Brand:
Drainage method is suitable for water-insoluble gases, upward exhaust method is suitable for gases heavier than air (that is, gases with a relative molecular mass greater than 29 can use oxygen 32, and the jar can be placed vertically, and the air is squeezed out because the collected gas is heavier than air), and downward exhaust method is suitable for gases lighter than air, such as hydrogen, ammonia, jar with a conduit extending into the bottom of the bottle upside down.
Oxygen can be collected by upward venting and drainage.
Hydrogen peroxide heating can produce oxygen, but it is generally not used in the laboratory because it will produce a lot of water vapor. In the laboratory, because potassium permanganate does not produce impurity gas, heating potassium permanganate will produce potassium permanganate, manganese chloride and oxygen. The laboratory can also heat potassium chlorate and manganese dioxide (manganese dioxide as catalyst) to produce potassium chloride and oxygen.
Air depressurization method is used in industry (80% of air is nitrogen and 20% is oxygen, and their boiling points are different).
High school textbooks say that submarines use sodium peroxide and carbon dioxide exhaled by people to make oxygen.
The purity of oxygen produced by drainage gas gathering method is much higher than that by exhaust method.
The decomposition cost of hydrogen peroxide is too high, and water vapor will be produced in the process of heating decomposition. Because potassium permanganate is solid, manganese dioxide can be easily decomposed to produce oxygen by adding catalyst.
Note: When heating potassium permanganate to generate oxygen, oxygen is collected by drainage method. The mouth of the test tube for heating potassium permanganate should be inclined downward at a certain angle to avoid the tube bursting caused by backward suction of water into the test tube. Hydrogen:
Hydrogen is the lightest gas known in the world. Its density is very small, only114 of air, that is, at standard atmospheric pressure and 0℃, the density of hydrogen is 0.0899 g/L.
Editor's Summary of Hydrogen-Introduction
Hydrogen is an important industrial gas. Colorless, tasteless, odorless and flammable. At atmospheric pressure, the boiling point is -252.8℃, the critical temperature is -239.9℃, the critical pressure is 1.32MPa, and the critical density is 30.1g/L. When the air content is 4% ~ 74% (by volume), explosive mixed gas is formed. Hydrogen has little solubility in various liquids and is difficult to dissolve in liquefaction. Liquid hydrogen is a colorless and transparent liquid with superconducting properties. Hydrogen is the lightest substance, which combines with oxygen, carbon and nitrogen to form water, hydrocarbons and ammonia. Natural gas fields, coal fields and organic matter fermentation also contain a small amount of hydrogen.
The mixed gas of hydrogen and carbon monoxide is an important chemical raw material-synthesis gas. The reaction between hydrogen and organic matter in the presence of catalyst is called hydrogenation, which is an important reaction process in industry.
Hydrogen discovery
1766 was discovered by H. cavendish in England.
In the history of chemistry, the discovery of hydrogen and the discovery and proof that water is a hydroxide compound rather than an element are mainly attributed to the British chemist and physicist cavendish (H.1731-1810).
/kloc-cavendish, an English chemist in the 0/8th century.
Cavendish is a millionaire, but his life is very simple. He built a large-scale laboratory at home with his own money and devoted his life to scientific research. A historian of science once said: cavendish "is the richest among the learned and the most learned among the rich." He has a keen observation of things and is good at experimental design. His experimental results are quite accurate, and his research scope is very wide. He made important discoveries in many chemical, mechanical and electrical problems and in the study of the average density of the earth. But he believed in phlogiston, which made him take some detours in chemical research. In the past 50 years, he has only published 18 papers, all of which are experimental and observational except one which is theoretical. After his death, it was found that he wrote a lot of valuable papers, but they were not published. These manuscripts of his are precious documents of scientific research, which were later compiled and published by physicist Maxwell and chemist Thorpe respectively.
There is an interesting story about these papers in the history of chemistry. Cavendish did an experiment in 1785. He let an electric spark pass through the mixture of ordinary air and oxygen, trying to oxidize all the nitrogen in it, and the nitrogen dioxide produced was absorbed by caustic potash. The experiment was done for three weeks, and finally there was a small bubble that could not be oxidized. His experimental records are kept in the manuscript, which reads: "The polluted air in the air is not a single substance (nitrogen), and there is another polluted air that is not combined with defluorinated air (oxygen), and the total amount does not exceed112. More than one hundred years later, 65,438+0,892, a physicist at Cambridge University, England. L.1842-1919), it is puzzling that the nitrogen obtained from the air is 0.0064 g per liter heavier than the nitrogen produced by ammoxidation. Chemist Ramsay (W.1852-1916) thinks that nitrogen in the air can contain heavier unknown gases. At this time, the chemistry professor Dewar (J. 1842- 1923) mentioned to them the above experiment of Cavendish, a doyen of Cambridge University, and the mystery of small bubbles. They immediately borrowed Cavendish's scientific data to read, and Rayleigh repeated Cavendish's experiment that year, and soon got a small bubble. Ramsar designed a new experiment. After removing water vapor, carbonic acid gas, oxygen and nitrogen from the air, this gas is also obtained, and its density is higher than that of nitrogen. It is proved by spectroscopic examination that it is a new element named argon. In this way, Cavendish's work in that year played an important role in the discovery of argon in 1894. From this story, we can see Cavendish's rigorous scientific research style and his great contribution to chemistry. 187 1 year, Cambridge university established a physics laboratory named after Cavendish. This is the famous Cavendish laboratory, which has been an important research center of modern physics in the world for decades.
The discovery of hydrogen and its properties.
Before the end of 18, many people had done experiments to make hydrogen, so it is hard to say who discovered hydrogen. Even cavendish, who has made great contributions to the discovery and research of hydrogen, thinks that the discovery of hydrogen is not only his credit. As early as16th century, the famous Swiss doctor's palace described that iron filings would produce a gas when they came into contact with acid. /kloc-in the 0/7th century, Helmont (J.B. 1579- 1644), a famous Belgian medical chemist, accidentally came into contact with this gas, but failed to separate and collect it.
Although Boyle collected this gas by accident, he didn't study it. They only know that it is flammable and know little about it. 1700, French pharmacist Lhemery (n.1645-1715) was also mentioned in the report of the Paris Academy of Sciences. It was cavendish who first collected hydrogen and studied its properties carefully.
1766, cavendish submitted a research report "Artificial Air Experiment" to the Royal Society, which described that he made "combustible air" (i.e. hydrogen) by reacting iron and zinc with dilute sulfuric acid and dilute hydrochloric acid, and collected it for research by the drainage gas collection method invented by priestley. He found that a certain amount of a metal reacts with a sufficient amount of various acids, and the amount of this gas produced is fixed, regardless of the type and concentration of the acid. He also found that when hydrogen is mixed with air and ignited, it will explode; It is also found that hydrogen combines with oxygen to form water, thus realizing that this gas is different from other known gases. However, because he is a devout believer in phlogiston theory, according to his understanding: this gas burns so violently that it is bound to be rich in phlogiston; Sulfur turns into sulfuric acid after combustion, so there is no phlogiston in sulfuric acid; According to phlogiston, metals also contain phlogiston. So he thinks that this gas is decomposed by metal, not by acid. He imagined that when metal was dissolved in acid, "the phlogiston contained in it was released, and this combustible air was formed". He even assumed that hydrogen was phlogiston at one time, which was quickly endorsed by some outstanding chemists at that time, such as Scheler and Kilwan (Kirwan, R.1735-1812). Because the bladder balloon is filled with hydrogen, the balloon will rise slowly. This phenomenon is used by some believers of phlogiston theory as the basis of their "argument" that phlogiston has negative weight. But cavendish is an extraordinary scientist after all. Later, he calculated the buoyancy of the balloon in the air. Through accurate research, it is proved that hydrogen has weight, but it is much lighter than air. The experiment he did was as follows: first, weigh the metal and the flask containing acid, then put the metal into the acid, collect hydrogen by drainage gas collection method and measure the volume, and then weigh the total amount of the flask and its contents after the reaction. In this way, he determined that the proportion of hydrogen is only 9% of that of air. But these chemists still refuse to give up the old theory easily. In view of the fact that hydrogen will produce water after burning, they say that hydrogen is a compound of phlogiston and water.
The synthesis of water denies the wrong view that water is an element. In ancient Greece, empedocles proposed that there were only four elements in the universe, namely, fire, air, water and earth, which constituted everything. From then until the 1970s, people always thought that water was an element. 178 1 year, priestley put hydrogen and air into a closed glass bottle and detonated it with an electric spark. Dewdrops appeared on the inner wall of the bottle In the same year, cavendish also repeated the experiment with a mixture of hydrogen and air in different proportions, confirming that the dew is pure water, indicating that hydrogen is a component of water. At this time, oxygen has been discovered. cavendish used pure oxygen instead of air to carry out experiments, which not only proved that hydrogen and oxidation synthesized water, but also confirmed that about 2 parts by volume of hydrogen and 1 part by volume of oxygen just synthesized water (published in 1784). These experimental results undoubtedly prove that water is a compound of hydrogen and oxygen, not an element, but cavendish, like priestley, still insists that water is an element, oxygen is water without phlogiston, and hydrogen is water with excessive phlogiston. He expressed the combustion of "combustible air" (hydrogen) with the following formula:
(water+phlogiston)+(water-phlogiston)-→ water
Combustible air (hydrogen) burns in air (oxygen).
1782, lavoisier repeated their experiment, decomposed water vapor with a red-hot barrel, and clearly put forward the correct conclusion: water is not an element, but a hydroxide compound, which corrected the wrong idea of taking water as an element for more than two thousand years. 1787, he named this gas "h-hydrogene", which means "producing water", and confirmed that it was an element.
Hydrogen-the name comes from the Greek word hydro +genes, which means "substance that produces water".
In Chinese, "hydrogen" was originally called "light gas" and "hydrogen" is a new pictophonetic word.
Japanese and Korean follow the original meaning of Greek and are called "water element". Hydrogen distribution
There is only extremely rare free hydrogen on the earth and in the earth's atmosphere. In the crust, if calculated by weight, hydrogen only accounts for 1% of the total weight, and if calculated by atomic percentage, it accounts for 17%. Hydrogen is widely distributed in nature, and water is the "warehouse" of hydrogen-calculated by weight percentage, water contains hydrogen11%; There is about 1.5% hydrogen in the soil; Oil, natural gas, animals and plants also contain hydrogen. In the air, hydrogen is not much, accounting for about one in two million of the total volume. In the whole universe, hydrogen is the element with the highest atomic percentage. According to research, in the atmosphere of the sun, the atomic percentage of hydrogen is 93%. In space, the number of hydrogen atoms is about 100 times more than the sum of all other elements.
Preparation: Coal can react with water vapor at high temperature to generate water gas. The main components of water gas are carbon monoxide and hydrogen, and the reaction equation is: C+H2O=CO+H2. Then hydrogen can be separated by separation technology to produce hydrogen. The main process is to spray steam on the burning coal and collect water gas on the other side. Ask what the pacing analyzer equipment is and how it works. You can have a look at this on Baidu Encyclopedia. Simply put, just like activated carbon absorbs harmful gases such as benzene and formaldehyde in the air, one of the two components is removed by using the molecular weight (molecular size) difference of different gases. In order to increase the adsorption capacity, it is necessary to increase the pressure of gas; After adsorption to a certain amount, the adsorbed components are released under reduced pressure, so that the adsorbent can be recycled. So it is called pressure swing adsorption. C: Definition of technical terms
Chinese name: carbon English name: carbon definition: symbol C, element 12 in the periodic table of elements, with atomic weight of 12, combines with other elements to form a large family of organic compounds. Carbon in the atmosphere mainly appears in the form of smoke and dust formed by incomplete combustion of organic matter.
Carbon is a nonmetallic element, which is located in the second periodic group of the periodic table of elements. Latin is Carbonium, which means "coal, charcoal". The Chinese character "carbon" consists of the word "carbon" and the word "stone" of charcoal. Carbon is a very common element, which exists widely in the atmosphere and crust in various forms. The understanding and utilization of simple carbon has a long history, and a series of compounds of carbon-organic matter are the basis of life. Carbon is one of the components of pig iron, wrought iron and steel. Carbon can chemically combine with itself to form a large number of compounds, which is an important molecule in biology and commerce. Most molecules in organisms contain carbon.
basic document
Radical: strokes outside the stone: 9 total strokes: 14 Chinese pronunciation: tàn English name: Carbon five strokes 86: dmdo five strokes 98: dmdo Cang Xie: MRUKF four-corner number: 12689 Meaning: a nonmetallic element, tasteless solid. Amorphous carbon includes coke and charcoal, while crystalline carbon includes diamond and graphite. Both ironmaking and steelmaking need coke. Carbon and its compounds are widely used in industry and medicine.
Edit the introduction of carbon elements in this paragraph.
Carbon compounds are generally obtained from fossil fuels, and then separated and further synthesized into various products needed for production and life, such as ethylene and plastics. Carbon has various forms, such as crystal element carbon, such as diamond and graphite; There is amorphous carbon such as coal; There are complex organic compounds such as animals and plants; Carbonate, such as marble. The physical and chemical properties of elemental carbon depend on its crystal structure. High hardness diamond and soft graphite have different crystal structures, each with its own appearance, density and melting point. At room temperature, elemental carbon is chemically inactive and insoluble in water, dilute acid, dilute alkali and organic solvents. Different reactions with oxygen at different high temperatures can generate carbon dioxide or carbon monoxide; Among halogens, only fluorine can react directly with elemental carbon; Under heating, elemental carbon is easily oxidized by acid; At high temperature, carbon can also react with many metals to form metal carbides. Carbon is reducible and can be used to smelt metal at high temperature. Chemical symbol: atomic weight of element C: 12.438+0 Usage
Proton number: 6 atomic number: 6 period: 2 group: IVA electron shell distribution: 2-4 atomic volume: 4.58 cubic centimeter/molar atomic radius (calculated value): 70(67)pm *** Valence radius: 77 pm Van der Waals radius: 170 pm Electronic configuration:1s 20. 2 (Weak acid) Color and appearance: black (graphite), colorless (diamond) charcoal, activated carbon and carbon. Contents of 23 elements on the surface of the Pacific Ocean in the crust: (ppm)4800 Mohs hardness: graphite 1-2, diamond 10 oxidation state: mainly -4, and C+2. The chemical bond energy of C+4 (and other oxidation states): (kj/mol) C-H411C-C348c = C 614C ≡ C839c = N 615c5438+0pmα = Kloc-0/086.2m+-m2+2352m2+-m3+4620m3+-M4+622m4+-M5+37827m5+-M6+47270 Element density: 3.5 13 g/cm3 (diamond). 20℃) Electronegativity: 2.55 (Pauling scale) Specific heat: 710J/(kg k) Electrical conductivity: 0.061×10-6/(m ohm) Thermal conductivity:129. The fifth ionization energy is 37836544 bonding: carbon atoms are generally tetravalent and need four single electrons, but their ground state has only two single electrons, so they always need hybridization when bonding. The most common hybridization method is sp3 hybridization, which makes full use of four valence electrons, evenly distributed in four orbits, and belongs to isotropic hybridization. This structure is completely symmetrical, and it is a stable σ bond after bonding, and it is very stable without the repulsion of lone electron pairs. All the carbon atoms in diamond are combined in this way. The carbon atoms of alkanes also belong to this category. According to requirements, carbon atoms can also be hybridized with sp2 or sp. Both of these methods appear in the case of re-bonding, and the non-hybridized P orbitals are perpendicular to the hybridized orbitals, forming π bonds with the P orbitals of adjacent atoms. The carbon atom connecting the double bond in olefins is sp 2 hybridization. Because sp2 hybridization can make the atom * * * plane, when multiple double bonds appear, all P orbitals perpendicular to the molecular plane may overlap each other, forming a * * * yoke system. Benzene is the most typical yoke system, which has lost some properties of double bonds. All the carbon atoms in graphite are in a large yoke system, one for each layer.
Edit carbon isotopes in this section.
There are twelve known isotopes * * *, ranging from carbon 8 to carbon 19, of which carbon 12 and carbon 13 are stable, while others are radioactive. Among them, the half-life of carbon 14 is more than 5000 years, and others are less than half an hour. In the nature of the earth, carbon 12 accounts for 98.93% of all carbon, while carbon 13 accounts for 1.07%. The atomic weight of C is the weighted average of carbon 12 and 13, and 12.05438+0 is generally taken in the calculation. Carbon 12 is the scale of moles defined in the international system of units, and the number of atoms contained in 12g carbon 1 2 is1mole. Carbon 14 is widely used to date antiquities because of its long half-life.
Edit the form of elemental carbon in this paragraph.
The two most common simple substances are high hardness diamond and soft and greasy graphite, and their crystal structures and bonding types are different. Each carbon of a diamond is tetrahedrally 4 coordinated, similar to aliphatic compounds; Each carbon of graphite is a triangle 3 coordination, which can be regarded as infinite benzene rings fused together. The chemical properties of elemental carbon are relatively stable at room temperature and insoluble in water, dilute acid, dilute alkali and organic solvents.
1. Diamond
Diamond structure diagram
The strongest carbon structure, in which carbon atoms are arranged in the form of crystal structure, and each carbon atom is closely combined with the other four carbon atoms to form a spatial network structure, and finally a solid with high hardness and poor activity is formed. The melting point of diamonds exceeds 3500℃, which is equivalent to the surface temperature of some stars. Main functions: decorations, cutting metal materials, etc.
2. Graphite
Graphite is a dark gray metallic opaque fine scale solid. Soft, greasy and has excellent electrical conductivity. The carbon atoms in graphite are bonded together in a plane layered structure, and the bonding between layers is fragile, so the layers are easily separated by sliding. Main functions: making pencils, electrodes, trolley wires, etc.
3. Fullerenes, C60, C72, etc. )
C60
1985 was discovered by scientists at Ross University in Texas, USA. The carbon atoms in fullerenes are bonded together in a spherical dome structure.
4. Other carbon structures
Hexagonal diamonds (also known as hexagonal diamonds) have the same bond type as diamonds, but the atoms are arranged in a hexagon.
Graphene (that is, single-layer graphite) carbon nanotubes (with typical layered hollow structure characteristics) monoclinic superhard carbon (M-type carbon, the high-pressure phase of graphite after low temperature, with monoclinic structure, and its hardness is close to that of diamond) amorphous carbon (amorphous, not a real alien, and its internal structure is graphite) Zhao graphite (that is, pyrophyllite, which is produced when graphite collides with meteorites and has a hexagonal pattern of atoms) mercury tetrahedrite structure (. Hexagonal layer twisted into the imaginary structure of "negative curvature" saddle) fibrous carbon (filamentary carbon, fiber formed by small pieces piled up in long chains) carbon aerogels (extremely low-density porous structure, similar to the well-known silicon aerogel) carbon nano-foam (cobweb-like, with fractal structure, the density of which is 1% of that of carbon aerogels, with ferromagnetism).
Compound of carbon element
Among the compounds of carbon, only the following compounds belong to inorganic substances: oxides of carbon, sulfides: carbon monoxide (CO), carbon dioxide (CO2), carbon disulfide (CS2), carbonate, bicarbonate, cyanide, a series of pseudohalogens and their pseudohalides, pseudohalides: cyanide (CN)2, cyanogen oxide and thiocyanate. Other carbon-containing compounds are organic compounds. Because the bonds formed by carbon atoms are relatively stable, the number and arrangement of carbon and the types and positions of substituents in organic compounds are very arbitrary, which leads to the phenomenon of a large number of organic substances. At present, among the compounds discovered by human beings, organic matter accounts for the vast majority. The properties of organic compounds are quite different from those of inorganic compounds. They are generally flammable and insoluble in water, and their reaction mechanism is complicated. Now they have formed an independent branch-organic chemistry. Distributed carbon exists in nature (such as diamond and graphite) and is the main component of coal, oil, asphalt, limestone, other carbonates and all organic compounds, and its content in the earth's crust is about 0.027% (the content calculated by different analytical methods is different). The elements with the highest content in the crust are O 46.6%, Si 27.7% and Al 8. 1% in turn. Carbon is the largest element in the dry weight of organisms. Carbon also circulates in the earth's atmosphere and stratosphere in the form of carbon dioxide. In most celestial bodies and their atmosphere, there are carbon combustion phenomena, combustion calorific value and combustion heat equation.
1. Carbon burns in oxygen.
Strong exotherm, dazzling white light, colorless and odorless gas, which can make calcium hydroxide solution (clarified limewater) turbid.
2. Carbon burns in the air
Exothermic, emitting red light, producing colorless and odorless gas that can make calcium hydroxide solution (clarified lime water) turbid; When the combustion is insufficient, that is, when the amount of oxygen is insufficient, carbon monoxide will be produced.
3. Combustion heat equation
c(s)+O2(g)= CO2(g)△H =-393.5 kj/mol
4. Combustion calorific value
393.5 kJ/mol
The discovery history of carbon
Diamonds and graphite have been known since prehistoric times. Fullerenes were discovered in 1985, and then a series of carbon elements with different arrangements were discovered. Isotope carbon 14 was discovered by American scientists Martin Carmen and Samuel Rubin in 1940. Hexagonal diamonds were discovered by American scientists Gafford Rongdile and Yusula Marvin in 1967. Monoclinic superhard carbon was discovered by American scientists Band-Aid and Casper in 1967, and its crystal structure was theoretically determined by Dr. James Li of Jilin University and his tutor Professor Ma Yanming in 2009. In 2004, Andre K. Geim of Manchester University in England prepared graphene. Heim and his colleagues came across a simple new method. They forcibly separated the graphite into smaller pieces, peeled off a thin graphite sheet from the pieces, and then glued the two sides of the sheet together with a special plastic tape, tearing the tape apart and the sheet split in half. By repeating this process, thinner and thinner graphite flakes can be obtained, and some samples consist of only one layer of carbon atoms-they have already made graphene. co；
Carbon monoxide (CO) is a colorless, odorless and non-irritating gas. The solubility in water is very low, but it is easily soluble in ammonia water. After carbon monoxide enters the human body, it will combine with hemoglobin in the blood, so that hemoglobin cannot combine with oxygen, resulting in hypoxia in body tissues and suffocation and death. Therefore, carbon monoxide is toxic. Common in the case of poor ventilation in family rooms, gas or liquefied gas pipeline leaks, coal stoves or industrial gas and carbon monoxide are inhaled into the mine, leading to poisoning.
Editor's summary carbon monoxide-physical properties
Colorless, odorless and tasteless gas.
Vapor pressure (kpa): 309 kpa/- 180℃
Solubility: low solubility in water, but easy to be absorbed by ammonia water.
Prohibited compounds: strong oxidant and alkali.
Decomposition products: decomposed into carbon and carbon dioxide at 400 ~ 700℃.
Hazard characteristics: flammable and explosive gas. Mixing with air can form an explosive mixture, which will cause combustion and explosion when exposed to open fire and high heat energy; The explosion limit of air mixture is 12% ~ 75%.
Other physical properties: spontaneous combustion point 608.89℃.
Carbon monoxide-chemical properties The valence of carbon element in carbon monoxide molecule is 12, which can be further converted into +4 by oxygen, thus making carbon monoxide flammable and reducible. Combustion of carbon monoxide in air or oxygen can generate carbon dioxide: 2co+O2 = ignition = 2CO+O2=.
When it burns, it gives off a blue flame and gives off a lot of heat. Therefore, carbon monoxide can be used as a gas fuel.
As a reducing agent, carbon monoxide can reduce many metal oxides to elemental metals at high temperature, so it is often used in metal smelting. For example, black copper oxide is reduced to red metal copper and zinc oxide is reduced to metal zinc;
CO+CuO=Cu+CO2
Cobalt+zinc oxide = zinc+carbon dioxide
The multi-step reduction reaction can take place in an iron smelting furnace:
CO+3Fe2O3= 2Fe3O4+CO2
Fe3O4+CO= 3FeO+CO2
FeO+CO=Fe+CO2
Under the conditions of heating and pressure, it can react with some simple metals to generate molecular compounds. Such as Ni(CO)4 (nickel tetracarbonyl) and Fe(CO)5 (iron pentacarbonyl). Unstable, it decomposes into corresponding metals and carbon monoxide immediately when heated, which is one of the methods to purify metals and prepare pure carbon monoxide.
Formation mechanism of carbon monoxide
Carbon monoxide is the most widely distributed and abundant pollutant in the atmosphere, and it is also one of the important pollutants produced in the combustion process. The main source of CO in the atmosphere is the exhaust gas from internal combustion engines, followed by the burning of fossil fuels by boilers.
Carbon monoxide is an intermediate product produced during the combustion of carbon-containing fuel, and all the carbon originally present in the fuel will form carbon monoxide. The formation and decomposition of carbon monoxide are controlled by the chemical reaction kinetics mechanism, which is one of the basic reactions in the combustion process of hydrocarbon fuels. Its formation mechanism is as follows:
RH → R → RO2 → RCHO → RCO → CO
Where r is a hydrocarbon radical. In the reaction, the RCO atomic group mainly generates CO through thermal decomposition, and can also generate CO after oxidizing hydrocarbon group R. In the combustion process, the rate of carbon monoxide oxidation to carbon dioxide is lower than that of carbon monoxide generation, so the basic oxidation reaction of carbon monoxide in hydrocarbon flame is as follows:
Carbon monoxide+hydroxyl → carbon dioxide+H2
Carbon monoxide is one of the products of incomplete combustion. If the combustion process can be well organized, that is, there is enough oxygen, sufficient mixing, high enough temperature and long residence time, the intermediate product CO will eventually burn out and produce CO2 or H2O. Therefore, controlling CO emission is not an attempt to inhibit its formation, but an effort to make it burn completely.
The results show that in the premixed combustion flame of hydrocarbon fuel and air, the CO concentration in the flame region rapidly rises to the maximum value, which is usually higher than the equilibrium value of the reaction mixture during adiabatic combustion, and then slowly decreases to the equilibrium value. Therefore, the CO content detected from the exhaust of the combustion equipment is lower than the maximum value in the combustion chamber, but obviously higher than the equilibrium value in the exhaust state. This shows that the chemical reaction kinetics controls the formation and destruction of co.
Carbon monoxide-a health hazard
Hazard classification (GB 5044-85): Grade II (highly dangerous).
1, acute toxicity
LC50: 2300-5700 mg/m3 for mice, 0/000-3300 mg/m3 for guinea pigs, 4600-0/7200 mg/m3 for rabbits, 4600-45800 mg/m3 for cats and 34400-45800 mg/m3 for dogs.
2, subacute and chronic toxicity
After inhaling 0.047~0.053mg/L/L/L, 4 ~ 8 h/d for 30 days, the growth of rats was slow, the number of hemoglobin and red blood cells increased, and the activities of succinate dehydrogenase and cytochrome oxidase in liver were destroyed. Monkey inhaled 0. 1 1mg/L, which caused myocardial damage after 3 ~ 6 months.
3. Metabolism
After inhaled with air, carbon monoxide enters the blood circulation through alveoli, and forms a reversible combination with hemoglobin in blood and some other ferritins outside blood (such as myoglobin and cytochrome of ferrous iron). ). Among them, more than 90% of carbon monoxide combined with Hb to form carboxyhemoglobin, about 7% of carbon monoxide combined with myoglobin to form carboxymyoglobin, and only a small amount of carbon monoxide combined with cytochrome. Experiments show that carbon monoxide will not accumulate in the body. Animals inhaled 200ppm carbon monoxide 1 month, and carbon monoxide was completely discharged 24 hours after stopping poisoning, of which 98.5% was discharged through the lungs in its original form, and only 1% was oxidized into carbon dioxide in the body. The absorption and discharge of carbon monoxide depends on the partial pressure of carbon monoxide in the air and the saturation of HbCO in the blood (that is, the percentage of Hb bound by carbon monoxide to the total Hb). The secondary factors are contact time and lung ventilation; The latter is directly related to labor intensity.
4. Poisoning mechanism
It is caused by the reversible combination of carbon monoxide and hemoglobin. It is generally believed that the affinity of carbon monoxide and hemoglobin is 230 ~ 270 times greater than that of oxygen and hemoglobin, so the oxygen in oxygenated hemoglobin in blood is squeezed out to form oxygenated hemoglobin (HbCO), and the dissociation of oxygenated hemoglobin is 3600 times slower than that of oxygenated hemoglobin, so oxygenated hemoglobin is more stable than oxygenated hemoglobin. Carboxyhemoglobin not only has no oxygen carrying function, but also affects the dissociation of carboxyhemoglobin, so the tissue suffers from double hypoxia. Eventually lead to tissue hypoxia and carbon dioxide retention, resulting in poisoning symptoms.
The central nervous system is most sensitive to hypoxia, and carbon monoxide poisoning is the first to affect it. Especially the white matter and globus pallidus in the cerebral cortex are the most serious. Pathologically, the cerebral blood vessels twitched first and then expanded, and the permeability increased in different degrees, brain edema and focal softening.
Too many, my hands are numb, pure handwriting, hope to adopt.