• Designation - C (Carbon);
• Period - II;
• Group - 14 (IVa);
• Atomic mass - 12.011;
• Atomic number - 6;
• Radius of an atom = 77 pm;
• Covalent radius = 77 pm;
• The distribution of electrons - 1s 2 2s 2 2p 2;
• melting point = 3550°C;
• boiling point = 4827°C;
• Electronegativity (according to Pauling / according to Alpred and Rochov) = 2.55 / 2.50;
• Oxidation state: +4, +3, +2, +1, 0, -1, -2, -3, -4;
• Density (n.a.) \u003d 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, carbon got its name in 1787, when the book "Method of Chemical Nomenclature" was published, in which the term "carbon" (carbone) appeared instead of the French name "pure coal" (charbone pur).

Carbon has the unique ability to form polymer chains of unlimited length, thus giving rise to a huge class of compounds, which are studied by a separate branch of chemistry - organic chemistry. Organic compounds of carbon underlie terrestrial life, therefore, about the importance of carbon, as chemical element, it makes no sense to say - he is the basis of life on Earth.

Now consider 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 outer energy level, carbon has 4 electrons: 2 paired on the s-sublevel + 2 unpaired on the p-orbitals. When a carbon atom goes into an excited state (requires energy costs), one electron from the s-sublevel "leaves" its pair and goes to the p-sublevel, where there is one free orbital. Thus, in the excited state, the electronic configuration of the carbon atom takes the following form: 1s 2 2s 1 2p 3 .

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

This "castling" significantly expands the valence possibilities 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 compounds has a valence of 2, for example, CO (II), and in an excited state it has 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 both give and attach with the same "success" electrons to form 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
• Carbine

Diamond

Rice. The crystal lattice of a diamond.

Diamond Properties:

• colorless crystalline substance;
• the hardest substance in nature;
• has a strong refractive effect;
• poor conductor of 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 connected by equally strong bonds with four neighboring atoms that form the vertices of the tetrahedron (see the figure above). Such a "construction" is, in turn, connected with neighboring tetrahedra.

Graphite

Rice. Graphite crystal lattice.

Graphite properties:

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

In graphite, carbon atoms form regular hexagons lying in the same plane, organized into infinite layers.

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

Rice. Distribution of orbitals of carbon atom in graphite.

fullerene

Rice. Fullerene crystal lattice.

Fullerene properties:

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

Carbine

Carbine properties:

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

Chemical properties of carbon

At 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 there are 4 electrons on the external energy level of carbon (neither there nor here), therefore carbon can both donate electrons and accept them, manifesting in some compounds restorative properties, and in others - oxidizing.

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

• when heated in air, it burns (with an excess of oxygen with the formation of carbon dioxide; with its lack - carbon monoxide (II)):
  C + O 2 \u003d CO 2;
  2C + O 2 \u003d 2CO.
• reacts at high temperatures with sulfur vapor, easily interacts with chlorine, fluorine:
  C+2S=CS2
  C + 2Cl 2 = CCl 4
  2F2+C=CF4
• when heated, it restores many metals and non-metals from oxides:
  C 0 + Cu +2 O \u003d Cu 0 + C +2 O;
  C 0 + C +4 O 2 \u003d 2C +2 O
• reacts with water at a temperature of 1000°C (gasification process) to form water gas:
  C + H 2 O \u003d 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 temperature):
CH 4 \u003d 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 wide application both in everyday life (for example, as an adsorbent for cleaning air and solutions), and in medicine (activated carbon tablets) and in industry (as a carrier for catalytic additives, polymerization catalyst etc.).

(IV) (CO 2, carbon dioxide, carbon dioxide) It is a colorless, tasteless, odorless gas that is heavier than air and soluble in water.

IN normal conditions solid carbon dioxide passes directly into the gaseous state, bypassing the liquid state.

With a large amount of carbon monoxide, people begin to suffocate. Concentrations of more than 3% lead to rapid breathing, and more than 10% there is loss of consciousness and death.

Chemical properties of carbon monoxide.

carbon monoxide - it is carbonic anhydride H 2 CO 3.

When carbon monoxide is passed through calcium hydroxide (lime water), a white precipitate is observed:

Ca(Oh) 2 + CO 2 = CaCO 3 ↓ + H 2 O

If carbon dioxide is taken in excess, then the formation of hydrocarbonates is observed, which dissolve in water:

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

which then decompose when heated.

2KNCO 3 \u003d K 2 CO 3 + H 2 O + CO 2

The use of carbon monoxide.

The use of carbon dioxide in various areas industry. IN chemical production- as a coolant.

In the food industry, it is used as a preservative E290. Although he was assigned "conditionally safe", in fact it is not. Doctors have proven that frequent eating of E290 leads to the accumulation of a toxic poisonous compound. Therefore, you need to carefully read the labels on the products.

Carbon monoxide (IV) (carbon dioxide, carbon dioxide) under normal conditions is a colorless gas, heavier than air, thermally stable, and when compressed and cooled, it easily turns into a liquid and solid state.

Density - 1.997 g / l. Solid CO2, called dry ice, sublimates at room temperature. Poorly soluble in water, partially reacting with it. Shows acidic properties. It is restored by active metals, hydrogen and carbon.

Chemical formula of carbon monoxide 4
Chemical formula of carbon monoxide (IV) CO2. It shows that this molecule contains one carbon atom (Ar = 12 a.m.u.) and two oxygen atoms (Ar = 16 a.m.u.). According to the chemical formula, you can calculate the molecular weight of carbon monoxide (IV):

Mr(CO2) = Ar(C) + 2×Ar(O);

Mr(CO2) = 12+ 2×16 = 12 + 32 = 44.

Examples of problem solving
EXAMPLE 1
Task When burning 26.7 g of amino acid (CxHyOzNk) in excess of oxygen, 39.6 g of carbon monoxide (IV), 18.9 g of water and 4.2 g of nitrogen are formed. Determine the amino acid formula.
Solution Let's draw up a scheme for the combustion reaction of an amino acid, denoting the number of carbon, hydrogen, oxygen and nitrogen atoms as "x", "y", "z" and "k", respectively:
CxHyOzNk+ Oz→CO2 + H2O + N2.

Let us determine the masses of the elements that make up this substance. Relative atomic mass values ​​taken from Periodic table DI. Mendeleev, rounded to integers: Ar(C) = 12 a.m.u., Ar(H) = 1 a.m.u., Ar(O) = 16 a.m.u., Ar(N) = 14 amu

M(C) = n(C)×M(C) = n(CO2)×M(C) = ×M(C);

M(H) = n(H)×M(H) = 2×n(H2O)×M(H) = ×M(H);

Calculate the molar masses of carbon dioxide and water. As is known, molar mass molecule is equal to the sum of the relative atomic masses of the atoms that make up the molecule (M = Mr):

M(CO2) = Ar(C) + 2×Ar(O) = 12+ 2×16 = 12 + 32 = 44 g/mol;

M(H2O) = 2×Ar(H) + Ar(O) = 2×1+ 16 = 2 + 16 = 18 g/mol.

M(C)=×12=10.8 g;

M(H) = 2×18.9 / 18×1= 2.1 g.

M(O) \u003d m (CxHyOzNk) - m (C) - m (H) - m (N) \u003d 26.7 - 10.8 - 2.1 - 4.2 \u003d 9.6 g.

Let's define chemical formula amino acids:

X:y:z:k = m(C)/Ar(C) : m(H)/Ar(H) : m(O)/Ar(O) : m(N)/Ar(N);

X:y:z:k= 10.8/12:2.1/1:9.6/16: 4.2/14;

X:y:z:k= 0.9: 2.1: 0.41: 0.3 = 3: 7: 1.5: 1 = 6: 14: 3: 2.

Means the simplest formula amino acids C6H14O3N2.

Answer C6H14O3N2
EXAMPLE 2
Task Make the simplest formula of a compound in which the mass fractions of elements are approximately equal: carbon - 25.4%, hydrogen - 3.17%, oxygen - 33.86%, chlorine - 37.57%.
Solution The mass fraction of element X in a molecule of composition HX is calculated by the following formula:
ω (X) = n × Ar (X) / M (HX) × 100%.

Let us denote the number of carbon atoms in the molecule as "x", the number of hydrogen nitrogen atoms as "y", the number of oxygen atoms as "z", and the number of chlorine atoms as "k".

Find the corresponding relative atomic masses elements of carbon, hydrogen, oxygen and chlorine (the values ​​of relative atomic masses taken from the Periodic Table of D.I. Mendeleev will be rounded up to whole numbers).

Ar(C) = 12; Ar(H) = 14; Ar(O) = 16; Ar(Cl) = 35.5.

We divide the percentage of elements by the corresponding relative atomic masses. Thus, we will find the relationship between the number of atoms in the molecule of the compound:

X:y:z:k = ω(C)/Ar(C) : ω(H)/Ar(H) : ω(O)/Ar(O) : ω(Cl)/Ar(Cl);

X:y:z:k= 25.4/12: 3.17/1: 33.86/16: 37.57/35.5;

X:y:z:k= 2.1: 3.17: 2.1: 1.1 = 2: 3: 2: 1.

This means that the simplest formula for the combination of carbon, hydrogen, oxygen and chlorine will be C2H3O2Cl.

Carbon (C) is a typical non-metal; in the periodic system is in the 2nd period of the IV group, the main subgroup. Ordinal number 6, Ar = 12.011 amu, nuclear charge +6.

Physical Properties: carbon forms many allotropic modifications: diamond- one of the most solids, graphite, coal, soot.

A carbon atom has 6 electrons: 1s 2 2s 2 2p 2 . The last two electrons are located in separate p-orbitals and are unpaired. In principle, this pair could occupy one orbital, but in this case the interelectron repulsion strongly increases. For this reason, one of them takes 2p x, and the other, either 2p y , or 2p z-orbitals.

The difference between the energies of the s- and p-sublevels of the outer layer is small, therefore, the atom quite easily passes into an excited state, in which one of the two electrons from the 2s-orbital passes to a free one. 2r. A valence state arises having the configuration 1s 2 2s 1 2p x 1 2p y 1 2p z 1 . It is this state of the carbon atom that is characteristic of the diamond lattice - the tetrahedral spatial arrangement of hybrid orbitals, the same bond length and energy.

This phenomenon is known to be called sp 3 -hybridization, and the resulting functions are sp 3 -hybrid . The formation of four sp 3 bonds provides the carbon atom with a more stable state than three rr- and one s-s-bond. In addition to sp 3 hybridization, sp 2 and sp hybridization are also observed at the carbon atom . In the first case, there is a mutual overlap s- and two p-orbitals. Three equivalent sp 2 - hybrid orbitals are formed, located in the same plane at an angle of 120 ° to each other. The third orbital p is unchanged and directed perpendicular to the plane sp2.

In sp hybridization, the s and p orbitals overlap. An angle of 180° arises between the two equivalent hybrid orbitals formed, while the two p-orbitals of each of the atoms remain unchanged.

Allotropy of carbon. diamond and graphite

In a graphite crystal, carbon atoms are located in parallel planes, occupying the vertices of regular hexagons in them. Each of the carbon atoms is linked to three adjacent sp 2 hybrid bonds. Between parallel planes, the connection is carried out due to van der Waals forces. Free p-orbitals of each of the atoms are directed perpendicular to the planes of covalent bonds. Their overlap explains the additional π-bond between carbon atoms. So from the valence state in which carbon atoms are in a substance, the properties of this substance depend.

Chemical properties of carbon

The most characteristic oxidation states: +4, +2.

At low temperatures, carbon is inert, but when heated, its activity increases.

Carbon as a reducing agent:

- with oxygen
C 0 + O 2 - t ° \u003d CO 2 carbon dioxide
with a lack of oxygen - incomplete combustion:
2C 0 + O 2 - t° = 2C +2 O carbon monoxide

- with fluorine
C + 2F 2 = CF 4

- with steam
C 0 + H 2 O - 1200 ° \u003d C + 2 O + H 2 water gas

— with metal oxides. In this way metal is smelted from ore.
C 0 + 2CuO - t ° \u003d 2Cu + C +4 O 2

- with acids - oxidizing agents:
C 0 + 2H 2 SO 4 (conc.) \u003d C +4 O 2 + 2SO 2 + 2H 2 O
С 0 + 4HNO 3 (conc.) = С +4 O 2 + 4NO 2 + 2H 2 O

- forms carbon disulfide with sulfur:
C + 2S 2 \u003d CS 2.

Carbon as an oxidizing agent:

- forms carbides with some metals

4Al + 3C 0 \u003d Al 4 C 3

Ca + 2C 0 \u003d CaC 2 -4

- with hydrogen - methane (as well as a huge amount organic compounds)

C 0 + 2H 2 \u003d CH 4

- with silicon, forms carborundum (at 2000 ° C in an electric furnace):

Finding carbon in nature

Free carbon occurs as diamond and graphite. In the form of compounds, carbon is found in minerals: chalk, marble, limestone - CaCO 3, dolomite - MgCO 3 * CaCO 3; bicarbonates - Mg (HCO 3) 2 and Ca (HCO 3) 2, CO 2 is part of the air; carbon is the main component of natural organic compounds - gas, oil, coal, peat, is part of organic matter, proteins, fats, carbohydrates, amino acids that are part of living organisms.

Inorganic carbon compounds

Neither C 4+ ions, nor C 4- - under any normal chemical processes are not formed: in carbon compounds there are covalent bonds of different polarity.

Carbon monoxide (II) SO

Carbon monoxide; colorless, odorless, sparingly soluble in water, soluble in organic solvents, poisonous, bp = -192°C; t sq. = -205°C.

Receipt
1) In industry (in gas generators):
C + O 2 = CO 2

2) In the laboratory - thermal decomposition of formic or oxalic acid in the presence of H 2 SO 4 (conc.):
HCOOH = H2O + CO

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

Chemical properties

Under ordinary conditions, CO is inert; when heated - reducing agent; non-salt-forming oxide.

1) with oxygen

2C +2 O + O 2 \u003d 2C +4 O 2

2) with metal oxides

C +2 O + CuO \u003d Cu + C +4 O 2

3) with chlorine (in the light)

CO + Cl 2 - hn \u003d COCl 2 (phosgene)

4) reacts with alkali melts (under pressure)

CO + NaOH = HCOONa (sodium formate)

5) forms carbonyls with transition metals

Ni + 4CO - t° = Ni(CO) 4

Fe + 5CO - t° = Fe(CO) 5

Carbon monoxide (IV) CO2

Carbon dioxide, colorless, odorless, solubility in water - 0.9V CO 2 dissolves in 1V H 2 O (under normal conditions); heavier than air; t°pl.= -78.5°C (solid CO 2 is called "dry ice"); does not support combustion.

Receipt

1. Thermal decomposition of salts of carbonic acid (carbonates). Limestone firing:

CaCO 3 - t ° \u003d CaO + CO 2

1. action strong acids for carbonates and bicarbonates:

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

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

ChemicalpropertiesCO2
Acid oxide: reacts with basic oxides and bases to form carbonic acid salts

Na 2 O + CO 2 \u003d Na 2 CO 3

2NaOH + CO 2 \u003d Na 2 CO 3 + H 2 O

NaOH + CO 2 \u003d NaHCO 3

May exhibit oxidizing properties at elevated temperatures

C +4 O 2 + 2Mg - t ° \u003d 2Mg +2 O + C 0

Qualitative reaction

Turbidity of lime water:

Ca (OH) 2 + CO 2 \u003d CaCO 3 ¯ (white precipitate) + H 2 O

It disappears when CO 2 is passed through lime water for a long time, because. insoluble calcium carbonate is converted to soluble bicarbonate:

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

carbonic acid and itssalt

H2CO3 — Weak acid, exists only in aqueous solution:

CO 2 + H 2 O ↔ H 2 CO 3

Dual base:
H 2 CO 3 ↔ H + + HCO 3 - Acid salts - bicarbonates, bicarbonates
HCO 3 - ↔ H + + CO 3 2- Medium salts - carbonates

All properties of acids are characteristic.

Carbonates and bicarbonates can be converted into each other:

2NaHCO 3 - t ° \u003d Na 2 CO 3 + H 2 O + CO 2

Na 2 CO 3 + H 2 O + CO 2 \u003d 2NaHCO 3

Metal carbonates (except alkali metals) when heated, decarboxylate to form an oxide:

CuCO 3 - t ° \u003d CuO + CO 2

Qualitative reaction- "boiling" under the action of a strong acid:

Na 2 CO 3 + 2HCl \u003d 2NaCl + H 2 O + CO 2

CO 3 2- + 2H + = H 2 O + CO 2

Carbides

calcium carbide:

CaO + 3 C = CaC 2 + CO

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

Acetylene is released when zinc, cadmium, lanthanum and cerium carbides react with water:

2 LaC 2 + 6 H 2 O \u003d 2La (OH) 3 + 2 C 2 H 2 + H 2.

Be 2 C and Al 4 C 3 are decomposed by water to form methane:

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

Titanium carbides TiC, tungsten W 2 C (hard alloys), silicon SiC (carborundum - as an abrasive and material for heaters) are used in technology.

cyanides

obtained by heating soda in an atmosphere of ammonia and carbon monoxide:

Na 2 CO 3 + 2 NH 3 + 3 CO \u003d 2 NaCN + 2 H 2 O + H 2 + 2 CO 2

Hydrocyanic acid HCN is an important chemical industry product widely used in organic synthesis. Its world production reaches 200 thousand tons per year. Electronic structure cyanide anion, similarly to carbon monoxide (II), such particles are called isoelectronic:

C = O:[:C = N:]-

Cyanides (0.1-0.2% water solution) are used in gold mining:

2 Au + 4 KCN + H 2 O + 0.5 O 2 \u003d 2 K + 2 KOH.

When cyanide solutions are boiled with sulfur or when solids are fused, thiocyanates:
KCN + S = KSCN.

When cyanides of low-active metals are heated, cyanide is obtained: Hg (CN) 2 \u003d Hg + (CN) 2. cyanide solutions are oxidized to cyanates:

2KCN + O2 = 2KOCN.

Cyanic acid exists in two forms:

H-N=C=O; H-O-C = N:

In 1828, Friedrich Wöhler (1800-1882) obtained urea from ammonium cyanate: NH 4 OCN \u003d CO (NH 2) 2 by evaporating an aqueous solution.

This event is usually seen as the victory of synthetic chemistry over "vitalistic theory".

There is an isomer of cyanic acid - fulminic acid

H-O-N=C.
Its salts (mercury fulminate Hg(ONC) 2) are used in impact igniters.

Synthesis urea(carbamide):

CO 2 + 2 NH 3 \u003d CO (NH 2) 2 + H 2 O. At 130 0 C and 100 atm.

Urea is an amide of carbonic acid, there is also its "nitrogen analogue" - guanidine.

Carbonates

The most important inorganic compounds of carbon are salts of carbonic acid (carbonates). H 2 CO 3 is a weak acid (K 1 \u003d 1.3 10 -4; K 2 \u003d 5 10 -11). Carbonate buffer supports carbon dioxide balance in the atmosphere. The oceans have a huge buffer capacity because they are an open system. The main buffer reaction is the equilibrium during the dissociation of carbonic acid:

H 2 CO 3 ↔ H + + HCO 3 -.

With a decrease in acidity, additional absorption of carbon dioxide from the atmosphere occurs with the formation of acid:
CO 2 + H 2 O ↔ H 2 CO 3.

With an increase in acidity, carbonate rocks (shells, chalk and limestone deposits in the ocean) dissolve; this compensates for the loss of hydrocarbonate ions:

H + + CO 3 2- ↔ HCO 3 -

CaCO 3 (tv.) ↔ Ca 2+ + CO 3 2-

Solid carbonates are converted into soluble hydrocarbons. It is this process of chemical dissolution of excess carbon dioxide that counteracts the "greenhouse effect" - global warming due to the absorption of the Earth's thermal radiation by carbon dioxide. Approximately one third of the world's production of soda (sodium carbonate Na 2 CO 3) is used in the manufacture of glass.

Carbon

In the free state, carbon forms 3 allotropic modifications: diamond, graphite and artificially obtained carbine.

In a diamond crystal, each carbon atom is bound by strong covalent bonds to four others placed at equal distances around it.

All carbon atoms are in a state of sp 3 hybridization. The atomic crystal lattice of diamond has a tetrahedral structure.

Diamond is a colorless, transparent, highly refractive substance. It has the highest hardness among all known substances. Diamond is brittle, refractory, poorly conducts heat and electricity. Small distances between adjacent carbon atoms (0.154 nm) determine the rather high density of diamond (3.5 g/cm 3 ).

In the crystal lattice of graphite, each carbon atom is in a state of sp 2 hybridization and forms three strong covalent bonds with carbon atoms located in the same layer. Three electrons of each atom, carbon, participate in the formation of these bonds, and the fourth valence electrons form n-bonds and are relatively free (mobile). They determine the electrical and thermal conductivity of graphite.

Length covalent bond between adjacent carbon atoms in the same plane is 0.152 nm, and the distance between C atoms in different layers is 2.5 times greater, so the bonds between them are weak.

Graphite is an opaque, soft, greasy to the touch substance of a gray-black color with a metallic sheen; conducts heat and electricity well. Graphite has a lower density than diamond and is easily split into thin flakes.

The disordered structure of fine-grained graphite underlies the structure various forms amorphous carbon, the most important of which are coke, brown and bituminous coals, soot, activated (active) carbon.

This allotropic modification of carbon is obtained by catalytic oxidation (dehydropolycondensation) of acetylene. Carbyne is a chain polymer that has two forms:

C=C-C=C-... and...=C=C=C=

Carbin has semiconductor properties.

At ordinary temperature, both modifications of carbon (diamond and graphite) are chemically inert. Fine-crystalline forms of graphite - coke, soot, activated carbon - are more reactive, but, as a rule, after they are preheated to a high temperature.

1. Interaction with oxygen

C + O 2 \u003d CO 2 + 393.5 kJ (in excess O 2)

2C + O 2 \u003d 2CO + 221 kJ (with a lack of O 2)

Coal burning is one of the most important sources energy.

2. Interaction with fluorine and sulfur.

C + 2F 2 = CF 4 carbon tetrafluoride

C + 2S \u003d CS 2 carbon disulfide

3. Coke is one of the most important reducing agents used in industry. In metallurgy, it is used to produce metals from oxides, for example:

ZS + Fe 2 O 3 \u003d 2Fe + ZSO

C + ZnO = Zn + CO

4. When carbon interacts with oxides of alkali and alkaline earth metals The reduced metal combines with carbon to form carbide. For example: 3C + CaO \u003d CaC 2 + CO calcium carbide

5. Coke is also used to obtain silicon:

2C + SiO 2 \u003d Si + 2CO

6. With an excess of coke, silicon carbide (carborundum) SiC is formed.

Obtaining "water gas" (solid fuel gasification)

By passing water vapor through hot coal, a combustible mixture of CO and H 2 is obtained, called water gas:

C + H 2 O \u003d CO + H 2

7. Reactions with oxidizing acids.

Activated or charcoal, when heated, reduces the anions NO 3 - and SO 4 2- from concentrated acids:

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

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

8. Reactions with molten alkali metal nitrates

In KNO 3 and NaNO 3 melts, crushed coal burns intensively with the formation of a blinding flame:

5C + 4KNO 3 \u003d 2K 2 CO 3 + ZCO 2 + 2N 2

1. Formation of salt-like carbides with active metals.

A significant weakening of the non-metallic properties of carbon is expressed in the fact that its functions as an oxidizing agent are manifested to a much lesser extent than the reducing functions.

2. Only in reactions with active metals, carbon atoms pass into negatively charged ions C -4 and (C \u003d C) 2-, forming salt-like carbides:

ZS + 4Al \u003d Al 4 C 3 aluminum carbide

2C + Ca \u003d CaC 2 calcium carbide

3. Ionic type carbides are very unstable compounds, they easily decompose under the action of acids and water, which indicates the instability of negatively charged carbon anions:

Al 4 C 3 + 12H 2 O \u003d ZSN 4 + 4Al (OH) 3

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

4. Formation of covalent compounds with metals

In melts of mixtures of carbon with transition metals, carbides are formed predominantly with a covalent type of bond. Their molecules have a variable composition, and substances in general are close to alloys. Such carbides are highly resistant, they are chemically inert with respect to water, acids, alkalis and many other reagents.

5. Interaction with hydrogen

At high T and P, in the presence of a nickel catalyst, carbon combines with hydrogen:

C + 2H 2 → CH 4

The reaction is very reversible and has no practical significance.

Carbon monoxide(II)– CO

(carbon monoxide, carbon monoxide, carbon monoxide)

Physical properties: colorless poisonous gas, tasteless and odorless, burns with a bluish flame, lighter than air, poorly soluble in water. The concentration of carbon monoxide in the air of 12.5-74% is explosive.

Receipt:

1) In industry

C + O 2 \u003d CO 2 + 402 kJ

CO 2 + C \u003d 2CO - 175 kJ

In gas generators, water vapor is sometimes blown through hot coal:

C + H 2 O \u003d CO + H 2 - Q,

a mixture of CO + H 2 - called synthesis - gas.

2) In the laboratory- thermal decomposition of formic or oxalic acid in the presence of H 2 SO 4 (conc.):

HCOOH t˚C, H2SO4 → H2O + CO

H 2 C 2 O 4 t˚C,H2SO4 → CO + CO 2 + H 2 O

Chemical properties:

Under ordinary conditions, CO is inert; when heated - reducing agent;

CO - non-salt-forming oxide.

1) with oxygen

2C +2 O + O 2 t ˚ C → 2C +4 O 2

2) with metal oxides CO + Me x O y \u003d CO 2 + Me

C +2 O + CuO t ˚ C → Сu + C +4 O 2

3) with chlorine (in the light)

CO + Cl 2 light → COCl 2 (phosgene is a poisonous gas)

4)* reacts with alkali melts (under pressure)

CO + NaOH P → HCOONa (sodium formate)

The effect of carbon monoxide on living organisms:

Carbon monoxide is dangerous because it makes it impossible for the blood to carry oxygen to vital organs like the heart and brain. Carbon monoxide combines with hemoglobin, which carries oxygen to the cells of the body, as a result of which it becomes unsuitable for transporting oxygen. Depending on the amount inhaled, carbon monoxide impairs coordination, exacerbates cardiovascular disease and causes fatigue, headache, weakness, The effect of carbon monoxide on human health depends on its concentration and time of exposure to the body. A concentration of carbon monoxide in the air above 0.1% leads to death within one hour, and a concentration of more than 1.2% within three minutes.

Applications of carbon monoxide:

Carbon monoxide is mainly used as a combustible gas mixed with nitrogen, the so-called generator or air gas, or water gas mixed with hydrogen. In metallurgy for the recovery of metals from their ores. To obtain high purity metals by decomposition of carbonyls.

Carbon monoxide (IV) CO2 - carbon dioxide

Physical properties: Carbon dioxide, colorless, odorless, solubility in water - 0.9V CO 2 dissolves in 1V H 2 O (under normal conditions); heavier than air; t°pl.= -78.5°C (solid CO 2 is called "dry ice"); does not support combustion.

Molecule structure:

Carbon dioxide has the following electron and structural formula -

3. Combustion of carbonaceous substances:

CH 4 + 2O 2 → 2H2O+CO2

4. With slow oxidation in biochemical processes (respiration, decay, fermentation)

Chemical properties: