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CARBON DIOXIDE(carbon(IV) monoxide, carbonic anhydride, carbon dioxide) CO 2 , a well-known bubbly ingredient in carbonated soft drinks. Man has known about the healing properties of “fizzy water” from natural sources since time immemorial, but only in the 19th century. I learned to get it myself. At the same time, the substance that makes water effervescent was identified - carbon dioxide. For the first time for carbonization purposes, this gas was obtained in 1887 during the reaction between crushed marble and sulfuric acid; it was also isolated from natural sources. Later, CO 2 began to be produced on an industrial scale by burning coke, calcining limestone and fermenting alcohol. For more than a quarter of a century, carbon dioxide was stored in pressurized steel cylinders and used almost exclusively to carbonate drinks. In 1923, solid CO 2 (dry ice) began to be produced as a commercial product, and around 1940, liquid CO 2 was produced, which was poured into special sealed tanks under high pressure.
Physical properties.
At normal temperatures and pressures, carbon dioxide is a colorless gas with a slightly sour taste and odor. It is 50% heavier than air, so it can be poured from one container to another. CO 2 is a product of most combustion processes and, in sufficiently large quantities, can extinguish flames by displacing oxygen from the air. When the concentration of CO 2 increases in a poorly ventilated room, the oxygen content in the air decreases so much that a person can suffocate. CO 2 dissolves in many liquids; solubility depends on the properties of the liquid, temperature and CO 2 vapor pressure. The ability of carbon dioxide to dissolve in water determines its widespread use in the production of soft drinks. CO 2 is highly soluble in organic solvents, such as alcohol, acetone and benzene.
With increasing pressure and cooling, carbon dioxide easily liquefies and is in a liquid state at temperatures from +31 to –57 ° C (depending on pressure). Below –57°C it turns into a solid state (dry ice). The pressure required for liquefaction depends on the temperature: at +21° C it is 60 atm, and at –18° C it is only 20 atm. Liquid CO 2 is stored in sealed containers under appropriate pressure. When it passes into the atmosphere, part of it turns into gas, and some into “carbon snow,” while its temperature drops to –84 ° C.
Absorbing heat from the environment, dry ice passes into a gaseous state, bypassing the liquid phase - sublimates. To reduce sublimation losses, it is stored and transported in sealed containers that are strong enough to withstand the increase in pressure as the temperature rises.
Chemical properties.
CO 2 is a low-active compound. When dissolved in water, it forms weak carbonic acid, which turns litmus paper red. Carbonic acid improves the taste of carbonated drinks and prevents the growth of bacteria. Reacting with alkali and alkaline earth metals, as well as with ammonia, CO 2 forms carbonates and bicarbonates.
Prevalence in nature and production.
CO 2 is formed during the combustion of carbon-containing substances, alcoholic fermentation, and the rotting of plant and animal residues; it is released when animals breathe, and it is released by plants in the dark. In the light, on the contrary, plants absorb CO 2 and release oxygen, which maintains the natural balance of oxygen and carbon dioxide in the air we breathe. The CO 2 content in it does not exceed 0.03% (by volume).
There are five main ways to produce CO 2: combustion of carbon-containing substances (coke, natural gas, liquid fuel); formation as a by-product during ammonia synthesis; calcination of limestone; fermentation; pumping from wells. In the last two cases, almost pure carbon dioxide is obtained, and when burning carbon-containing substances or calcining limestone, a mixture of CO 2 with nitrogen and traces of other gases is formed. This mixture is passed through a solution that absorbs only CO 2 . Then the solution is heated and almost pure CO 2 is obtained, which is separated from the remaining impurities. Water vapor is removed by freezing and chemical drying.
The purified CO 2 is liquefied by cooling it at high pressure and stored in large containers. To produce dry ice, liquid CO 2 is fed into a closed chamber of a hydraulic press, where the pressure is reduced to atmospheric pressure. With a sharp decrease in pressure, loose snow and very cold gas are formed from CO 2. The snow is compressed and dry ice is obtained. CO 2 gas is pumped out, liquefied and returned to the storage tank.
APPLICATION
Receiving low temperatures.
In liquid and solid form, CO 2 is used mainly as a refrigerant. Dry ice is a compact material, easy to handle and allows you to create different temperature conditions. With the same mass, it is more than twice as cold as ordinary ice, occupying half the volume. Dry ice is used in food storage. It is used to cool champagne, soft drinks and ice cream. It is widely used in the “cold grinding” of heat-sensitive materials (meat products, resins, polymers, dyes, insecticides, paints, seasonings); when tumbling (cleaning from burrs) stamped rubber and plastic products; during low-temperature testing of aircraft and electronic devices in special chambers; for “cold mixing” of semi-finished muffins and cakes so that they remain homogeneous during baking; for rapid cooling of containers with transported products by blowing them with a stream of crushed dry ice; when hardening alloy and stainless steels, aluminum, etc. in order to improve their physical properties; for tight fit of machine parts during their assembly; for cooling cutters when processing high-strength steel workpieces.
Carbonization.
The main application of CO 2 gas is the carbonation of water and soft drinks. First, water and syrup are mixed in the required proportions, and then the mixture is saturated with CO 2 gas under pressure. Carbonation in beers and wines usually occurs as a result of chemical reactions occurring in them.
Applications based on inertia.
CO 2 is used as an antioxidant during long-term storage of many food products: cheese, meat, milk powder, nuts, instant tea, coffee, cocoa, etc. As a combustion suppressant, CO 2 is used in the storage and transportation of flammable materials, such as rocket fuel, oils, gasoline, paints, varnishes, and solvents. It is used as a protective medium in electric welding of carbon steels in order to obtain a uniform, strong weld, while welding work is cheaper than when using inert gases.
CO 2 is one of the most effective means of extinguishing fires that occur when flammable liquids ignite and electrical breakdowns. Various carbon dioxide fire extinguishers are produced: from portable ones with a capacity of no more than 2 kg to stationary automatic supply units with a total cylinder capacity of up to 45 kg or low-pressure gas tanks with a capacity of up to 60 tons of CO 2. Liquid CO 2, which is under pressure in such fire extinguishers, when released, forms a mixture of snow and cold gas; the latter has a higher density than air and displaces it from the combustion zone. The effect is also enhanced by the cooling effect of snow, which, evaporating, turns into gaseous CO 2.
Chemical aspects.
Carbon dioxide is used in the production of aspirin, white lead, urea, perborates, and chemically pure carbonates. Carbonic acid, formed when CO 2 is dissolved in water, is an inexpensive reagent for neutralizing alkalis. In foundries, carbon dioxide is used to cure sand molds by reacting CO 2 with sodium silicate mixed with sand. This allows you to obtain higher quality castings. Refractory bricks used to line furnaces for smelting steel, glass and aluminum become more durable after treatment with carbon dioxide. CO 2 is also used in urban water softening systems using soda lime.
Creation of increased pressure.
CO 2 is used for pressure testing and leak testing of various containers, as well as for calibrating pressure gauges, valves, and spark plugs. It is used to fill portable containers for inflating life belts and inflatable boats. A mixture of carbon dioxide and nitrous oxide has long been used to pressurize aerosol cans. CO 2 is injected under pressure into sealed containers with ether (in devices for quick engine starting), solvents, paints, insecticides for subsequent spraying of these substances.
Application in medicine.
CO 2 is added in small quantities to oxygen (to stimulate breathing) and during anesthesia. In high concentrations it is used for the humane killing of animals.
Before considering the chemical properties of carbon dioxide, let's find out some characteristics of this compound.
General information
It is the most important component of sparkling water. It is this that gives the drinks freshness and sparkling quality. This compound is an acidic, salt-forming oxide. carbon dioxide is 44 g/mol. This gas is heavier than air, so it accumulates in the lower part of the room. This compound is poorly soluble in water.
Chemical properties
Let us briefly consider the chemical properties of carbon dioxide. When interacting with water, weak carbonic acid is formed. Almost immediately after formation, it dissociates into hydrogen cations and carbonate or bicarbonate anions. The resulting compound reacts with active metals, oxides, and also with alkalis.
What are the basic chemical properties of carbon dioxide? The reaction equations confirm the acidic nature of this compound. (4) capable of forming carbonates with basic oxides.
Physical properties
Under normal conditions, this compound is in a gaseous state. When the pressure increases, it can be converted to a liquid state. This gas is colorless, odorless, and has a slight sour taste. Liquefied carbon dioxide is a colorless, transparent, highly mobile acid, similar in its external parameters to ether or alcohol.
The relative molecular weight of carbon dioxide is 44 g/mol. This is almost 1.5 times more than air.
If the temperature drops to -78.5 degrees Celsius, formation occurs. It is similar in hardness to chalk. When this substance evaporates, carbon monoxide gas is formed (4).
Qualitative reaction
When considering the chemical properties of carbon dioxide, it is necessary to highlight its qualitative reaction. When this chemical interacts with lime water, a cloudy precipitate of calcium carbonate is formed.
Cavendish was able to discover such characteristic physical properties of carbon monoxide (4), as solubility in water, as well as high specific gravity.
Lavoisier conducted a study in which he tried to isolate pure metal from lead oxide.
The chemical properties of carbon dioxide revealed as a result of such studies became confirmation of the reducing properties of this compound. Lavoisier managed to obtain metal by calcining lead oxide with carbon monoxide (4). To make sure that the second substance was carbon monoxide (4), he passed lime water through the gas.
All the chemical properties of carbon dioxide confirm the acidic nature of this compound. This compound is found in sufficient quantities in the earth's atmosphere. With the systematic growth of this compound in the earth's atmosphere, serious climate change (global warming) is possible.
It is carbon dioxide that plays an important role in living nature, because this chemical takes an active part in the metabolism of living cells. It is this chemical compound that is the result of various oxidative processes associated with the respiration of living organisms.
Carbon dioxide contained in the earth's atmosphere is the main source of carbon for living plants. In the process of photosynthesis (in the light), the process of photosynthesis occurs, which is accompanied by the formation of glucose and the release of oxygen into the atmosphere.
Carbon dioxide is not toxic and does not support respiration. With an increased concentration of this substance in the atmosphere, a person experiences breath holding and severe headaches. In living organisms, carbon dioxide has important physiological significance; for example, it is necessary for the regulation of vascular tone.
Features of receiving
On an industrial scale, carbon dioxide can be separated from flue gas. In addition, CO2 is a by-product of the decomposition of dolomite and limestone. Modern installations for the production of carbon dioxide involve the use of an aqueous solution of ethanamine, which adsorbs the gas contained in the flue gas.
In the laboratory, carbon dioxide is released by the reaction of carbonates or bicarbonates with acids.
Applications of carbon dioxide
This acidic oxide is used in industry as a leavening agent or preservative. On product packaging this compound is indicated as E290. In liquid form, carbon dioxide is used in fire extinguishers to extinguish fires. Carbon monoxide (4) is used to produce carbonated water and lemonade drinks.
(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 it is also obtained by other, more advanced 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.
Physical and chemical properties of carbon dioxide
DEFINITION
Carbon dioxide (carbon dioxide, carbonic anhydride, carbon dioxide) is carbon monoxide (IV).
The formula is \(\ \mathrm(CO)_(2) \). Molar mass – 44 g/mol.
Chemical properties of carbon dioxide
Carbon dioxide belongs to the class of acidic oxides, i.e. When interacting with water, it forms an acid called carbonic acid. Carbonic acid is chemically unstable and at the moment of formation it immediately breaks down into its components, i.e. The reaction between carbon dioxide and water is reversible:
\(\ \mathrm(CO)_(2)+\mathrm(H)_(2) \mathrm(O) \leftrightarrow \mathrm(CO)_(2) \times \mathrm(H)_(2) \ mathrm(O)(\text ( solution )) \leftrightarrow \mathrm(H)_(2) \mathrm(CO)_(3) \).
When heated, carbon dioxide breaks down into carbon monoxide and oxygen:
\(\ 2 \mathrm(CO)_(2)=2 \mathrm(CO)+\mathrm(O)_(2) \)
Like all acidic oxides, carbon dioxide is characterized by reactions of interaction with basic oxides (formed only by active metals) and bases:
\(\ \mathrm(CaO)+\mathrm(CO)_(2)=\mathrm(CaCO)_(3) \);
\(\ \mathrm(Al)_(2) \mathrm(O)_(3)+3 \mathrm(CO)_(2)=\mathrm(Al)_(2)\left(\mathrm(CO) _(3)\right)_(3)\);
\(\ \mathrm(CO)_(2)+\mathrm(NaOH)_((\text ( dilute )))=\mathrm(NaHCO)_(3) \);
\(\ \mathrm(CO)_(2)+2 \mathrm(NaOH)_((\mathrm(conc)))=\mathrm(Na)_(2) \mathrm(CO)_(3)+\ mathrm(H)_(2) \mathrm(O) \).
Carbon dioxide does not support combustion; only active metals burn in it:
\(\ \mathrm(CO)_(2)+2 \mathrm(Mg)=\mathrm(C)+2 \mathrm(MgO)\left(\mathrm(t)^(\circ)\right) \) ;
\(\ \mathrm(CO)_(2)+2 \mathrm(Ca)=\mathrm(C)+2 \mathrm(CaO)\left(\mathrm(t)^(\circ)\right) \) .
Carbon dioxide reacts with simple substances such as hydrogen and carbon:
\(\ \mathrm(CO)_(2)+4 \mathrm(H)_(2)=\mathrm(CH)_(4)+2 \mathrm(H)_(2) \mathrm(O)\ left(\mathrm(t)^(\circ), \mathrm(kat)=\mathrm(Cu)_(2) \mathrm(O)\right) \);
\(\ \mathrm(CO)_(2)+\mathrm(C)=2 \mathrm(CO)\left(\mathrm(t)^(\circ)\right) \).
When carbon dioxide reacts with peroxides of active metals, carbonates are formed and oxygen is released:
\(\ 2 \mathrm(CO)_(2)+2 \mathrm(Na)_(2) \mathrm(O)_(2)=2 \mathrm(Na)_(2) \mathrm(CO)_ (3)+\mathrm(O)_(2) \uparrow \).
A qualitative reaction to carbon dioxide is the reaction of its interaction with lime water (milk), i.e. with calcium hydroxide, in which a white precipitate is formed - calcium carbonate:
\(\ \mathrm(CO)_(2)+\mathrm(Ca)(\mathrm(OH))_(2)=\mathrm(CaCO)_(3 \downarrow)+\mathrm(H)_(2 ) \mathrm(O) \).
Physical properties of carbon dioxide Carbon dioxide is a gaseous substance without color or odor. Heavier than air. Thermally stable. When compressed and cooled, it easily transforms into liquid and solid states. Carbon dioxide in a solid aggregate state is called “dry ice” and easily sublimes at room temperature. Carbon dioxide is poorly soluble in water and partially reacts with it. Density – 1.977 g/l.
Production and use of carbon dioxide There are industrial and laboratory methods for producing carbon dioxide. Thus, in industry it is obtained by burning limestone (1), and in the laboratory by the action of strong acids on carbonic acid salts (2):
\(\ \mathrm(CaCO)_(3)=\mathrm(CaO)+\mathrm(CO)_(2)\left(\mathrm(t)^(\circ)\right)(1) \);
\(\ \mathrm(CaCO)_(3)+2 \mathrm(HCl)=\mathrm(CaCl)_(2)+\mathrm(CO)_(2) \uparrow+\mathrm(H)_(2) \mathrm(O)(2)\).
Carbon dioxide is used in the food (carbonating lemonade), chemical (temperature control in the production of synthetic fibers), metallurgical (environmental protection, such as brown gas precipitation) and other industries.
Examples of problem solving
Task What volume of carbon dioxide will be released by the action of 200 g of a 10% solution of nitric acid per 90 g of calcium carbonate containing 8% impurities insoluble in acid? Solution Molar masses of nitric acid and calcium carbonate, calculated using the table of chemical elements D.I. Mendeleev - 63 and 100 g/mol, respectively. Let us write the equation for the dissolution of limestone in nitric acid:
\(\ \mathrm(CaCO)_(3)+2 \mathrm(HNO)_(3) \rightarrow \mathrm(Ca)\left(\mathrm(NO)_(3)\right)_(2)+ \mathrm(CO)_(2) \uparrow+\mathrm(H)_(2) \mathrm(O) \).
\(\ \omega\left(\mathrm(CaCO)_(3)\right)_(\mathrm(cl))=100 \%-\omega_(\text ( admixture ))=100 \%-8 \% =92\%=0.92\).
Then, the mass of pure calcium carbonate is:
\(\ m\left(\mathrm(CaCO)_(3)\right)_(\mathrm(cl))=\mathrm(m)_(\text ( limestone )) \times \omega\left(\mathrm (CaCO)_(3)\right)_(\mathrm(cl)) / 100 \% \);
\(\ \mathrm(m)\left(\mathrm(CaCO)_(3)\right)_(\mathrm(cl))=90 \times 92 / 100 \%=82.8 \mathrm(g) \ ).
The amount of calcium carbonate substance is equal to:
\(\n\left(C a C O_(3)\right)=m\left(C a C O_(3)\right)_(C l) / M\left(C a C O_(3)\ right) \);
\(\n\left(\mathrm(CaCO)_(3)\right)=82.8 / 100=0.83 \mathrm(mol)\)
The mass of nitric acid in solution will be equal to:
\(\ \mathrm(m)\left(\mathrm(HNO)_(3)\right)=\mathrm(m)\left(\mathrm(HNO)_(3)\right)_(\text ( solution )) \times \omega\left(\mathrm(HNO)_(3)\right) / 100 \% \);
\(\ \mathrm(m)\left(\mathrm(HNO)_(3)\right)=200 \times 10 / 100 \%=20 \mathrm(g) \)
The amount of calcium nitric acid is equal to:
\(\ \mathrm(n)\left(\mathrm(HNO)_(3)\right)=\mathrm(m)\left(\mathrm(HNO)_(3)\right) / \mathrm(M) \left(\mathrm(HNO)_(3)\right) \)
\(\n\left(H N O_(3)\right)=20 / 63=0.32 \) mol
By comparing the amounts of substances that reacted, we determine that nitric acid is in short supply, therefore, further calculations are made using nitric acid. According to the reaction equation \(\n(H N O 3) : n(C O 2)=2: 1\), therefore n(CO2) = 1/2×n(HNO3) = 0.16 mol. Then, the volume of carbon dioxide will be equal to:
V(CO2) = n(CO2)×Vm ;
V(CO2) = 0.16×22.4 = 3.58 g.
Answer The volume of carbon dioxide is 3.58 g.
Task Find the volume of carbon dioxide weighing 35 g.
Solution The mass of a substance and its volume are related to each other through the amount of substance. Let's write the formulas for calculating the amount of a substance using its mass and volume:
\(\ \mathrm(n)=\mathrm(m) / \mathrm(M) \);
\(\ \mathrm(n)=\mathrm(V) / \mathrm(V)_(\mathrm(m)) \).
Equate the expressions written on the right and express the volume:
\(\ \mathrm(m) / \mathrm(M)=\mathrm(V) / \mathrm(V)_(\mathrm(m)) \);
\(\ \mathrm(V)=\mathrm(m) \times \mathrm(V)_(\mathrm(m)) / \mathrm(M) \).
Let us calculate the volume of carbon dioxide using the formula derived. Molar mass of carbon dioxide, calculated using the table of chemical elements by D.I. Mendeleev – 44 g/mol.
\(\V\left(C O_(2)\right)=35 \times 22.4 / 44=17.82 \) l.
Answer The volume of carbon dioxide is 17.82 liters.
The most common processes for the formation of this compound are the rotting of animal and plant remains, the combustion of various types of fuel, and the respiration of animals and plants. For example, one person emits about a kilogram of carbon dioxide into the atmosphere per day. Carbon monoxide and dioxide can also be formed in inanimate nature. Carbon dioxide is released during volcanic activity and can also be produced from mineral water sources. Carbon dioxide is found in small quantities in the Earth's atmosphere.
The peculiarities of the chemical structure of this compound allow it to participate in many chemical reactions, the basis for which is carbon dioxide.
Formula
In the compound of this substance, the tetravalent carbon atom forms a linear bond with two oxygen molecules. The appearance of such a molecule can be represented as follows:
The hybridization theory explains the structure of the carbon dioxide molecule as follows: the two existing sigma bonds are formed between the sp orbitals of carbon atoms and the two 2p orbitals of oxygen; The p-orbitals of carbon, which do not take part in hybridization, are bonded in conjunction with similar orbitals of oxygen. In chemical reactions, carbon dioxide is written as: CO 2.
Physical properties
Under normal conditions, carbon dioxide is a colorless, odorless gas. It is heavier than air, which is why carbon dioxide can behave like a liquid. For example, it can be poured from one container to another. This substance is slightly soluble in water - about 0.88 liters of CO 2 dissolve in one liter of water at 20 ⁰C. A slight decrease in temperature radically changes the situation - 1.7 liters of CO 2 can dissolve in the same liter of water at 17⁰C. With strong cooling, this substance precipitates in the form of snow flakes - the so-called “dry ice” is formed. This name comes from the fact that at normal pressure the substance, bypassing the liquid phase, immediately turns into a gas. Liquid carbon dioxide is formed at a pressure just above 0.6 MPa and at room temperature.
Chemical properties
When interacting with strong oxidizing agents, 4-carbon dioxide exhibits oxidizing properties. The typical reaction of this interaction is:
C + CO 2 = 2CO.
Thus, with the help of coal, carbon dioxide is reduced to its divalent modification - carbon monoxide.
Under normal conditions, carbon dioxide is inert. But some active metals can burn in it, removing oxygen from the compound and releasing carbon gas. A typical reaction is the combustion of magnesium:
2Mg + CO 2 = 2MgO + C.
During the reaction, magnesium oxide and free carbon are formed.
In chemical compounds, CO 2 often exhibits the properties of a typical acid oxide. For example, it reacts with bases and basic oxides. The result of the reaction is carbonic acid salts.
For example, the reaction of a compound of sodium oxide with carbon dioxide can be represented as follows:
Na 2 O + CO 2 = Na 2 CO 3;
2NaOH + CO 2 = Na 2 CO 3 + H 2 O;
NaOH + CO 2 = NaHCO 3.
Carbonic acid and CO 2 solution
Carbon dioxide in water forms a solution with a small degree of dissociation. This solution of carbon dioxide is called carbonic acid. It is colorless, weakly expressed and has a sour taste.
Recording a chemical reaction:
CO 2 + H 2 O ↔ H 2 CO 3.
The equilibrium is shifted quite strongly to the left - only about 1% of the initial carbon dioxide is converted into carbonic acid. The higher the temperature, the fewer carbonic acid molecules in the solution. When the compound boils, it disappears completely, and the solution disintegrates into carbon dioxide and water. The structural formula of carbonic acid is presented below.
Properties of carbonic acid
Carbonic acid is very weak. In solutions, it breaks down into hydrogen ions H + and compounds HCO 3 -. CO 3 - ions are formed in very small quantities.
Carbonic acid is dibasic, so the salts formed by it can be medium and acidic. In the Russian chemical tradition, medium salts are called carbonates, and strong salts are called bicarbonates.
Qualitative reaction
One possible way to detect carbon dioxide gas is to change the clarity of the lime mortar.
Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 O.
This experience is known from a school chemistry course. At the beginning of the reaction, a small amount of white precipitate is formed, which subsequently disappears when carbon dioxide is passed through water. The change in transparency occurs because during the interaction process, an insoluble compound - calcium carbonate - is converted into a soluble substance - calcium bicarbonate. The reaction proceeds along this path:
CaCO 3 + H 2 O + CO 2 = Ca(HCO 3) 2.
Production of carbon dioxide
If you need to get a small amount of CO2, you can start the reaction of hydrochloric acid with calcium carbonate (marble). The chemical notation for this interaction looks like this:
CaCO 3 + HCl = CaCl 2 + H 2 O + CO 2.
Also for this purpose, combustion reactions of carbon-containing substances, for example acetylene, are used:
CH 4 + 2O 2 → 2H 2 O + CO 2 -.
A Kipp apparatus is used to collect and store the resulting gaseous substance.
For the needs of industry and agriculture, the scale of carbon dioxide production must be large. A popular method for this large-scale reaction is to burn limestone, which produces carbon dioxide. The reaction formula is given below:
CaCO 3 = CaO + CO 2.
Applications of carbon dioxide
The food industry, after large-scale production of “dry ice,” switched to a fundamentally new method of storing food. It is indispensable in the production of carbonated drinks and mineral water. The CO 2 content in drinks gives them freshness and significantly increases shelf life. And carbidization of mineral waters allows you to avoid mustiness and unpleasant taste.
In cooking, the method of extinguishing citric acid with vinegar is often used. The carbon dioxide released during this process imparts fluffiness and lightness to confectionery products.
This compound is often used as a food additive to increase the shelf life of food products. According to international standards for the classification of chemical additives contained in products, it is coded E 290,
Powdered carbon dioxide is one of the most popular substances included in fire extinguishing mixtures. This substance is also found in fire extinguisher foam.
It is best to transport and store carbon dioxide in metal cylinders. At temperatures above 31⁰C, the pressure in the cylinder can reach critical and liquid CO 2 will go into a supercritical state with a sharp rise in operating pressure to 7.35 MPa. The metal cylinder can withstand internal pressure up to 22 MPa, so the pressure range at temperatures above thirty degrees is considered safe.
