- UN hazard class 2.3
- Secondary hazard UN 2.1
Molecule structure
The CO molecule, like the isoelectronic nitrogen molecule, has a triple bond. Since these molecules are similar in structure, their properties are also similar - very low melting and boiling points, close values of standard entropies, etc.
Within the framework of the valence bond method, the structure of the CO molecule can be described by the formula: C≡O:, and the third bond is formed by the donor-acceptor mechanism, where carbon is an acceptor of an electron pair, and oxygen is a donor.
Due to the presence of a triple bond, the CO molecule is very strong (the dissociation energy is 1069 kJ / mol, or 256 kcal / mol, which is higher than that of any other diatomic molecules) and has a small internuclear distance (d C≡O = 0.1128 nm or 1, 13Å).
The molecule is weakly polarized, the electric moment of its dipole is μ = 0.04 · 10 -29 C · m (the direction of the dipole moment is O - → C +). Ionization potential 14.0 V, force coupling constant k = 18.6.
Discovery history
Carbon monoxide was first obtained by the French chemist Jacques de Lasson in heating zinc oxide with coal, but was initially mistaken for hydrogen as it burned with a blue flame. The fact that this gas contains carbon and oxygen was discovered by the English chemist William Crookshank. Carbon monoxide outside the Earth's atmosphere was first discovered by the Belgian scientist M. Migeotte in 1949 by the presence of the main vibrational-rotational band in the IR spectrum of the Sun.
Carbon monoxide in the Earth's atmosphere
Distinguish between natural and anthropogenic sources of entry into the Earth's atmosphere. Under natural conditions, on the surface of the Earth, CO is formed by incomplete anaerobic decomposition organic compounds and during the combustion of biomass, mainly during forest and steppe fires. Carbon monoxide is formed in the soil both biologically (excreted by living organisms) and non-biological. It has been experimentally proven that carbon monoxide is released due to phenolic compounds common in soils containing OCH 3 or OH groups in the ortho or para-positions with respect to the first hydroxyl group.
The overall balance between the production of non-biological CO and its oxidation by microorganisms depends on the specific environmental conditions, primarily on humidity and value. For example, carbon monoxide is released from arid soils directly into the atmosphere, thus creating local maxima in the concentration of this gas.
In the atmosphere, CO is a product of chains of reactions involving methane and other hydrocarbons (primarily isoprene).
The main anthropogenic source of CO is currently engine exhaust. internal combustion... Carbon monoxide is formed when hydrocarbon fuels are burned in internal combustion engines at insufficient temperatures or poorly tuned air supply (not enough oxygen is supplied to oxidize CO to CO 2). In the past, a significant proportion of anthropogenic CO2 emissions came from luminous gas, which was used for indoor lighting in the 19th century. In composition, it approximately corresponded to water gas, that is, it contained up to 45% carbon monoxide. Currently, in the public sector, this gas has been replaced by a much less toxic gas. natural gas (inferior representatives homologous series of alkanes - propane, etc.)
CO input from natural and anthropogenic sources is approximately the same.
Carbon monoxide in the atmosphere is in a fast cycle: its average residence time is about 0.1 year, being oxidized by hydroxyl to carbon dioxide.
Receiving
Industrial way
2C + O 2 → 2CO (the thermal effect of this reaction is 22 kJ),
2. or when reducing carbon dioxide with hot coal:
CO 2 + C ↔ 2CO (ΔH = 172 kJ, ΔS = 176 J / K).
This reaction often occurs in an oven fire, when the oven damper is closed too early (until the coals are completely burnt out). The resulting carbon monoxide, due to its toxicity, causes physiological disorders ("waste") and even death (see below), hence one of the trivial names - "carbon monoxide". The picture of the reactions taking place in the furnace is shown in the diagram.
The reduction reaction of carbon dioxide is reversible; the effect of temperature on the equilibrium state of this reaction is shown in the graph. The reaction proceeding to the right provides the entropy factor, and to the left - the enthalpy factor. At temperatures below 400 ° C, the equilibrium is almost completely shifted to the left, and at temperatures above 1000 ° C to the right (towards the formation of CO). At low temperatures the rate of this reaction is very low; therefore, carbon monoxide is quite stable under normal conditions. This balance has a special name balance of boudoir.
3. Mixtures of carbon monoxide with other substances are obtained by passing air, water vapor, etc., through a layer of incandescent coke, coal or brown coal, etc. (see generator gas, water gas, mixed gas, synthesis gas).
Laboratory method
TLV (maximum threshold concentration, USA): 25 MPC r.z. according to the Hygienic Standards GN 2.2.5.1313-03 is 20 mg / m³
Carbon monoxide protection
Thanks to such a good calorific value, CO is a component of various technical gas mixtures (see, for example, generator gas) used, inter alia, for heating.
halogens. The greatest practical use got a reaction with chlorine:
CO + Cl 2 → COCl 2
The reaction is exothermic, its thermal effect is 113 kJ, in the presence of a catalyst (activated carbon) it takes place already at room temperature... As a result of the reaction, phosgene is formed - a substance that has become widespread in various branches of chemistry (as well as a chemical warfare agent). COF 2 (carbonyl fluoride) and COBr 2 (carbonyl bromide) can be obtained by analogous reactions. No carbonyl iodide was obtained. The exothermicity of reactions rapidly decreases from F to I (for reactions with F 2, the thermal effect is 481 kJ, with Br 2 - 4 kJ). You can also get mixed derivatives, for example COFCl (for more details, see the halogenated derivatives of carbonic acid).
By the reaction of CO with F 2, in addition to carbonyl fluoride, a peroxide compound (FCO) 2 O 2 can be obtained. Its characteristics: melting point -42 ° C, boiling point + 16 ° C, has a characteristic odor (similar to the smell of ozone), when heated above 200 ° C it decomposes with an explosion (reaction products of CO 2, O 2 and COF 2), in acidic environment reacts with potassium iodide according to the equation:
(FCO) 2 O 2 + 2KI → 2KF + I 2 + 2CO 2
Carbon monoxide reacts with chalcogenes. Forms carbon sulfide COS with sulfur, the reaction proceeds when heated, according to the equation:
CO + S → COS ΔG ° 298 = −229 kJ, ΔS ° 298 = −134 J / K
Similar selenium oxide COSe and telluride COTe have also been obtained.
Restores SO 2:
SO 2 + 2CO → 2CO 2 + S
Forms very volatile, flammable and toxic compounds with transition metals - carbonyls, such as Cr (CO) 6, Ni (CO) 4, Mn 2 CO 10, Co 2 (CO) 9, etc.
As mentioned above, carbon monoxide is slightly soluble in water, but does not react with it. Also, it does not react with solutions of alkalis and acids. However, it reacts with alkali melts:
CO + KOH → HCOOK
An interesting reaction is the reaction of carbon monoxide with metallic potassium in an ammonia solution. This forms an explosive compound potassium dioxodicarbonate:
2K + 2CO → K + O - -C 2 -O - K +
The reaction with ammonia at high temperatures you can get an important for the industry compound - hydrogen cyanide HCN. The reaction takes place in the presence of a catalyst (oxide
Carbon monoxide (carbon monoxide, carbon monoxide, carbon monoxide (II)) is a colorless, extremely toxic gas, odorless and tasteless, lighter than air (under normal conditions). Chemical formula- CO.
Molecule structure
Due to the presence of a triple bond, the CO molecule is very strong (the dissociation energy is 1069 kJ / mol, or 256 kcal / mol, which is more than that of any other diatomic molecules) and has a small internuclear distance ( d C≡O = 0.1128 nm or 1.13 Å).
The molecule is weakly polarized, its electric dipole moment μ = 0.04⋅10 −29 C · m. Numerous studies have shown that the negative charge in the CO molecule is concentrated on the carbon atom C - ← O + (the direction of the dipole moment in the molecule is opposite to that assumed earlier). Ionization energy 14.0 eV, force coupling constant k = 18,6 .
Properties
Carbon monoxide (II) is a colorless, odorless and tasteless gas. Combustible. The so-called "carbon monoxide smell" is actually the smell of organic impurities.
| Standard Gibbs energy of formation Δ G | −137.14 kJ / mol (g) (at 298 K) |
| Standard entropy of education S | 197.54 J / mol K (g) (at 298 K) |
| Standard molar heat capacity C p | 29.11 J / mol K (g) (at 298 K) |
| Enthalpy of melting Δ H pl | 0.838 kJ / mol |
| Boiling enthalpy Δ H bale | 6.04 kJ / mol |
| Critical temperature t Crete | −140.23 ° C |
| Critical pressure P Crete | 3.499 MPa |
| Critical density ρ crit | 0.301 g / cm³ |
Basic types chemical reactions, in which carbon monoxide (II) is involved, are addition reactions and redox reactions, in which it exhibits reducing properties.
At room temperatures, CO is inactive, its chemical activity increases significantly when heated and in solutions. So, in solutions, it reduces salts, and others to metals already at room temperature. When heated, it also reduces other metals, for example, CO + CuO → Cu + CO 2. It is widely used in pyrometallurgy. A method for the qualitative detection of CO is based on the reaction of CO in solution with palladium chloride, see below.
CO oxidation in solution often proceeds at a noticeable rate only in the presence of a catalyst. When selecting the latter, the nature of the oxidizing agent plays the main role. So, KMnO 4 oxidizes CO most rapidly in the presence of finely crushed silver, K 2 Cr 2 O 7 - in the presence of salts, KClO 3 - in the presence of OsO 4. In general, CO is similar to molecular hydrogen in its reducing properties.
Below 830 ° C, CO is the stronger reducing agent, and above, hydrogen. Therefore, the equilibrium of the reaction
H 2 O + C O ⇄ C O 2 + H 2 (\ displaystyle (\ mathsf (H_ (2) O + CO \ rightleftarrows CO_ (2) + H_ (2))))up to 830 ° C displaced to the right, above 830 ° C to the left.
It is interesting that there are bacteria that are capable of obtaining the energy they need for life due to the oxidation of CO.
Carbon monoxide (II) burns with a flame of blue color(reaction start temperature 700 ° C) in air:
2 C O + O 2 → 2 C O 2 (\ displaystyle (\ mathsf (2CO + O_ (2) \ rightarrow 2CO_ (2)))) (Δ G° 298 = −257 kJ, Δ S° 298 = −86 J / K).The combustion temperature of CO can reach 2100 ° C. The combustion reaction is a chain one, and the initiators are small amounts of hydrogen-containing compounds (water, ammonia, hydrogen sulfide, etc.)
Thanks to this good heating value, CO is a component of various technical gas mixtures (see, for example, generator gas), also used for heating. Explosive when mixed with air; lower and upper concentration limits of flame spread: from 12.5 to 74% (by volume).
halogens. The reaction with chlorine has received the greatest practical application:
C O + C l 2 → C O C l 2. (\ displaystyle (\ mathsf (CO + Cl_ (2) \ rightarrow COCl_ (2))).)By reacting CO with F 2, in addition to carbonyl fluoride COF 2, a peroxide compound (FCO) 2 O 2 can be obtained. Its characteristics: melting point -42 ° C, boiling point +16 ° C, has a characteristic odor (similar to the smell of ozone), when heated above 200 ° C it decomposes with an explosion (reaction products of CO 2, O 2 and COF 2), in acidic medium reacts with potassium iodide according to the equation:
(F C O) 2 O 2 + 2 K I → 2 K F + I 2 + 2 C O 2. (\ displaystyle (\ mathsf ((FCO) _ (2) O_ (2) + 2KI \ rightarrow 2KF + I_ (2) + 2CO_ (2).)))Carbon monoxide (II) reacts with chalcogenes. Forms carbon sulfide COS with sulfur, the reaction proceeds when heated, according to the equation:
C O + S → C O S (\ displaystyle (\ mathsf (CO + S \ rightarrow COS))) (Δ G° 298 = −229 kJ, Δ S° 298 = −134 J / K).Similar carbon selenoxide COSe and carbon telluride COTe have also been obtained.
Restores SO 2:
2 C O + S O 2 → 2 C O 2 + S. (\ displaystyle (\ mathsf (2CO + SO_ (2) \ rightarrow 2CO_ (2) + S.)))Forms flammable and toxic compounds with transition metals - carbonyls, such as,,,, etc. Some of them are volatile.
n C O + M e → [M e (C O) n] (\ displaystyle (\ mathsf (nCO + Me \ rightarrow)))Carbon monoxide (II) is slightly soluble in water, but does not react with it. Also, it does not react with solutions of alkalis and acids. However, it reacts with alkali melts to form the corresponding formates:
C O + K O H → H C O O K. (\ displaystyle (\ mathsf (CO + KOH \ rightarrow HCOOK.)))An interesting reaction is the reaction of carbon monoxide (II) with metallic potassium in an ammonia solution. This forms an explosive compound potassium dioxodicarbonate:
2 K + 2 C O → K 2 C 2 O 2. (\ displaystyle (\ mathsf (2K + 2CO \ rightarrow K_ (2) C_ (2) O_ (2).))) x C O + y H 2 → (\ displaystyle (\ mathsf (xCO + yH_ (2) \ rightarrow))) alcohols + linear alkanes.This process is the source for the production of critical industrial products such as methanol, synthetic diesel fuels, polyhydric alcohols, oils and greases.
Physiological action
Toxicity
Carbon monoxide very toxic.
The toxic effect of carbon monoxide (II) is due to the formation of carboxyhemoglobin - a much stronger carbonyl complex with hemoglobin, compared to the complex of hemoglobin with oxygen (oxyhemoglobin). Thus, the processes of oxygen transport and cellular respiration are blocked. Concentration in air of more than 0.1% will result in death within one hour.
- The victim should be taken to Fresh air... In case of mild poisoning, hyperventilation of the lungs with oxygen is sufficient.
- Artificial ventilation of the lungs.
- Lobelin or caffeine under the skin.
- Intravenous carboxylase.
World medicine knows no reliable antidotes for use in case of carbon monoxide poisoning.
Carbon monoxide (II) protection
Endogenous carbon monoxide
Endogenous carbon monoxide is produced normally by cells of the human and animal body and acts as a signaling molecule. It plays a well-known physiological role in the body, in particular, it is a neurotransmitter and causes vasodilation. Due to the role of endogenous carbon monoxide in the body, metabolic disorders are associated with various diseases, such as neurodegenerative diseases, atherosclerosis of blood vessels, hypertension, heart failure, various inflammatory processes.
Endogenous carbon monoxide is formed in the body due to the oxidizing effect of the heme oxygenase enzyme on heme, which is a product of the destruction of hemoglobin and myoglobin, as well as other heme-containing proteins. This process causes the formation of a small amount of carboxyhemoglobin in the blood of a person, even if the person does not smoke and breathes not atmospheric air (always containing small amounts of exogenous carbon monoxide), but pure oxygen or a mixture of nitrogen and oxygen.
Following the first data that appeared in 1993 that endogenous carbon monoxide is a normal neurotransmitter in the human body, as well as one of the three endogenous gases that normally modulate the course of inflammatory reactions in the body (the other two are nitric oxide (II) and hydrogen sulfide ), endogenous carbon monoxide has attracted considerable attention from clinicians and researchers as an important biological regulator. It has been shown that in many tissues all three of the aforementioned gases are anti-inflammatory agents, vasodilators, and also induce angiogenesis. However, not everything is so simple and unambiguous. Angiogenesis - not always beneficial effect as it plays a role in particular in the growth malignant tumors and is also one of the causes of retinal damage in macular degeneration. In particular, it is important to note that smoking (the main source of carbon monoxide in the blood, giving it several times higher concentration than natural production) increases the risk of macular retinal degeneration by 4-6 times.
There is a theory that in some synapses nerve cells, where long-term storage of information takes place, the receiving cell in response to the received signal produces endogenous carbon monoxide, which transmits a signal back to the transmitting cell, thereby informing it of its readiness to further receive signals from it and increasing the activity of the signal transmitter cell. Some of these nerve cells contain guanylate cyclase, an enzyme that is activated when exposed to endogenous carbon monoxide.
Research into the role of endogenous carbon monoxide as an anti-inflammatory agent and cytoprotectant has been carried out in many laboratories around the world. These properties of endogenous carbon monoxide make the effect on its metabolism an interesting therapeutic target for the treatment of such various pathological conditions as tissue damage caused by ischemia and subsequent reperfusion (and this, for example, myocardial infarction, ischemic stroke), graft rejection, vascular atherosclerosis, severe sepsis , severe malaria, autoimmune diseases. Human clinical trials have also been carried out, but the results have not yet been published.
To summarize, what is known for 2015 about the role of endogenous carbon monoxide in the body can be summarized as follows:
- Endogenous carbon monoxide is one of the important endogenous signaling molecules;
- Endogenous carbon monoxide modulates the functions of the central nervous system and cardiovascular system;
- Endogenous carbon monoxide inhibits platelet aggregation and adhesion to the walls of blood vessels;
- The influence on the exchange of endogenous carbon monoxide in the future may be one of the important therapeutic strategies for a number of diseases.
Discovery history
The toxicity of the smoke released during the combustion of coal was described by Aristotle and Galen.
Carbon monoxide (II) was first obtained by the French chemist Jacques de Lasson in heating zinc oxide with coal, but was initially mistaken for hydrogen because it burned with a blue flame.
The fact that this gas includes carbon and oxygen was discovered by the English chemist William Kruykshenk. The toxicity of the gas was investigated in 1846 by the French physician Claude Bernard in experiments on dogs.
Carbon monoxide (II) outside the Earth's atmosphere was first discovered by the Belgian scientist M. Migeotte in 1949 by the presence of the main vibrational-rotational band in the IR spectrum of the Sun. Carbon monoxide (II) was discovered in the interstellar medium in 1970.
Receiving
Industrial way
- Formed by combustion of carbon or compounds based on it (for example, gasoline) in conditions of lack of oxygen:
- or when reducing carbon dioxide with hot coal:
This reaction occurs in an oven fire, when the oven damper is closed too early (until the coals are completely burnt out). The resulting carbon monoxide (II), due to its toxicity, causes physiological disorders ("waste") and even death (see below), hence one of the trivial names - "carbon monoxide".
The reduction reaction of carbon dioxide is reversible; the effect of temperature on the equilibrium state of this reaction is shown in the graph. The reaction proceeding to the right provides the entropy factor, and to the left - the enthalpy factor. At temperatures below 400 ° C, the equilibrium is almost completely shifted to the left, and at temperatures above 1000 ° C to the right (towards the formation of CO). At low temperatures, the rate of this reaction is very low; therefore, carbon monoxide (II) is quite stable under normal conditions. This balance has a special name balance of boudoir.
- Mixtures of carbon monoxide (II) with other substances are obtained by passing air, water vapor, etc. through a layer of hot coke, coal or brown coal, etc. (see generator gas, water gas, mixed gas, synthesis gas ).
Laboratory method
- Decomposition of liquid formic acid under the action of hot concentrated sulfuric acid or passing gaseous formic acid over phosphorus oxide P 2 O 5. Reaction scheme:
- Heating a mixture of oxalic and concentrated sulfuric acids. The reaction goes according to the equation:
- Heating a mixture of potassium hexacyanoferrate (II) with concentrated sulfuric acid. The reaction goes according to the equation:
- Reduction from zinc carbonate with magnesium on heating:
Determination of carbon monoxide (II)
The presence of CO can be qualitatively determined by the darkening of palladium chloride solutions (or paper impregnated with this solution). Darkening is associated with the release of finely dispersed metallic palladium according to the following scheme:
P d C l 2 + C O + H 2 O → P d ↓ + C O 2 + 2 H C l. (\ displaystyle (\ mathsf (PdCl_ (2) + CO + H_ (2) O \ rightarrow Pd \ downarrow + CO_ (2) + 2HCl.)))This reaction is very sensitive. Standard solution: 1 gram of palladium chloride per liter of water.
The quantitative determination of carbon monoxide (II) is based on the iodometric reaction:
5 C O + I 2 O 5 → 5 C O 2 + I 2. (\ displaystyle (\ mathsf (5CO + I_ (2) O_ (5) \ rightarrow 5CO_ (2) + I_ (2).)))Application
- Carbon monoxide (II) is an intermediate reagent used in reactions with hydrogen in the most important industrial processes for the production of organic alcohols and unbranched hydrocarbons.
- Carbon monoxide (II) is used for processing meat of animals and fish, gives them a bright red color and a kind of freshness, without changing the taste (technologies Clear smoke and Tasteless smoke). The permissible CO concentration is 200 mg / kg meat.
- Carbon monoxide (II) is the main component of generator gas used as a fuel in gas generating vehicles.
- Carbon monoxide from engine exhaust was used by the Nazis during World War II to massacre people by poisoning.
Carbon monoxide (II) in the Earth's atmosphere
Distinguish between natural and anthropogenic sources of entry into the Earth's atmosphere. Under natural conditions, on the Earth's surface, CO is formed during incomplete anaerobic decomposition of organic compounds and during the combustion of biomass, mainly during forest and steppe fires. Carbon monoxide (II) is formed in the soil both biologically (excreted by living organisms) and non-biological. The release of carbon monoxide (II) due to phenolic compounds common in soils, containing OCH 3 or OH groups in the ortho- or para-positions with respect to the first hydroxyl group, has been experimentally proven.
The overall balance of non-biological CO production and its oxidation by microorganisms depends on specific environmental conditions, primarily on humidity and value. For example, carbon monoxide (II) is released from arid soils directly into the atmosphere, thus creating local maxima of the concentration of this gas.
In the atmosphere, CO is a product of chains of reactions involving methane and other hydrocarbons (primarily isoprene).
The main anthropogenic source of CO is currently the exhaust gases from internal combustion engines. Carbon monoxide is formed when hydrocarbon fuels are burned in internal combustion engines at insufficient temperatures or poorly tuned air supply (not enough oxygen is supplied to oxidize CO to CO 2). In the past, a significant proportion of anthropogenic CO2 emissions came from luminous gas, which was used for indoor lighting in the 19th century. In composition, it approximately corresponded to water gas, that is, it contained up to 45% carbon monoxide (II). It is not used in the utility sector due to the availability of a much cheaper and energy efficient analogue -
Considered the physical properties of carbon monoxide (carbon monoxide CO) under normal atmospheric pressure depending on the temperature at negative and positive values.
In tables the following physical properties of CO are presented: carbon monoxide density ρ , specific heat at constant pressure C p, thermal conductivity coefficients λ and dynamic viscosity μ .
The first table shows the density and specific heat of carbon monoxide CO in the temperature range from -73 to 2727 ° C.
The second table gives the values of such physical properties of carbon monoxide as thermal conductivity and its dynamic viscosity in the temperature range from minus 200 to 1000 ° C.
The density of carbon monoxide, as well, significantly depends on temperature - when carbon monoxide CO is heated, its density decreases. For example, at room temperature, the density of carbon monoxide has a value of 1.129 kg / m 3, but in the process of heating to a temperature of 1000 ° C, the density of this gas decreases by 4.2 times - to a value of 0.268 kg / m 3.
Under normal conditions (temperature 0 ° C) carbon monoxide has a density of 1.25 kg / m 3. If we compare its density with that of other common gases, then the density of carbon monoxide relative to air is less important - carbon monoxide is lighter than air. It is also lighter than argon, but heavier than nitrogen, hydrogen, helium, and other light gases.
The specific heat capacity of carbon monoxide under normal conditions is 1040 J / (kg · deg). As the temperature of this gas rises, its specific heat capacity increases. For example, at 2727 ° C, its value is 1329 J / (kg · deg).
| t, ° С | ρ, kg / m 3 | C p, J / (kg deg) | t, ° С | ρ, kg / m 3 | C p, J / (kg deg) | t, ° С | ρ, kg / m 3 | C p, J / (kg deg) |
|---|---|---|---|---|---|---|---|---|
| -73 | 1,689 | 1045 | 157 | 0,783 | 1053 | 1227 | 0,224 | 1258 |
| -53 | 1,534 | 1044 | 200 | 0,723 | 1058 | 1327 | 0,21 | 1267 |
| -33 | 1,406 | 1043 | 257 | 0,635 | 1071 | 1427 | 0,198 | 1275 |
| -13 | 1,297 | 1043 | 300 | 0,596 | 1080 | 1527 | 0,187 | 1283 |
| -3 | 1,249 | 1043 | 357 | 0,535 | 1095 | 1627 | 0,177 | 1289 |
| 0 | 1,25 | 1040 | 400 | 0,508 | 1106 | 1727 | 0,168 | 1295 |
| 7 | 1,204 | 1042 | 457 | 0,461 | 1122 | 1827 | 0,16 | 1299 |
| 17 | 1,162 | 1043 | 500 | 0,442 | 1132 | 1927 | 0,153 | 1304 |
| 27 | 1,123 | 1043 | 577 | 0,396 | 1152 | 2027 | 0,147 | 1308 |
| 37 | 1,087 | 1043 | 627 | 0,374 | 1164 | 2127 | 0,14 | 1312 |
| 47 | 1,053 | 1043 | 677 | 0,354 | 1175 | 2227 | 0,134 | 1315 |
| 57 | 1,021 | 1044 | 727 | 0,337 | 1185 | 2327 | 0,129 | 1319 |
| 67 | 0,991 | 1044 | 827 | 0,306 | 1204 | 2427 | 0,125 | 1322 |
| 77 | 0,952 | 1045 | 927 | 0,281 | 1221 | 2527 | 0,12 | 1324 |
| 87 | 0,936 | 1045 | 1027 | 0,259 | 1235 | 2627 | 0,116 | 1327 |
| 100 | 0,916 | 1045 | 1127 | 0,241 | 1247 | 2727 | 0,112 | 1329 |
The thermal conductivity of carbon monoxide under normal conditions is 0.02326 W / (m · deg). It increases with an increase in its temperature and at 1000 ° C it becomes equal to 0.0806 W / (m · deg). It should be noted that the value of the thermal conductivity of carbon monoxide is slightly less than this value y.
The dynamic viscosity of carbon monoxide at room temperature is 0.0246 · 10 -7 Pa · s. When carbon monoxide is heated, its viscosity increases. This character of the dependence of the dynamic viscosity on temperature is observed in y. It should be noted that carbon monoxide is more viscous than water vapor and carbon dioxide CO 2, but has a lower viscosity than nitrogen oxide NO and air.
Carbon monoxide (II ), or carbon monoxide, CO was discovered by the English chemist Joseph Priestley in 1799. It is a colorless gas, tasteless and odorless, it is poorly soluble in water (3.5 ml in 100 ml of water at 0 ° C), has low melting temperature (-205 ° C) and boiling point (-192 ° C).
Carbon monoxide enters the Earth's atmosphere during incomplete combustion of organic substances, during volcanic eruptions, as well as as a result of the vital activity of some lower plants(algae). The natural level of CO in the air is 0.01-0.9 mg / m 3. Carbon monoxide is highly toxic. In the human body and higher animals, it actively reacts with
The flame of burning carbon monoxide is a beautiful blue-violet color. It is easy to observe it yourself. To do this, you need to light a match. Bottom part glowing flame - this color is given to it by incandescent carbon particles (a product of incomplete combustion of wood). Above, the flame is surrounded by a blue-violet border. This burns carbon monoxide formed during the oxidation of wood.
a complex compound of iron - blood heme (associated with the protein globin), disrupting the function of transferring and consuming oxygen by tissues. In addition, it enters into irreversible interaction with some enzymes involved in the energy metabolism of the cell. At a concentration of carbon monoxide in a room of 880 mg / m 3, death occurs in a few hours, and at 10 g / m 3 - almost instantly. The maximum permissible content of carbon monoxide in the air is 20 mg / m 3. The first signs of CO poisoning (at a concentration of 6-30 mg / m 3) are decreased sensitivity of vision and hearing, headache, changes in heart rate. If a person is poisoned by carbon monoxide, he must be taken out into the fresh air, made to him artificial respiration, in mild cases of poisoning - give strong tea or coffee.
Large amounts of carbon monoxide ( II ) enter the atmosphere as a result of human activity. For example, a car emits about 530 kg of CO into the air on average per year. When 1 liter of gasoline is burned in an internal combustion engine, carbon monoxide emissions fluctuate from 1 50 to 800 g. On highways in Russia, the average concentration of CO is 6-57 mg / m 3, that is, it exceeds the poisoning threshold ... Carbon monoxide accumulates in poorly ventilated courtyards in front of houses located near highways, in basements and garages. V last years on the highways, special points have been organized to control the content of carbon monoxide and other products of incomplete combustion of fuel (CO-CH-control).
At room temperature, carbon monoxide is fairly inert. It does not interact with water and alkali solutions, that is, it is a non-salt-forming oxide, however, when heated, it reacts with solid alkalis: CO + KOH = NSOOK (potassium formate, formic acid salt); CO + Ca (OH) 2 = CaCO 3 + H 2. These reactions are used to evolve hydrogen from synthesis gas (CO + 3H 2) formed by the interaction of methane with superheated steam.
An interesting property of carbon monoxide is its ability to form compounds with transition metals - carbonyls, for example: Ni + 4CO ® 70 ° C Ni (CO) 4.
Carbon monoxide (II ) Is an excellent reducing agent. When heated, it is oxidized by atmospheric oxygen: 2CO + O 2 = 2CO 2. This reaction can be carried out at room temperature using a catalyst - platinum or palladium. These catalysts are installed in automobiles to reduce CO emissions into the atmosphere.
When CO reacts with chlorine, very poisonous gas phosgene (t bale = 7.6 ° C): CO + Cl 2 = COCl 2 ... Previously, it was used as a chemical warfare agent, and now it is used in the production of synthetic polymers of polyurethanes.
Carbon monoxide is used in the smelting of cast iron and steel for the reduction of iron from oxides; it is also widely used in organic synthesis. When a mixture of carbon monoxide interacts ( II ) with hydrogen, depending on the conditions (temperature, pressure), various products are formed - alcohols, carbonyl compounds, carboxylic acids... Especially great importance has the reaction of synthesis of methanol: CO + 2H 2 = CH 3 OH , which is one of the main products of organic synthesis. Carbon monoxide is used for the synthesis of phos-gene, formic acid, as a high-calorie fuel.
Carbon monoxide is a colorless and odorless gas that is slightly soluble in water.
t pl. 205 ° C,
t bales 191 ° C
critical temperature = 140 ° С
critical pressure = 35 atm.
the solubility of CO in water is about 1:40 by volume.
Chemical properties.
CO is inert under normal conditions; when heated - a reducing agent; non-salt-forming oxide.
1) with oxygen
2C +2 O + O 2 = 2C +4 O 2
2) with metal oxides
C +2 O + CuO = Cu + C +4 O 2
3) with chlorine (in the light)
CO + Cl 2 --hn-> COCl 2 (phosgene)
4) reacts with alkali melts (under pressure)
CO + NaOH = HCOONa (sodium formate (sodium formate))
5) forms carbonyls with transition metals
Ni + 4CO = t ° = Ni (CO) 4
Fe + 5CO = t ° = Fe (CO) 5
Carbon monoxide does not react chemically with water. CO also does not react with alkalis and acids. It is extremely poisonous.
WITH chemical side carbon monoxide is characterized mainly by its tendency to addition reactions and by its reducing properties. However, both of these tendencies usually manifest themselves only at elevated temperatures. Under these conditions, CO combines with oxygen, chlorine, sulfur, some metals, etc. At the same time, carbon monoxide, when heated, reduces many oxides to metals, which is very important for metallurgy. Along with heating, an increase in the reactivity of CO is often caused by its dissolution. So, in solution, it is able to reduce salts of Au, Pt and some other elements to free metals even at ordinary temperatures.
At elevated temperatures and high pressures there is an interaction of CO with water and caustic alkalis: in the first case, HCOOH is formed, and in the second, sodium formate. The last reaction proceeds at 120 ° C, a pressure of 5 atm and finds technical use.
Recovery of palladium chloride, easily going in solution, according to the general scheme:
PdCl 2 + H 2 O + CO = CO 2 + 2 HCl + Pd
is the most commonly used reaction for the opening of carbon monoxide in a mixture of gases. Already very small amounts of CO are easily detected by the slight coloration of the solution due to the release of finely crushed metallic palladium. The quantitative determination of CO is based on the reaction:
5 CO + I 2 O 5 = 5 CO 2 + I 2.
CO oxidation in solution often proceeds at a noticeable rate only in the presence of a catalyst. When selecting the latter, the nature of the oxidizing agent plays the main role. So, KMnO 4 oxidizes CO most rapidly in the presence of finely crushed silver, K 2 Cr 2 O 7 - in the presence of mercury salts, KClO 3 - in the presence of OsO 4. In general, in its reducing properties, CO is similar to molecular hydrogen, and its activity under normal conditions is higher than that of the latter. It is interesting that there are bacteria that are capable of obtaining the energy they need for life due to the oxidation of CO.
The comparative activity of CO and H 2 as reducing agents can be estimated by studying the reversible reaction:
H 2 O + CO = CO 2 + H 2 + 42 kJ,
the equilibrium state of which at high temperatures is established rather quickly (especially in the presence of Fe 2 O 3). At 830 ° C, the equilibrium mixture contains equal amounts of CO and H 2, i.e., the affinity of both gases for oxygen is the same. Below 830 ° C, CO is a stronger reducing agent, and above H 2.
The binding of one of the products of the above reaction in accordance with the law of mass action shifts its equilibrium. Therefore, by passing a mixture of carbon monoxide and water vapor over calcium oxide, hydrogen can be obtained according to the following scheme:
H 2 O + CO + CaO = CaCO 3 + H 2 + 217 kJ.
This reaction takes place already at 500 ° C.
In air, CO lights up at about 700 ° C and burns with a blue flame to CO 2:
2 CO + O 2 = 2 CO 2 + 564 kJ.
The significant heat generation accompanying this reaction makes carbon monoxide valuable. gaseous fuel... However, it is most widely used as a starting product for the synthesis of various organic substances.
The combustion of thick layers of coal in the furnaces takes place in three stages:
1) C + O 2 = CO 2; 2) CO 2 + C = 2 CO; 3) 2 CO + O 2 = 2 CO 2.
If the pipe is closed prematurely, a lack of oxygen is created in the furnace, which can cause the spread of CO through the heated room and lead to poisoning (waste). It should be noted that the smell of "carbon monoxide" is not caused by CO, but by impurities of some organic substances.
The CO flame can have a temperature of up to 2100 ° C. The CO combustion reaction is interesting in that when heated to 700-1000 ° C, it proceeds at a noticeable rate only in the presence of traces of water vapor or other hydrogen-containing gases (NH 3, H 2 S, etc.). This is due to the chain nature of the reaction under consideration, which occurs through the intermediate formation of OH radicals according to the following schemes:
H + O 2 = HO + O, then O + CO = CO 2, HO + CO = CO 2 + H, etc.
At very high temperatures, the CO combustion reaction becomes markedly reversible. The content of CO 2 in the equilibrium mixture (under a pressure of 1 atm) above 4000 ° C can be only negligible. The CO molecule itself is so thermally stable that it does not decompose even at 6000 ° C. CO molecules have been discovered in the interstellar medium. When CO acts on metal K at 80 ° C, a colorless crystalline highly explosive compound of the composition K 6 C 6 O 6 is formed. This substance, with the elimination of potassium, easily transforms into carbon monoxide C 6 O 6 ("trichinone"), which can be considered as a product of CO polymerization. Its structure corresponds to a six-membered cycle formed by carbon atoms, each of which is connected by a double bond with oxygen atoms.
Interaction of CO with sulfur by reaction:
CO + S = COS + 29 kJ
goes quickly only at high temperatures. The resulting carbon thioxide (O = C = S) is a colorless and odorless gas (mp -139, bp -50 ° C). Carbon monoxide (II) is able to directly combine with some metals. As a result, metal carbonyls are formed, which should be considered as complex compounds.
Carbon monoxide (II) also forms complex compounds with some salts. Some of them (OsCl 2 · 3CO, PtCl 2 · CO, etc.) are stable only in solution. The formation of the latter substance is associated with the absorption of carbon monoxide (II) by a solution of CuCl in strong HCl. Similar compounds are apparently formed in the ammonia solution of CuCl, which is often used for the absorption of CO in the analysis of gases.
Receiving.
Carbon monoxide is formed when carbon is burned in a lack of oxygen. Most often, it is obtained as a result of the interaction of carbon dioxide with hot coal:
CO 2 + C + 171 kJ = 2 CO.
This reaction is reversible, and its equilibrium below 400 ° C is almost entirely shifted to the left, and above 1000 ° C - to the right (Fig. 7). However, it sets in at a noticeable rate only at high temperatures. Therefore, CO is quite stable under normal conditions.
Rice. 7. Equilibrium CO 2 + C = 2 CO.
The formation of CO from elements follows the equation:
2 С + О 2 = 2 СО + 222 kJ.
Small amounts of CO are conveniently obtained by decomposition of formic acid: HCOOH = Н 2 О + CO
This reaction proceeds easily upon interaction of HCOOH with hot strong sulfuric acid. In practice, this production is carried out either by the action of conc. sulfuric acid to liquid HCOOH (when heated), or by passing the vapors of the latter over phosphorus hemipentaoxide. Interaction of HCOOH with chlorosulfonic acid according to the scheme:
HCOOH + СISO 3 H = H 2 SO 4 + HCI + CO
goes already at normal temperatures.
Heating from conc. Can serve as a convenient method for laboratory production of CO. sulfuric acid oxalic acid or ferrous potassium. In the first case, the reaction proceeds according to the scheme: Н 2 С 2 О 4 = СО + СО 2 + Н 2 О.
Along with CO, and carbon dioxide that can be delayed by passing gas mixture through a solution of barium hydroxide. In the second case, the only gaseous product is carbon monoxide:
K 4 + 6 H 2 SO 4 + 6 H 2 O = 2 K 2 SO 4 + FeSO 4 + 3 (NH 4) 2 SO 4 + 6 CO.
Large amounts of CO can be obtained by incomplete combustion of coal in special furnaces - gas generators. Ordinary ("air") generator gas contains on average (vol.%): CO-25, N2-70, CO 2 -4 and small admixtures of other gases. When burned, it gives 3300-4200 kJ per m 3. Replacing regular air with oxygen leads to a significant increase in the CO content (and an increase in the calorific value of the gas).
Even more CO contains water gas, consisting (in the ideal case) of a mixture of equal volumes of CO and H 2 and giving 11700 kJ / m 3 during combustion. This gas is obtained by blowing water vapor through a layer of hot coal, and about 1000 ° C there is an interaction according to the equation:
H 2 O + C + 130 kJ = CO + H 2.
The reaction of the formation of water gas proceeds with the absorption of heat, the coal gradually cools down and to maintain it in a red-hot state, it is necessary to alternate the passage of water vapor with the passage of air (or oxygen) into the gas generator. In this regard, the water gas contains approximately CO-44, H 2 -45, CO 2 -5 and N 2 -6%. It is widely used for the synthesis of various organic compounds.
Mixed gas is often obtained. The process of its production is reduced to the simultaneous blowing of air and water vapor through the layer of hot coal, i.e. a combination of both methods described above - Therefore, the composition of the mixed gas is intermediate between the generator and water. On average, it contains: CO-30, H 2 -15, CO 2 -5 and N 2 -50%. A cubic meter gives it when burning about 5400 kJ.
