compounds of carbon and silicon

CARBON(II) OXIDE CO, or carbon monoxide, under normal conditions is a colorless and odorless gas, t pl = -205 °C, t kip \u003d -191.5 ° C. It is highly poisonous, burns with a bluish flame, lighter than air, poorly soluble in water (2.3 volumes of CO per 100 volumes of H 2 O at 293 K).

Carbon monoxide is formed when carbon is burned in a lack of oxygen, in addition, CO can be obtained by reacting hot coal with water vapor or carbon dioxide:

C + H 2 O CO + H 2;

CO2 + C2CO.

Receipt.In the laboratoryCO is obtained by dehydration of formic or oxalic acid in the presence of sulfuric acid as a water-removing agent:

HCOOH CO + H 2 O;

H 2 C 2 O 4 CO + CO 2 + H 2 O.

Chemical properties. 1. When carbon monoxide (II) is passed into an alkali melt at high pressure, a formic acid salt is formed:

CO + KOH = HCOOK.

This reaction, as well as the laboratory method for obtaining CO by dehydration of formic acid, allows us to formally assume that CO - formic anhydride. However, this statement is just formal, since the reverse process of obtaining formic acid during the hydration of carbon monoxide cannot be carried out.

The oxidation state of carbon in carbon monoxide - +2 - does not correspond to the structure of the CO molecule, in which, in addition to two bonds formed by the pairing of carbon and oxygen electrons, there is another one formed by the donor-acceptor mechanism due to the lone pair of oxygen electrons (depicted by an arrow) :

The presence of the triple bond explains the strength of the CO molecule and its low reactivity at ordinary temperature. Under normal conditions, carbon monoxide does not interact with water, alkalis and acids.

2. At elevated temperatures, CO interacts with oxygen and metal oxides:

2CO + O 2 \u003d 2CO 2;

FeO + CO \u003d Fe + CO 2.

3. When passing a mixture of carbon monoxide with chlorine through a layer activated carbon you can get a poisonous substance - poisonous gas phosgene causing paralysis of the respiratory tract:

CO + Cl 2 \u003d COCl 2.

4. When carbon monoxide is heated with hydrogen at elevated pressure, methyl alcohol is formed:

CO + 2H 2 → C H 3 OH.

Carbonyls.Carbon monoxide (II) interacts with many transition metals to form volatile compounds - carbonyls:

Ni + 4CO = Ni(CO) 4 .

In the CO molecule, the carbon atom has an unshared electron pair, which determines the donor properties of this molecule. The Ni-C covalent bond in the nickel carbonyl molecule is formed by the donor-acceptor mechanism, with the electron density shifting from the carbon atom to the nickel atom. The increase in the negative charge on the metal atom is compensated by the participation of its d-electrons in bond formation, so the oxidation state of the metal in the carbonyl is zero.

Metal carbonyls are soluble in non-polar solvents, volatile. They are used to obtain pure metals, since when heated they decompose into metal and carbon monoxide (II). To determine the composition of carbonyls, the so-called rule 18 electrons: the total number of valence electrons of the metal and electrons provided by CO molecules (2 from each) should be equal to 18. Metals with an odd atomic number cannot form an 18-electron shell in this way, therefore they are characterized by polymeric (mostly dimeric) carbonyls, for example 2 . In dimeric carbonyls, a metal-metal bond occurs, and CO molecules bridge the bond.

Carbon monoxide CO is a good reducing agent of silver salts from ammonia solutions of its salts:

2OH + CO \u003d 2Ag ↓ + (NH 4) 2 CO 3 + 2 NH 3

SILICON(II) OXIDESiO is obtained by co-evaporation in vacuum of a mixture of SiO 2 and Si at a temperature of 1100–1300 ° C. Hydrogen or carbon can also be used to reduce SiO 2 oxide to SiO monoxide, the processes must be carried out at a temperature of 1000 ° C.

SiO 2 + H 2 \u003d SiO + H 2 O;

SiO 2 + C \u003d SiO + CO.

Silicon(II) oxide is a brown powder that quickly oxidizes to dioxide in air. In alkalis and hydrofluoric acid, SiO is easily soluble.

This compound is mainly used as a pigment for oil paints and polishing agent.

CARBON(IV) OXIDE (carbon dioxide, carbon dioxide, carbonic anhydride) CO 2 - a colorless and odorless gas that does not support breathing and combustion, is heavier than air, t mp = -57 ° C at a pressure of 5 atm, soluble in water (88 volumes of CO 2 in 100 volumes of H 2 O at 20 ° C). At normal pressure, solid carbon dioxide passes into a gaseous state, bypassing the liquid ( sublimated). At normal temperature, under a pressure of 60 atm, the gas turns into a liquid. The CO 2 molecule is linear, with two double bonds:

O=C=O

In industry to obtain carbon monoxide (IV), high-temperature decomposition of marble is used:

CaCO 3 CaO + CO 2 .

In the laboratoryto obtain large amounts of carbon dioxide, marble is treated with hydrochloric acid:

CaCO 3 + 2HCl \u003d CaCl 2 + H 2 O + CO 2.

To detect the released CO 2, it is passed through lime water, and a white precipitate of calcium carbonate precipitates:

Ca(OH) 2 + CO 2 = CaCO 3 ¯ + H 2 O.

It must be remembered that in an atmosphere of CO 2, ignited magnesium does not go out, but continues to burn:

2Mg + CO 2 \u003d 2MgO + C

CARBONIC ACID H 2 CO 3 is formed in small quantities when carbon dioxide is dissolved in water, while the following equilibria exist in the solution:

H 2 O + CO 2 ↔ H 2 CO 3 ↔ H + + ↔ 2H + +.

At 25°C K 1 \u003d 4 × 10 -7, K 2 \u003d 5 × 10 -11.Carbonic acid is very weak and unstable in free form. It has the following structure:

As a dibasic acid, it forms medium salts ¾ carbonates and sour ¾ bicarbonates. When strong acids act on salts of carbonic acid, carbon dioxide is released, which is used as qualitative reaction for these salts:

NaHCO 3 + HCl \u003d NaCl + CO 2 + H 2 O;

BaCO 3 + 2HCl \u003d BaCl 2 + CO 2 + H 2 O.

Of all the carbonates, only alkali metal carbonates are soluble in water (Li 2 CO 3 is the worst soluble) and ammonium. Hydrogen carbonates of most metals are highly soluble in water.

Under the action of an excess of carbon monoxide (IV), water-insoluble carbonates are converted into soluble hydrocarbons:

CaCO 3 + H 2 O + CO 2 \u003d Ca (HCO 3) 2.

When heated, hydrocarbons decompose into carbonates, carbon dioxide and water:

2NaHCO 3 Na 2 CO 3 + H 2 O + CO 2.

All carbonates, except for the thermally stable alkali metal carbonates, decompose on heating into metal oxide and carbon dioxide:

CaCO 3 CaO + CO 2 .

In addition to medium and acid carbonates, there are known main carbonates. They are formed by the action of medium carbonates on salts of low-active metals:

2CuSO 4 + 3Na 2 CO 3 + 2H 2 O =
\u003d Cu (OH) 2 CuCO 3 + 2NaHCO 3 + 2Na 2 SO 4.

The basic copper carbonate Cu(OH) 2 CuCO 3 is known in nature under the name "malachite".

Of the salts of carbonic acid, soda Na 2 CO 3 and its various crystalline hydrates are of the greatest practical importance: Na 2 CO 3 × 10H 2 O (crystalline soda), Na 2 CO 3 × 7H 2 O and Na 2 CO 3 × H 2 O, and also potash K 2 CO 3 , chalk, limestone and marble having the composition CaCO 3 .

SILICON(IV) OXIDE, or silica, SiO 2 ¾ solid, very refractory substance (melting point over 1700 ° C), occurs in nature in the form of minerals quartz, cristobalite And tridymite.

At ordinary temperature, quartz is a stable modification, with increasing temperature, polymorphic transformations are observed:

quartz tridymite cristobalite melt.

Structure.In all its modifications, silicon dioxide is always polymeric (SiO 2) n and built from tetrahedra, forming a very strong atomic lattice. Each silicon atom in crystals (SiO 2) n surrounded by four oxygen atoms that are bridging and link at different angles to tetrahedra. As a result, a three-dimensional crystal lattice is formed, in which the mutual arrangement of tetrahedra in space determines one or another modification of silica.

Quartzoccurs naturally as well-formed colorless crystals called rock crystal. There are also colored varieties of quartz: rose quartz, purple ( amethyst), dark brown (smoky topaz), green ( chrysoprase). Fine-crystalline modification of quartz with impurities of other substances is called chalcedony. The varieties of chalcedony are agate, jasper etc. Rock crystal and colored varieties of quartz are used as precious and semi-precious stones.

Quartz is widely used in various fields of science, technology and microelectronics, and artificial crystals with certain parameters are often grown for the needs of the latter. crystal lattice.

Some quartz crystals are able to rotate the plane of polarization of light, and can be both right-handed and left-handed. Those and other crystals differ from each other as an object from its mirror image. Such crystals are optical isomers.

Tridymitefound in small quantities in volcanic rocks. Known tridymite and meteoric origin. Cristobalite, like tridymite, sometimes occurs as small crystals embedded in lava. Tridymite and cristobalite have a looser structure than quartz. Thus, the density of cristobalite, tridymite and quartz is 2.32, respectively; 2.26 and 2.65 g/cm3.

When the silica melt is slowly cooled, amorphous quartz glass. Silica in the form of glass is also found in nature. The density of amorphous glass is 2.20 g/cm 3 - lower than that of all crystalline modifications. At temperatures above 1000°C, quartz glass "devitrifies" and transforms into cristobalite, so experiments can only be carried out in quartz laboratory glassware at temperatures below 1000°C.

Chemical properties. 1. All forms of SiO 2 are practically insoluble in water; under normal conditions, they are only affected by alkali solutions, fluorine, gaseous hydrogen fluoride And hydrofluoric acid:

SiO 2 + 2KOH = K 2 SiO 3 + H 2 O;

SiO 2 + 4HF = SiF 4 + 2H 2 O;

SiO 2 + 6HF = H 2 + 2H 2 O.

The latter reaction is used in glass etching.

2. Silicon dioxide - typical acid oxide, therefore, when fused, it reacts with basic oxides, alkalis and carbonates to form silicates:

SiO 2 + CaO \u003d CaSiO 3;

SiO 2 + 2NaOH \u003d Na 2 SiO 3 + H 2 O;

SiO 2 + Na 2 CO 3 \u003d Na 2 SiO 3 + CO 2.

The above reactions of silicon dioxide with oxides and salts underlie the industrial production of various glasses, and cement.

Glass.Ordinary glass, having the composition Na 2 O × CaO × 6SiO 2, is obtained by fusing a mixture of soda, sand and limestone at a temperature of about 1400 ° C until the gases are completely removed:

Na 2 CO 3 + CaCO 3 + 6SiO 2 \u003d Na 2 O × CaO × 6SiO 2 + 2CO 2.

When oxides of barium, lead and boron are added, special types of glass are obtained, for example, refractory, unbreakable. To obtain colored glasses, various transition metal oxides are used, for example, the addition of cobalt (III) oxide Co 2 O 3 gives Blue colour, chromium oxide (III) Cr 2 O 3 ¾ green, manganese dioxide MnO 2 ¾ pink.

cements.Silicates are widely used in the production cement- a binder that hardens when mixed with water. Two types of cements can be distinguished according to the principle of their setting ¾ ordinary cement and portland cement. The setting process of ordinary cement occurs due to the formation of calcium carbonate during the interaction of carbon dioxide in the air and calcium silicate:

CaSiO 3 + CO 2 + H 2 O \u003d CaCO 3 ¯ + H 2 SiO 3 ¯.

The setting of Portland cement occurs as a result of the hydrolysis of silicates, followed by the formation of insoluble crystalline hydrates:

Ca 3 SiO 5 + H 2 O \u003d Ca 2 SiO 4 + Ca (OH) 2;

Ca 2 SiO 4 + 4H 2 O \u003d Ca 2 SiO 4 × 4H 2 O ¯.

Silicic acids obtained by the action of mineral acids on silicate solutions or by the hydrolysis of silicon halides and sulfides, since the direct interaction of silica with water is impossible.

The composition of silicic acids can be expressed general formula x SiO 2 × y H 2 O, where x And y¾ whole numbers. At x = 1, y= 1: we get SiO 2 × H 2 O i.e. H 2 SiO 3 ¾ metasilicon acid; at x = 1, y\u003d 2 - SiO 2 × 2H 2 O, i.e. H 4 SiO 4 ¾ ortho silicic acid; at x = 2, y\u003d 1 - 2SiO 2 × H 2 O, i.e. H 2 Si 2 O 5 ¾ two-methosilicon acid.

If y> 2, then acids are assigned to polysilicon.

silicates -salts of metasilicic, or simply silicic acid H 2 SiO 3 . Of these, only sodium and potassium silicates, called liquid glass, are soluble in water. Liquid glass is used to strengthen soils, for the manufacture of silicate glue and refractory fabrics. The remaining silicates are ¾ refractory, water-insoluble substances. When heated, silicic acid decomposes:

H 2 SiO 3 SiO 2 + H 2 O.

When stored in air, silicate solutions become cloudy due to the displacement of silicic acid. carbon dioxide contained in the air: silicic acid is weaker than carbonic; the dissociation constant of H 2 SiO 3 in the first step is 2.2 × 10–10.

The reaction of silicates with carbon dioxide is quality for the detection of silicate ions:

Na 2 SiO 3 + CO 2 + H 2 O \u003d Na 2 CO 3 + H 2 SiO 3 ¯.

Aqueous solutions of soluble silicates have a strongly alkaline reaction of the medium due to hydrolysis:

K 2 SiO 3 + H 2 O 2KOH + H 2 SiO 3 ¯.

§ 4.4. Carbides and silicides

Compounds of carbon and silicon with less electronegative elements (most often with metals) are called carbides And silicides. In addition to the reactions whose equations are given above (see § 13.2), silicides are obtained by fusing metal hydrides with silicon:

2CaH 2 + Si \u003d Ca 2 Si + 2H 2;

reduction of metals from their oxides with silicon or carbon in the presence of silicon oxide:

2CaO + 3Si \u003d 2CaSi + SiO 2;

CaO + SiO 2 + 3C = CaSi + 3CO;

interaction of metals with SiCl 4 in a hydrogen atmosphere:

Ba + SiCl 4 + 2H 2 = BaSi + 4HCl.

All these reactions proceed at high temperature and sometimes at elevated pressure.

Among the ionic carbides, the so-called methanides and acetylenides are distinguished. Methanides can be considered as methane derivatives containing carbon in the –4 oxidation state: Be 2 C, Al 4 C 3 . They are intensively decomposed by water with the release of methane:

Al 4 C 3 + 12H 2 O \u003d 4Al (OH) 3 ¯ + 3CH 4.

Acetylides- acetylene derivatives, in which the oxidation state of carbon is -1: Li 2 C 2, Ag 2 C 2, Cu 2 C 2, CaC 2, Al 2 (C 2) 3, Fe 2 (C 2) 3. Silver and copper(I) acetylenides are obtained by passing acetylene through an ammonia solution of silver oxide or copper(I) chloride. Acetylides are highly explosive and are intensively decomposed by water and acids with the release of acetylene:

CaC 2 + 2H 2 O \u003d Ca (OH) 2 + C 2 H 2;

CuC 2 + 2HCl \u003d CuCl 2 + C 2 H 2.

§ 4.5. Hydrogen compounds of elements of the fourth group

Let us consider only hydrogen compounds of silicon (silanes), germanium (germanes), tin (stannanes) and lead (plumbanes), since the chemistry of hydrogen compounds of carbon will be described in organic chemistry.

Receipt.When active metal silicides (Mg, Ca, Li) interact with water and acids, the simplest hydrogen compound of silicon is released - monosilane SiH 4 , which is most often referred to simply silane:

Ca 2 Si + 4HCl \u003d 2CaCl 2 + SiH 4.

The most common way to obtain hydrogen-containing compounds of the elements of the fourth group is the interaction of tetrachlorides of elements with lithium tetrahydroaluminate:

GeCl 4 + Li [ AlH 4 ] \u003d GeH 4 + LiCl + AlCl 3

Structure and properties. Silicon hydrogens are structurally similar to hydrocarbons. The silane molecule has the shape of a regular tetrahedron with a silicon atom in the center. Silane is a colorless gas with a musty odor that ignites spontaneously in air. t pl = -185 °C, t bp = -112 °C. Silane is highly toxic.

Unlike methane, silane interacts with alkali solutions:

SiH 4 + 2KOH + H 2 O \u003d K 2 SiO 3 + 4H 2.

Water also hydrolyzes silane, but much more slowly:

SiH 4 + 2H 2 O \u003d SiO 2 + 4H 2.

When heated above 400 ° C, silane decomposes into silicon and hydrogen, this property is used to obtain pure silicon:

SiH 4 \u003d Si + 2H 2.

Like hydrocarbons, silanes form the homologous series Si n H2 n+2 . IN individual form silanes up to n = 14 inclusive are selected. Like alkanes, silanes are colorless, the first members of the homologous series are gaseous under normal conditions, the next ¾ are liquids. The reactivity of silanes is much higher than that of hydrocarbons. This is due to the lower affinity of silicon to hydrogen compared to carbon and the very high affinity of silicon to oxygen, as well as the lower strength of the Si-Si bond compared to the C-C bond. The low strength of the Si-Si bond is also due to the limited homologous series of silanes.

Silane, Herman and stannan are strong reducing agents:

SiH 4 + 2AgCl \u003d SiH 3 Cl + HCl + 2Ag

§ 4.6. Silicon compounds with halogens

Silicon compounds with halogens can be considered as derivatives of silanes in which hydrogen atoms are completely or partially replaced by halogen. Silicon tetrahalides are obtained directly from simple substances. The reaction of silicon with fluorine occurs already at ordinary temperature, with chlorine, bromine and iodine - when heated. When current SiF 4 is passed through water, fluorosilicic acid acid H 2 SiF 6:

3SiF 4 + 2H 2 O \u003d SiO 2 + 2H 2 SiF 6.

Anhydrous fluorosilicic acid has not been isolated. Its aqueous solution is one of the strongest inorganic acids. Diluted solutions are used as a disinfectant in the food industry. Soluble salts of fluorosilicic acid are used to impregnate the walls of buildings built from calcium-containing building materials:

2CaCO 3 + MgSiF 6 \u003d SiO 2 + 2CaF 2 + MgF 2 + 2CO 2.

As a result of the reaction, a fine SiO 2 powder is formed, which closes all the pores, makes the walls waterproof and resistant.

§ 4.7. Some features of the elements of the germanium subgroup

Germaniumfound in many minerals, but in very small amounts, so it is called scattered element. The most important minerals germanium: germanite Cu 2 S × CuS × GeS 2, argyrodite Ag 8 GeS 6 , rennyrite Cu 3 (Fe, Ge)S 4 .

Basic minerals tin - cassiterite SnO 2 ( tin stone), lead - galena PbS( galena). Lead as the end product of the radioactive decay of uranium is found in uranium minerals.

In the Ge - Sn - Pb series, the activity of substances with respect to oxygen increases. Under normal conditions, Ge and Sn are stable in air, while lead oxidizes to the oxide PbO.

Tin and lead react with dilute hydrochloric and sulfuric acids to release hydrogen, while germanium does not react with non-oxidizing acids.

Germanium is oxidized with concentrated nitric, sulfuric and hydrofluoric acids:

Ge + 4H 2 SO 4 Ge(SO 4) 2 + 2SO 2 + 4H 2 O;

Ge + 6HF \u003d H 2 GeF 6 + 2H 2;

Ge + 4HNO 3 \u003d GeO 2 + 4NO 2 + 2H 2 O.

Germanium dissolves in "royal vodka":

3Ge + 4HNO 3 + 12HCl = 3GeCl 4 + 4NO + 8H 2 O

and in alkali solutions in the presence of oxidizing agents:

Ge + 2NaOH + 2H 2 O 2 \u003d Na 2.

When tin interacts with concentrated nitric acid, tin acid H 2 SnO 3 is formed:

Sn + 4HNO 3 \u003d H 2 SnO 3 + 4NO 2 + H 2 O.

In dilute HNO 3, tin behaves like a metal, forming tin(II) nitrate:

3Sn + 8HNO 3 \u003d 3Sn (NO 3) 2 + 2NO + 4H 2 O.

Lead in reactions with nitric acid of any concentration acts as a metal and forms lead(II) nitrate Pb(NO 3) 2 .

Among the compounds of the germanium subgroup in the oxidation state (IV), lead oxide is characterized by oxidizing properties, it is able to oxidize water to oxygen, the Mn +2 ion to MnO 4 -:

2MnSO 4 + 5PbO 2 + H 2 SO 4 = 5PbSO 4 ↓ + 2HMnO 4 + 2H 2 O.

In the series of compounds Ge (II) - Sn (II) - Pb (II), the reducing properties weaken, the strongest reducing agents are derivatives of germanium and tin:

Na + 2Bi(NO 3) 3 9NaOH = 2Bi↓+ 3 Na 2 ]Sn(OH) 6 ] + 6NaNO 3

Carbon is a chemical element with non-metallic properties. It is denoted by the letter C and is considered chemical element the fourth group of the second period in the periodic system of Mendeleev. Its serial number is 6, and atomic mass is 12.0107. Today, several types of carbon modifications are known. Diamond, graphite are carbon, while they differ in the structure of their crystal lattice. There are also fullerene, carbine, and the lesser known lonsdaleite, which has been found in meteorites that have fallen to earth. Carbon is also found in very large quantities in bituminous coals that are used as fuel. It is also used to produce carbon electrodes for industrial furnaces, etc.

Industrial ways to make carbon

There are four most common ways to obtain carbon black today. They are based on the thermal-oxidative decomposition of gaseous and liquid hydrocarbons. However, depending on the raw materials used, there are: furnace, lamp, thermal and channel methods. In addition to industrial methods, there are several ways in which carbon can also be obtained.

A great way to get carbon at home is to make a carbon compound with sugar. For this experiment, you will need sulfuric acid concentrate, gloves, sugar, water, and sulfuric acid.

• Before you get carbon, you need to take a glass flask.
• Next, add some sugar to it.
• After that, pour water into the same flask. The amount of water should be two centimeters higher than the sugar level.
• Next, you should be very careful, since you have to deal with sulfuric acid.
• Take concentrated sulfuric acid, then carefully add it in small drops to the same flask with sugar. After some time, pure carbon will form in the flask.

There is also another way when using rubber:

• Take a metal container, which additionally has a tight-fitting lid and a gas outlet tube.
• Next, immerse a piece of rubber in this container.
• After that, you need to put the container on the gas burner.
• The end of the gas outlet tube will need to be lowered into the jar. During heating without air, the rubber will not burn, it will decompose, and gases (methane, liquid hydrocarbons) will come out of the gas outlet tube.
• After a while, you should have carbon left at the bottom of the container. The formula of this compound will contain a large amount of C, that is, carbon.

More in a simple way considered to be carbon monoxide. Note that before you get carbon monoxide, you need to have simple ethylene. When it burns (C 2 H 4 + 3O 2 \u003d 2CO 2 + 2H 2 O), you will get carbon monoxide and water.

Please note: When working with acid, you must take precautions (wear gloves and goggles). During the thermal decomposition of rubber, this experiment should only be carried out on outdoors or in a ventilated area.