Carbon dioxide, also known as carbon monoxide 4, reacts with a number of substances, forming compounds that vary in composition and chemical properties. Consisting of non-polar molecules, it has very weak intermolecular bonds and can only be present if the temperature is higher than 31 degrees Celsius. Carbon dioxide is a chemical compound consisting of one carbon atom and two oxygen atoms.
Carbon Monoxide 4: Formula and Basic Information
Carbon dioxide is present in the Earth's atmosphere at low concentrations and acts as its chemical formula CO 2 . At high temperatures it can exist exclusively in a gaseous state. In its solid state, it is called dry ice.
Carbon dioxide is an important component of the carbon cycle. It comes from many natural sources, including volcanic degassing, combustion of organic matter and respiratory processes of living aerobic organisms. Anthropogenic sources of carbon dioxide mainly come from the combustion of various fossil fuels for electricity generation and transportation.
It is also produced by various microorganisms from fermentation and cellular respiration. Plants convert carbon dioxide into oxygen during a process called photosynthesis, using both carbon and oxygen to form carbohydrates. In addition, plants also release oxygen into the atmosphere, which is then used for respiration by heterotrophic organisms.
Carbon dioxide (CO2) in the body
Carbon monoxide 4 reacts with different substances and is a gaseous waste product from metabolism. There is more than 90% of it in the blood in the form of bicarbonate (HCO 3). The rest is either dissolved CO 2 or carbonic acid (H2CO 3). Organs such as the liver and kidneys are responsible for balancing these compounds in the blood. Bicarbonate is a chemical that acts as a buffer. It keeps the blood pH level at the required level, avoiding an increase in acidity.
Structure and properties of carbon dioxide
Carbon dioxide (CO2) is a chemical compound that is a gas when room temperature and higher. It consists of one carbon atom and two oxygen atoms. Humans and animals release carbon dioxide when they exhale. In addition, it is formed whenever something organic is burned. Plants use carbon dioxide to produce food. This process is called photosynthesis.
The properties of carbon dioxide were studied by Scottish scientist Joseph Black back in the 1750s. capable of catching thermal energy and influence our planet's climate and weather. He is the reason global warming and rising temperatures of the Earth's surface.
Biological role
Carbon monoxide 4 reacts with various substances and is the end product in organisms that obtain energy from the breakdown of sugars, fats and amino acids. This process is known to be characteristic of all plants, animals, many fungi and some bacteria. In higher animals, carbon dioxide moves in the blood from body tissues to the lungs, where it is exhaled. Plants obtain it from the atmosphere for use in photosynthesis.
Dry ice
Dry ice or solid carbon dioxide is the solid state of CO 2 gas with a temperature of -78.5 °C. IN natural form this substance does not occur in nature, but is produced by humans. It is colorless and can be used in the preparation of carbonated drinks, as a cooling element in ice cream containers and in cosmetology, for example for freezing warts. Dry ice vapor is suffocating and can cause death. Use caution and professionalism when using dry ice.
Under normal pressure it will not melt from a liquid, but instead goes directly from a solid to a gas. This is called sublimation. It will change directly from solid to gas at any temperature exceeding extremely low temperatures. Dry ice sublimates at normal air temperatures. This releases carbon dioxide, which is odorless and colorless. Carbon dioxide can be liquefied at pressures above 5.1 atm. The gas that comes from dry ice is so cold that when mixed with air, it cools the water vapor in the air into a mist that looks like thick white smoke.
Preparation, chemical properties and reactions
In industry, carbon monoxide 4 is produced in two ways:
- By burning fuel (C + O 2 = CO 2).
- By thermal decomposition of limestone (CaCO 3 = CaO + CO 2).
The resulting volume of carbon monoxide 4 is purified, liquefied and pumped into special cylinders.
Being acidic, carbon monoxide 4 reacts with substances such as:
- Water. When dissolved, carbonic acid (H 2 CO 3) is formed.
- Alkaline solutions. Carbon monoxide 4 (formula CO 2) reacts with alkalis. In this case, medium and acidic salts (NaHCO 3) are formed.
- Basic oxides. These reactions produce carbonate salts (CaCO 3 and Na 2 CO 3).
- Carbon. When carbon monoxide 4 reacts with hot coal, carbon monoxide 2 is formed ( carbon monoxide), which can cause poisoning. (CO 2 + C = 2CO).
- Magnesium. As a rule, carbon dioxide does not support combustion, only under very high temperatures it can react with some metals. For example, ignited magnesium will continue to burn in CO 2 during a redox reaction (2Mg + CO 2 = 2MgO + C).
The qualitative reaction of carbon monoxide 4 manifests itself when passing it through limestone water (Ca(OH) 2 or through barite water (Ba(OH) 2). Turbidity and precipitation can be observed. If you continue to pass carbon dioxide after this, the water will become clear again , since insoluble carbonates are converted into soluble bicarbonates (acid salts of carbonic acid).
Carbon dioxide is also produced by the combustion of all carbon-containing fuels, such as methane ( natural gas), petroleum distillates (gasoline, diesel fuel, kerosene, propane), coal or wood. In most cases, water is also released.
Carbon dioxide (carbon dioxide) is made up of one carbon atom and two oxygen atoms, which are held together by covalent bonds (or sharing of electrons). Pure carbon is very rare. It occurs in nature only in the form of minerals, graphite and diamond. Despite this, he is building block life, which combines with hydrogen and oxygen to form the basic compounds that make up everything on the planet.
Hydrocarbons such as coal, oil and natural gas are compounds made of hydrogen and carbon. This element is found in calcite (CaCo 3), minerals in sedimentary and metamorphic rocks, limestone and marble. It is the element that contains all organic matter - from fossil fuels to DNA.
The interaction of carbon with carbon dioxide proceeds according to the reaction
The system under consideration consists of two phases - solid carbon and gas (f = 2). Three interacting substances are interconnected by one reaction equation, therefore, the number of independent components k = 2. According to the Gibbs phase rule, the number of degrees of freedom of the system will be equal to
C = 2 + 2 – 2 = 2.
This means that the equilibrium concentrations of CO and CO 2 are functions of temperature and pressure.
Reaction (2.1) is endothermic. Therefore, according to Le Chatelier's principle, an increase in temperature shifts the equilibrium of the reaction in the direction of the formation of additional amount of CO.
When reaction (2.1) occurs, 1 mole of CO 2 is consumed, which at normal conditions has a volume of 22400 cm 3, and 1 mole of solid carbon has a volume of 5.5 cm 3. As a result of the reaction, 2 moles of CO are formed, the volume of which under normal conditions is 44800 cm 3.
From the above data on the change in the volume of reagents during reaction (2.1), it follows:
- The transformation under consideration is accompanied by an increase in the volume of interacting substances. Therefore, in accordance with Le Chatelier's principle, an increase in pressure will promote the reaction towards the formation of CO 2.
- The change in the volume of the solid phase is negligible compared to the change in the volume of the gas. Therefore, for heterogeneous reactions involving gaseous substances with sufficient accuracy we can assume that the change in the volume of interacting substances is determined only by the number of moles of gaseous substances on the right and left sides of the reaction equation.
The equilibrium constant of reaction (2.1) is determined from the expression
If we take graphite as the standard state when determining the activity of carbon, then a C = 1
The numerical value of the equilibrium constant of reaction (2.1) can be determined from the equation
Data on the effect of temperature on the value of the reaction equilibrium constant are given in Table 2.1.
Table 2.1– Values of the equilibrium constant of reaction (2.1) at different temperatures
From the given data it is clear that at a temperature of about 1000K (700 o C) the equilibrium constant of the reaction is close to unity. This means that in the region of moderate temperatures, reaction (2.1) is almost completely reversible. At high temperatures the reaction proceeds irreversibly towards the formation of CO, and at low temperatures in the opposite direction.
If the gas phase consists only of CO and CO 2, by expressing the partial pressures of the interacting substances in terms of their volume concentrations, equation (2.4) can be reduced to the form
IN industrial conditions CO and CO 2 are obtained as a result of the interaction of carbon with oxygen in the air or blast enriched with oxygen. At the same time, another component appears in the system - nitrogen. The introduction of nitrogen into the gas mixture affects the ratio equilibrium concentrations CO and CO 2 are similar to decreasing pressure.
From equation (2.6) it is clear that the composition of the equilibrium gas mixture is a function of temperature and pressure. Therefore, the solution to equation (2.6) is graphically interpreted using a surface in three-dimensional space in coordinates T, Ptot and (%CO). The perception of such dependence is difficult. It is much more convenient to depict it in the form of a dependence of the composition of an equilibrium mixture of gases on one of the variables, with the second of the system parameters being constant. As an example, Figure 2.1 shows data on the effect of temperature on the composition of the equilibrium gas mixture at Ptot = 10 5 Pa.
Given the known initial composition of the gas mixture, one can judge the direction of reaction (2.1) using the equation
If the pressure in the system remains unchanged, relation (2.7) can be reduced to the form
Figure 2.1– Dependence of the equilibrium composition of the gas phase for the reaction C + CO 2 = 2CO on temperature at P CO + P CO 2 = 10 5 Pa.
For a gas mixture whose composition corresponds to point a in Figure 2.1, . Wherein
and G > 0. Thus, points above the equilibrium curve characterize systems whose approach to the state of thermodynamic equilibrium proceeds through the reaction
Similarly, it can be shown that points below the equilibrium curve characterize systems that approach the equilibrium state by reaction
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It is good to observe the interaction of carbon dioxide with alkali like this. A large round-bottomed flask is filled with carbon dioxide, a few pieces of alkali are thrown into it and quickly closed with a rubber stopper. After the reaction takes place (pay attention to the droplets of water formed and the release of heat), the neck of the flask is lowered into a vessel with water and the stopper is opened. Almost the entire flask is filled with water.
When carbon dioxide interacts with ammonia, heat is released, which raises the temperature in the apparatus above 30, which, as we already know, entails the decomposition of the acidic sodium carbonate salt.
For the process of interaction of carbon dioxide with water with the formation of carbohydrates and the release of oxygen, in addition to supplying a large amount of heat, one more condition is necessary: the presence of substances that stimulate the reaction of interaction between carbon dioxide and water. This substance is found in plant leaves - it is chlorophyll.
It is obtained as a result of the interaction of carbon dioxide with ammonia at high blood pressure and temperature.
Urea is produced by the interaction of carbon dioxide and ammonia. The modern chemical industry successfully combines atmospheric nitrogen with hydrogen into ammonia, which reacts with carbon dioxide to form urea.
What processes occur when carbon dioxide interacts with water. What molecules and ions are in the resulting solution?
Sodium carbonate, formed by the reaction of carbon dioxide in the air with some caustic alkali present, does not appear to dissolve in methanol.
The above reaction characterizes only the final result of the interaction of carbon dioxide with dissolved ammonia. In reality, the process is much more complex, passing through a number of intermediate stages.
The production of potassium bicarbonate is based on the reaction of carbon dioxide with a solution of potassium carbonate.
Schematically, photosynthesis can be represented as a redox process of interaction between carbon dioxide and water, which occurs with the participation of chlorophyll, which has absorbed energy sun rays.
The satisfactory results obtained can be explained by the formation of carbon monoxide CO during the interaction of carbon dioxide with solid carbon. Carbon monoxide is a very effective protective gas - it is insoluble in the metal, reduces oxides and does not affect the carbon contained in the metal. A small CO content in the gas mixture is sufficient to significantly improve the quality of the deposited metal. The carbon electrode can be used for welding steel, cast iron, aluminum, copper, bronze and other metals.
Purpose:
Carbon dioxide fire extinguishers are designed to extinguish fires of various electrical equipment that are under voltage up to 10,000 V. They are used effectively for volumetric extinguishing and when extinguishing a fire requires fire extinguishing compounds that do not damage the protected equipment or objects (museum exhibits, computer equipment, electronic equipment, archives etc.). Carbon dioxide, falling on a burning substance, cools and extinguishes it. It leaves no trace as it evaporates
Physico- Chemical properties:
Physico-chemical properties of carbon dioxide CO2:
Chemical name: carbon dioxide
Chemical formula: CO2
Molecular weight: 44.01
Liquid density at 20°C: 777 kg/cu.m.
Critical temperature: 31.0°C
Critical pressure: 73.82 bar
Pressure at 21°C: 5.88 MPa
Steam pressure at 20°C: 57.2 bar
Maximum density when filling, kg/l: 0.72
Estimated concentration during extinguishing: 36.5%.
Properties of carbon dioxide. Carbon dioxide under pressure can be converted into liquid or solid. At -43°C, carbon dioxide is a solid called “dry ice.” At temperatures above the critical temperature (31°C), carbon dioxide is always in gaseous form, regardless of pressure. Carbon dioxide does not support the combustion of ordinary materials, but there are a few exceptions, for example, it enters chemical reaction with magnesium and other metals. Carbon dioxide is about 1.5 times heavier than air, which improves its fire extinguishing properties as it sinks down and covers the fire. Due to its weight, it does not dissipate very quickly. In addition, carbon dioxide is non-conductive, which is why it is used to extinguish electrical fires.
Fire extinguishing properties of carbon dioxide. Carbon dioxide helps extinguish fires, mainly due to the effect of volumetric extinguishing. It dilutes the air around the fire until its oxygen content is so low that it is insufficient to support combustion. Therefore, it can be successfully used to extinguish class B fires, in which the main task is to separate flammable vapors from the oxygen contained in the air.
Carbon dioxide has a very limited cooling effect. It can be used to fight Class A fires in confined spaces where the oxygen content may be reduced enough to stop the fire.
Safety precautions during operation:
1. When working carbon dioxide fire extinguishers of all types, it is prohibited to hold the bell with an unprotected hand, since when carbon dioxide escapes, a snow-like mass with a temperature of minus 800 is formed.
2. When using carbon dioxide fire extinguishers, it must be borne in mind that carbon dioxide in large concentrations relative to the volume of the room can cause poisoning of personnel, so after using them it is necessary to ventilate the premises.
3. It is not allowed to place OS fire extinguishers close to heating devices, the temperature of which reaches 500C, direct exposure of the cylinders to sunlight should be avoided.
3. Purpose, design, principle of operation and technical characteristics of OS fire extinguishers. Labor protection rules during operation.
Carbon dioxide fire extinguishers.
There are: OU-2, OU-3, OU-5, OU-6, OU-8, OU-10, OU-20, OU-40, OU-80 depending on the cylinder capacity from 2 liters to 80 liters.
Purpose: To extinguish small initial fires of various substances and materials, with the exception of substances that burn without air access. Fire extinguishers can be used to extinguish electrical installations under voltage not exceeding 1000 V. Fire extinguishers are used at temperatures from - 25˚С to + 50˚С.
Device: Fire extinguishers of this series consist of a steel cylinder, into the neck of which either a shut-off valve(OB-84M), or a shut-off and release head (UN-50000) with a siphon tube that does not reach the bottom of the cylinder by 3-4 mm. A socket is attached to the body of the locking devices of fire extinguishers OU-2, OU-3, OU-5, OU-6, OU-8, and a socket with a hose is attached to the fire extinguishers OU-10, OU-20, OU-40, OU-80. The locking device has safety device membrane type, which automatically discharges the cylinder when the pressure in it exceeds the permissible limit. The charge of fire extinguishers is carbon dioxide according to GOST 8050-64.
Operating principle: Based on the displacement of carbon dioxide overpressure. When the shut-off and release device is opened, carbon dioxide flows through the siphon tube to the socket and changes from a liquefied state to a solid (snow-like) state. During this transition, the temperature is minus 720C, so it is not recommended to touch the socket and the locking device with bare hands, as frostbite is possible.
Technical specifications carbon dioxide fire extinguishers
It is prohibited to extinguish materials that burn without air access.
Fire extinguishers should be used in accordance with the manufacturer's passports and instructions on the procedure on the labels. If there are dents, swelling or cracks on the body, the shut-off and starting device, the union nut, as well as in the event of a leak in the connections of the fire extinguisher components and if the pressure indicator is faulty, it is strictly prohibited to operate the fire extinguishers. Fire extinguishers must not be struck, thrown into a fire, or disassembled or reloaded by unauthorized persons. Do not point the extinguisher nozzle (flexible hose or bell) towards people as this may cause injury. The use of fire extinguishers for purposes other than firefighting is prohibited.
It is advisable to remind you that you need to extinguish a fire outdoors from the windward side. When a fire is being extinguished with several fire extinguishers at the same time, the jets should not be directed towards each other. For extinguishing fires in museums, art galleries, archives, computer centers, as well as for extinguishing fires computer equipment, radio-electronic devices, etc. Carbon dioxide fire extinguishers should be used. As an exception, if there is a shortage of gas extinguishers, powder extinguishers may be used to protect electronic equipment.
When using a carbon dioxide or powder fire extinguisher to extinguish a fire in electrical equipment with voltage up to 1000 V, you must maintain a safe distance (at least 1 m) from the fire extinguisher spray nozzle to live parts of the electrical equipment. To extinguish fires of energized equipment, as well as to extinguish substances that enter into a chemical reaction with water (for example, calcium carbide) with intense heat release, it is prohibited to use water and water-foam fire extinguishers. This also applies to cases where fuel is sprayed during a fire.
When using powder fire extinguishers It should be remembered that high dust levels are generated in the air and this leads to a significant decrease in visibility. In the air of a room, especially a small one, in which flames are extinguished with carbon dioxide fire extinguishers, there is a danger of a decrease in oxygen concentration.
When using mobile carbon dioxide fire extinguishers, a dangerous concentration of gases can form in the indoor air, therefore it is necessary to use insulating respiratory protective equipment and limit the number of personnel in the premises to a minimum.
The rules for operating the fire extinguisher are indicated on the label placed on the body of the fire extinguisher.
When extinguishing electrical installations that are under voltage, it is not allowed to bring the socket closer than 1 m to the electrical installation and the flame.
Recharging and repair of fire extinguishers should be carried out in specialized organizations at charging stations.
Operation of fire extinguishers without receipts and seals from the manufacturer or the organization that carried out the recharging is not allowed.
Fire extinguishers should be located in easily accessible and visible places. It is not allowed to store and operate fire extinguishers in places where the temperature may exceed 50°C and in direct sunlight.
Care must be taken when releasing fire extinguishing agent from the bell because the temperature on its surface drops to minus 60-70 C.
After using a fire extinguisher indoors, the room must be ventilated.
The total mass of the fire extinguisher is determined by adding to it the mass of CO2 indicated on the label or in the passport.
It is necessary to recharge and re-examine the cylinder after 5 years.
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