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Lesson type: lesson on learning new material
Target: create conditions for students to master the chemistry course material on the topic: “Carbon oxides” at the level of competence through active study of theoretical material.
Techniques, methods and technologies used: problem-based approach to teaching, gaming technologies, conversation, individual and group work, experiment.
Tasks:
- Educational- fostering a caring attitude towards one’s health and the surrounding nature, the formation of a scientific worldview (about the reality of the existence of these oxides and the transformations associated with them), giving each student the opportunity to achieve success
- Educational– systematize students’ knowledge about acid oxides using the example of carbon oxides, learn the structure, physical properties, chemical properties, production and use of carbon dioxide and carbon dioxide, qualitative reaction to carbon dioxide, the physiological effect of carbon dioxide and carbon dioxide on the human body, continue work on developing skills compare, draw up reaction equations, work with textbook text, obtain information from the Internet
- Developmental - develop the ability to work in an atmosphere of search, cognitive interest in chemistry, using data on the significance of the studied substances and phenomena in the surrounding life, the development of communication skills, the formation of pair and group work skills in revealing cause-and-effect relationships, the development of the ability to independently formulate and formulate for oneself new tasks, determine methods of action and correlate with planned results.
Methods: verbal, visual, research
Teacher equipment: computer, multimedia projector.
Equipment for students: laboratory glassware (test tubes, test tube rack, beakers), handouts (support notes, student handouts).
During the classes
1. Organizational moment.
Hello. It's nice to see familiar faces. We are partners today.
The motto of our lesson today can be the words of Confucius:
There are three paths to reason for a person:
- The path of reflection is the most noble;
- The path of imitation is the easiest;
- The path of personal experience is the heaviest.
I propose to choose path 3 today, but each of you may not listen to my words and choose any other.
2. Preparation for the main stage of the lesson
The teacher formulates the objectives of the lesson
In the work of Odoevsky V.D. “Moroz Ivanovich” contains the following excerpt:
“Why do you, Moroz Ivanovich,” asked the Needlewoman, “walk the streets in winter and knock on windows?”
“And then I knock on the windows,” answered Moroz Ivanovich, “so that they don’t forget to light the stoves and close the pipes in time; Otherwise, I know, there are such slobs that they will heat up the stove and not close the chimney, or they will close it at the wrong time, when not all the coals have burned out yet, and because of this there is carbon monoxide in the room, people get headaches, green in the eyes; You can even completely die from fumes."
What will we talk about in class today?
Teacher: In another work by V. Korotkevich “Black Castle Olshansky. Wild Hunt of King Stach” we read:
“You’ve heard about the “dog cave” effect in Italy. There is a pit cave there. A person will go in and walk around, but a dog or a rabbit will die in a few minutes.
Carbon dioxide is released from a volcanic fissure..."
And since he...”
Finish the sentence. Explain the “mysterious death of animals”
ANSWER: (And since carbon dioxide is heavier than air, it remains below. The human head is above this zone. A dog’s head is not...”
Can you answer this question now?
The topic of today's lesson is “Oxides of carbon (II) and (IV) - friends or enemies?” Propose a plan for studying this topic (the plan is entered in the table)
Teacher: Do you have all the necessary information to fill out this table now???
2. Assimilation of new knowledge and methods of action
Teacher: Do these oxides exist in nature? Together with students, he names the ways in which carbon oxides enter the atmosphere. Carbon dioxide is often called a “greenhouse gas.” Why do you think? and what is this connected with?
Express opinions and explain the essence of the greenhouse effect
(The Earth receives energy from the Sun and itself radiates some of the heat into outer space. But many gases contained in its atmosphere, including CO2, retain some of the heat.
Over the past decades, the concentration of CO 2 in the atmosphere has been slowly but steadily increasing, and with it, due to the greenhouse effect, so has the temperature (by half a degree over the last 100 years). It is predicted that by 2025, the amount of carbon dioxide in the air could double. It would seem like a trifle; it’s not important for human breathing, but it’s beneficial for plants. But the average annual temperature will increase by several degrees. This is a lot: the ice of the Arctic and Antarctic will begin to melt, the level of the World Ocean will rise, and vast areas will be under water. If this happens, most of the fields will be destroyed. Some countries will lose all cultivated land, while in other countries the best agricultural regions will change their location. In addition, the Earth's climate will change, and we do not even know exactly what catastrophic consequences this will lead to.
Scientists predict that a doubling of CO 2 levels in the atmosphere compared to pre-industrial times will raise the overall average temperature by 2.8 0 C. The largest increase in temperature will occur in the northern hemisphere at a latitude of about 40 0, where the most fuel is burned and seasonal influences are greater. plant life.
According to American experts, climate warming in the next 100 years will lead the United States to flooding 80% of coastal areas.)
We learned where these oxides come from in nature and why CO2 is called a “greenhouse gas.” Will we have enough of this knowledge? What else do we need to know about these substances? And how will we do this?
Teacher. A wise Chinese proverb says
“I hear - I forget, I see - I remember, I do - I understand.”
3. Initial check of understanding
Teacher suggests using additional materials that are on the tables to obtain the information necessary to fill out the table. Students study this information.
Group 1 Structure of CO and CO 2 molecules
I. Carbon monoxide - carbon monoxide (II)
Consider the structure of CO by determining the oxidation state of the elements C +2 O -2 and, accordingly, deducing how many electrons the carbon atom transferred for general use (two), and therefore how many electrons the more electronegative oxygen pulled towards itself - two.
However, further examination of the structure of CO shows that in this situation, carbon will not have the coveted eight electrons at the outer level - four of its own and two shared with the oxygen atom. What should I do? Obviously, the oxygen atom will have to donate one of its free electron pairs for common use, i.e., act as a donor. The acceptor, of course, will be the carbon atom:
those. There will be three covalent bonds, and two electrons drawn from carbon to oxygen (s.b. +2). The bond in the CO molecule is polar covalent. The number of electrons shifted from carbon to oxygen is two, which means the oxidation state of the carbon atom is +2. The carbon atom in the CO molecule has two free electrons, which means CO can participate in reactions, exhibiting reducing properties. This is possible with oxidizing agents such as oxygen, halogens and even metal oxides.
II Carbon dioxide
All four bonds are polar covalent bonds and were formed due to the sharing of electrons by carbon and oxygen atoms. However, due to its linear structure, the CO 2 molecule is generally non-polar. Shows oxidizing properties.
Group 2 Physical properties of oxides
A colorless, odorless gas (it is impossible to feel it) is what makes it insidious! This gas is also insidious because it is distributed evenly in the air. Мr (СО) = 28 and approximately equal to Мr (air) = 29 Insoluble in water. Burns with a bluish flame. Toxic, MPC (CO) = 20 mg/m 3 By combining with hemoglobin of red blood cells, oxygen carriers from the lungs to the tissues of the body, carbon monoxide causes oxygen starvation, and a person can die. If air containing up to 0.1% CO is inhaled, a person may lose consciousness and die. In case of poisoning, there is a sudden loss of consciousness, and in severe cases, death. Carbon monoxide irreversibly binds to hemoglobin in the blood, preventing gas exchange, and a person suffocates. Providing assistance - breathing pure oxygen, blood transfusion. Where can you find such a “monster”? You can observe it in the flame of a candle or firebox. It is present in the exhaust gases of internal combustion engines and in cigarette smoke. Formed during the combustion of most flammable materials under conditions of limited air access.
The gas is colorless, odorless, highly soluble in water, Mr(CO2) = 44. Compare with Mr(air) = 29. 1.5 times heavier than air. At t = - 76 0 C – dry ice.
It has a narcotic effect on humans, irritates the skin and mucous membranes, has a central vasoconstrictor and local vasodilator effect, causes an increase in the content of amino acids in the blood, and inhibits the action of enzymes in tissues. MPC (CO 2) = 30 mg/m 3 Both its excess and its deficiency are harmful to humans. In small quantities (up to 2%), carbon dioxide stimulates the activity of the respiratory center. With increasing concentration, serious disorders arise, and at 10% concentration, breathing stops, loss of consciousness occurs, at 20%, paralysis of the vital centers within a few seconds. Fortunately, people rarely encounter such high concentrations of CO 2 in the air (this is possible, for example, in basements without ventilation where dry ice is stored).
How to help a person who has carbon dioxide poisoning? - remove to fresh air.
Group 3 Chemical properties of oxides
I CO - flammable gas, burns with a blue flame:
2CO +O 2 = 2CO 2 (carbon dioxide) +577 kJ
CO +Cl 2 =COCl 2 (phosgene)
Carbon(II) monoxide can reduce most metals from their oxides, for example:
CO + CuO -> Cu+ CO 2
CO +FeO =CO 2 +Fe
CO +2H 2 =CH 3 OH (methanol)
II Carbon dioxide– acidic oxide, it interacts with basic oxides and bases to form acidic and medium salts, with some salts, water:
CaO+ CO 2 -> CaCO 3
Ca(OH) 2 + CO 2 -> CaCO 3 + H 2 O ( qualitative reaction to CO 2)
Ca(OH) 2 + 2CO 2 -> Ca(HCO 3) 2
CaCO 3 + CO 2 + H 2 O -> Ca (HCO 3) 2
CO 2 + H 2 O = H 2 CO 3
CO 2 – oxidizing agent
a) CO 2 + C = 2CO
b) Magnesium is able to burn in a CO 2 atmosphere, thereby reducing carbon.
2Mg + CO 2 -> 2MgO+ C(500 0 C )
Do not extinguish fireworks fires with a carbon dioxide fire extinguisher!
Sodium peroxide absorbs carbon dioxide:
2Na 2 O 2 + 2CO 2 -> 2Na 2 CO 3 +O 2 ^
This reaction is used in submarines and spacecraft to regenerate air.
A huge mass of carbon dioxide is converted into organic matter and oxygen as a result of photosynthesis:
6CO 2 + 6H 2 O -> C 6 H 12 O 6 + 6O 2 ^
Group 4 Preparation of oxides and application
1. In industry, C + O 2 = 2CO
2. In the laboratory HCOOH = H 2 O + CO^
1. In industry, CaCO 3 = CaO + CO 2 ^
2. In the laboratory CaCO 3 +2HCl=CaCl 2 +CO 2 ^+H 2 O
Application of oxides
1) Fuel.
2) The main part of the generator gas is one of the types of gaseous fuel.
3) As a reducing agent in metallurgy.
4) The starting material in the synthesis of organic substances.
5) Applicable for processing animal meat and fish, gives them a bright red color and a fresh look without changing the taste
6) It was recently discovered that carbon monoxide can reduce brain damage during stroke: Based on research in mice, scientists have found that treatment with low doses of carbon monoxide can help limit brain damage.
1) In the production of sugar, soda, carbonated drinks;
2) Does not support the vital activity of bacteria and mold - food is preserved in its atmosphere. Dry ice - for storing food.
3) In liquid form – in fire extinguishers;
4. Consolidation of knowledge and methods of action
Representatives of each group cover their issue. The rest listen, enter the material into a table, and ask questions.
5. Generalization and systematization of knowledge.
Teacher: let’s generalize the knowledge gained in practical application
1. In the volcanic zone near Naples there is a “dog cave”. A terrible secret has long excited the imagination of the local population. Let's answer the question asked at the beginning of the lesson.
2. Our school’s laboratory technician does not respect carbon dioxide because it makes jars of alkali solutions impossible to open after school holidays. Explain why the laboratory technician blames carbon dioxide for this?
3. The problem of purifying the air from carbon dioxide at space stations and submarines is a painful problem. The science fiction writer J. Verne tried to solve it. What solution have modern scientists found?
4. A noisy group of city residents decided to celebrate the New Year outdoors, in a village house with a stove. When the wood burned out, they closed the window near the stove without looking inside, so that, as they decided, the heat would remain longer. What could have happened, but, fortunately, did not happen, since the door to the house was very often open?
5. The driver, breaking his usual rules, drove into the garage in reverse in order to leave faster in the morning. But in the morning it was very cold and the driver, without opening the gate, decided to warm up the engine. After some time, the unexpected happened...
6. The main question of the lesson is “Carbon oxides – friends or enemies?”
7. Explain the expression: “I got burned in a hut (bathhouse).”
8. Set a feature that combines the specified objects
9. Conduct a qualitative analysis of sparkling soft drinks for carbon dioxide content.
A. Assemble a device for obtaining gases.
b. The determinant of the presence of carbon dioxide is lime water.
c.Carefully heat the drink, passing the resulting gas through lime water.
d. Cloudiness of lime water is observed. A white precipitate forms.
10. It is known that when undergoing a technical inspection of a car, the driver provides a certificate about the condition of the car’s exhaust gases. What gas concentration is indicated in the certificate?
11. Place a candle in a large open container and light it (Fig. 1).
The candle burned normally. Then a ring of cotton wool was placed around the edge of the vessel and set on fire.
The cotton wool caught fire, and after a few seconds the candle went out (Fig. 2). Explain what is happening.
Rice. 1 Fig. 2
12. You have everything you need to carry out a high-quality reaction for carbon (IV) monoxide. Do this reaction.
6. Consolidation of knowledge
“The fifth wheel”
Four substances can have something in common, but the fifth substance stands out from the series, is superfluous. Find this substance.
1. Carbon, diamond, graphite, carbide, carbine.
2. Anthracite, peat, coke, oil, glass.
3. Limestone, chalk, marble, malachite, calcite.
4. Crystalline soda, marble, potash, caustic, malachite.
5. Phosgene, phosphine, hydrocyanic acid, potassium cyanide, carbon disulfide
6. Sea water, mineral water, distilled water, ground water, hard water.
7. Lime milk, fluff, slaked lime, limestone, lime water.
8. Li 2 CO 3; (NH 4) 2 CO 3; CaCO 3; K 2 CO 3 , Na 2 CO 3 .
“Synonyms”
Write the chemical formulas of the substances or their names.
1. Producer gas-....
2. Greenhouse gas -...
3. Non-salt-forming oxide - .....
4. The connection of CO with hemoglobin - ...
5. Reagent for CO 2 - ...
6. “Dry ice” – ...
7.Car exhaust component-.....
8. Conditionally poisonous gas -.....
9. Natural gas -...
“Antonyms”
Write chemical terms that are opposite in meaning to those proposed.
1. Oxidizing agent –...
2. Electron donor –...
3. Acid properties –...
4. Covalent polar bond –...
5. Adsorption –...
6. Excess –...
7. Anion – .....
8. Metal –...
9. Starting substances –...
“Search for patterns”
Establish a sign that combines the specified substances and phenomena.
1. Diamond, carbine, graphite – ...
2. Glass, cement, brick – ...
3. Breathing, rotting, volcanic eruption - ...
4. CO, NO, N 2 O- ...
5. NaHCO 3, CO, CaCO 3, CO 2, H 2 CO 3 – ...
“Noughts and crosses.” Determine winning paths:
Substances with which carbon monoxide reacts
7. Summing up
What did we learn in class today and did we answer the main question: are carbon oxides friends or enemies?
8. Reflection
- I found out)....
- I learned....
- I felt that.....
- I will need this in life...
- During the lesson I worked .....
- Achieved the objectives of the lesson.....
- I received a grade -.........
9. Information about homework
At home, look at the contents of the first aid kit, bathroom, kitchen and find household chemicals containing CO 2 and other carbon compounds. Fill out the table completely. P.30.
Thank you for the lesson and the knowledge you showed today. And let the wise Russian proverb guide you through life: “It’s not a shame not to know, it’s a shame not to teach.” The lesson is over. Goodbye!
Two carbon oxides are known: CO and CO 2 .
Carbon monoxide (II) CO (carbon monoxide). In the molecule of this oxide, the carbon atom is in an unexcited state. Due to two p-electrons, it forms two bonds with the oxygen atom. The third bond is formed by a donor-acceptor mechanism, with oxygen being the donor of an electron pair, which the carbon atom accepts into the free 2p orbital.
Carbon monoxide (II) CO is formed during the combustion of coal with a lack of oxygen. It is produced industrially by passing carbon dioxide over hot coal:
CO 2 + C = 2 CO
In laboratory conditions, CO is obtained by the action of concentrated sulfuric acid on formic acid when heated (H 2 SO 4 takes away water):
HCOOH®H 2 O+CO
Carbon monoxide (II) CO is a colorless, odorless gas. Very
slightly soluble in water. Poisonous. Permissible CO content in
industrial premises is 0.03 mg in 1 liter of air. It is found in life-threatening quantities in car exhaust gases. The poisonous effect is
that it irreversibly interacts with blood hemoglobin,
As a result, the transfer of oxygen from the lungs to the
Chemically, CO is an inert compound (at low temperatures). When the temperature rises to 200°C and a pressure of 15 10 5 Pa, carbon monoxide reacts with NaOH, forming sodium salt of formic acid:
Oxidation to CO 2 occurs at a temperature of 700°C: 2CO + O 2 = 2CO 2
When interacting with water vapor, CO 2 and H 2 are formed: CO + H 2 O®CO 2 + H 2
CO is an energetic reducing agent. It reduces many metals from their oxides, which is used in metallurgy to obtain metals from ores:
Fe 2 O 3 +3CO=2Fe+3CO2
In the presence of catalysts (platinum or activated carbon) or under the influence of direct sunlight, carbon monoxide combines with chlorine to form an extremely poisonous gas - phosgene:
СО+Сl 2 ®СОСl 2
Unique is the ability of carbon (II) monoxide to form unusual (complex) compounds called carbonyls with some metals at elevated temperatures and pressures:
Under normal conditions, liquids are the carbonyls Ni(CO) 4 , Fe(CO) 5 , Ru(CO) 5 , Os(CO) 5 . All others are crystalline substances. Metal carbonyls are diamagnetic, indicating the presence of paired electrons. All of them are highly resistant to various chemicals. Relative independence in the interpretation of behavior s - and p-electrons allows us to understand the peculiarity of the electronic structure of carbonyl complexes. If a metal, when combining with a ligand, exhibits low valency values, then in s-bonds the charge is transferred from the ligand to the metal, and in p-bonds, on the contrary, from the metal to the ligand. As a result, the metal atom goes into a state close to neutral. This is exactly how the CO molecule behaves, acting as an acceptor in p - connections.
When heated, metal carbonyls decompose into CO and metal, which is used to obtain high-purity metals.
Carbon monoxide (IV) CO 2 (carbon dioxide) It is formed in nature during the combustion and decay of organic substances. Contained in the air (volume fraction 0.03%), as well as in many mineral springs (Narzan, Borjomi). Released during the respiration of animals and plants.
In the laboratory it can be obtained by the action of dilute acids on carbonates:
CaCO 3 +2HCl=CaCl 2 +CO 2 +H 2 O
In industry it is obtained by burning limestone:
CaCO 3 = CaO + CO 2
Structural formula of the CO 2 molecule: O=C=O. It has a linear shape. The bond between carbon and oxygen is polar. However, due to the symmetrical arrangement of bonds, the CO 2 molecule itself is non-polar.
Under normal conditions, CO 2 is a colorless gas, 1.5 times heavier than air. Soluble in water (at 0°C 1.7 l CO 2 in 1 l H 2 O). It does not support combustion or respiration, but serves as a source of nutrition for green plants. When strongly cooled, CO 2 crystallizes in the form of a white snow-like mass, which, when compressed, evaporates very slowly, lowering the ambient temperature. This explains its use as “dry ice”.
Carbon monoxide (CO) is a colorless, odorless gas that reduces the ability of hemoglobin to carry and supply oxygen.
Spreading. Carbon monoxide is produced by burning organic material such as coal, wood, paper, oil, gasoline, gas, explosives, or any other type of carbonate material under conditions of insufficient air or oxygen. 90% of atmospheric CO is produced naturally, and 10% is produced by human activities. Vehicle engines account for 55 to 60% of the total amount of CO of artificial origin. Gasoline engine exhaust gas (electric ignition) is a common source of CO formation. Diesel engine exhaust (compression ignition) contains approximately 0.1% CO when the engine is running properly, but an incorrectly tuned, overloaded or poorly maintained diesel engine can emit significant amounts of CO. Thermal or catalytic afterburners in the exhaust pipes significantly reduce the amount of CO. Other major sources of CO include foundries, catalytic crackers in petroleum refineries, coal and wood distillation processes, lime kilns and reduction kilns in kraft paper mills, production of synthetic methanol and other organic compounds from carbon monoxide, blast furnace feed sintering, manufacturing carbide, formaldehyde production, carbon black plants, coke oven batteries, gas plants and waste treatment plants.
Any process in which incomplete combustion of organic material may occur is a potential source of carbon monoxide.
Carbon monoxide is believed to be the single most common cause of poisoning, both in industrial and domestic settings. Thousands of people die every year as a result of CO intoxication. It is assumed that the number of victims of non-fatal poisoning suffering from permanent nervous system disorder exceeds this figure. The magnitude of the health hazards, fatal and non-fatal, posed by carbon monoxide is enormous, and poisonings are likely to occur in far greater numbers than are currently recognized.
A significant proportion of the total workforce in any country is exposed to significant CO exposure in the workplace. CO is a ubiquitous hazard in the automotive industry, in garages and service stations. Road vehicle drivers may be at risk if there is a leak that allows exhaust gases to enter the driver's compartment. There are a huge number of occupations in which workers can be exposed to CO, such as garage mechanics, charcoal burners, coke oven workers, blast furnace workers, blacksmiths, miners, tunnel workers, gas workers, boiler workers, pottery kiln workers, cooks, bakers, firefighters, workers involved in the production of formaldehyde, and many others. Welding work in tanks, tanks and other enclosed spaces can result in the release of hazardous amounts of CO if there is no effective ventilation.
Toxic effects. Small amounts of CO are produced by the human body through the catabolism of hemoglobin and other blood pigments, leading to an endogenous blood saturation of approximately 0.3 to 0.8% carboxyhemoglobin (COHb). The concentration of endogenous COHb increases in hemolytic anemia and after significant bruises or hematomas, which cause an increase in hemoglobin catabolism.
The biological half-life of blood COHb concentrations in sedentary adults is approximately 3 to 4 hours. The process of CO removal slows down over time and the lower the initial level of COHb, the slower the rate of CO release.
Acute poisoning. The occurrence of symptoms depends on the concentration of CO in the air, time of exposure, degree of physical effort and individual susceptibility. If the exposure is massive, the person may lose consciousness almost instantly with few or no warning symptoms or signs. Exposure to concentrations between 10,000 and 40,000 within minutes results in death. Concentration levels between 1,000 and 10,000 cause symptoms of headache, dizziness and nausea within 13 to 15 minutes and loss of consciousness and death if exposure continues for 10 to 45 minutes. The lower the concentration levels, the longer it takes before symptoms begin: level a concentration level of 500 causes a headache after 20 minutes, and a concentration level of 200 after approximately 50 minutes.
The main sign of a poisoning victim is classically described as a cherry red color. In the early stages, the patient may appear pale. Later, the skin, nail beds and mucous membranes may become cherry red due to the high concentration of carboxyhemoglobin and low concentration of reduced hemoglobin in the blood. This symptom can be detected at more than 30% COHb concentration, but this sign is not a reliable or regular sign of CO poisoning. The patient's pulse accelerates and becomes spasmodic. Little or no hyperpnea may be noted until COHb levels become very high.
Where the signs and symptoms described above occur in a person whose job may expose them to carbon monoxide, gas poisoning should be immediately suspected. Differential diagnosis from drug poisoning, acute alcohol poisoning, cerebral or cardiac infarction, or diabetic or uremic coma can be difficult, and carbon monoxide exposure is often unrecognized or simply overlooked. A diagnosis of carbon monoxide poisoning cannot be made until it is determined that the body contains an unnaturally high amount of CO. Carbon monoxide is readily detectable in a blood sample or, if a person has healthy lungs, a calculation of the blood COHb concentration can be made fairly quickly by examining a sample of exhaled internal alveolar air that is in equilibrium with the blood COHb concentration.
When looking at CO, the critical organs include the brain and heart, as they both depend on a continuous supply of oxygen to function. Carbon monoxide impedes the heart's function in two ways: the heart's work is increased to cover the lack of peripheral oxygen supply, while its own oxygen supply is reduced by CO. Carbon monoxide can thus cause myocardial infarction.
In acute poisoning, neurological and cardiovascular complications may occur, the symptoms of which become obvious when the patient emerges from the initial coma. Severe poisoning can result in pulmonary edema (excess fluid in the lung tissues). Pneumonia may develop within hours or days, sometimes due to aspiration. Temporary glycosuria and proteinuria may also occur. In rare cases, acute renal failure can cause complications in recovery from poisoning. From time to time, skin manifestations of poisoning occur.
Following severe CO intoxication, the patient may suffer from cerebral edema with varying degrees of irreversible brain damage. Primary recovery may be followed by a subsequent neuropsychiatric relapse several days or even weeks after poisoning. Pathological studies of hopeless cases show predominant damage to the white matter of the nervous system compared to neuronal damage in those victims who survive for several days after poisoning. The extent of brain damage following CO poisoning is determined by the intensity and duration of exposure. When regaining consciousness after serious CO poisoning, in 50% of cases victims reported an abnormal mental state, which manifested itself as irritability, impatience, prolonged bouts of delirium, depression or anxiety.
Repeated exposure. Carbon monoxide does not accumulate in the body. It is completely eliminated after each period of exposure if a person spends a sufficient amount of time in the fresh air. However, it is possible that repeated minor or moderate poisonings that do not cause loss of consciousness will lead to the death of brain cells and ultimately damage to the central nervous system with a large number of possible symptoms such as headache, dizziness, irritability, memory impairment, etc.
Individuals repeatedly exposed to moderate concentrations of CO may be adapted to some extent to withstand its effects. The adaptation mechanisms are thought to be similar to the development of tolerance to hypoxia at high altitudes.
Carbon monoxide easily crosses the placenta and affects the fetus, which is sensitive to any lack of oxygen, and the effects can be so severe as to jeopardize the normal development of the fetus.
At-risk groups.
Particularly sensitive to the effects of CO are individuals whose oxygen-carrying capacity is already reduced due to anemia or hemoglobinosis; those who need extra oxygen due to fever, hyperthyroidism or pregnancy; patients with systemic hypoxia due to respiratory failure; and patients with coronary heart disease and cerebral or general arteriosclerosis. Children and adolescents, whose lungs work faster than adults, reach COHb toxicity levels more quickly than healthy adults. And smokers, whose starting COHb levels are higher than those of non-smokers, can approach dangerous COHb concentrations much more quickly with high exposure.
Carbon forms two extremely stable oxides (CO and CO 2), three much less stable oxides (C 3 O 2, C 5 O 2 and C 12 O 9), a number of unstable or poorly studied oxides (C 2 O, C 2 O 3 etc.) and non-stoichiometric graphite oxide. Among the listed oxides, CO and CO 2 play a special role.
DEFINITION
Carbon monoxide Under normal conditions, a flammable gas is colorless and odorless.
It is quite toxic due to its ability to form a complex with hemoglobin, which is approximately 300 times more stable than the oxygen-hemoglobin complex.
DEFINITION
Carbon dioxide under normal conditions, it is a colorless gas, approximately 1.5 times heavier than air, due to which it can be poured like a liquid from one vessel to another.
The mass of 1 liter of CO 2 under normal conditions is 1.98 g. The solubility of carbon dioxide in water is low: 1 volume of water at 20 o C dissolves 0.88 volumes of CO 2, and at 0 o C - 1.7 volumes.
Direct oxidation of carbon with a lack of oxygen or air leads to the formation of CO; with a sufficient amount of them, CO 2 is formed. Some properties of these oxides are presented in table. 1.
Table 1. Physical properties of carbon oxides.
Production of carbon monoxide
Pure CO can be obtained in the laboratory by dehydrating formic acid (HCOOH) with concentrated sulfuric acid at ~140 °C:
HCOOH = CO + H2O.
In small quantities, carbon dioxide can be easily obtained by the action of acids on carbonates:
CaCO 3 + 2HCl = CaCl 2 + H 2 O + CO 2.
On an industrial scale, CO 2 is produced mainly as a by-product in the process of ammonia synthesis:
CH 4 + 2H 2 O = CO 2 + 4H 2;
CO + H 2 O = CO 2 + H 2.
Large quantities of carbon dioxide are produced by burning limestone:
CaCO 3 = CaO + CO 2.
Chemical properties of carbon monoxide
Carbon monoxide is chemically reactive at high temperatures. It proves to be a strong reducing agent. Reacts with oxygen, chlorine, sulfur, ammonia, alkalis, metals.
CO + NaOH = Na(HCOO) (t = 120 - 130 o C, p);
CO + H 2 = CH 4 + H 2 O (t = 150 - 200 o C, cat. Ni);
CO + 2H 2 = CH 3 OH (t = 250 - 300 o C, cat. CuO/Cr 2 O 3);
2CO + O 2 = 2CO 2 (cat. MnO 2 /CuO);
CO + Cl 2 = CCl 2 O(t = 125 - 150 o C, kat. C);
4CO + Ni = (t = 50 - 100 o C);
5CO + Fe = (t = 100 - 200 o C, p).
Carbon dioxide exhibits acidic properties: it reacts with alkalis and ammonia hydrate. Reduced by active metals, hydrogen, carbon.
CO 2 + NaOH dilute = NaHCO 3 ;
CO 2 + 2NaOH conc = Na 2 CO 3 + H 2 O;
CO 2 + Ba(OH) 2 = BaCO 3 + H 2 O;
CO 2 + BaCO 3 + H 2 O = Ba(HCO 3) 2;
CO 2 + NH 3 ×H 2 O = NH 4 HCO 3;
CO 2 + 4H 2 = CH 4 + 2H 2 O (t = 200 o C, cat. Cu 2 O);
CO 2 + C = 2CO (t > 1000 o C);
CO 2 + 2Mg = C + 2MgO;
2CO 2 + 5Ca = CaC 2 + 4CaO (t = 500 o C);
2CO 2 + 2Na 2 O 2 = 2Na 2 CO 3 + O 2.
Applications of carbon monoxide
Carbon monoxide is widely used as a fuel in the form of generator gas or water gas and is also formed when many metals are separated from their oxides by reduction with coal. Producer gas is produced by passing air through hot coal. It contains about 25% CO, 4% CO2 and 70% N2 with traces of H2 and CH4 62.
The use of carbon dioxide is most often due to its physical properties. It is used as a cooling agent, for carbonating drinks, in the production of lightweight (foamed) plastics, and also as a gas for creating an inert atmosphere.
Examples of problem solving
EXAMPLE 1
EXAMPLE 2
| Exercise | Determine how many times carbon monoxide (IV)CO 2 is heavier than air. |
| Solution | The ratio of the mass of a given gas to the mass of another gas taken in the same volume, at the same temperature and the same pressure is called the relative density of the first gas to the second. This value shows how many times the first gas is heavier or lighter than the second gas. The relative molecular weight of air is taken to be 29 (taking into account the content of nitrogen, oxygen and other gases in the air). It should be noted that the concept of “relative molecular mass of air” is used conditionally, since air is a mixture of gases. D air (CO 2) = M r (CO 2) / M r (air); D air (CO 2) = 44 / 29 = 1.517. M r (CO 2) = A r (C) + 2×A r (O) = 12 + 2× 16 = 12 + 32 = 44. |
| Answer | Carbon monoxide (IV)CO 2 is 1.517 times heavier than air. |
Carbon monoxide is a colorless, odorless and irritating gas that is formed wherever combustion of carbon-containing materials takes place in the absence of sufficient oxygen; may also be released during the synthesis of some chemical pharmaceuticals. Enters the body through the respiratory tract without causing any irritation. The maximum permissible concentration in the air is 20 mg/m3.
The toxic effect depends on the concentration of the gas in the air and the duration of its exposure. Already at a concentration of 50-60 mg/m 3, mild signs of poisoning may appear, and when it is contained in the air in an amount of 0.1-0.2%, intoxication is severe. The toxicity of carbon monoxide is explained by the fact that, displacing oxygen from oxy-hemoglobin in the blood, it quickly combines with hemoglobin and forms stable carboxyhemoglobin. The latter, being unable to transfer oxygen to the tissues, entails an insufficient supply of oxygen to them - anoxemia. The rapid formation of carboxyhemoglobin in the blood is due to the fact that carbon monoxide has a 300 times stronger affinity for hemoglobin than oxygen. As a result of the resulting oxygen starvation of tissues, the normal functioning of the body is disrupted, primarily the central nervous and cardiovascular systems. The amount and rate of carboxyhemoglobin formation determine the severity of intoxication. In mild cases, headache, dizziness, tinnitus, nausea and vomiting, and general increasing weakness are observed. In some cases, stiffness of movement occurs, as a result of which the victim is unable to leave the poisoned zone on his own. This symptom is especially pronounced in cases of moderate and severe poisoning. In these cases, these phenomena are accompanied by redness of the face, increasing drowsiness, vomiting, blackout and loss of consciousness. In especially severe cases, mental agitation occurs, convulsions occur, and serious changes in the cardiovascular system are observed (small arrhythmic pulse, muffled heart sounds, etc.). Possible death from paralysis of the respiratory center. If you take the victim out into the fresh air, carboxyhemoglobin completely dissociates quite quickly (after 1-2 hours for mild poisoning and 1-2 days for severe poisoning). Acute symptoms of poisoning pass, but residual effects persist for a long time - headaches, dizziness, general weakness, etc.
To prevent carbon monoxide poisoning, careful monitoring of its content in the air is necessary (preferably automatic, using alarms that indicate that the CO concentration exceeds the permissible norm). All technological measures must be applied to eliminate the possibility of its release into the air, and effective ventilation must be installed.
An individual means of protecting the respiratory system from carbon monoxide is a special CO filter gas mask.