Carbon (eng. Carbon, Franz. Carbone, it. Kohlenstoff) in the form of coal, soot and soot are known to humanity from time immemorial; About 100 thousand years ago, when our ancestors captured fire, they were daily dealing with coal and soot. Probably, very early people became acquainted with allotropic carbon modes - diamond and graphite, as well as fossil coal. It is not surprising that the burning of carbon-containing substances was one of the first chemical processes interested in a person. Since the burning substance disappeared, devoured by fire, the burning was considered as the process of decomposition of the substance, and therefore coal (or carbon) were not considered an element. The element was a fire - a phenomenon accompanying combustion; In the exercises on elements of antiquity, the fire typically appears as one of the elements. At the turn of the XVII - XVIII centuries. A phlogiston theory extended beheads and a panel arose. This theory recognized the presence of a special elementary substance in each combustible body - the weightless fluid - phlogiston, catering in the process of burning. Since, when combustion of a large amount of coal, only a little ash remains, the flogistic believed that coal was almost pure phlogiston. This was explained, in particular, the "flustering" action of coal - its ability to restore metals from the "famous" and ore. Latest Flogistics, Reomyur, Bergman, and others, have already begun to understand that the coal is an elementary substance. However, for the first time, the "pure coal" was recognized by Lavoisier, which studied the combustion process in the air and oxygen of coal and other substances. In the book of Hiton de Morvo, Lavoisier, Bertolls and Fourkrua "Method of Chemical Nomenclature" (1787) The name "Carbon" (Carbone) appeared instead of French "Clean Coal" (Charbone Pur). Under the same name, carbon appears in the "table of simple bodies" in the "elementary textbook of chemistry" Lavoisier. In 1791, the English Chemist Tennant was first received free carbon; He missed the phosphorus pair over the calcined chalk, as a result of which the calcium phosphate and carbon was formed. The fact that diamond is burning with strong heating without a balance, it has been known for a long time. Back in 1751, the French king Franz I agreed to give Diamond and Rubin for burning experiments, after which these experiments even became fashionable. It turned out that only diamond burns, and ruby \u200b\u200b(aluminum oxide with chromium admissions) withstands prolonged heating in the focus of the incendiary lens. Lavoisier has put a new diamond burning experience with a large incendiary machine, concluded that the diamond is crystalline carbon. The second altotrope of carbon - graphite in the alochemical period was considered a modified lead glitter and was called Plumbago; Only in 1740 Pott found the lack of lead in graphite any impurity. Shelele explored graphite (1779) and being Flocistry found him with a sulfur body of a special kind, special mineral coal containing aircroic acid (CO 2,) and a large amount of phlogiston.
Twenty years later, Hyton de Morvo by cautious heating turned diamond to graphite, and then into coalic acid.
The international name Carboneum comes from Lat. CARBO (coal). The word is very ancient origin. It is compared with Cremare - burn; Root Sag, Cal, Russian Gar, Gal, Goal, Sanskrit Stowe means boiling, cook. With the word "Carbo" related to the names of carbon and in other European languages \u200b\u200b(Carbon, Charbone, etc.). German Kohlenstoff comes from Kohle - coal (Starogerman Kolo, Swedish Kylla - heated). Ancient Russian refinery, or Ugrati (burn, beaten) has a root of gar, or mountains, with a possible transition to the goal; Coal in Old Russian Yugil, or coal, the same origin. The word Almaz (Diamante) comes from ancient Greek - disadvantageous, adamant, solid, and graphite from Greek - I write.
Carbon (Latin carboneum), C, chemical element IV group of periodic Mendeleev system, atomic number 6, atomic weight 12,011. Two stable isotop are known: 12 C (98.892%) and 13 C (1.108%). From radioactive isotopes, 14 C is most important with a half-life (T \u003d 5.6? 10 3 years). Small amounts 14 C (about 2? 10-10% by weight) are constantly forming in the upper layers of the atmosphere under the action of cosmic radiation neutrons on a nitrogen isotope 14 n. According to the specific activity of the isotope 14 C in the remains of biogenic origin, their age is determined. 14 C is widely used as .
Historical reference . W. is known with deep antiquity. Charcoal served to restore metals from ores, diamond - like a gem. Graphite for the manufacture of crucibles and pencils began to be used much later.
In 1778 K. Shelele, Heated graphite with Selutyrah, discovered that, as well as when heating coal with saltort, carbon dioxide is distinguished. Chemical composition Diamond was established as a result of experiments A. Lavoisier (1772) to study the burning of diamond in air and research S. Tennant (1797), which has proven that the same amounts of diamond and coal are given in oxidation equal amounts of carbon dioxide. W. was recognized as a chemical element in 1789 lavanise. Latin name Carboneum W. received from Carbo - coal.
Distribution in nature. The average content of U. in earth Kore 2.3? 10 -2% by weight (1? 10 -2 in ultrasound, 1? 10 -2 - in the main, 2? 10 -2 - on average, 3? 10 -2 - in acidic rocks). W. accumulates in the upper part of the earth's crust (biosphere): in a living substance 18% of US, the wood is 50%, a stone corner of 80%, oil 85%, anthracite 96%. A significant part of W. Lithosphere is concentrated in limestone and dolomites.
The number of own minerals U. - 112; An exceptionally large number of organic compounds of U. - hydrocarbons and their derivatives.
With the accumulation of W. In the earth's crust is associated with the accumulation and many others. Elements sorbed by organic matter and precipitating in the form of insoluble carbonates, etc. A large geochemical role in the earth's crust is played by CO 2 and coal acid. A huge amount of CO 2 stands out at a volcanism - in the history of the Earth, it was the main source of U. for the biosphere.
Compared to an average content in the earth's crust, humanity in extremely large quantities extracts W. from subsoil (coal, oil, natural gas), since these fossils are the main source of energy.
A huge geochemical value has a cycle of U.
W. Widespread also in space; In the sun, it ranks 4th after hydrogen, helium and oxygen.
Physics I. chemical properties. Four crystalline modifications are known: graphite, diamond, carbines and lansdalet. Graphite is gray-black, opaque, fat to the touch, scaly, very soft mass with a metal glitter. Built from crystals of a hexagonal structure: A \u003d 2.462 A, C \u003d 6.701 A. For room temperature and normal pressure (0.1 MN / m 2, or 1. kgf / cm 2) graphite is thermodynamically stable. Diamond is very solid, crystalline. Crystals have a cubic grazenarized lattice: a \u003d. 3,560 a. For room temperature and normal pressure, diamond metastable (for details about the structure and properties of diamond and graphite, see the relevant articles). A noticeable conversion of diamond into graphite is observed at temperatures above 1400 ° C in vacuo or in an inert atmosphere. For atmospheric pressure And the temperature is about 3700 ° C graphite is removed. Liquid u. Can be obtained at pressures above 10.5 MN / m 2(105 kgf / cm 2) and temperatures above 3700 ° C. For solid u. ( coke, soot, charcoal) It is also characteristic of a state with an unordered structure - the so-called "amorphous" u., which does not represent an independent modification; The basis of its structure is the structure of small-crystalline graphite. Heating some varieties of "amorphous" W. Above 1500-1600 ° C without air access causes them to transform into graphite. The physical properties of the "amorphous" u. Very strongly depend on the dispersion of particles and the presence of impurities. Density, heat capacity, thermal conductivity and electrical conductivity of "amorphous" W. is always higher than graphite. Karbin is artificially obtained. It is a small crystalline black powder (1.9-2 density g / cm 3) . Built from long chains of atoms with, laid parallel to each other. Lonsdaleit found in meteorites and obtained artificially; Its structure and properties are finally installed.
Configuration of the outer electronic shell atom of the U. 2s 2 2p 2. For W. Characterized by the formation of four covalent bonds due to the excitation of the external electron shell to state 2 sP 3. Therefore, W. is capable equally to attract and give electrons. Chemical Communication can be carried out by sP 3 -, SP 2 -and sp.-Hybrid orbitals, which correspond to coordination numbers 4, 3 and 2. The number of valence electrons U. and the number of valence orbital elements is equally; This is one of the reasons for the sustainability of the connection between atoms.
The unique ability of U. atoms to connect to each other with the formation of durable and long chains and cycles led to the emergence of a huge number of various compounds of U., studied organic chemistry.
In compounds, W. shows the degrees of oxidation -4; +2; +4. Atomic radius 0.77 A, covalent radii 0.77 A, 0.67 A, 0.60 A, respectively, in single, double and triple bonds; ion radius c 4- 2.60 A, C 4+ 0.20 a. Under normal conditions, W. Chemically inert, when high temperatures It connects with many elements, showing strong rehabilitation properties. Chemical activity decreases in a row: "amorphous", u., graphite, diamond; The interaction with air oxygen (combustion) occurs, respectively, at temperatures above 300-500 ° C, 600-700 ° C and 850-1000 ° C with the formation of carbon dioxide CO 2 and carbon monoxide CO.
cO 2 dissolves in water to form coalic acid. In 1906 O. Dils.removed W. C 3 O 2. All forms of U. are resistant to alkalis and acids and are slowly oxidized only by very strong oxidizing agents (chromium mixture, a mixture of concentrated HNO 3 and KCLO 3, etc.). "Amorphous" W. reacts with fluorine at room temperature, graphite and diamond - when heated. Direct compound W. With chlorine occurs in an electric arc; with bromine and iodom u. does not react, so numerous carbon halides Synthesized indirect way. From oxygaloids general formula Cox 2 (where x - halogen) the most famous COCL 2 ( phosgene) . Hydrogen with diamond does not interact; With graphite and "amorphous" W. Reacts at high temperatures in the presence of catalysts (Ni, Pt): at 600-1000 ° C, it is formed mainly methane CH 4, at 1500- 2000 ° C - acetylene C 2 H 2 , Dr. hydrocarbons may also be present in the products, such as ethane C 2 H 6 , Benzole C 6 H 6. The interaction of sulfur with "amorphous" and graphite begins at 700-800 ° C, with a diamond at 900-1000 ° C; In all cases, CS 2 serougo harvester is formed. Dr. Compounds U., containing sulfur (CS tyooca, cyanide C 3 S 2, COS and thiophosgene CSCl 2) are obtained by indirect way. When CS 2 interacts with metals sulphides, thiocarbonates are formed - salts of weak thyggolic acid. The interaction of U. with nitrogen to obtain cyan (CN) 2 occurs when the electrical discharge is passed between the coal electrodes in the nitrogen atmosphere. Among the nitrogen-containing compounds of W. An important practical value is hydrogen HCN cyanice and its numerous derivatives: cyanides, halo-gentials, nitriles, etc. at temperatures above 1000 ° C. U. interacts with many metals, giving carbides. All forms of U. When heated, the oxides of metals are restored to form free metals (Zn, CD, CU, PB, etc.) or carbides (CAC 2, MO 2 C, WO, TAC, etc.). W. Reacts at temperatures above 600- 800 ° C with water vapor and carbon dioxide . A distinctive feature Graphite is the ability at moderate heating to 300-400 ° C to interact with alkaline metals and halides to form inclusion connections Type C 8 ME, C 24 ME, C 8 x (where x - halogen, ME - metal). Known compounds of inclusion of graphite with HNO 3, H 2 SO 4, FECL 3, etc. (for example, graphite bisulfate C 24 SO 4 H 2). All forms of U. are insoluble in conventional inorganic and organic solvents, but dissolve in some molten metals (for example, Fe, Ni, CO).
The national economic significance of W. is determined by the fact that over 90% of all the primary sources of energy consumed in the world fall on the organic fuel, The principal role of which will continue for the coming decades, despite the intensive development of nuclear energy. Only about 10% of the produced fuel is used as a raw material for basic organic synthesis and petrochemical synthesis, for getting plastic masses and etc.
B. A. Popovkin.
W. In the body . U. is the most important biogenic element that makes up the basis of life on Earth, a structural unit of a huge number of organic compounds involved in building organisms and ensuring their livelihoods ( biopolymers As well as numerous low molecular weight biologically active substances - vitamins, hormones, mediators, etc.). A significant part of the necessary energy organisms is formed in cells due to oxidation of W. The emergence of life on Earth is considered in modern science as a complex process of evolution of carbon compounds .
The unique role of W. In the wildlife is due to its properties, which, in the aggregation, no other element of the periodic system is posted. Between the atoms of U., as well as between U. and other elements, strong chemical bonds are formed, which, however, can be broken in relatively soft physiological conditions (these bonds can be single, double and triple). Ability to form 4 equivalent valence communications with other atoms of U. Creates the ability to build carbon skeletons of various types - linear, branched, cyclic. It is significant that only three elements are C, O and H - amount to 98% of the total mass of living organisms. This achieves a certain economy in wildlife: with a practically limitless structural variety of carbon compounds, a small number of types of chemical bonds allows much to reduce the number of enzymes required for splitting and synthesis organic substances. The features of the structure of the U. atom underlie different species isomeria organic compounds (the ability to optical isomerism turned out to be decisive in the biochemical evolution of amino acids, carbohydrates and some alkaloids).
According to the generally accepted hypothesis, A. I. Oparin, The first organic compounds on Earth had abiogenic origins. Sources of W. served methane (CH 4) and cyanide hydrogen (HCN) contained in the primary atmosphere of the Earth. With the emergence of life the only source of inorganic W., due to which the whole organic matter of the biosphere is formed, is carbon dioxide(CO 2), located in the atmosphere, as well as dissolved in natural waters In the form of HCO - 3. The most powerful mechanism of assimilation (assimilation) U. (in the form of CO 2) - photosynthesis - It is carried out throughout the green plants (about 100 billion is assimilated annually. t. CO 2). On Earth, there is an evolutionary more ancient way to assimilate CO 2 by chemosynthesis; In this case, chemosynthetic microorganisms use not the radiant energy of the Sun, and the energy of oxidation of inorganic compounds. Most animals consume u. With food in the form of ready-made organic compounds. Depending on the method of absorption of organic compounds, it is customary to distinguish autotrophic organisms and heterotrophic organisms. Application for protein biosynthesis and other nutrients of microorganisms that use as the only source of W. hydrocarbons Oil, is one of the important modern scientific and technical problems.
The content of W. in living organisms in the calculation of the dry matter is: 34.5-40% in aqueous plants and animals, 45.4-46.5% in land plants and animals and 54% from bacteria. In the process of livelihoods of organisms, mainly due to tissue breathing There is an oxidizing decomposition of organic compounds with highlighting external environment CO 2. W. Also allocated as part of more complex end products metabolism. After the death of animals and plants, part of U. again turns into CO 2 as a result of rotation processes carried out by microorganisms. Thus, there is a cycle of W. In nature . Significant part of W. Mineralizes and forms the deposits of the fossil in the fossil: stone coals, oil, limestone, etc. In addition to the main functions - the source of U.-CO 2, dissolved in natural waters and in biological fluids, is involved in maintaining the optimal environmental acidity processes . As part of CACO 3 U. forms the outer skeleton of many invertebrates (for example, molluscs), and also contained in corals, eggshell of birds, etc. Such compounds of W., like HCN, CO, CCL 4, which prevail in the primary atmosphere of the Earth the period, in the future, in the process of biological evolution, turned into strong antimetabolites metabolism.
In addition to stable isotopes, O., in nature, the radioactive 14 C is spread (in the human body it contains about 0.1 iCCURI) . Using Isotopes W. In biological and medical research, many major achievements are connected in the study of metabolism and cycle of U. in nature . So, using a radiocarbon tag, the possibility of fixing H 14 CO - 3 plants and tissues of animals was proved, the sequence of photosynthesis reactions was established, the exchange of amino acids were studied, the biosynthesis paths were traced many biologically active compounds, etc. Application 14 C contributed to the successes of molecular biology in the study of protein biosynthesis mechanisms and the transfer of hereditary information. The determination of the specific activity of 14 C in carbon-containing organic residues allows you to judge their age, which is used in paleontology and archeology.
N. N. Chernov.
LIT: Shafranovsky I. I., Diamonds, M. - L., 1964; Ubbelyod A. R., Lewis F. A., Graphite and its crystal compounds, per. from English, M., 1965; Remy, course not organic Chemistry, Per. with him., Vol. 1, M., 1972; Perelman A. I., geochemistry of elements in the zone of hypergenesis, M., 1972; Nekrasov B.V., Fundamentals of general chemistry, 3 ed., M., 1973; Akhmetov N. S., inorganic chemistry, 2 ed., M., 1975; Vernadsky V. I., Essays of geochemistry, 6 ed., M., 1954; Roginsky S. Z., Schnol S. E., Isotopes in Biochemistry, M., 1963; Biochemistry horizons, lane. from English, M., 1964; Problems of evolutionary and technical biochemistry, M., 1964; Calvin M., Chemical Evolution, Per. from English, M., 1971; Leo A., Siciewits F., Structure and Functions of the cell, lane. from English, 1971, ch. 7; Biosphere, per. from English, M., 1972.
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Carbon dioxide, carbon monoxide, carbon dioxide - all of these names of a substance known to us like carbon dioxide. So what properties this gas has, and what are the areas of its use?
Carbon dioxide and its physical properties
Carbon dioxide consists of carbon and oxygen. Carbon dioxide formula looks like this - CO₂. In nature, it is formed when burning or rotting organic substances. In the air and mineral sources, the gas content is also large enough. In addition, people and animals also distinguish carbon dioxide when exhaled.
Fig. 1. Carbon dioxide molecule.
Carbon dioxide is absolutely colorless gas, it is impossible to see it. He also does not have the smell. However, at its large concentration, a person can develop hypercupnia, that is, suffocation. The lack of carbon dioxide can also cause health problems. As a result of the lack, this gas can develop the opposite state to suffocation - hinders.
If you put carbon dioxide in the conditions of low temperature, then at -72 degrees it crystallizes and becomes like snow. Therefore, carbon dioxide in solid state is called "dry snow".
Fig. 2. Dry snow - carbon dioxide.
Carbon dioxide is 1.5 times tight. Its density is 1.98 kg / m³ Chemical bond in the carbon dioxide molecule covalent polar. Polar it is due to the fact that oxygen is larger than the value of electronegability.
An important concept when studying substances is molecular and molar mass. The molar mass of carbon dioxide is 44. This number is formed from the sum of the relative atomic masses of atoms that are part of the molecule. The values \u200b\u200bof the relative atomic masses are taken from the Table D.I. Mendeleev and are rounded up to integer numbers. Accordingly, the molar mass of CO₂ \u003d 12 + 2 * 16.
To calculate the mass fractions of the elements in carbon dioxide, it is necessary to follow the formulascent of the mass fractions of each chemical element in substance.
n. - Number of atoms or molecules.
A. r. - relative atomic weight of the chemical element.
Mr. - relative molecular weight of the substance.
Calculate the relative molecular weight of carbon dioxide.
Mr (CO₂) \u003d 14 + 16 * 2 \u003d 44 W (C) \u003d 1 * 12/44 \u003d 0.27 or 27% Since two oxygen atoms are included in the carbon dioxide formula, then n \u003d 2 w (o) \u003d 2 * 16/44 \u003d 0.73 or 73%
Answer: W (C) \u003d 0.27 or 27%; W (O) \u003d 0.73 or 73%
Chemical and biological properties of carbon dioxide
Carbon dioxide has acidic properties, as it is acidic oxide, and when dissolved in water forms coalic acid:
CO₂ + H₂O \u003d H₂CO₃
It reacts with alkalis, resulting in carbonates and bicarbonates. This gas is not susceptible to burning. It burns only some active metals, such as magnesium.
When heated, carbon dioxide decays on furine gas and oxygen:
2Co₃ \u003d 2Co + O₃.
Like other acidic oxides, this gas easily reacts with other oxides:
SAO + CO₃ \u003d CACO₃.
Carbon dioxide is part of all organic matter. The cycle of this gas in nature is carried out with the help of producers, consumers and reasons. In the course of vital activity, a person produces about 1 kg of carbon dioxide per day. When inhaling, we get oxygen, however, at this moment carbon dioxide is formed in the alveols. At this moment there is an exchange: oxygen falls into the blood, and carbon dioxide comes out.
The preparation of carbon dioxide occurs during the production of alcohol. Also, this gas is a bypass product upon receipt of nitrogen, oxygen and argon. The use of carbon dioxide is necessary in the food industry, where carbon dioxide acts as a preservative, as well as carbon dioxide in the form of a liquid is contained in fire extinguishers.
Fig. 3. Fire extinguisher.
What did we know?
Carbon dioxide is a substance that in normal conditions There is no color and smell. In addition to its usual name - carbon dioxide, it is also called carbon oxide or carbon dioxide.
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Carbon C is in the periodic table of Mendeleev at number 6. More primitive people noticed that after burning wood, coal is formed, which can be drawn on the walls of the cave. As part of any organic compounds there are carbon. The most studied two allotropic carbon modifications: graphite and diamond.
Carbon in organic chemistry
Carbon takes a special place in the periodic system. Due to its structure, it forms long chains of linear or cyclic structure. There are more than 10 million organic compounds. Despite its diversity, in air and under the action of temperature, they will always turn into carbon dioxide and.
The role of carbon in our daily life is enormous. Without carbon dioxide, photosynthesis will not occur - one of the main biological processes.
Using carbon
Carbon is widely used in medicine to create various organic nature medicines. Carbon isotopes allow radiocarbon analysis. Without carbon, the work of the metallurgical industry is impossible. Coal burning in solid fuel pyrolysis boilers serves as a source of energy. In the oil refining industry, gasoline and diesel fuel are produced from organic compounds of carbon. To a large extent, carbon is necessary for the production of sugar. It is also used in the synthesis of organic compounds, important for all spheres of everyday life.
Carbon (C) - Typical nonmetall; In the periodic system in the 2nd period of the IV group, the main subgroup. The sequence number is 6, Ar \u003d 12,011 A.E.m., the charge of the core +6.Physical properties: Carbon forms many allotropic modifications: diamond - one of the solids, graphite, coal, soot.
Carbon atom has 6 electrons: 1S 2 2S 2 2p 2 . The last two electrons are located on separate p-orbitals and are unpaired. In principle, this couple could occupy one orbital, but in this case the interelectronic repulsion increases. For this reason, one of them occupies 2p x, and the other, or 2r y , either 2r z -Orbitali.
The difference in the energy of the S- and p-pylons of the outer layer is small, so the atom is quite easy to go into an excited state, at which one of two electrons with 2S orbitals goes to a free 2p. Valented state occurs, having a 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 length and energy of bonds.
This phenomenon is known, called sP 3-hybridization, And emerging functions - SP 3-hybrid . Education of four SP 3 -Cound provides carbon atom a more stable state than three p-r- And one S-S communication. In addition to SP 3-hybridization, SP 2 - and SP-hybridization also observes at the carbon atom. . In the first case there is a mutual imposition s- and two p-orbitals. Three equivalent SP 2 - hybrid orbitals located in the same plane at an angle of 120 ° are formed. The third orbital p is unchanged and sent perpendicular to the plane sP 2.
At sp-hybridization, the orbitals of s and p are imposed. Between two formed equivalent hybrid orbital, an angle of 180 ° occurs, with two p-orbitals in each of the atoms remain unchanged.
Allotrorkia carbon. Diamond and graphite
In the graphite crystal, carbon atoms are located in parallel planes, taking the tops of the right hexagons. Each of the carbon atoms is associated with three adjacent SP 2-hybrid connections. Between parallel planes, the connection is carried out at the expense of van der Waals forces. Free p-orbitals of each of the atoms are directed perpendicular to the planes of covalent bonds. Their overlapping explains the additional π-bond between carbon atoms. Thus, from a valence state in which carbon atoms are in substance, the properties of this substance depend on.
Chemical properties of carbon
The most characteristic degrees of oxidation: +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 ° \u003d 2c +2 o Curly gas
- with fluorine
C + 2F 2 \u003d CF 4
- Water ferry
C 0 + H 2 O - 1200 ° \u003d C +2 O + H 2 Water Gas
- with metal oxides. Thus, metal from ore is paid.
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
C 0 + 4HNO 3 (conc.) \u003d C +4 O 2 + 4NO 2 + 2H 2 O
- With gray forms a servo carbon:
C + 2S 2 \u003d CS 2.
Carbon like oxidizing agent:
- with some metals forms carbides
4Al + 3C 0 \u003d Al 4 C 3
Ca + 2C 0 \u003d CAC 2 -4
- with hydrogen - methane (as well as a huge amount of organic compounds)
C 0 + 2H 2 \u003d CH 4
- with silicon, forms carbarund (at 2000 ° C in the electric furnace):
Finding carbon in nature
Cobrel carbon is found in the form of diamond and graphite. In the form of compounds, carbon is located as part of minerals: chalk, marble, limestone - Saco 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 part of Natural organic compounds - gas, oil, coal, peat, is part of organic substances, proteins, fats, carbohydrates, amino acids that are part of living organisms.
Inorganic carbon compounds
No 4+ ions, nor with 4- - no under any conventional chemical processes: in carbon compounds there are covalent bonds of various polarity.
Carbon oxide (II)SO
Carbon monoxide; colorless, odorless, alive in water, soluble in organic solvents, poisonous, t ° Kip \u003d -192 ° C; T pl. \u003d -205 ° C.
Obtaining
1) In industry (in gas generators):
C + O 2 \u003d CO 2
2) in the laboratory - the thermal decomposition of formic or oxalic acid in the presence of H 2 SO 4 (conc.):
HCOOH \u003d H 2 O + CO
H 2 C 2 O 4 \u003d CO + CO 2 + H 2 O
Chemical properties
Under normal conditions CO inert; When heated - reducing agent; Non-working 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 alkalis melt (under pressure)
CO + NaOH \u003d HCoona (sodium formate)
5) with transition metals forms carbonyls
Ni + 4Co - T ° \u003d Ni (CO) 4
Fe + 5Co - T ° \u003d Fe (CO) 5
Carbon Oxide (IV) CO2
Carbon dioxide, colorless, odorless, solubility in water - in 1V H 2 O dissolves 0.9V CO 2 (under normal conditions); heavier air; t ° pl. \u003d -78.5 ° C (solid CO 2 is called "dry ice"); Does not support combustion.
Obtaining
- Thermal decomposition of carbonic acid salts (carbonates). Limestone firing:
Caco 3 - T ° \u003d Cao + CO 2
- The effect of strong acids on carbonates and bicarbonates:
Caco 3 + 2HCl \u003d CaCl 2 + H 2 O + CO 2
NaHCO 3 + HCl \u003d NaCl + H 2 O + CO 2
ChemicalpropertiesCo.2
Acid oxide: reacts with basic oxides and bases, forming carbon 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
At elevated temperatures may show oxidative properties
C +4 O 2 + 2MG - T ° \u003d 2mg +2 O + C 0
Quality reaction
Linding lime water:
Ca (OH) 2 + CO 2 \u003d Caco 3 ¯ (white precipitate) + H 2 O
It disappears with prolonged transmission CO 2 through lime water, because Insoluble calcium carbonate goes into a soluble bicarbonate:
Caco 3 + H 2 O + CO 2 \u003d SA (HCO 3) 2
Coalic acid and hersololi.
H 2.CO 3 -The acid is weak, exists only in an aqueous solution:
CO 2 + H 2 O ↔ H 2 CO 3
Two-mine:
H 2 CO 3 ↔ H + + HCO 3 - acidic salts - bicarbonates, bicarbonates
HCO 3 - ↔ H + + CO 3 2-Current Salts - Carbonates
All properties of acids are characteristic.
Carbonates and bicarbonates can turn 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 for alkali metals) when heated is decarboxyylized with oxide formation:
CUCO 3 - T ° \u003d CUO + CO 2
Quality reaction - "boiling" under the action of severe acid:
Na 2 CO 3 + 2HCl \u003d 2NACL + H 2 O + CO 2
CO 3 2- + 2H + \u003d H 2 O + CO 2
Carbide
Calcium carbide:
Cao + 3 C \u003d CAC 2 + CO
CAC 2 + 2 H 2 O \u003d Ca (OH) 2 + C 2 H 2.
Acetylene is released when reactions with zinc carbides, cadmium, lanthanum and cerium:
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 with water to form methane:
Al 4 C 3 + 12 H 2 O \u003d 4 AL (OH) 3 \u003d 3 CH 4.
The technique use TiC titanium carbides, tungsten W 2 C (solid alloys), SIC silicon (carborund - as an abrasive and material for heaters).
Cianida
obtained by heating soda in ammonia and carbon monoxide atmosphere:
Na 2 CO 3 + 2 NH 3 + 3 CO \u003d 2 NACN + 2 H 2 O + H 2 + 2 CO 2
HCN Sinyl Acid is an important product of the chemical industry, widely used in organic synthesis. Her world production reaches 200 thousand tons per year. The electronic structure of cyanide anion is similar to carbon monoxide (II), such particles are called isoelectronic:
C. = O: [: C = N:] -
Cyanides (0.1-0.2% aqueous solution) are used during gold mining:
2 AU + 4 KCN + H 2 O + 0.5 O 2 \u003d 2 K + 2 KOH.
When boiling of cyanide solutions with gray or fusion of solids are formed rodanudy:
KCN + S \u003d KSCN.
When heating cyanides of low-effective metals, ditian is obtained: Hg (Cn) 2 \u003d Hg + (Cn) 2. Cyanide solutions are oxidized to cianatov:
2 kcn + o 2 \u003d 2 kocn.
Cianaic acid exists in two forms:
H-N \u003d C \u003d O; H-O-C = N:
In 1828, Friedrich Völer (1800-1882) received from the ammonium cyanate urea: NH 4 OCN \u003d CO (NH 2) 2 when evaporation of aqueous solution.
This event is usually considered as the victory of synthetic chemistry over the "vitalistic theory".
There is a cyanic acid isomer - hardening acid
H-O - N \u003d C.
Its salts (rattling Hg (onc) 2) are used in shock ignitions.
Synthesis urea (carbamide):
CO 2 + 2 NH 3 \u003d CO (NH 2) 2 + H 2 O. at 130 0 s and 100 atm.
Urea is an amide of coalic acid, there is also its "nitrogen analog" - guanidine.
Carbonates
Major inorganic carbon compounds - carbonic acid salts (carbonates). H 2 CO 3 is weak acid (K 1 \u003d 1.3 · 10 -4; K 2 \u003d 5 · 10 -11). Carbonate buffer supports carbon dioxide equilibrium In the atmosphere. The world ocean has a huge buffer capacity because it is open system. The main buffer reaction is equilibrium during dissociation of coalic acid:
H 2 CO 3 ↔ H + + HCO 3 -.
With lower acidity, an additional absorption of carbon dioxide from the atmosphere with an acid formation is occurring:
CO 2 + H 2 O ↔ H 2 CO 3.
With increasing acidity, the dissolution of carbonate rocks (sinks, chalk and limestone sediments in the ocean occurs); This compensates for the decline of bicarbonate ions:
H + + CO 3 2- ↔ HCO 3 -
Caco 3 (TV.) ↔ CA 2+ + CO 3 2-
Solid carbonates are transferred to soluble hydrocarbonates. It is this process of chemical dissolution of excess carbon dioxide opposes the "greenhouse effect" - global warming Due to the absorption of the thermal radiation of the Earth with carbon dioxide. Approximately one third of the global production of soda (sodium carbonate Na 2 CO 3) is used in glass production.