Physical and chemical properties of carbon. Carbon - chemical and physical properties Compounds of carbon with halogens

Carbon type Carbonic type is the most common among patients, which is no coincidence. Carbon is the central element of organic life, and all substances are divided into organic and inorganic depending on the presence or absence of carbon in their composition.

2. Electrochemistry of carbon

2. Electrochemistry of carbon Currently, carbon, due to its layered structure in the form of graphite, is widely used for the synthesis of graphite interstitial compounds, which, in turn, has found application in a lithium current source (battery), used in science,

Pb. All of them belong to R-elements, since they are being completed R-electronic shell of the outer layer (Table 15).

As the nuclear charge increases, the radius of the atom increases and electronegativity decreases noticeably. In this regard, metallic properties noticeably increase from carbon to lead. Thus, it has well-defined metallic properties, while it is considered a non-metal.
The four-electron outer layer and small atomic radii of carbon and silicon promote the formation of covalent bonds that are typical of these elements. A feature of both carbon and silicon is the ability to form long chains of atoms of the same name, which leads to a wide variety of organic and organosilicon substances. Carbon and can form either two or four valence bonds. The maximum oxidation state of elements of the main subgroup of group IV is +4. This suggests that it is conditionally possible for their atoms to give up 4 electrons. They are also capable of accepting no more than electrons to the outer layer. In redox reactions they behave as reducing agents.

The higher of these elements exhibit acidic properties. They correspond to acids, which are very weak electrolytes. This suggests that among the main subgroups of groups IV-VII, the carbon subgroup combines elements with the least pronounced non-metallic properties. The strength of volatile hydrides noticeably decreases from carbon CH4 to lead PbH4. It is impossible not to note the nature of the properties of oxides in which elements exhibit an oxidation state of +2. If carbon forms the non-salt-forming oxide CO, lead oxide PbO has pronounced amphoteric properties.

■ 1. Among the elements of the carbon group, indicate:
a) the element with the smallest atomic radius;
b) an element with the most pronounced metallic properties;
c) formulas of higher oxides of elements of the carbon group;
d) formulas of higher oxygen acids corresponding to the named oxides;
e) formulas of lower oxides;
f) change in the stability of volatile hydrogen compounds (write a series of formulas and use an arrow to indicate the direction of decrease in stability).

Carbon

The atomic weight of carbon is 12.011. The outer electron layer of the carbon atom has 4 electrons, its electronic configuration is 2s 2 2p 2, the distribution of electrons among orbitals.

Among the elements of the subgroup, carbon has the highest electronegativity value.
Carbon has three allotropic modifications - and amorphous carbon. and are found in nature, and amorphous carbon can only be obtained artificially.
- a solid crystalline substance, refractory and chemically inactive. Pure diamond is colorless transparent crystals. Among minerals, diamond has the highest hardness, equal to 10, and its density is 3.514. Such high hardness is explained by the structure of its atomic-type crystal lattice, in which carbon atoms are located at the same distance from each other (see Fig. 11).
Due to its hardness, diamond is widely used for cutting glass, drilling hard rocks, in wire drawing machines, grinding discs, etc. For these purposes, diamonds contaminated with various impurities are used.
Pure colorless crystals are cut and polished with diamond powder and turned into diamonds. The more facets, the better the diamond “plays”. Diamonds are most often small, their weight is measured in carats (1 carat equals 0.2 g). But there are also large diamonds.
- a fine-crystalline mineral, in the crystal lattice of which the distance between atoms is the same in only two directions, and in the third it is much greater. This makes graphite crystals fragile and the mineral itself soft. The hardness of graphite is 1, the density is 2.22, and the melting point is about 3000°. Graphite has good electrical conductivity, so it is used for the manufacture of electrodes and plates for electrolytic baths. Graphite powder mixed with mineral oil is a good lubricant. Since graphite is softer than paper and can leave a mark on it, it is used to make pencil leads, ink, printing ink, and copy paper. The high heat resistance of graphite allows it to be used to make fireproof crucibles. Graphite can be obtained artificially - by heating coke to 2500-3000°.

■ 2. What type of crystal lattices do diamond and graphite have?

3. Explain in terms of the electronic configuration of the electron layers why carbon can form either two or four valence bonds.

There is an opinion that artificially produced amorphous carbon (soot, charcoal) is not an independent allotropic modification, since its microcrystalline structure is the same as that of graphite.
Amorphous carbon in the form of charcoal is obtained by dry distillation of wood in the form of a very light, brittle, porous mass. The structure of amorphous carbon is very similar to the structure of graphite, but the crystals in it are arranged randomly.
The huge surface of charcoal causes its characteristic adsorption phenomenon. Carbon molecules located on the surface of a piece of coal attract molecules of substances from its environment, overcoming the energy of thermal motion of the molecules. It is clear that the larger the surface, the stronger it goes, so the crushed adsorbent adsorbs better. If you grind charcoal thoroughly and then place it under a hood containing bromine vapor, you will notice how the bromine's color gradually weakens and eventually disappears.

If the coal powder is shaken in a test tube with a solution of potassium permanganate, fuchsin or tea tincture, then these solutions soon become discolored. If you boil the adsorbent together with the substance adsorbed on its surface in clean water, the color of the solution appears again, since the thermal movement of the molecules increases and they break off from the surface of the adsorbent - desorption occurs.
It should also be noted that the phenomenon of catalysis, which was discussed above, is closely related to the phenomenon of adsorption.

■ 4. What phenomenon is called adsorption?
5. Where else does the phenomenon of adsorption take place, besides the processes associated with charcoal?
6. Give an explanation for the phenomenon of desorption and indicate the reasons contributing to this phenomenon.

When treated with superheated water steam, the foreign impurities that are sometimes present there are removed from the pores of the coal, and the porosity of the coal increases. This type of carbon is called activated carbon.

Activated carbon is very widely used, in particular, in a gas mask, first proposed by Academician. N. D. Zelinsky to protect the respiratory tract from toxic gases in the air. For the first time such a gas mask was used during the First World War (Fig. 64). A gas mask consists of a rubber mask or helmet that fits tightly around the face and head, a corrugated rubber tube connecting the mask to a box containing air purifying agents.

The valve system allows inhaled air into the mask only through the box, and exhaled air directly into the surrounding space. The gas mask box contains an anti-smoke filter arranged in layers that traps solid and droplet particles, a chemical absorber that chemically binds poisonous substances entering the box, and activated carbon.
Activated carbon is sometimes given as a suspension in water orally in case of toxic substances entering the stomach. Charcoal is also used to make black powder.
Amorphous carbon in the form of coke is used in metallurgy. Coke is produced in coke ovens from coal. It is a solid, porous substance that is almost pure carbon. Coke is an excellent fuel and a good reducing agent.

Rice. 64. Gas mask device by N. D. Zelinsky. 1-helmet; 2 - corrugated tube; 3 - exhalation valve; 4 - filter box; 5 - activated carbon; 6 - chemical absorber; 7 - anti-smoke filter.

Soot is produced by burning gaseous substances with a high percentage of carbon content. In the form of soot, amorphous carbon is widely used in the rubber industry and in the printing industry for the production of printing ink. The highest quality soot is produced by burning gaseous fuels such as acetylene.

■ 7. Make and fill out the following table:

Chemical properties of carbon

It should be noted that the main property of carbon is its reducing ability. Carbon is one of the best reducing agents. It easily reduces their oxides when heated:

and burns easily in oxygen to form carbon monoxide or carbon dioxide
2C + O2 = 2СО —

C + O2 = CO2
When alloyed with metals, carbon forms carbides, which have a very unique molecular structure. For example, calcium carbide CaC2, which is especially widely used in technology, has the following structure:

Carbon combines with hydrogen only at a temperature of about 1200°, forming the organic compound methane CH4:
C + 2H2 = CH4

■ 8. Calculate how much copper can be reduced from its oxide CuO using 24 kg of carbon if the loss of copper is 5%.

When superheated water vapor is passed through hot coal, the latter is reduced from water, resulting in the formation of water gas:
C + H2O = CO + Na
water gas
Despite the high reducing ability of carbon, its use as a reducing agent is not always convenient, since it is a solid substance. It is much more convenient to use gaseous reducing agents. Then the contact between the reducing agent and the substance being reduced becomes more complete. In this regard, it is advisable to convert carbon into carbon monoxide, which retains its reducing properties and is at the same time a gaseous substance.

■ 9. What volume of water gas (normal conditions) can be obtained by passing water vapor through 5 gram carbon atoms?
10. Copper nitrate was calcined until the evolution of brown gas completely stopped, after which it was mixed with crushed coal and calcined again. What happened as a result of the reaction? Give your answer, justifying it with reaction equations.

Carbon oxides

There are two known carbon oxides in which it exhibits different oxidation states: CO and CO2.
Carbon monoxide (II) CO, or carbon monoxide as it is called, is a colorless, odorless gas. Boiling point -191.5º. It is slightly lighter than air and extremely poisonous. The toxicity of carbon monoxide is explained by the fact that in combination with hemoglobin in the blood, with which it comes into contact when it enters the lungs, it forms carboxyhemoglobin, which is a strong compound that does not have the ability to react with oxygen. Thus, hemoglobin in the blood is destroyed, and in case of severe poisoning, a person may die from oxygen starvation. Carbon monoxide can enter a room heated by stoves if the chimney closes too early and unburned carbon monoxide enters the living room.

The chemical properties of carbon monoxide are very diverse. It is a flammable gas that readily burns with a blue flame in oxygen and air to form carbon dioxide:
2CO + O2 = 2CO2
Carbon in this reaction is oxidized, moving from C +2 to C +4, i.e. it exhibits reducing properties. Therefore, carbon monoxide can be used as a reducing agent. Indeed, carbon monoxide can be reduced from oxides:
FeO + CO = CO2 + Fe

It should also be noted that carbon monoxide is a non-salt-forming oxide.

■ 11. The element lead Pb, which also belongs to the main subgroup of group IV, can form an oxide in which it exhibits an oxidation state of +2; carbon can also form an oxide, where it exhibits the same oxidation state. Compare the chemical properties of these two oxides and illustrate them with reaction equations.

The flammability of carbon monoxide, as well as its reducing properties, make it a very valuable fuel and reducing agent in many industrial processes, especially in metallurgy, which is why carbon monoxide is specially produced in furnaces called gasifiers (Fig. 65).

Rice. 65. Gas generator circuit

The gas generator is a furnace into which coke is poured on top. The coke is set on fire from below, and air is supplied from below to maintain the combustion of the coke. When oxygen in the air comes into contact with hot coal, the latter burns to form carbon dioxide:
C + O2 = CO2
Passing through subsequent coal salts, carbon dioxide is reduced to carbon monoxide: CO2 + C = 2CO
As a result, generator gas of the following composition comes out of the gas generator: CO + CO2 + N2 (air). This gas is called air. Air gas contains only one flammable substance, CO, and carbon dioxide, CO2, is ballast. To ensure that there is no ballast in the gas, superheated water vapor is passed through the generator, which, reacting with carbon, forms water gas:
C + H2O ⇄ CO + H2

Water gas has no ballast, since carbon monoxide burns and is a good reducing agent, but when water vapor is passed through coal for a long time, the latter cools and stops working. To prevent this from happening, air and water vapor are passed alternately through the gas generator, resulting in a mixed gas.
Producer gases are widely used in technology.

Rice. 66. Scheme of underground coal gasification.

■ 12. What volume of water gas will be produced by passing water vapor through 36 kg of coal?
13. Write the equations for the reactions that occur during the reduction of iron (III) oxide with water gas.
14. How can you separate the gases that make up the air generator gas?
15. Air generator gas was passed through a calcium solution. How has the composition of the gas mixture changed? Confirm with reaction equations.
16. How does mixed gas differ from air gas? Indicate the composition of the components of the mixed gas.

In 1888, D.I. Mendeleev proposed a method for underground gasification of coal. It consists in the following. In the coal seam (Fig. 66), two wells are drilled from the surface downwards at a distance of 25-30 m from one another. Using electric heaters, the coal seam below is set on fire. When air is passed into the blowing well, a channel is burned between it and the gas outlet well, through which gases flow into the gas outlet well and rise to the surface along it. In the lowest part of the seam, as in a gas generator, coal is burned to carbon dioxide. Somewhat higher, carbon dioxide is reduced to carbon monoxide, and even higher, under the influence of the heat of a heated coal seam, dry distillation is carried out, the products of which are also removed through a gas outlet well. Dry distillation products are very valuable. Subsequently, the escaping gas is separated from them, after which it can be used for its intended purpose.

Producer gas is used in metallurgy, in the production of glass and ceramics, in gas turbines and internal combustion engines, and in everyday life.
Carbon monoxide is widely used in the organic synthesis industry - in the production of ammonia, hydrogen chloride, artificial fuel, detergents, etc.

■ 17. Calculate the consumption of coal in the gas generator if the result is 112 liters of water gas.

Carbon dioxide CO2 is the highest carbon oxide, its 44 cu. e. (it is more than one and a half times heavier than air). Boiling point (sublimation) -78.5°.
When strongly cooled, carbon dioxide turns into a solid snow-like mass - “dry ice”, which at normal pressure does not transform into a liquid, but sublimes, which is of great convenience when storing perishable products: firstly, there is no moisture, and secondly, the atmosphere Carbon dioxide inhibits the growth of bacteria and molds. Carbon dioxide is a typical acidic oxide that has all the characteristic properties.

■ 18. Write equations for chemical reactions that characterize the properties of carbon dioxide as an acidic oxide.

Carbon dioxide is quite soluble in water: one volume of CO2 dissolves in one volume of water. In this case, it interacts with water to form very unstable carbonic acid: H2O + CO2 ⇄ H2CO3
As the pressure increases, carbon dioxide increases sharply. This is the basis for the use of CO2 in the production of fizzy drinks.

■ 19. Knowing the patterns of equilibrium shifts, indicate in which direction the equilibrium can be shifted in a reaction
CO2+ H2O ⇄ H2CO3
a) increasing blood pressure; b) increasing the temperature.

Carbon dioxide does not support combustion or respiration, and in its atmosphere animals die not from poisoning, but from lack of oxygen. Only burning at a very high temperature can burn in carbon dioxide, decomposing it and thereby reducing carbon:
2Mg + CO2 = 2MgO + C
At the same time, carbon dioxide is necessary for green plants for the process of photosynthesis. Enriching the atmosphere with carbon dioxide in greenhouses enhances the formation of organic matter by plants.
The earth's atmosphere contains 0.04% carbon dioxide. A small amount of carbon dioxide in the air stimulates the activity of the respiratory center.
Carbon dioxide is usually produced by reacting carbonic acid salts with some stronger acid:
CaCO3 + 2HCl = CaCl2 + H2CO3
This process is carried out in the laboratory in a Kipp apparatus, charging it with marble and hydrochloric acid.

Rice. 67. Foam fire extinguisher. 1-tank with an aqueous solution of soda; 2 - ampoule with sulfuric acid; 3 - drummer; 4 - iron mesh; 5 - outlet; b - handle

A similar method for producing carbon dioxide is used in so-called foam fire extinguishers (Fig. 67). This fire extinguisher is a steel cylinder filled with Na2CO3 soda solution. A glass ampoule containing sulfuric acid is placed in this solution. A striker is mounted above the ampoule, which, if necessary, can be used to break the ampoule, and then it will begin to interact with soda according to the equation:
Na2CO3 + H2SO4 = Na2SO4 + H2CO3

The carbon dioxide released in large quantities forms abundant foam, which is expelled by gas pressure through a hole in the side wall and, covering the burning object, stops the access of air oxygen to it.

For industrial purposes, carbon dioxide is obtained from the decomposition of limestone:
CaCO3 = CaO + CO2
Carbon dioxide is produced when coal burns and is also released during the fermentation of sugars and other processes.

■ 20. Is it possible to fill a foam fire extinguisher with a solution of another carbonate instead of a soda solution, and replace sulfuric acid with another acid. Give examples.
21. A mixture of gases consisting of carbon dioxide, hydrogen sulfide and sulfur dioxide was passed through iodine water. What is the composition of the gas mixture at the outlet? What is in the solution?
22. What volume of carbon dioxide will be produced by burning 112 liters of carbon monoxide?
23. What volume of carbon monoxide is formed during the oxidation of 4 moles of carbon?

24. How much carbon dioxide can be obtained from the decomposition of 250 g of limestone containing 20% ​​impurities, if the CO2 yield is 80% of the theoretical?
25. How much does 1 m 3 of a gas mixture consisting of 70% carbon monoxide and 30% carbon dioxide weigh?

Carbonic acid and its salts

Carbon dioxide is carbonic anhydride. H2CO3 itself is a very fragile substance. It exists only in aqueous solutions. When you try to isolate it from these solutions, it easily breaks down into water and carbon dioxide:
H2CO3 ⇄ H2O + CO2
H2CO3 ⇄ H + + HCO - 3 ⇄ 2H + + CO 2 3 -
is a very weak electrolyte; however, being dibasic, it forms two series of salts: medium - and acidic - bicarbonates. Carbon dioxide salts are interesting because when they are exposed to acid, carbon dioxide is released:
K2CO3 + 2HCl = 2KCl + H2CO3

■ 26. Write the above equation in ionic form, and also give two more reaction equations illustrating the effect of acids on.
27. Write the reaction equation for the action of hydrochloric acid on magnesium bicarbonate in molecular and ionic forms.

When treated with carbon dioxide and water they turn into bicarbonates. When heated, the reverse transformation occurs:
normal conditions
CaCO3 + CO2 + H2O ⇄ Ca(HCO3)2
heating
The transition of insoluble carbonate into soluble bicarbonate leads to the leaching of carbonate from the earth's crust, resulting in the formation of voids - caves. Carbonates are mostly insoluble in water, with the exception of alkali metal and ammonium carbonates. Bicarbonates are more soluble.

Among carbonates, CaCO3 deserves special attention, occurring in three forms: marble, limestone and chalk. In addition, in combination with magnesium carbonate, it is part of the dolomite rock MgCO3 · CaCO3. Despite the same chemical composition, the physical properties of these rocks are completely different.
Marble is a hard, crystalline substance of igneous origin. It gradually crystallized inside the cooling magma. Marble is often colored with impurities in different colors. Marble is very well polished and is therefore widely used as a finishing material for cladding building structures and in sculpture.

Limestone is a sedimentary rock of organic origin. Often in limestone you can find the remains of ancient animals, mainly mollusks in calcareous shells. Sometimes they are quite large, and sometimes they are visible only under a microscope. Over millions of years, limestone has compacted and become so hard that it is used as a building material. But now it is gradually being replaced by cheaper, lighter and more comfortable artificial materials. Limestone is used mainly to produce lime.

Chalk is a soft, white sedimentary rock. Used in construction for whitewashing. When making tooth powder, chalk is first dissolved in acid and then precipitated again, since the natural substance contains tiny solid particles of silica that can scratch tooth enamel.
Calcium bicarbonate Ca(HCO3)2 occurs in nature in a dissolved state. Formed by the action of water in combination with carbon dioxide on limestone. The presence of this salt gives the water temporary (carbonate) hardness.
Of exceptional interest is Na2CO3 soda, which sometimes occurs naturally in so-called soda lakes. But currently, the extraction of soda from natural sources is being replaced by cheaper artificial production of this product. If the soda contains water of crystallization, then it is called crystalline soda Na2CО3 · 10Н2О, but if it does not contain it, then it is called soda ash. Soda is very widely used in the soap, textile, paper and glass industries.

Bicarbonate of soda, or sodium bicarbonate, or baking soda, NaHCO3 is used in baking confectionery products as a leavening agent, as well as in medicine for high acidity of the stomach, heartburn, diabetes, etc.
Potassium carbonate K2CO3, or potash, like soda, is used in the soap industry and in the production of refractory glass.
It should be noted that carbon forms so-called organic compounds, the number and variety of which far exceed the compounds of all other elements taken together. The detailed study of carbon compounds is separated into an independent field called organic chemistry.

■ 28. How to distinguish sodium carbonate, presented in solid form, from each other?
29. They placed potassium nitrate in one porcelain cup, potassium nitrate in another, and began calcining it in a third, forgetting to note which cup contained which salt. How can you recognize the salts taken by observing the calcination process and studying the reaction products?
30. How to carry out a series of transformations:

31. How does the transformation of calcium carbonate into bicarbonate occur in nature?
32. 2 kg of calcium carbonate was calcined. The weight of the residue after calcination turned out to be 1 kg 800 g. What percentage of the carbonate was decomposed?
33. How to get rid of calcium nitrate impurities?
34. How, with only hydrochloric acid at your disposal, can you recognize barium carbonate, barium sulfite and barium sulfate?
35. Iron (III) oxide was reduced with carbon monoxide obtained from 5 kg of coal. How much iron was obtained?

Carbon is a vital element for animals and plants. Plants use carbon dioxide from the air and energy from the sun to create organic matter. Herbivores that feed on plants, using these ready-made substances, in turn serve

Rice. 68. Carbon cycle in nature

food for predators. Plants and animals, dying, rot, oxidizing and partially turning into carbon dioxide, which is again consumed by plants, and partially gradually decompose in the soil, forming different types of fuel. When fuel burns, carbon dioxide is released, which enters the atmosphere and is consumed by plants (Fig. 68).
This cycle can only occur through the process of photosynthesis.

Chemical properties: At ordinary temperatures, carbon is chemically inert; at sufficiently high temperatures it combines with many elements and exhibits strong reducing properties. The chemical activity of different forms of carbon decreases in the following order: amorphous carbon, graphite, diamond; in air they ignite at temperatures respectively above 300-500 °C, 600-700 °C and 850-1000 °C Oxidation state +4 (e.g. CO 2), −4 (for example, CH 4), rarely +2 (CO, metal carbonyls), +3 (C 2 N 2); electron affinity 1.27 eV; The ionization energy during the sequential transition from C 0 to C 4+ is 11.2604, 24.383, 47.871 and 64.19 eV, respectively.

The most famous are three carbon oxide:

1)Carbon monoxide CO(is a colorless, tasteless and odorless gas. It is flammable. The so-called “carbon monoxide odor” is actually the odor of organic impurities.)

2) Carbon dioxide CO 2 (Not toxic, but does not support breathing. High concentrations in the air cause suffocation. Lack of carbon dioxide is also dangerous. Carbon dioxide in animal bodies also has physiological significance, for example, it is involved in the regulation of vascular tone)

3)Tricarbon dioxide C 3 O 2 (a colored poisonous gas with a pungent, suffocating odor, which easily polymerizes under normal conditions to form a product insoluble in water, yellow, red or violet in color.)

Compounds with non-metals have their own names - methane, tetrafluoromethane.

Products combustion carbon in oxygen are CO and CO 2 (carbon monoxide and carbon dioxide, respectively). Also known to be unstable underoxide carbon C 3 O 2 (melting point −111 ° C, boiling point 7 ° C) and some other oxides (for example C 12 O 9, C 5 O 2, C 12 O 12). Graphite and amorphous carbon begin to react with hydrogen at a temperature of 1200 °C, with fluoride at 900 °C.

Carbon dioxide reacts with water, forming weak carbonic acid - H 2 CO 3, which forms salts - carbonates. The most widespread on Earth are calcium carbonates (mineral forms - chalk, marble, calcite, limestone, etc.) and magnesium

43 Question. Silicon

Silicon (Si) – stands in the 3rd period, IV group of the main periodic subgroup. systems.

Phys. saints: silicon exists in two modifications: amorphous and crystalline. Amorphous silicon is a brown powder dissolved in metal melts. Crystallic. Silicon is dark gray crystals with a steely luster, hard and brittle. Silicon consists of three isotopes.

Chem. saints: electronic configuration: 1s 2 2s 2 2p 6 3 s 2 3p 2 . Silicon is a non-metal. On external energy. ur-non-silicon has 4 e, which determines its oxidation states: +4, -4, -2. Valency – 2.4. Amorphous silicon has greater reactivity than crystalline silicon. Under normal conditions, it interacts with fluorine: Si + 2F 2 = SiF 4.

Silicon reacts only with a mixture of nitric and hydrofluoric acids:

It behaves differently in relation to metals: in molten Zn, Al, Sn, Pb it dissolves well, but does not react with them; Silicon interacts with other metal melts - with Mg, Cu, Fe - to form silicides: Si + 2Mg = Mg2Si. Silicon burns in oxygen: Si + O2 = SiO2 (sand).

Receipt: Free silicon can be obtained by calcining fine white sand with magnesium, which, according to chemical composition is almost pure silicon oxide, SiO2+2Mg=2MgO+Si.

Silicon(II)OxideSiO- a resin-like amorphous substance, under normal conditions it is resistant to oxygen. Refers to non-salt-forming oxides. SiO does not occur in nature. Gaseous silicon monoxide has been discovered in gas and dust clouds of interstellar media and on sunspots. Receipt: Silicon monoxide can be obtained by heating silicon in a lack of oxygen at a temperature of 2Si + O 2 weeks → 2SiO. When heated in excess oxygen, silicon(IV) oxide SiO2 is formed: Si + O 2 g → SiO 2 .

SiO is also formed when SiO2 is reduced by silicon at high temperatures: SiO 2 + Si → 2SiO.

Silicon oxide (IV)SiO2 - colorless crystals, have high hardness and strength. Saints: Belongs to the acid group. oxides. When heated, it interacts with the base. oxides and alkalis. It is found in the hydrofluoric acid group. SiO2 belongs to the group of glass-forming oxides, i.e. prone to the formation of a supercooled melt - glass. One of the best dielectrics (does not conduct electricity). Has an atomic crystal lattice.

Nitride is a binary inorganic. a chemical compound that is a compound of silicon and nitrogen Si 3 N 4 . Saints: Silicon nitride has good mechanical and physical-chemical properties. Holy you. Thanks to the silicon nitride bond. the performance properties of refractories based on silicon carbide, periclase, forsterite, etc. are improved. Refractories based on a nitride binder have high thermal and wear resistance, have excellent resistance to cracking, as well as the effects of compounds, alkalis, aggressive melts and metal vapors .

Silicon(IV) chloride tetrachloride silicon - colorless substance, chemical. cat formula SiCl 4.Used in the production of organic silicon. connections; used to create smoke screens. Technical Silicon tetrachloride is intended for the production of ethyl silicates and aerosil.

Silicon carbide- binary inorganic chem. compound of silicon with carbon SiC. It occurs in nature in the form of an extremely rare mineral - moissanite.

Silicon dioxide or silica– stable connection Si, widely distributed in nature. It reacts by fusing it with alkalis and basic oxides, forming silicic acid salts - silicates. Receipt: in industry, silicon in its pure form is obtained by reducing silicon dioxide with coke in electric furnaces: SiO 2 + 2C = Si + 2CO 2.

In the laboratory, silicon is obtained by calcination of white sand with magnesium or aluminum:

SiO 2 + 2Mg = 2MgO + Si.

3SiO 2 + 4Al = Al 2 O 3 + 3Si.

Silicon forms the following: H 2 SiO 3 – meta-silicon acid; H 2 Si 2 O 5 – two-metal silicon.

Finding in nature: quartz mineral – SiO2. Quartz crystals have the shape of a hexagonal prism, colorless and transparent, called rock crystal. Amethyst is a rock crystal colored purple with impurities; smoky topaz is brownish in color; agate and jasper - crystalline. varieties of quartz. Amorphous silica is less common and exists as the mineral opal. Diatomite, tripoli or kieselguhr (ciliate earth) are earthy forms of amorphous silicon. General. silicon formula - n SiO2?m H2O. In nature, it is found mainly in the form of salts, free. Few forms have been identified, for example, HSiO (orthosilicon) and H 2 SiO 3 (silicon or metasilicon).

Preparation of silicic acid:

1) interaction of silicates with alkali. metals with compounds: Na 2 SiO 3 + 2HCl = H 2 SiO 3 + 2NaCl;

2) flint substance. thermally unstable: H 2 SiO 3 = H 2 O + SiO 2.

H 2 SiO 3 forms supersaturated solutions, in which As a result of polymerization, it forms colloids. Using stabilizers, stable colloids (sols) can be obtained. They are used in production. Without stabilizers, a gel is formed from the silicon solution; after drying it, you can get silica gel (used as an adsorbent).

Silicates– silicon salts. Silicates are common in nature; the earth's crust consists mostly of silica and silicates (feldspars, mica, clay, talc, etc.). Granite, basalt and other rocks contain silicates. Emerald, topaz, aquamarine are silicate crystals. Only sodium and potassium silicates are soluble, the rest are insoluble. Silicates are complex. chem. compound: Kaolin Al 2 O 3 ; 2SiO 2 ; 2H 2 O or H 4 Al 2 SiO 9 .

Asbestos CaO; 3MgO; 4SiO 2 or CaMgSi 4 O 12 .

Receipt: fusion of silicon oxide with alkalis or carbonates.

Soluble glass– sodium and potassium silicates. Liquid glass– aq. solutions of potassium and sodium silicates. Its use for the production of acid-resistant cement and concrete, kerosene-proof plasters, fire-retardant paints. Aluminosilicates– silicates containing aluminum ( feldspar, mica). Feldspars In addition to silicon and aluminum oxides, they consist of potassium, sodium, and calcium oxides. Mica In addition to silicon and aluminum, they also contain hydrogen, sodium or potassium, and less often calcium, magnesium, and iron. Granites and gneisses (rocks)– comp. from quartz, feldspar and mica. Horn. rocks and minerals, located on the surface of the Earth, interact with water and air, which causes their change and destruction. This process is called. weathering.

Application: silicate rocks (granite) use. as a building material, silicates - as raw materials in the production of cement, glass, ceramics, fillers; mica and asbestos - as electrical and thermal insulation.

Municipal educational institution "Nikiforovskaya secondary school No. 1"

Carbon and its main inorganic compounds

Essay

Completed by: student of grade 9B

Sidorov Alexander

Teacher: Sakharova L.N.

Dmitrievka 2009

Introduction

Chapter I. All about carbon

1.1. Carbon in nature

1.2. Allotropic modifications of carbon

1.3. Chemical properties of carbon

1.4. Application of carbon

Chapter II. Inorganic carbon compounds

Conclusion

Literature

Introduction

Carbon (lat. Carboneum) C is a chemical element of group IV of the periodic system of Mendeleev: atomic number 6, atomic mass 12.011(1). Let's consider the structure of the carbon atom. The outer energy level of the carbon atom contains four electrons. Let's depict it graphically:

Carbon has been known since ancient times, and the name of the discoverer of this element is unknown.

At the end of the 17th century. Florentine scientists Averani and Tardgioni tried to fuse several small diamonds into one large one and heated them with a burning glass using sunlight. The diamonds disappeared, burning in the air. In 1772, the French chemist A. Lavoisier showed that when diamonds burn, CO 2 is formed. Only in 1797 did the English scientist S. Tennant prove the identity of the nature of graphite and coal. After burning equal amounts of coal and diamond, the volumes of carbon monoxide (IV) turned out to be the same.

The variety of carbon compounds, explained by the ability of its atoms to combine with each other and the atoms of other elements in various ways, determines the special position of carbon among other elements.

Chapter I . All about carbon

1.1. Carbon in nature

Carbon is found in nature, both in a free state and in the form of compounds.

Free carbon occurs in the form of diamond, graphite and carbyne.

Diamonds are very rare. The largest known diamond, the Cullinan, was found in 1905 in South Africa, weighed 621.2 g and measured 10x6.5x5 cm. The Diamond Fund in Moscow houses one of the largest and most beautiful diamonds in world – “Orlov” (37.92 g).

Diamond got its name from the Greek. "adamas" - invincible, indestructible. The most significant diamond deposits are located in South Africa, Brazil, and Yakutia.

Large deposits of graphite are located in Germany, Sri Lanka, Siberia, and Altai.

The main carbon-containing minerals are: magnesite MgCO 3, calcite (lime spar, limestone, marble, chalk) CaCO 3, dolomite CaMg(CO 3) 2, etc.

All fossil fuels - oil, gas, peat, coal and brown coal, shale - are built on a carbon basis. Some fossil coals, containing up to 99% C, are close in composition to carbon.

Carbon accounts for 0.1% of the earth's crust.

In the form of carbon monoxide (IV) CO 2, carbon enters the atmosphere. A large amount of CO 2 is dissolved in the hydrosphere.

1.2. Allotropic modifications of carbon

Elementary carbon forms three allotropic modifications: diamond, graphite, carbine.

1. Diamond is a colorless, transparent crystalline substance that refracts light rays extremely strongly. Carbon atoms in diamond are in a state of sp 3 hybridization. In the excited state, the valence electrons in the carbon atoms are paired and four unpaired electrons are formed. When chemical bonds are formed, the electron clouds acquire the same elongated shape and are located in space so that their axes are directed towards the vertices of the tetrahedron. When the tops of these clouds overlap with clouds of other carbon atoms, covalent bonds occur at an angle of 109°28", and an atomic crystal lattice characteristic of diamond is formed.

Each carbon atom in diamond is surrounded by four others, located from it in directions from the center of the tetrahedrons to the vertices. The distance between atoms in tetrahedra is 0.154 nm. The strength of all connections is the same. Thus, the atoms in diamond are “packed” very tightly. At 20°C, the density of diamond is 3.515 g/cm 3 . This explains its exceptional hardness. Diamond is a poor conductor of electricity.

In 1961, the Soviet Union began industrial production of synthetic diamonds from graphite.

In the industrial synthesis of diamonds, pressures of thousands of MPa and temperatures from 1500 to 3000°C are used. The process is carried out in the presence of catalysts, which can be some metals, for example Ni. The bulk of the diamonds formed are small crystals and diamond dust.

When heated without access to air above 1000°C, diamond turns into graphite. At 1750°C, the transformation of diamond into graphite occurs quickly.

Diamond structure

2. Graphite is a gray-black crystalline substance with a metallic sheen, greasy to the touch, and inferior in hardness even to paper.

Carbon atoms in graphite crystals are in a state of sp 2 hybridization: each of them forms three covalent σ bonds with neighboring atoms. The angles between the bond directions are 120°. The result is a grid made up of regular hexagons. The distance between adjacent nuclei of carbon atoms inside the layer is 0.142 nm. The fourth electron in the outer layer of each carbon atom in graphite occupies a p orbital that does not participate in hybridization.

Non-hybrid electron clouds of carbon atoms are oriented perpendicular to the plane of the layer and, overlapping each other, form delocalized σ bonds. Adjacent layers in a graphite crystal are located at a distance of 0.335 nm from each other and are weakly connected to each other, mainly by van der Waals forces. Therefore, graphite has low mechanical strength and easily splits into flakes, which themselves are very strong. The bond between layers of carbon atoms in graphite is partially metallic in nature. This explains the fact that graphite conducts electricity well, but not as well as metals.

Graphite structure

Physical properties in graphite vary greatly in directions - perpendicular and parallel to the layers of carbon atoms.

When heated without air access, graphite does not undergo any changes up to 3700°C. At the specified temperature, it sublimes without melting.

Artificial graphite is produced from the best grades of coal at 3000°C in electric furnaces without air access.

Graphite is thermodynamically stable over a wide range of temperatures and pressures, so it is accepted as the standard state of carbon. The density of graphite is 2.265 g/cm3.

3. Carbin is a fine-crystalline black powder. In its crystal structure, carbon atoms are connected by alternating single and triple bonds in linear chains:

−С≡С−С≡С−С≡С−

This substance was first obtained by V.V. Korshak, A.M. Sladkov, V.I. Kasatochkin, Yu.P. Kudryavtsev in the early 60s of the XX century.

It was subsequently shown that carbyne can exist in different forms and contains both polyacetylene and polycumulene chains in which the carbon atoms are linked by double bonds:

C=C=C=C=C=C=

Later, carbyne was found in nature - in meteorite matter.

Carbyne has semiconducting properties; when exposed to light, its conductivity increases greatly. Due to the existence of different types of bonds and different ways of laying chains of carbon atoms in the crystal lattice, the physical properties of carbyne can vary within wide limits. When heated without access to air above 2000°C, carbine is stable; at temperatures around 2300°C, its transition to graphite is observed.

Natural carbon consists of two isotopes

Previously, it was believed that charcoal, soot and coke are similar in composition to pure carbon and differ in properties from diamond and graphite, representing an independent allotropic modification of carbon (“amorphous carbon”). However, it was found that these substances consist of tiny crystalline particles in which the carbon atoms are bonded in the same way as in graphite.

4. Coal – finely ground graphite. It is formed during the thermal decomposition of carbon-containing compounds without air access. Coals vary significantly in properties depending on the substance from which they are obtained and the method of production. They always contain impurities that affect their properties. The most important types of coal are coke, charcoal, and soot.

Coke is produced by heating coal without access to air.

Charcoal is formed when wood is heated without access to air.

Soot is a very fine graphite crystalline powder. Formed by the combustion of hydrocarbons (natural gas, acetylene, turpentine, etc.) with limited air access.

Activated carbons are porous industrial adsorbents consisting mainly of carbon. Adsorption is the absorption of gases and dissolved substances by the surface of solids. Activated carbons are obtained from solid fuel (peat, brown and hard coal, anthracite), wood and its processed products (charcoal, sawdust, paper waste), leather industry waste, and animal materials, such as bones. Coals, characterized by high mechanical strength, are produced from the shells of coconuts and other nuts, and from fruit seeds. The structure of coals is represented by pores of all sizes, however, the adsorption capacity and adsorption rate are determined by the content of micropores per unit mass or volume of granules. When producing active carbon, the starting material is first subjected to heat treatment without access to air, as a result of which moisture and partially resins are removed from it. In this case, a large-porous structure of coal is formed. To obtain a microporous structure, activation is carried out either by oxidation with gas or steam, or by treatment with chemical reagents.

Carbon in the free state is a typical reducing agent. When oxidized by oxygen in excess air, it turns into carbon monoxide (IV):

if there is a deficiency - into carbon monoxide (II):

Both reactions are highly exothermic.

When carbon is heated in an atmosphere of carbon monoxide (IV), carbon monoxide is formed:

Carbon reduces many metals from their oxides:

This is how reactions occur with oxides of cadmium, copper, and lead. When carbon interacts with oxides of alkaline earth metals, aluminum and some other metals, carbides are formed:

This is explained by the fact that active metals are stronger reducing agents than carbon, therefore, when heated, the resulting metals are oxidized by excess carbon:

Carbon monoxide (II).

With incomplete oxidation of carbon, carbon monoxide (II) CO is formed - carbon monoxide. It is poorly soluble in water. The formal oxidation state of carbon 2+ does not reflect the structure of the CO molecule.

In the CO molecule, in addition to the double bond formed by sharing electrons of carbon and oxygen, there is an additional, third bond (depicted by an arrow), formed according to the donor-acceptor mechanism due to the lone pair of oxygen electrons

In this regard, the CO molecule is extremely strong. Carbon monoxide (II) is non-salt-forming and does not react under normal conditions with water, acids and alkalis. At elevated temperatures it is prone to addition and oxidation-reduction reactions. In air, CO burns with a blue flame:

It reduces metals from their oxides:

Under the influence of irradiation in direct sunlight or in the presence of catalysts, CO combines with phosgene, an extremely poisonous gas:

With many metals, CO forms volatile carbonyls:

The covalent bond in the nickel carbonyl molecule is formed by a donor-acceptor mechanism, with the electron density shifting from the carbon atom to the nickel atom. The increase in negative charge on the metal atom is compensated by the participation of its d-electrons in the bond, so the oxidation state of the metal is 0. When heated, metal carbonyls decompose into metal and carbon oxide (II), which is used to obtain metals of high purity.

Carbon monoxide (II) is practically never found in nature. It can be formed during the dehydration of formic acid (laboratory method of preparation):

Based on the last transformation, purely formally, CO can be considered formic acid anhydride. This is confirmed by the following reaction, which occurs when CO is passed into a molten alkali at high pressure:

Carbon monoxide (IV) and carbonic acid. Carbon monoxide (IV) is carbonic anhydride and has all the properties of acid oxides (see § 8).

When dissolved in water, carbonic acid is partially formed, and the following equilibrium exists in the solution.