Carbon forms two extremely stable oxides (CO and CO 2), three significantly less stable oxides (C 3 O 2, C 5 O 2 and C 12 O 9), a number of unstable or poorly studied oxides (C 2 O, C 2 O 3 and others) and non-stoichiometric graphite oxide. Among the listed oxides, CO and CO 2 play a special role.

DEFINITION

Carbon monoxide under normal conditions, a flammable gas, colorless and odorless.

It is quite toxic due to its ability to form a complex with hemoglobin, which is about 300 times more stable than an oxygen-hemoglobin complex.

DEFINITION

Carbon dioxide under normal conditions, it is a colorless gas, about 1.5 times heavier than air, so that it can be poured like a liquid from one vessel to another.

The mass of 1 liter of CO 2 under normal conditions is 1.98 g. The solubility of carbon dioxide in water is low: 1 volume of water at 20 o C dissolves 0.88 volumes of CO 2, and at 0 o C - 1.7 volumes.

Direct oxidation of carbon with a lack of oxygen or air leads to the formation of CO, with a sufficient amount of them, CO 2 is formed. Some properties of these oxides are presented in table. 1.

Table 1. Physical properties of carbon oxides.

Obtaining carbon monoxide

Pure CO can be obtained in the laboratory by dehydration of formic acid (HCOOH) with concentrated sulfuric acid at ~ 140 ° C:

HCOOH = CO + H 2 O.

In small quantities, carbon dioxide can be easily obtained by the action of acids on carbonates:

CaCO 3 + 2HCl = CaCl 2 + H 2 O + CO 2.

On an industrial scale, CO 2 is obtained mainly as a by-product in the ammonia synthesis process:

CH 4 + 2H 2 O = CO 2 + 4H 2;

CO + H 2 O = CO 2 + H 2.

Large amounts of carbon dioxide are obtained by calcining limestone:

CaCO 3 = CaO + CO 2.

Chemical properties of carbon monoxide

Carbon monoxide is reactive at high temperatures. He manifests himself as a powerful restorer. Reacts with oxygen, chlorine, sulfur, ammonia, alkalis, metals.

CO + NaOH = Na (HCOO) (t = 120 - 130 o C, p);

CO + H 2 = CH 4 + H 2 O (t = 150 - 200 o C, kat. Ni);

CO + 2H 2 = CH 3 OH (t = 250 - 300 o C, kat. CuO / Cr 2 O 3);

2CO + O 2 = 2CO 2 (kat. MnO 2 / CuO);

CO + Cl 2 = CCl 2 O (t = 125 - 150 ° C, kat. C);

4CO + Ni = (t = 50 - 100 o C);

5CO + Fe = (t = 100 - 200 o C, p).

Carbon dioxide exhibits acidic properties: it reacts with alkalis, ammonia hydrate. Reduced with active metals, hydrogen, carbon.

CO 2 + NaOH dilute = NaHCO 3;

CO 2 + 2NaOH conc = Na 2 CO 3 + H 2 O;

CO 2 + Ba (OH) 2 = BaCO 3 + H 2 O;

CO 2 + BaCO 3 + H 2 O = Ba (HCO 3) 2;

CO 2 + NH 3 × H 2 O = NH 4 HCO 3;

CO 2 + 4H 2 = CH 4 + 2H 2 O (t = 200 o C, kat. Cu 2 O);

CO 2 + C = 2CO (t> 1000 o C);

CO 2 + 2Mg = C + 2MgO;

2CO 2 + 5Ca = CaC 2 + 4CaO (t = 500 o C);

2CO 2 + 2Na 2 O 2 = 2Na 2 CO 3 + O 2.

Application of carbon monoxide

Carbon monoxide is widely used as a fuel in the form of producer gas or water gas and is also formed in the separation of many metals from their oxides by reduction with coal. Generator gas is obtained by passing air through hot coal. It contains about 25% CO, 4% CO2 and 70% N 2 with traces of H 2 and CH 4 62.

The use of carbon dioxide is most often due to its physical properties. It is used as a cooling agent, for carbonating beverages, in the production of lightweight (foamed) plastics, and as a gas to create an inert atmosphere.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	Determine how much heavier than air is carbon monoxide (IV) CO 2.
Solution	The ratio of the mass of a given gas to the mass of another gas taken in the same volume, at the same temperature and the same pressure, is called the relative density of the first gas over the second. This value shows how many times the first gas is heavier or lighter than the second gas. The relative molecular weight of air is taken to be 29 (taking into account the content of nitrogen, oxygen and other gases in the air). It should be noted that the concept of "relative molecular weight of air" is used conventionally, since air is a mixture of gases. D air (CO 2) = M r (CO 2) / M r (air); D air (CO 2) = 44/29 = 1.517. M r (CO 2) = A r (C) + 2 × A r (O) = 12 + 2 × 16 = 12 + 32 = 44.
Answer	Carbon monoxide (IV) CO 2 is 1.517 times heavier than air.

Carbon dioxide, also known as 4, reacts with a number of substances to form compounds of the most varied composition and chemical properties. Composed of non-polar molecules, it has very weak intermolecular bonds and can only be found if the temperature is higher than 31 degrees Celsius. Carbon dioxide is a chemical compound made up of one carbon and two oxygen atoms.

Carbon monoxide 4: formula and basic information

Carbon dioxide is present in the Earth's atmosphere at low concentrations and acts as a greenhouse gas. Its chemical formula is CO 2. At high temperatures, it can exist exclusively in a gaseous state. In its solid state, it is called dry ice.

Carbon dioxide is an essential component of the carbon cycle. It comes from the multitude natural sources including volcanic degassing, combustion of organic matter and respiratory processes of living aerobic organisms. Anthropogenic sources of carbon dioxide are mainly associated with the burning of various fossil fuels to generate electricity and transport.

It is also produced by various microorganisms from fermentation and cellular respiration. Plants convert carbon dioxide to oxygen during a process called photosynthesis, using both carbon and oxygen to form carbohydrates. In addition, plants also release oxygen into the atmosphere, which is then used for respiration by heterotrophic organisms.

Carbon dioxide (CO2) in the body

Carbon monoxide 4 reacts with different substances and is a gaseous waste product from metabolism. More than 90% of it exists in the blood in the form of bicarbonate (HCO 3). The rest is either dissolved CO 2 or carbonic acid (H2CO 3). Organs such as the liver and kidneys are responsible for balancing these compounds in the blood. Bicarbonate is Chemical substance which acts as a buffer. It keeps the blood pH level at the required level, avoiding acidity increase.

Structure and properties of carbon dioxide

Carbon dioxide (CO 2) is a chemical compound that is a gas at room temperature and above. It consists of one carbon atom and two oxygen atoms. People and animals give off carbon dioxide when they breathe out. In addition, it is always formed when something organic is burned. Plants use carbon dioxide to produce food. This process is called photosynthesis.

The properties of carbon dioxide were studied by Scottish scientist Joseph Black in the 1750s. capable of capturing heat energy and affecting the climate and weather on our planet. It is he who is the cause of global warming and an increase in the temperature of the Earth's surface.

Biological role

Carbon monoxide 4 reacts with various substances and is the final product in organisms that get energy from the breakdown of sugars, fats and amino acids. This process is known to be characteristic of all plants, animals, many fungi and some bacteria. In higher animals, carbon dioxide travels in the blood from body tissues to the lungs, where it is exhaled. Plants obtain it from the atmosphere for use in photosynthesis.

Dry ice

Dry ice or solid carbon dioxide is the solid state of CO 2 gas with a temperature of -78.5 ° C. In its natural form, this substance does not occur in nature, but is produced by man. It is colorless and can be used for the preparation of carbonated drinks, as a cooling element in ice cream containers and in cosmetology, for example, for freezing warts. Dry ice vapors cause suffocation and can be fatal. Care and professionalism is worth exercising when using dry ice.

Under normal pressure, it will not melt from into a liquid, but instead goes directly from a solid to a gas. This is called sublimation. It will change directly from solid to gas at any temperature exceeding extremely low temperatures. Dry ice sublimes at normal air temperatures. This produces carbon dioxide, which is odorless and colorless. Carbon dioxide can be liquefied at pressures above 5.1 atm. The gas that comes out of dry ice is so cold that, when mixed with air, it cools the water vapor in the air to a mist that looks like thick white smoke.

Preparation, chemical properties and reactions

In industry, carbon monoxide 4 is obtained in two ways:

1. By burning fuel (C + O 2 = CO 2).
2. By thermal decomposition of limestone (CaCO 3 = CaO + CO 2).

The resulting volume of carbon monoxide 4 is purified, liquefied and pumped into special cylinders.

Being acidic, carbon monoxide 4 reacts with substances such as:

• Water. Dissolution produces carbonic acid (H 2 CO 3).
• Alkaline solutions. Carbon monoxide 4 (formula CO 2) reacts with alkalis. In this case, medium and acidic salts (NaHCO 3) are formed.
• These reactions form carbonate salts (CaCO 3 and Na 2 CO 3).
• Carbon. When carbon monoxide 4 reacts with hot coal, carbon monoxide 2 (carbon monoxide) is formed, which can cause poisoning. (CO 2 + C = 2CO).
• Magnesium. As a rule, carbon dioxide does not support combustion, only at very high temperatures can it react with some metals. For example, ignited magnesium will continue to burn in CO 2 during a redox reaction (2Mg + CO 2 = 2MgO + C).

The qualitative reaction of carbon monoxide 4 is manifested when it is passed through limestone water (Ca (OH) 2 or through barite water (Ba (OH) 2). Cloudiness and precipitation can be observed. , since insoluble carbonates are converted into soluble bicarbonates (acidic salts of carbonic acid).

Carbon dioxide is also produced when all carbonaceous fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), coal, or wood are burned. In most cases, water is released as well.

Carbon dioxide (carbon dioxide) is made up of one carbon atom and two oxygen atoms, which are held together by covalent bonds (or electron fission). Pure carbon is very rare. It is found in nature only in the form of minerals, graphite and diamond. Despite this, it is the building block of life, which, when combined with hydrogen and oxygen, forms the basic compounds that make up everything on the planet.

Hydrocarbons such as coal, oil and natural gas are compounds made up of hydrogen and carbon. This element is found in calcite (CaCo 3), minerals in sedimentary and metamorphic rocks, limestone and marble. It is the element that contains all organic matter, from fossil fuels to DNA.

Carbon oxides (II) and (IV)

Integrated lesson in chemistry and biology

Tasks: study and systematize knowledge about carbon oxides (II) and (IV); to reveal the relationship between living and inanimate nature; to consolidate knowledge about the effect of carbon oxides on the human body; to consolidate the skills of the ability to work with laboratory equipment.

Equipment: HCl solution, litmus, Ca (OH) 2, CaCO 3, glass rod, homemade tables, portable board, ball-and-stick model.

DURING THE CLASSES

Biology teacher communicates the topic and objectives of the lesson.

Chemistry teacher. Based on the theory of covalent bonds, write the electronic and structural formulas of carbon oxides (II) and (IV).

The chemical formula of carbon monoxide (II) is CO, the carbon atom is in its normal state.

Due to the pairing of unpaired electrons, two covalent polar bonds are formed, and the third covalent bond is formed by the donor-acceptor mechanism. The donor is an oxygen atom, because it provides a free pair of electrons; the acceptor is a carbon atom, since provides a free orbital.

In industry, carbon monoxide (II) is obtained by passing CO 2 over a hot coal at a high temperature. It is also formed during the combustion of coal with a lack of oxygen. ( Pupil writing the reaction equation on the blackboard)

In the laboratory, CO is obtained by the action of concentrated H 2 SO 4 on formic acid. ( The teacher writes down the reaction equation.)

Biology teacher. So, you got acquainted with the production of carbon monoxide (II). And what are the physical properties of carbon monoxide (II)?

Student. It is a colorless gas, poisonous, odorless, lighter than air, poorly soluble in water, boiling point –191.5 ° C, solidifies at –205 ° C.

Chemistry teacher. Carbon monoxide in quantities hazardous to human life contained in the exhaust gases of cars. Therefore, garages should be well ventilated, especially when starting the engine.

Biology teacher. What is the effect of carbon monoxide on the human body?

Student. Carbon monoxide is extremely toxic to humans - this is due to the fact that it forms carboxyhemoglobin. Carboxyhemoglobin is a very strong compound. As a result of its formation, blood hemoglobin does not interact with oxygen, and in case of severe poisoning, a person can die from oxygen starvation.

Biology teacher. What first aid should be given to a person in case of carbon monoxide poisoning?

Students. It is necessary to call an ambulance, the victim should be taken out into the street, artificial respiration should be given, the room should be well ventilated.

Chemistry teacher. Write the chemical formula of carbon monoxide (IV) and, using a ball-and-stick model, build its structure.

The carbon atom is in an excited state. All four covalent polar bonds are formed by pairing unpaired electrons. However, due to its linear structure, its molecule is generally non-polar.
In industry, CO 2 is obtained from the decomposition of calcium carbonate in the production of lime.
(The student writes down the reaction equation.)

In the laboratory, CO 2 is obtained by the interaction of acids with chalk or marble.
(Students perform a laboratory experiment.)

Biology teacher. As a result of what processes carbon dioxide is formed in the body?

Student. Carbon dioxide is produced in the body as a result of oxidation reactions organic matter that make up the cell.

(Students perform a laboratory experiment.)

The lime slurry became cloudy because calcium carbonate is formed. In addition to the breathing process, CO2 is released as a result of fermentation and decay.

Biology teacher. Does physical activity affect the breathing process?

Student. With excessive physical (muscle) load, the muscles use oxygen faster than the blood can deliver it, and then they synthesize the ATP necessary for their work by fermentation. In the muscles, lactic acid C 3 H 6 O 3 is formed, which enters the bloodstream. The accumulation of large amounts of lactic acid is harmful to the body. After heavy physical exertion, we breathe heavily for some time - we pay the "oxygen debt".

Chemistry teacher. A large amount of carbon monoxide (IV) is released into the atmosphere when fossil fuels are burned. At home, we use natural gas as fuel, and it is almost 90% methane (CH 4). I suggest one of you go to the blackboard, write the equation for the reaction, and analyze it in terms of oxidation-reduction.

Biology teacher. Why can't gas ovens be used to heat a room?

Student. Methane is an integral part natural gas... When it burns, the content of carbon dioxide in the air increases, and oxygen decreases. ( Working with the table "Contents CO 2 in the air".)
When the air contains 0.3% CO 2, a person experiences rapid breathing; at 10% - loss of consciousness, at 20% - instant paralysis and quick death. A child especially needs clean air, because the consumption of oxygen by the tissues of a growing organism is greater than that of an adult. Therefore, it is necessary to regularly ventilate the room. If there is an excess of CO 2 in the blood, the excitability of the respiratory center increases and breathing becomes more frequent and deeper.

Biology teacher. Consider the role of carbon monoxide (IV) in plant life.

Student. In plants, the formation of organic matter occurs from CO 2 and H 2 O in the light, in addition to organic matter, oxygen is formed.

Photosynthesis regulates the carbon dioxide content in the atmosphere, which prevents the planet from rising temperatures. Plants absorb 300 billion tons of carbon dioxide from the atmosphere annually. In the process of photosynthesis, 200 billion tons of oxygen are released into the atmosphere annually. Ozone is formed from oxygen during a thunderstorm.

Chemistry teacher. Consider Chemical properties carbon monoxide (IV).

Biology teacher. What is the importance of carbonic acid in the human body during respiration? ( Film strip fragment.)
The enzymes in the blood convert carbon dioxide into carbonic acid, which dissociates into hydrogen and bicarbonate ions. If the blood contains an excess of H + ions, i.e. if the acidity of the blood is increased, then some of the H + ions combine with bicarbonate ions, forming carbonic acid and thereby freeing the blood from excess H + ions. If there are too few H + -ions in the blood, then carbonic acid dissociates and the concentration of H + -ions in the blood increases. At 37 ° C, the blood pH is 7.36.
In the body, carbon dioxide is carried by the blood in the form chemical compounds- sodium and potassium bicarbonates.

Securing the material

Test

Of the proposed gas exchange processes in the lungs and tissues, those performing the first option must choose the ciphers of the correct answers on the left, and the second on the right.

(1) Transfer of O 2 from the lungs to the blood. (13)
(2) Transfer of O 2 from blood to tissue. (fourteen)
(3) Transfer of CO 2 from tissues to blood. (15)
(4) Transfer of CO 2 from the blood to the lungs. (16)
(5) Uptake of O 2 by erythrocytes. (17)
(6) Release of O 2 from erythrocytes. (eighteen)
(7) Conversion of arterial blood to venous blood. (19)
(8) Conversion of venous blood into arterial. (twenty)
(9) Breaking of the chemical bond of O 2 with hemoglobin. (21)
(10) Chemical binding of O 2 to hemoglobin. (22)
(11) Capillaries in tissues. (23)
(12) Pulmonary capillaries. (24)

First Option Questions

1. Processes of gas exchange in tissues.
2. Physical processes during gas exchange.

Second Option Questions

1. Gas exchange processes in the lungs.
2. Chemical processes during gas exchange

Task

Determine the volume of carbon monoxide (IV) that is released during the decomposition of 50 g of calcium carbonate.

Carbon monoxide (IV), carbonic acid and their salts

Complex purpose of the module: know the ways of producing carbon (IV) oxide and hydroxide; describe them physical properties; know the characteristics of acid-base properties; to characterize the redox properties.

All elements of the carbon subgroup form oxides with general formula EO 2. CO 2 and SiO 2 exhibit acidic properties, GeO 2, SnO 2, PbO 2 exhibit amphoteric properties with a predominance of acidic properties, and in the subgroup from top to bottom, acidic properties weaken.

The oxidation state (+4) for carbon and silicon is very stable, therefore oxidizing properties connections are shown with great difficulty. In the germanium subgroup, the oxidizing properties of compounds (+4) are enhanced due to destabilization the highest degree oxidation.

Carbon monoxide (IV), carbonic acid and their salts

Carbon dioxide CO 2 (carbon dioxide) - under normal conditions it is a colorless and odorless gas, slightly sour taste, about 1.5 times heavier than air, soluble in water, liquefies quite easily - at room temperature it can be converted into a liquid under a pressure of about 60 10 5 Pa. When cooled to 56.2 ° C, liquid carbon dioxide solidifies and turns into a snow-like mass.

In all aggregate states consists of non-polar linear molecules. Chemical structure CO 2 is determined by sp-hybridization of the central carbon atom and the formation of additional p p-p-connections: O = C = O

Some part of the CO 2 dissolved in the will interacts with it to form carbonic acid

CO 2 + H 2 O - CO 2 H 2 O - H 2 CO 3.

Carbon dioxide is very easily absorbed by alkali solutions to form carbonates and bicarbonates:

CO 2 + 2NaOH = Na 2 CO 3 + H 2 O;

CO 2 + NaOH = NaHCO 3.

CO2 molecules are very thermally stable, decomposition begins only at a temperature of 2000єС. Therefore, carbon dioxide does not burn and does not support the combustion of conventional fuels. But in its atmosphere there are some simple substances, atoms of which show a great affinity for oxygen, for example, magnesium, when heated, ignites in an atmosphere of CO 2.

Carbonic acid and its salts

Carbonic acid H 2 CO 3 is a fragile compound, it exists only in aqueous solutions. Most of the carbon dioxide dissolved in water is in the form of hydrated CO 2 molecules, a smaller part forms carbonic acid.

Aqueous solutions in equilibrium with the CO 2 atmosphere are acidic: = 0.04 M and pH? 4.

Carbonic acid is dibasic, belongs to weak electrolytes, dissociates stepwise (K 1 = 4, 4 10? 7; K 2 = 4, 8 10? 11). Dissolving CO 2 in water establishes the following dynamic equilibrium:

H 2 O + CO 2 - CO 2 H 2 O - H 2 CO 3 - H + + HCO 3?

When heated aqueous solution With carbon dioxide, the solubility of the gas decreases, CO 2 is released from the solution, and the equilibrium shifts to the left.

Carbonic acid salts

Being dibasic, carbonic acid forms two series of salts: medium salts (carbonates) and acidic (hydrocarbonates). Most carbonic acid salts are colorless. Of carbonates, only salts are soluble in water. alkali metals and ammonium.

In water, carbonates undergo hydrolysis, and therefore their solutions have an alkaline reaction:

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

Further hydrolysis with the formation of carbonic acid under normal conditions practically does not take place.

Dissolution of hydrocarbonates in water is also accompanied by hydrolysis, but to a much lesser extent, and the medium is weakly alkaline (pH ≈ 8).

Ammonium carbonate (NH 4) 2 CO 3 is highly volatile at elevated and even normal temperatures, especially in the presence of water vapor, which causes strong hydrolysis

Strong acids and even weak acetic acid displace carbonic acid from carbonates:

K 2 CO 3 + H 2 SO 4 = K 2 SO 4 + H 2 O + CO 2 ^.

Unlike most carbonates, all bicarbonates are soluble in water. They are less stable than carbonates of the same metals and, when heated, easily decompose, turning into the corresponding carbonates:

2KHCO 3 = K 2 CO 3 + H 2 O + CO 2 ^;

Ca (HCO 3) 2 = CaCO 3 + H 2 O + CO 2 ^.

Strong acids decompose bicarbonates, like carbonates:

KHCO 3 + H 2 SO 4 = KHSO 4 + H 2 O + CO 2

From salts of carbonic acid greatest value have: sodium carbonate (soda), potassium carbonate (potash), calcium carbonate (chalk, marble, limestone), sodium bicarbonate (baking soda) and basic copper carbonate (CuOH) 2 CO 3 (malachite).

Basic salts of carbonic acid in water are practically insoluble and easily decompose when heated:

(CuOH) 2 CO 3 = 2CuO + CO 2 + H 2 O.

In general, the thermal stability of carbonates depends on the polarization properties of the ions that make up the carbonate. The more the cation has a polarizing effect on the carbonate ion, the lower the decomposition temperature of the salt. If the cation can be easily deformed, then the carbonate ion itself will also have a polarizing effect on the cation, which will lead to a sharp decrease in the decomposition temperature of the salt.

Sodium and potassium carbonates melt without decomposition, while most of the remaining carbonates decompose into metal oxide and carbon dioxide when heated.

• Designation - C (Carbon);
• Period - II;
• Group - 14 (IVa);
• Atomic mass - 12.011;
• Atomic number - 6;
• Atom radius = 77 pm;
• Covalent radius = 77 pm;
• Distribution of electrons - 1s 2 2s 2 2p 2;
• melting point = 3550 ° C;
• boiling point = 4827 ° C;
• Electronegativity (Pauling / Alpred and Rohov) = 2.55 / 2.50;
• Oxidation state: +4, +3, +2, +1, 0, -1, -2, -3, -4;
• Density (n. At.) = 2.25 g / cm 3 (graphite);
• Molar volume = 5.3 cm 3 / mol.

Carbon compounds:

Carbon in the form of charcoal has been known to man since time immemorial, therefore, it makes no sense to talk about the date of its discovery. Actually its name "carbon" got in 1787, when the book "Method of chemical nomenclature" was published, in which instead of the French name "pure coal" (charbone pur) the term "carbon" (carbone) appeared.

Carbon has the unique ability to form polymer chains of unlimited length, thereby giving rise to a huge class of compounds, which are studied in a separate branch of chemistry - organic chemistry... Organic carbon compounds are at the heart of life on earth, therefore, the importance of carbon, as chemical element, it makes no sense to speak - he is the basis of life on Earth.

Now let's look at carbon from the point of view of inorganic chemistry.

Rice. The structure of the carbon atom.

The electronic configuration of carbon is 1s 2 2s 2 2p 2 (see. Electronic structure of atoms). At the external energy level, carbon has 4 electrons: 2 paired at the s-sublevel + 2 unpaired at p-orbitals. When a carbon atom passes into an excited state (requires energy consumption), one electron from the s-sublevel "leaves" its pair and goes to the p-sublevel, where there is one free orbital. Thus, in an excited state electronic configuration carbon atom takes the following form: 1s 2 2s 1 2p 3.

Rice. The transition of a carbon atom to an excited state.

Such "castling" significantly expands the valence capabilities of carbon atoms, which can take the oxidation state from +4 (in compounds with active non-metals) to -4 (in compounds with metals).

In the unexcited state, the carbon atom in the compounds has a valency of 2, for example, CO (II), and in the excited state it has a valence of 4: CO 2 (IV).

The "uniqueness" of the carbon atom lies in the fact that there are 4 electrons on its external energy level, therefore, to complete the level (which, in fact, the atoms of any chemical element strive for), it can, with the same "success", both give and attach electrons with the formation of covalent bonds (see. Covalent bond).

Carbon as a simple substance

As a simple substance, carbon can be in the form of several allotropic modifications:

• Diamond
• Graphite
• Fullerene
• Carbin

Diamond

Rice. The crystal lattice of a diamond.

Diamond properties:

• colorless crystalline substance;
• the hardest substance in nature;
• has a strong refractive effect;
• poorly conducts heat and electricity.

Rice. Diamond tetrahedron.

The exceptional hardness of diamond is explained by the structure of its crystal lattice, which has the shape of a tetrahedron - in the center of the tetrahedron there is a carbon atom, which is bonded by equally strong bonds with four neighboring atoms that form the vertices of the tetrahedron (see the figure above). This "construction", in turn, is associated with neighboring tetrahedra.

Graphite

Rice. Crystal lattice of graphite.

Graphite properties:

• a soft crystalline gray substance of a layered structure;
• has a metallic luster;
• conducts electricity well.

In graphite, carbon atoms form regular hexagons lying in one plane, organized in endless layers.

In graphite, chemical bonds between adjacent carbon atoms are formed by three valence electrons of each atom (shown in blue in the figure below), while the fourth electron (shown in red) of each carbon atom is located on a p-orbital lying perpendicular to the plane of the graphite layer. does not participate in the formation of covalent bonds in the plane of the layer. Its "purpose" is different - interacting with its "brother" lying in an adjacent layer, it provides a bond between the graphite layers, and the high mobility of p-electrons determines the good electrical conductivity of graphite.

Rice. Distribution of the orbitals of the carbon atom in graphite.

Fullerene

Rice. Fullerene crystal lattice.

Fullerene properties:

• a fullerene molecule is a collection of carbon atoms enclosed in hollow spheres such as a soccer ball;
• it is a yellow-orange fine crystalline substance;
• melting point = 500-600 ° C;
• semiconductor;
• is part of the shungite mineral.

Carbin

Carbine properties:

• inert black substance;
• consists of polymeric linear molecules in which atoms are linked by alternating single and triple bonds;
• semiconductor.

Chemical properties of carbon

Under normal conditions, carbon is an inert substance, but when heated, it can react with a variety of simple and complex substances.

It has already been said above that at the external energy level of carbon there are 4 electrons (neither there nor here), therefore carbon can both donate and receive electrons, exhibiting reducing properties in some compounds, and oxidizing in others.

Carbon is reducing agent in reactions with oxygen and other elements with a higher electronegativity (see the table of electronegativity of elements):

• when heated in air, it burns (with an excess of oxygen with the formation of carbon dioxide; with a lack of it - carbon monoxide (II)):
  C + O 2 = CO 2;
  2C + O 2 = 2CO.
• reacts at high temperatures with sulfur vapors, easily interacts with chlorine, fluorine:
  C + 2S = CS 2
  C + 2Cl 2 = CCl 4
  2F 2 + C = CF 4
• when heated, it reduces many metals and non-metals from oxides:
  C 0 + Cu +2 O = Cu 0 + C +2 O;
  C 0 + C +4 O 2 = 2C +2 O
• at a temperature of 1000 ° C, it reacts with water (gasification process), with the formation of water gas:
  C + H 2 O = CO + H 2;

Carbon exhibits oxidizing properties in reactions with metals and hydrogen:

• reacts with metals to form carbides:
  Ca + 2C = CaC 2
• interacting with hydrogen, carbon forms methane:
  C + 2H 2 = CH 4

Carbon is obtained by thermal decomposition of its compounds or by pyrolysis of methane (at high temperatures):
CH 4 = C + 2H 2.

Application of carbon

Carbon compounds are widely used in national economy, it is not possible to list all of them, we will indicate only a few:

• graphite is used for the manufacture of pencil leads, electrodes, melting crucibles, as a neutron moderator in nuclear reactors as a lubricant;
• diamonds are used in jewelry, as a cutting tool, in drilling equipment, as an abrasive material;
• as a reducing agent, carbon is used to obtain certain metals and non-metals (iron, silicon);
• carbon makes up the bulk of activated carbon, which has found widespread use both in everyday life (for example, as an adsorbent for purifying air and solutions), and in medicine (activated carbon tablets) and in industry (as a carrier for catalytic additives, polymerization catalyst etc.).