Does co2 burn? Carbon dioxide. Properties, production, application. Medicine, tests and ecology

12.03.2021

Carbon dioxide is a colorless gas with a barely perceptible odor, non-toxic, heavier than air. Carbon dioxide is widely distributed in nature. Dissolves in water, forming carbonic acid H 2 CO 3 gives it a sour taste. The air contains about 0.03% carbon dioxide. The density is 1.524 times greater than the density of air and is equal to 0.001976 g/cm 3 (at zero temperature and pressure 101.3 kPa). Ionization potential 14.3V. Chemical formula– CO 2 .

In welding production the term is used "carbon dioxide" cm. . In the “Rules for the Design and Safe Operation of Pressure Vessels” the term "carbon dioxide", and in - term "carbon dioxide".

There are many ways to produce carbon dioxide, the main ones are discussed in the article.

The density of carbon dioxide depends on pressure, temperature and the state of aggregation in which it is found. At atmospheric pressure and a temperature of -78.5°C, carbon dioxide, bypassing the liquid state, turns into a white snow-like mass "dry ice".

Under a pressure of 528 kPa and at a temperature of -56.6 ° C, carbon dioxide can be in all three states (the so-called triple point).

Carbon dioxide is thermally stable, dissociating into carbon monoxide only at temperatures above 2000°C.

Carbon dioxide is first gas to be described as a discrete substance. In the seventeenth century, a Flemish chemist Jan Baptist van Helmont (Jan Baptist van Helmont) noticed that after burning coal in a closed vessel, the mass of ash was much less than the mass of the burned coal. He explained this by saying that coal was transformed into an invisible mass, which he called “gas.”

The properties of carbon dioxide were studied much later in 1750. Scottish physicist Joseph Black (Joseph Black).

He discovered that limestone (calcium carbonate CaCO 3), when heated or reacted with acids, releases a gas, which he called “bound air.” It turned out that “bound air” is denser than air and does not support combustion.

CaCO 3 + 2HCl = CO 2 + CaCl 2 + H 2 O

By passing “bound air” i.e. carbon dioxide CO 2 through an aqueous solution of lime Ca(OH) 2 calcium carbonate CaCO 3 is deposited to the bottom. Joseph Black used this experiment to prove that carbon dioxide is released through animal respiration.

CaO + H 2 O = Ca(OH) 2

Ca(OH) 2 + CO 2 = CaCO 3 + H 2 O

Liquid carbon dioxide is a colorless, odorless liquid whose density varies greatly with temperature. It exists at room temperature only at pressures above 5.85 MPa. The density of liquid carbon dioxide is 0.771 g/cm 3 (20°C). At temperatures below +11°C it is heavier than water, and above +11°C it is lighter.

The specific gravity of liquid carbon dioxide varies significantly with temperature, therefore, the amount of carbon dioxide is determined and sold by weight. The solubility of water in liquid carbon dioxide in the temperature range 5.8-22.9°C is no more than 0.05%.

Liquid carbon dioxide turns into gas when heat is supplied to it. Under normal conditions (20°C and 101.3 kPa) When 1 kg of liquid carbon dioxide evaporates, 509 liters of carbon dioxide are formed. When gas is withdrawn too quickly, the pressure in the cylinder decreases and the heat supply is insufficient, the carbon dioxide cools, the rate of its evaporation decreases and when it reaches the “triple point” it turns into dry ice, which clogs the hole in the reduction gear, and further gas extraction stops. When heated, dry ice directly turns into carbon dioxide, bypassing the liquid state. To evaporate dry ice, it is necessary to supply significantly more heat than to evaporate liquid carbon dioxide - therefore, if dry ice has formed in the cylinder, it evaporates slowly.

Liquid carbon dioxide was first produced in 1823. Humphry Davy(Humphry Davy) and Michael Faraday(Michael Faraday).

Solid carbon dioxide "dry ice", according to appearance resembles snow and ice. The carbon dioxide content obtained from dry ice briquettes is high - 99.93-99.99%. Moisture content is in the range of 0.06-0.13%. Dry ice, being in the open air, evaporates rapidly, so containers are used for its storage and transportation. Carbon dioxide is produced from dry ice in special evaporators. Solid carbon dioxide (dry ice), supplied in accordance with GOST 12162.

Carbon dioxide is most often used:

to create a protective environment for metals;
in the production of carbonated drinks;
refrigeration, freezing and storage of food products;
for fire extinguishing systems;
for cleaning surfaces with dry ice.

The density of carbon dioxide is quite high, which allows the arc reaction space to be protected from contact with air gases and prevents nitriding at relatively low carbon dioxide consumption in the jet. Carbon dioxide is, during the welding process, it interacts with the weld metal and has an oxidizing and also carburizing effect on the metal of the weld pool.

Previously obstacles to the use of carbon dioxide as a protective medium were in the seams. The pores were caused by boiling of the solidifying metal of the weld pool from the release of carbon monoxide (CO) due to its insufficient deoxidation.

At high temperatures, carbon dioxide dissociates to form highly active free, monoatomic oxygen:

Oxidation of the weld metal released free from carbon dioxide during welding is neutralized by the content of an additional amount of alloying elements with a high affinity for oxygen, most often silicon and manganese (in excess of the amount required for alloying the weld metal) or fluxes introduced into the welding zone (welding).

Both carbon dioxide and carbon monoxide are practically insoluble in solid and molten metal. The free active oxidizes the elements present in the weld pool depending on their oxygen affinity and concentration according to the equation:

Me + O = MeO

where Me is a metal (manganese, aluminum, etc.).

In addition, carbon dioxide itself reacts with these elements.

As a result of these reactions, when welding in carbon dioxide, significant burnout of aluminum, titanium and zirconium is observed, and less intense burnout of silicon, manganese, chromium, vanadium, etc.

The oxidation of impurities occurs especially vigorously at . This is due to the fact that when welding with a consumable electrode, the interaction of the molten metal with the gas occurs when a drop remains at the end of the electrode and in the weld pool, and when welding with a non-consumable electrode, it occurs only in the pool. As is known, the interaction of gas with metal in the arc gap occurs much more intensely due to the high temperature and the larger contact surface of the metal with the gas.

Due to the chemical activity of carbon dioxide in relation to tungsten, welding in this gas is carried out only with a consumable electrode.

Carbon dioxide is non-toxic and non-explosive. At concentrations greater than 5% (92 g/m3), carbon dioxide has bad influence on human health, since it is heavier than air and can accumulate in poorly ventilated areas near the floor. This reduces the volume fraction of oxygen in the air, which can cause oxygen deficiency and suffocation. Premises where welding is carried out using carbon dioxide must be equipped with general supply and exhaust ventilation. The maximum permissible concentration of carbon dioxide in the air of the working area is 9.2 g/m 3 (0.5%).

Carbon dioxide is supplied by. To obtain high-quality seams, gaseous and liquefied carbon dioxide of the highest and first grades is used.

Carbon dioxide is transported and stored in steel cylinders or large-capacity tanks in a liquid state, followed by gasification at the plant, with a centralized supply to welding stations through ramps. A standard one with a water capacity of 40 liters is filled with 25 kg of liquid carbon dioxide, which at normal pressure occupies 67.5% of the volume of the cylinder and produces 12.5 m 3 of carbon dioxide upon evaporation. Air accumulates in the upper part of the cylinder along with carbon dioxide gas. Water, which is heavier than liquid carbon dioxide, collects at the bottom of the cylinder.

To reduce the humidity of carbon dioxide, it is recommended to install the cylinder with the valve down and, after settling for 10...15 minutes, carefully open the valve and release moisture from the cylinder. Before welding, it is necessary to release a small amount of gas from a normally installed cylinder to remove any air trapped in the cylinder. Some of the moisture is retained in carbon dioxide in the form of water vapor, worsening the welding of the seam.

When gas is released from the cylinder, due to the throttling effect and heat absorption during the evaporation of liquid carbon dioxide, the gas cools significantly. With intensive gas extraction, the reducer may become clogged with frozen moisture contained in carbon dioxide, as well as dry ice. To avoid this, when extracting carbon dioxide, a gas heater is installed in front of the reducer. The final removal of moisture after the gearbox is carried out with a special desiccant filled with glass wool and calcium chloride, silica gel, copper sulfate or other moisture absorbers

The carbon dioxide cylinder is painted black, with the words “CARBON ACID” written in yellow letters..

Carbon dioxide, carbon monoxide, carbon dioxide - all these are names for one substance known to us as carbon dioxide. So what properties does this gas have, and what are its areas of application?

Carbon dioxide and its physical properties

Carbon dioxide consists of carbon and oxygen. The formula for carbon dioxide looks like this – CO₂. In nature, it is formed during combustion or decay organic matter. The gas content in the air and mineral springs is also quite high. In addition, humans and animals also emit carbon dioxide when they exhale.

Rice. 1. Carbon dioxide molecule.

Carbon dioxide is a completely colorless gas and cannot be seen. It also has no smell. However, with high concentrations, a person may develop hypercapnia, that is, suffocation. Lack of carbon dioxide can also cause health problems. As a result of a lack of this gas, the opposite condition to suffocation can develop - hypocapnia.

If you place carbon dioxide in low temperature conditions, then at -72 degrees it crystallizes and becomes like snow. Therefore, solid carbon dioxide is called “dry snow.”

Rice. 2. Dry snow – carbon dioxide.

Carbon dioxide is 1.5 times denser than air. Its density is 1.98 kg/m³ Chemical bond in a carbon dioxide molecule, covalent is polar. It is polar due to the fact that oxygen has a higher electronegativity value.

An important concept in the study of substances is molecular and molar mass. The molar mass of carbon dioxide is 44. This number is formed from the sum of the relative atomic masses of the atoms that make up the molecule. The values of relative atomic masses are taken from the table of D.I. Mendeleev and are rounded to whole numbers. Accordingly, the molar mass of CO₂ = 12+2*16.

To calculate the mass fractions of elements in carbon dioxide, you must follow the calculation formula mass fractions everyone chemical element in matter.

n– number of atoms or molecules.
A r– relative atomic mass chemical element.
Mr– relative molecular mass of the substance.
Let's calculate the relative molecular mass of carbon dioxide.

Mr(CO₂) = 14 + 16 * 2 = 44 w(C) = 1 * 12 / 44 = 0.27 or 27% Since the formula of carbon dioxide includes two oxygen atoms, then n = 2 w(O) = 2 * 16 / 44 = 0.73 or 73%

Answer: w(C) = 0.27 or 27%; w(O) = 0.73 or 73%

Chemical and biological properties of carbon dioxide

Carbon dioxide has acidic properties because it is an acidic oxide, and when dissolved in water it forms carbonic acid:

CO₂+H₂O=H₂CO₃

Reacts with alkalis, resulting in the formation of carbonates and bicarbonates. This gas does not burn. Only certain active metals, such as magnesium, burn in it.

When heated, carbon dioxide breaks down into carbon monoxide and oxygen:

2CO₃=2CO+O₃.

Like other acidic oxides, this gas easily reacts with other oxides:

СaO+Co₃=CaCO₃.

Carbon dioxide is part of all organic substances. The circulation of this gas in nature is carried out with the help of producers, consumers and decomposers. In the process of life, a person produces approximately 1 kg of carbon dioxide per day. When we inhale, we receive oxygen, but at this moment carbon dioxide is formed in the alveoli. At this moment, an exchange occurs: oxygen enters the blood, and carbon dioxide comes out.

Carbon dioxide is produced during the production of alcohol. This gas is also a by-product in the production of nitrogen, oxygen and argon. The use of carbon dioxide is necessary in Food Industry, where carbon dioxide acts as a preservative, and carbon dioxide in liquid form is found in fire extinguishers.

Carbon monoxide (CO) is a colorless, very light gas (lighter than air) and odorless. But the “smell of carbon monoxide” is felt due to impurities of organic elements in the fuel. Carbon monoxide appears every time you burn wood in your home. The main cause of carbon monoxide is an insufficient amount of oxygen in the combustion area.

The occurrence of waste

Carbon monoxide in the home occurs when carbon is burned due to a lack of oxygen. Combustion of fuel in furnaces occurs in several stages:

First, the carbon burns, releasing carbon dioxide CO2;
The carbon dioxide then comes into contact with the hot remains of coke or coal, creating carbon monoxide;
The carbon monoxide then burns (blue flame) to produce carbon dioxide, which escapes through the chimney.

Without draft in the stove (the chimney is clogged, there is no supply air for combustion, the damper is closed prematurely), the coals continue to smolder without a weak supply of oxygen, so carbon monoxide does not burn and can disperse throughout the heated room, causing a toxic effect on the body and poisoning (carbon monoxide).

Factors of carbon dioxide poisoning

Carbon monoxide is odorless and colorless, making it very dangerous. The causes of smoke inhalation poisoning can be:

Malfunctioning fireplace stove and chimney (clogged chimney, cracks in the stove).
Violation (closing of the stove damper untimely, poor draft, insufficient access to the firebox of fresh air).
The presence of a person at the source of the fire.
Car maintenance in a low-ventilated area.
The use of low-quality air in breathing apparatus and scuba gear.
Sleeping in a car with the engine running.
Using a grill with low ventilation.

Signals and signs of poisoning

At a low concentration of gas, the first signs of toxic effects and poisoning may form: lacrimation, dizziness and pain, nausea and weakness, confusion, dry cough, and there may be auditory and visual hallucinations. If you feel the symptoms of poisoning, you need to get out into fresh air as soon as possible.

If you spend a long period of time in a room with a low density of carbon monoxide, symptoms of poisoning occur: tachycardia, difficulty breathing, loss of coordination, drowsiness, visual hallucinations, blue discoloration of the facial skin and mucous membranes, vomiting, loss of consciousness, and there may be convulsions.

With increased concentrations, loss of consciousness and coma with convulsions occur. Without the first medical care, the victim may die from smoke inhalation.

The effects of carbon monoxide in the home on the human body

Carbon monoxide enters through the lungs, contacts hemoglobin in the blood and prevents the transfer of oxygen to organs and tissues. Oxygen starvation disrupts the nervous system and brain function. The higher the carbon monoxide concentration and the longer the period spent in the room, the stronger the poisoning and the greater the likelihood of death.

After poisoning, medical supervision is required for several days, as complications are often observed. Victims with severe poisoning must be hospitalized. Problems with nervous system and lungs are possible even weeks after the incident. Interestingly, carbon monoxide affects women less than men.

Carbon monoxide detector for home

Poisoning or carbon inhalation can be prevented by using a self-contained carbon monoxide alarm or sensor. If the volume of carbon monoxide in a residential or technical room exceeds the permissible level, the sensor will signal, warning of the threat. Carbon monoxide alarms are electrochemical sensors designed to continuously monitor indoor CO levels and respond with light and sound signals to high levels of carbon monoxide in the air.

When you decide to buy a carbon monoxide alarm for your home, pay attention to the features (even if they are similar in appearance) of the devices: an open fire detector and a smoke alarm, a carbon monoxide and carbon dioxide detector reacts to different elements in the air of the room. Carbon monoxide detectors for the home are installed at a height of one and a half meters from the floor (some recommend installing 15–20 cm from the ceiling). The carbon dioxide detector should be placed near the instrument panel or at floor level (carbon dioxide is much heavier than air), and the smoke detector should be on the ceiling.

In many countries, the use of the above sensors is a mandatory condition required by law to ensure the safety and health of the population. In Europe, only a smoke detector is required. For us, installing a carbon monoxide detector is currently voluntary. Such sensors are generally an inexpensive device, so it is better not to risk your life and buy a carbon monoxide alarm for your home.

How to avoid carbon monoxide poisoning in the house

By following safety rules, smoke inhalation poisoning can be prevented:

— Do not use fuel-burning appliances without sufficient skills, knowledge and tools.

— Do not burn charcoal in a room with poor ventilation.

— Make sure the stove, exhaust and supply ventilation and chimney are working properly.

— On the smoke ducts of wood-burning stoves, it is necessary to install 2 tight valves in series, and on the ducts of stoves operating on coal or peat, only one valve with a 15 mm hole.

— Do not leave a car in the garage with the engine running.

Sensors that signal an increase in carbon monoxide concentration can additionally protect against poisoning, but they should not replace other preventive work.

Carbon monoxide from stove heating

A fireplace or stove with a closed valve and the remains of unburnt fuel is a source of carbon monoxide and an invisible poisoner. Assuming that the fuel has completely burned, stove owners close the chimney damper to preserve heat. Smoldering embers with a lack of air create carbon monoxide, which penetrates into the room through unsealed areas of the furnace system.

Also in the chimney, with weak draft and without air supply, chemical underburning of the fuel occurs, and as a result, the appearance and accumulation of carbon monoxide at home.

(IV), carbon dioxide or carbon dioxide. It is also called carbonic anhydride. It is a completely colorless, odorless gas with a sour taste. Carbon dioxide is heavier than air and is poorly soluble in water. At temperatures below - 78 degrees Celsius, it crystallizes and becomes like snow.

This substance goes from a gaseous state to a solid, since it cannot exist in a liquid state under atmospheric pressure. The density of carbon dioxide under normal conditions is 1.97 kg/m3 - 1.5 times higher. Carbon dioxide in solid form is called “dry ice”. It becomes a liquid state in which it can be stored for a long time when the pressure increases. Let's take a closer look at this substance and its chemical structure.

Carbon dioxide, whose formula is CO2, consists of carbon and oxygen, and it is obtained as a result of the combustion or decay of organic substances. Carbon monoxide is found in the air and underground mineral springs. Humans and animals also emit carbon dioxide when they exhale. Plants without light release it and intensively absorb it during photosynthesis. Thanks to the metabolic process of the cells of all living beings, carbon monoxide is one of the main components of the surrounding nature.

This gas is not toxic, but if it accumulates in high concentrations, suffocation (hypercapnia) can begin, and with its deficiency, the opposite condition develops - hypocapnia. Carbon dioxide transmits and reflects infrared. It is which directly affects global warming. This is due to the fact that the level of its content in the atmosphere is constantly increasing, which leads to the greenhouse effect.

Carbon dioxide is produced industrially from smoke or furnace gases, or by the decomposition of dolomite and limestone carbonates. The mixture of these gases is thoroughly washed with a special solution consisting of potassium carbonate. Next, it turns into bicarbonate and decomposes when heated, resulting in the release of carbon dioxide. Carbon dioxide (H2CO3) is formed from carbon dioxide dissolved in water, but in modern conditions They also obtain it by other, more progressive methods. After the carbon dioxide is purified, it is compressed, cooled and pumped into cylinders.

In industry, this substance is widely and universally used. Food producers use it as a leavening agent (for example, for making dough) or as a preservative (E290). With the help of carbon dioxide, various tonic drinks and sodas are produced, which are so loved not only by children, but also by adults. Carbon dioxide is used in the production of baking soda, beer, sugar, and sparkling wines.

Carbon dioxide is also used in the production of effective fire extinguishers. With the help of carbon dioxide, an active medium is created, which is necessary at high temperatures of the welding arc, carbon dioxide breaks down into oxygen and carbon monoxide. Oxygen interacts with liquid metal and oxidizes it. Carbon dioxide in cans is used in air guns and pistols.

Aircraft modelers use this substance as fuel for their models. With the help of carbon dioxide, you can significantly increase the yield of crops grown in a greenhouse. It is also widely used in industry in which food products are preserved much better. It is used as a refrigerant in refrigerators, freezers, electric generators and other thermal power plants.

, carbon dioxide, properties of carbon dioxide, production of carbon dioxide

It is not suitable for supporting life. However, this is what plants “feed” on, turning it into organic substances. In addition, it is a kind of “blanket” for the Earth. If this gas suddenly disappeared from the atmosphere, the Earth would become much cooler and rain would virtually disappear.

"Blanket of the Earth"

(carbon dioxide, carbon dioxide, CO 2) is formed when two elements combine: carbon and oxygen. It is formed during the combustion of coal or hydrocarbon compounds, during the fermentation of liquids, and also as a product of the respiration of people and animals. It is also found in small quantities in the atmosphere, from where it is assimilated by plants, which, in turn, produce oxygen.

Carbon dioxide is colorless and heavier than air. Freezes at −78.5°C to form snow consisting of carbon dioxide. In aqueous solution it forms carbonic acid, but it is not stable enough to be easily isolated.

Carbon dioxide is the Earth's blanket. It easily transmits ultraviolet rays that heat our planet and reflects infrared rays emitted from its surface into outer space. And if carbon dioxide suddenly disappears from the atmosphere, this will primarily affect the climate. It will become much cooler on Earth, and rain will fall very rarely. It’s not hard to guess where this will ultimately lead.

True, such a catastrophe does not yet threaten us. Quite the contrary. Combustion of organic substances: oil, coal, natural gas, wood - gradually increases the carbon dioxide content in the atmosphere. This means that over time we must expect significant warming and humidification of the earth’s climate. By the way, old-timers believe that it is already noticeably warmer than it was in the days of their youth...

Carbon dioxide is released liquid low temperature, high pressure liquid And gaseous. It is obtained from waste gases from ammonia and alcohol production, as well as from special fuel combustion and other industries. Gaseous carbon dioxide is a colorless and odorless gas at a temperature of 20 ° C and a pressure of 101.3 kPa (760 mm Hg), density - 1.839 kg / m 3. Liquid carbon dioxide is simply a colorless, odorless liquid.

Non-toxic and non-explosive. At concentrations of more than 5% (92 g/m3), carbon dioxide has a harmful effect on human health - it is heavier than air and can accumulate in poorly ventilated areas near the floor. This reduces the volume fraction of oxygen in the air, which can cause oxygen deficiency and suffocation.

Producing carbon dioxide

In industry, carbon dioxide is obtained from furnace gases, from decomposition products of natural carbonates(limestone, dolomite). The mixture of gases is washed with a solution of potassium carbonate, which absorbs carbon dioxide, turning into bicarbonate. When heated, the bicarbonate solution decomposes, releasing carbon dioxide. During industrial production, gas is pumped into cylinders.

In laboratory conditions small amounts are obtained interaction of carbonates and bicarbonates with acids, for example, marble with hydrochloric acid.

"Dry ice" and other beneficial properties of carbon dioxide

Carbon dioxide is used quite widely in everyday practice. For example, sparkling water with the addition of aromatic essences - a wonderful refreshing drink. IN Food Industry carbon dioxide is also used as a preservative - it is indicated on the packaging under the code E290, and also as a dough leavening agent.

Carbon dioxide fire extinguishers used in fires. Biochemists have found that fertilization... of the air with carbon dioxide a very effective means for increasing the yield of various crops. Perhaps this fertilizer has a single, but significant drawback: it can only be used in greenhouses. At plants that produce carbon dioxide, liquefied gas is packaged in steel cylinders and sent to consumers. If you open the valve, snow comes out with a hiss. What kind of miracle?

Everything is explained simply. The work expended on compressing the gas is significantly less than that required to expand it. And in order to somehow compensate for the resulting deficit, carbon dioxide cools sharply, turning into "dry ice". It is widely used for food preservation and preserving regular ice has significant advantages: firstly, its “cooling capacity” is twice as high per unit weight; secondly, it evaporates without a trace.

Carbon dioxide is used as an active medium in wire welding, since at arc temperature, carbon dioxide decomposes into carbon monoxide CO and oxygen, which, in turn, interacts with the liquid metal, oxidizing it.

Carbon dioxide in cans is used in air guns and as energy source for engines in aircraft modeling.