Carbon oxides (II) and (IV)

Integrated lesson in chemistry and biology

Tasks: study and systematize knowledge about carbon oxides (II) and (IV); reveal the relationship between living and inanimate nature; to consolidate knowledge about the effect of carbon oxides on the human body; to consolidate the skills of the ability to work with laboratory equipment.

Equipment: HCl solution, litmus, Ca (OH) 2, CaCO 3, glass rod, homemade tables, portable board, ball-and-stick model.

DURING THE CLASSES

Biology teacher communicates the topic and objectives of the lesson.

Chemistry teacher. Based on the theory of the covalent bond, make up the electronic and structural formulas of carbon oxides (II) and (IV).

The chemical formula of carbon monoxide (II) is CO, the carbon atom is in its normal state.

Due to the pairing of unpaired electrons, two covalent polar bonds are formed, and the third covalent bond is formed by the donor-acceptor mechanism. The donor is an oxygen atom, because it provides a free pair of electrons; the acceptor is a carbon atom, since provides a free orbital.

In industry, carbon monoxide (II) is obtained by passing CO 2 over a hot coal at high temperature... It is also formed during the combustion of coal with a lack of oxygen. ( Pupil writing the reaction equation on the blackboard)

In the laboratory, CO is obtained by the action of concentrated H 2 SO 4 on formic acid. ( The reaction equation is written by the teacher.)

Biology teacher. So, you got acquainted with the production of carbon monoxide (II). And what are the physical properties of carbon monoxide (II)?

Student. It is a colorless gas, poisonous, odorless, lighter than air, poorly soluble in water, boiling point –191.5 ° C, solidifies at –205 ° C.

Chemistry teacher. Carbon monoxide in quantities hazardous to human life contained in the exhaust gases of cars. Therefore, garages should be well ventilated, especially when starting the engine.

Biology teacher. What is the effect of carbon monoxide on the human body?

Student. Carbon monoxide is extremely toxic to humans - this is due to the fact that it forms carboxyhemoglobin. Carboxyhemoglobin is a very strong compound. As a result of its formation, blood hemoglobin does not interact with oxygen, and in case of severe poisoning, a person can die from oxygen starvation.

Biology teacher. What first aid should be given to a person in case of carbon monoxide poisoning?

Students. It is necessary to call an ambulance, the victim should be taken out into the street, artificial respiration should be given, the room should be well ventilated.

Chemistry teacher. Write the chemical formula of carbon monoxide (IV) and, using the ball-and-stick model, build its structure.

The carbon atom is in an excited state. All four covalent polar bonds are formed by pairing unpaired electrons. However, due to its linear structure, its molecule is generally non-polar.
In industry, CO 2 is obtained from the decomposition of calcium carbonate in the production of lime.
(The student writes down the reaction equation.)

In the laboratory, CO 2 is obtained by the interaction of acids with chalk or marble.
(Students perform a laboratory experiment.)

Biology teacher. As a result of what processes carbon dioxide is formed in the body?

Student. Carbon dioxide is produced in the body as a result of oxidation reactions organic matter that make up the cell.

(Students perform a laboratory experiment.)

The lime slurry became cloudy because calcium carbonate is formed. In addition to the breathing process, CO2 is released as a result of fermentation and decay.

Biology teacher. Does physical activity affect the breathing process?

Student. With excessive physical (muscle) load, the muscles use oxygen faster than the blood can deliver it, and then they synthesize the ATP necessary for their work by fermentation. In the muscles, lactic acid C 3 H 6 O 3 is formed, which enters the bloodstream. The accumulation of large amounts of lactic acid is harmful to the body. After heavy physical exertion, we breathe heavily for some time - we pay the "oxygen debt".

Chemistry teacher. A large amount of carbon monoxide (IV) is released into the atmosphere when fossil fuels are burned. At home, we use natural gas as fuel, and it is almost 90% methane (CH 4). I suggest one of you go to the blackboard, write a reaction equation and analyze it in terms of oxidation-reduction.

Biology teacher. Why can't gas ovens be used to heat a room?

Student. Methane is an integral part of natural gas. When it burns, the content of carbon dioxide in the air increases, and oxygen decreases. ( Working with the table "Contents CO 2 in the air".)
When the air contains 0.3% CO 2, a person experiences rapid breathing; at 10% - loss of consciousness, at 20% - instant paralysis and quick death. A child especially needs clean air, because the consumption of oxygen by the tissues of a growing organism is greater than that of an adult. Therefore, it is necessary to regularly ventilate the room. If there is an excess of CO 2 in the blood, the excitability of the respiratory center increases and breathing becomes more frequent and deeper.

Biology teacher. Consider the role of carbon monoxide (IV) in plant life.

Student. In plants, the formation of organic substances occurs from CO 2 and H 2 O in the light, in addition to organic substances, oxygen is formed.

Photosynthesis regulates the carbon dioxide content in the atmosphere, which prevents the planet's temperature from rising. Plants absorb 300 billion tons of carbon dioxide from the atmosphere annually. In the process of photosynthesis, 200 billion tons of oxygen are released into the atmosphere annually. Ozone is formed from oxygen during a thunderstorm.

Chemistry teacher. Consider the chemical properties of carbon monoxide (IV).

Biology teacher. What is the importance of carbonic acid in the human body during respiration? ( Film strip fragment.)
The enzymes in the blood convert carbon dioxide into carbonic acid, which dissociates into hydrogen and bicarbonate ions. If the blood contains an excess of H + ions, i.e. if the acidity of the blood is increased, then some of the H + ions combine with bicarbonate ions, forming carbonic acid and thereby freeing the blood from excess H + ions. If there are too few H + ions in the blood, then carbonic acid dissociates and the concentration of H + ions in the blood increases. At 37 ° C, the blood pH is 7.36.
In the body, carbon dioxide is carried by the blood in the form chemical compounds- sodium and potassium bicarbonates.

Securing the material

Test

From the proposed gas exchange processes in the lungs and tissues, those performing the first option must choose the ciphers of the correct answers on the left, and the second on the right.

(1) Transfer of O 2 from the lungs to the blood. (13)
(2) Transfer of O 2 from blood to tissue. (fourteen)
(3) Transfer of CO 2 from tissues to blood. (15)
(4) Transfer of CO 2 from the blood to the lungs. (16)
(5) Uptake of O 2 by erythrocytes. (17)
(6) Release of O 2 from erythrocytes. (eighteen)
(7) Conversion of arterial blood to venous blood. (19)
(8) Conversion of venous blood into arterial blood. (twenty)
(9) Break chemical bond O 2 with hemoglobin. (21)
(10) Chemical binding of O 2 to hemoglobin. (22)
(11) Capillaries in tissues. (23)
(12) Pulmonary capillaries. (24)

First Option Questions

1. Processes of gas exchange in tissues.
2. Physical processes during gas exchange.

Second Option Questions

1. Gas exchange processes in the lungs.
2. Chemical processes during gas exchange

Task

Determine the volume of carbon monoxide (IV) that is released during the decomposition of 50 g of calcium carbonate.

Carbon monoxide (IV), carbonic acid and their salts

Complex purpose of the module: know the ways of producing carbon (IV) oxide and hydroxide; describe their physical properties; know the characteristics of acid-base properties; to characterize the redox properties.

All elements of the carbon subgroup form oxides with the general formula EO 2. СО 2 and SiО 2 exhibit acidic properties, GeО 2, SnО 2, PbО 2 exhibit amphoteric properties with a predominance of acidic, and in the subgroup from top to bottom, acidic properties weaken.

The oxidation state (+4) for carbon and silicon is very stable, so the oxidizing properties of the compound are very difficult to show. In the germanium subgroup, the oxidizing properties of compounds (+4) are enhanced due to the destabilization of the highest oxidation state.

Carbon monoxide (IV), carbonic acid and their salts

Carbon dioxide CO 2 (carbon dioxide) - under normal conditions it is a colorless and odorless gas, slightly sour taste, about 1.5 times heavier than air, soluble in water, liquefies quite easily - at room temperature it can be converted into a liquid under a pressure of about 60 10 5 Pa. When cooled to 56.2 ° C, liquid carbon dioxide solidifies and turns into a snow-like mass.

In all aggregate states consists of non-polar linear molecules. Chemical structure CO 2 is determined by sp-hybridization of the central carbon atom and the formation of additional p p-p-connections: O = C = O

Some part of the CO 2 dissolved in the will interacts with it to form carbonic acid

CO 2 + H 2 O - CO 2 H 2 O - H 2 CO 3.

Carbon dioxide is very easily absorbed by alkali solutions to form carbonates and bicarbonates:

CO 2 + 2NaOH = Na 2 CO 3 + H 2 O;

CO 2 + NaOH = NaHCO 3.

CO2 molecules are very thermally stable, decomposition begins only at a temperature of 2000єС. Therefore, carbon dioxide does not burn and does not support the combustion of conventional fuels. But in its atmosphere there are some simple substances, whose atoms exhibit a great affinity for oxygen, for example, magnesium, when heated, ignites in an atmosphere of CO 2.

Carbonic acid and its salts

Carbonic acid H 2 CO 3 is a fragile compound, it exists only in aqueous solutions. Most of the carbon dioxide dissolved in water is in the form of hydrated CO 2 molecules, a smaller part forms carbonic acid.

Aqueous solutions in equilibrium with the CO 2 atmosphere are acidic: = 0.04 M and pH? 4.

Carbonic acid is dibasic, belongs to weak electrolytes, dissociates stepwise (K 1 = 4, 4 10? 7; K 2 = 4, 8 10? 11). Dissolving CO 2 in water establishes the following dynamic equilibrium:

H 2 O + CO 2 - CO 2 H 2 O - H 2 CO 3 - H + + HCO 3?

When an aqueous solution of carbon dioxide is heated, the solubility of the gas decreases, CO 2 is released from the solution, and the equilibrium shifts to the left.

Carbonic acid salts

Being dibasic, carbonic acid forms two series of salts: medium salts (carbonates) and acidic (hydrocarbonates). Most carbonic acid salts are colorless. Of carbonates, only salts are soluble in water alkali metals and ammonium.

In water, carbonates undergo hydrolysis, and therefore their solutions have an alkaline reaction:

Na 2 CO 3 + H 2 O - NaHCO 3 + NaOH.

Further hydrolysis with the formation of carbonic acid under normal conditions practically does not take place.

Dissolution of hydrocarbonates in water is also accompanied by hydrolysis, but to a much lesser extent, and the medium is weakly alkaline (pH ≈ 8).

Ammonium carbonate (NH 4) 2 CO 3 is highly volatile at elevated and even normal temperatures, especially in the presence of water vapor, which causes strong hydrolysis

Strong acids and even weak acetic acid displace carbonic acid from carbonates:

K 2 CO 3 + H 2 SO 4 = K 2 SO 4 + H 2 O + CO 2 ^.

Unlike most carbonates, all bicarbonates are soluble in water. They are less stable than carbonates of the same metals and when heated easily decompose, turning into the corresponding carbonates:

2KHCO 3 = K 2 CO 3 + H 2 O + CO 2 ^;

Ca (HCO 3) 2 = CaCO 3 + H 2 O + CO 2 ^.

Strong acids decompose bicarbonates, like carbonates:

KHCO 3 + H 2 SO 4 = KHSO 4 + H 2 O + CO 2

From salts of carbonic acid greatest value have: sodium carbonate (soda), potassium carbonate (potash), calcium carbonate (chalk, marble, limestone), sodium bicarbonate (baking soda) and basic copper carbonate (CuOH) 2 CO 3 (malachite).

Basic salts of carbonic acid in water are practically insoluble and easily decompose when heated:

(CuOH) 2 CO 3 = 2CuO + CO 2 + H 2 O.

In general, the thermal stability of carbonates depends on the polarization properties of the ions that make up the carbonate. The more the cation has a polarizing effect on the carbonate ion, the lower the decomposition temperature of the salt. If the cation can be easily deformed, then the carbonate ion itself will also have a polarizing effect on the cation, which will lead to a sharp decrease in the decomposition temperature of the salt.

Sodium and potassium carbonates melt without decomposition, while most of the remaining carbonates decompose into metal oxide and carbon dioxide when heated.

(IV) (CO 2, carbon dioxide, carbon dioxide) is a colorless, odorless and tasteless gas that is heavier than air and soluble in water.

Under normal conditions, solid carbon dioxide passes directly into a gaseous state, bypassing the liquid state.

With a lot of carbon monoxide, people begin to suffocate. A concentration of more than 3% leads to rapid breathing, and over 10% there is loss of consciousness and death.

Chemical properties of carbon monoxide.

Carbon monoxide - this is carbonic anhydride H 2 CO 3.

If carbon monoxide is passed through calcium hydroxide (lime water), a white precipitate is observed:

Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 Oh,

If carbon dioxide is taken in excess, then the formation of bicarbonates is observed, which dissolve in water:

CaCO 3 + H 2 O + CO 2 = Ca (HCO 3) 2,

Which then disintegrate when heated:

2KNCO 3 = K 2 CO 3 + H 2 O + CO 2

Application of carbon monoxide.

They use carbon dioxide in various industries. In the chemical industry, it is used as a refrigerant.

In the food industry, it is used as a preservative E290. Although it was assigned "conditionally safe", in fact it is not. Doctors have proven that frequent consumption of E290 leads to the accumulation of a toxic poisonous compound. Therefore, you need to carefully read the labels on the products.

Carbon (C)- typical non-metal; v periodic system is in the 2nd period of the IV group, the main subgroup. Atomic number 6, Ar = 12.011 amu, nuclear charge +6.

Physical properties: carbon forms many allotropic modifications: diamond- one of the hardest substances graphite, coal, soot.

A carbon atom has 6 electrons: 1s 2 2s 2 2p 2 . The last two electrons are located on separate p-orbitals and are unpaired. In principle, this pair could occupy one orbital, but in this case the electron-electron repulsion greatly increases. For this reason, one of them takes 2p x, and the other, or 2p y , or 2p z-orbitals.

The difference between the energies of the s- and p-sublevels of the outer layer is small; therefore, the atom quite easily passes into an excited state, in which one of the two electrons from the 2s-orbital passes to the free one. 2p. A valence state with the configuration 1s 2 2s 1 2p x 1 2p y 1 2p z 1 . It is this state of the carbon atom that is characteristic of the diamond lattice - the tetrahedral spatial arrangement of hybrid orbitals, the same bond length and energy.

This phenomenon is known to be called sp 3 -hybridization, and the arising functions are sp 3 -hybrid . The formation of four sp 3 bonds provides the carbon atom with a more stable state than three p-p- and one s-s-link. In addition to sp 3 hybridization at the carbon atom, sp 2 and sp hybridization is also observed . In the first case, there is a mutual overlap s- and two p-orbitals. Three equivalent sp 2 - hybrid orbitals are formed, located in one plane at an angle of 120 ° to each other. The third orbital p is unchanged and directed perpendicular to the plane sp 2.

During sp-hybridization, the s and p orbitals overlap. An angle of 180 ° arises between the two formed equivalent hybrid orbitals, while the two p-orbitals for each of the atoms remain unchanged.

Allotropy of carbon. Diamond and graphite

In a graphite crystal, carbon atoms are located in parallel planes, occupying the vertices of regular hexagons in them. Each of the carbon atoms is bonded to three adjacent sp 2 -hybrid bonds. The connection between the parallel planes is carried out by van der Waals forces. Free p-orbitals of each of the atoms are directed perpendicular to the planes of covalent bonds. Their overlap explains the additional π-bond between carbon atoms. So from valence state in which carbon atoms in a substance are located, the properties of this substance depend.

Chemical properties of carbon

The most typical oxidation states are +4, +2.

At low temperatures, carbon is inert, but when heated, its activity increases.

Carbon as a reducing agent:

- with oxygen
C 0 + O 2 - t ° = CO 2 carbon dioxide
with a lack of oxygen - incomplete combustion:
2C 0 + O 2 - t ° = 2C +2 O carbon monoxide

- with fluorine
C + 2F 2 = CF 4

- with water vapor
C 0 + H 2 O - 1200 ° = C +2 O + H 2 water gas

- with metal oxides. Thus, metal is smelted from ore.
C 0 + 2CuO - t ° = 2Cu + C +4 O 2

- with acids - oxidizing agents:
C 0 + 2H 2 SO 4 (conc.) = C +4 O 2 + 2SO 2 + 2H 2 O
C 0 + 4HNO 3 (conc.) = C +4 O 2 + 4NO 2 + 2H 2 O

- forms carbon disulfide with sulfur:
C + 2S 2 = CS 2.

Carbon as an oxidizing agent:

- forms carbides with some metals

4Al + 3C 0 = Al 4 C 3

Ca + 2C 0 = CaC 2 -4

- with hydrogen - methane (as well as a huge amount organic compounds)

C 0 + 2H 2 = CH 4

- with silicon, forms carborundum (at 2000 ° C in an electric furnace):

Finding carbon in nature

Free carbon occurs in the form of diamond and graphite. In the form of compounds, carbon is in the composition of minerals: chalk, marble, limestone - CaCO 3, dolomite - MgCO 3 * CaCO 3; hydrocarbonates - Mg (HCO 3) 2 and Ca (HCO 3) 2, CO 2 is part of the air; carbon is the main constituent of natural organic compounds - gas, oil, coal, peat; it is a part of organic substances, proteins, fats, carbohydrates, amino acids that make up living organisms.

Inorganic carbon compounds

Neither C 4+ nor C 4- ions are formed under any ordinary chemical processes: carbon compounds contain covalent bonds different polarity.

Carbon monoxide (II) CO

Carbon monoxide; colorless, odorless, slightly soluble in water, soluble in organic solvents, poisonous, t ° bale = -192 ° C; t pl. = -205 ° C.

Receiving
1) In industry (in gas generators):
C + O 2 = CO 2

2) In the laboratory - by thermal decomposition of formic or oxalic acid in the presence of H 2 SO 4 (conc.):
HCOOH = H 2 O + CO

H 2 C 2 O 4 = CO + CO 2 + H 2 O

Chemical properties

CO is inert under normal conditions; when heated - a reducing agent; non-salt-forming oxide.

1) with oxygen

2C +2 O + O 2 = 2C +4 O 2

2) with metal oxides

C +2 O + CuO = Cu + C +4 O 2

3) with chlorine (in the light)

CO + Cl 2 - hn = COCl 2 (phosgene)

4) reacts with alkali melts (under pressure)

CO + NaOH = HCOONa (sodium formate)

5) forms carbonyls with transition metals

Ni + 4CO - t ° = Ni (CO) 4

Fe + 5CO - t ° = Fe (CO) 5

Carbon monoxide (IV) CO2

Carbon dioxide, colorless, odorless, solubility in water - 0.9V CO 2 dissolves in 1V H 2 O (under normal conditions); heavier than air; t ° pl. = -78.5 ° C (solid CO 2 is called "dry ice"); does not support combustion.

Receiving

1. Thermal decomposition of carbonic acid salts (carbonates). Limestone roasting:

CaCO 3 - t ° = CaO + CO 2

1. Action strong acids for carbonates and hydrocarbons:

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

NaHCO 3 + HCl = NaCl + H 2 O + CO 2

ChemicalpropertiesCO2
Acidic Oxide: Reacts with basic oxides and bases to form carbonic acid salts

Na 2 O + CO 2 = Na 2 CO 3

2NaOH + CO 2 = Na 2 CO 3 + H 2 O

NaOH + CO 2 = NaHCO 3

May exhibit oxidizing properties at elevated temperatures

С +4 O 2 + 2Mg - t ° = 2Mg +2 O + C 0

Qualitative reaction

Turbidity of lime water:

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

It disappears with prolonged passage of CO 2 through lime water, because insoluble calcium carbonate transforms into soluble bicarbonate:

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

Carbonic acid and itssalt

H 2CO 3 - The acid is weak, exists only in aqueous solution:

CO 2 + H 2 O ↔ H 2 CO 3

Two-base:
H 2 CO 3 ↔ H + + HCO 3 - Acidic salts- bicarbonates, hydrocarbons
HCO 3 - ↔ H + + CO 3 2- Medium salts - carbonates

All properties of acids are characteristic.

Carbonates and hydrocarbons can be converted into each other:

2NaHCO 3 - t ° = Na 2 CO 3 + H 2 O + CO 2

Na 2 CO 3 + H 2 O + CO 2 = 2NaHCO 3

Metal carbonates (except for alkali metals) decarboxylate when heated to form an oxide:

CuCO 3 - t ° = CuO + CO 2

Qualitative reaction- "boiling" under the action of a strong acid:

Na 2 CO 3 + 2HCl = 2NaCl + H 2 O + CO 2

CO 3 2- + 2H + = H 2 O + CO 2

Carbides

Calcium carbide:

CaO + 3 C = CaC 2 + CO

CaC 2 + 2 H 2 O = Ca (OH) 2 + C 2 H 2.

Acetylene is released when zinc, cadmium, lanthanum and cerium carbides react with water:

2 LaC 2 + 6 H 2 O = 2La (OH) 3 + 2 C 2 H 2 + H 2.

Be 2 C and Al 4 C 3 decompose with water to form methane:

Al 4 C 3 + 12 H 2 O = 4 Al (OH) 3 = 3 CH 4.

In technology, titanium carbides TiC, tungsten W 2 C (hard alloys), silicon SiC (carborundum - as an abrasive and a material for heaters) are used.

Cyanide

obtained by heating soda in an atmosphere of ammonia and carbon monoxide:

Na 2 CO 3 + 2 NH 3 + 3 CO = 2 NaCN + 2 H 2 O + H 2 + 2 CO 2

Hydrocyanic acid HCN is an important product of the chemical industry and is widely used in organic synthesis. Its world production reaches 200 thousand tons per year. Electronic structure cyanide anion is similar to carbon monoxide (II), such particles are called isoelectronic:

C = O: [: C = N:] -

Cyanides (0.1-0.2% water solution) are used in gold mining:

2 Au + 4 KCN + H 2 O + 0.5 O 2 = 2 K + 2 KOH.

When boiling solutions of cyanide with sulfur or fusion of solids, thiocyanates:
KCN + S = KSCN.

When cyanides of low-activity metals are heated, cyanogen is obtained: Hg (CN) 2 = Hg + (CN) 2. Cyanide solutions are oxidized to cyanates:

2 KCN + O 2 = 2 KOCN.

Cyanic acid comes in two forms:

H-N = C = O; H-O-C = N:

In 1828, Friedrich Wöhler (1800-1882) obtained urea from ammonium cyanate: NH 4 OCN = CO (NH 2) 2 by evaporation of an aqueous solution.

This event is usually seen as the victory of synthetic chemistry over "vitalist theory".

There is an isomer of cyanic acid - oxyhydrogen

H-O-N = C.
Its salts (explosive mercury Hg (ONC) 2) are used in impact ignitors.

Synthesis urea(urea):

CO 2 + 2 NH 3 = CO (NH 2) 2 + H 2 O. At 130 0 С and 100 atm.

Urea is an amide of carbonic acid, there is also its "nitrogen analogue" - guanidine.

Carbonates

The most important inorganic carbon compounds are carbonic acid salts (carbonates). H 2 CO 3 is a weak acid (K 1 = 1.3 · 10 -4; K 2 = 5 · 10 -11). Carbonate buffer supports carbon dioxide equilibrium in the atmosphere. The oceans have a huge buffer capacity because they are an open system. The main buffer reaction is equilibrium in the dissociation of carbonic acid:

H 2 CO 3 ↔ H + + HCO 3 -.

With a decrease in acidity, additional absorption of carbon dioxide from the atmosphere occurs with the formation of acid:
CO 2 + H 2 O ↔ H 2 CO 3.

With an increase in acidity, dissolution of carbonate rocks (shells, chalk and limestone deposits in the ocean) occurs; this compensates for the loss of hydrocarbonate ions:

H + + CO 3 2- ↔ HCO 3 -

CaCO 3 (solid) ↔ Ca 2+ + CO 3 2-

Solid carbonates are converted into soluble hydrocarbonates. It is this process of chemical dissolution of excess carbon dioxide that counteracts the "greenhouse effect" - global warming due to the absorption of thermal radiation from the Earth by carbon dioxide. About a third of the world's soda production (sodium carbonate Na 2 CO 3) is used in glass production.

Carbon monoxide (IV) (carbon dioxide, carbon dioxide) under normal conditions is a colorless gas, heavier than air, thermally stable, and when compressed and cooled, it easily turns into a liquid and solid state.

Density - 1.997 g / l. Solid CO2, called dry ice, sublimes at room temperature. It dissolves poorly in water, partially reacts with it. Shows acidic properties. Reduced with active metals, hydrogen and carbon.

Chemical formula of carbon monoxide 4
Chemical formula of carbon monoxide (IV) CO2. It shows that this molecule contains one carbon atom (Ar = 12 amu) and two oxygen atoms (Ar = 16 amu). By the chemical formula, you can calculate molecular weight carbon monoxide (IV):

Mr (CO2) = Ar (C) + 2 × Ar (O);

Mr (CO2) = 12+ 2 × 16 = 12 + 32 = 44.

Examples of problem solving
EXAMPLE 1
Task When 26.7 g of amino acid (CxHyOzNk) are burned in an excess of oxygen, 39.6 g of carbon monoxide (IV), 18.9 g of water and 4.2 g of nitrogen are formed. Determine the amino acid formula.
Solution Let us draw up a scheme for the combustion reaction of an amino acid, denoting the number of carbon atoms, hydrogen, oxygen and nitrogen by "x", "y", "z" and "k", respectively:
CxHyOzNk + Oz → CO2 + H2O + N2.

Let us determine the masses of the elements that make up this substance. The values ​​of the relative atomic masses taken from Periodic table DI. Mendeleev, round up to whole numbers: Ar (C) = 12 amu, Ar (H) = 1 amu, Ar (O) = 16 amu, Ar (N) = 14 amu

M (C) = n (C) × M (C) = n (CO2) × M (C) = × M (C);

M (H) = n (H) × M (H) = 2 × n (H2O) × M (H) = × M (H);

Let's calculate the molar masses of carbon dioxide and water. As you know, the molar mass of a molecule is equal to the sum of the relative atomic masses of the atoms that make up the molecule (M = Mr):

M (CO2) = Ar (C) + 2 × Ar (O) = 12+ 2 × 16 = 12 + 32 = 44 g / mol;

M (H2O) = 2 × Ar (H) + Ar (O) = 2 × 1 + 16 = 2 + 16 = 18 g / mol.

M (C) = x 12 = 10.8 g;

M (H) = 2 × 18.9 / 18 × 1 = 2.1 g.

M (O) = m (CxHyOzNk) - m (C) - m (H) - m (N) = 26.7 - 10.8 - 2.1 - 4.2 = 9.6 g.

We define chemical formula amino acids:

X: y: z: k = m (C) / Ar (C): m (H) / Ar (H): m (O) / Ar (O): m (N) / Ar (N);

X: y: z: k = 10.8 / 12: 2.1 / 1: 9.6 / 16: 4.2 / 14;

X: y: z: k = 0.9: 2.1: 0.41: 0.3 = 3: 7: 1.5: 1 = 6: 14: 3: 2.

Means simplest formula amino acids C6H14O3N2.

Answer C6H14O3N2
EXAMPLE 2
Task Draw up the simplest formula of a compound in which the mass fractions of elements are approximately equal: carbon - 25.4%, hydrogen - 3.17%, oxygen - 33.86%, chlorine - 37.57%.
Solution The mass fraction of element X in a molecule of composition HX is calculated using the following formula:
ω (X) = n × Ar (X) / M (HX) × 100%.

Let's denote the number of carbon atoms in a molecule by "x", the number of nitrogen atoms of hydrogen by "y", the number of oxygen atoms by "z" and the number of chlorine atoms by "k".

Let us find the corresponding relative atomic masses of the elements carbon, hydrogen, oxygen and chlorine (the values ​​of the relative atomic masses taken from the Periodic Table of D.I.Mendeleev, rounded to whole numbers).

Ar (C) = 12; Ar (H) = 14; Ar (O) = 16; Ar (Cl) = 35.5.

We divide the percentage of elements by the corresponding relative atomic masses. Thus, we will find the ratio between the number of atoms in the molecule of the compound:

X: y: z: k = ω (C) / Ar (C): ω (H) / Ar (H): ω (O) / Ar (O): ω (Cl) / Ar (Cl);

X: y: z: k = 25.4 / 12: 3.17 / 1: 33.86 / 16: 37.57 / 35.5;

X: y: z: k = 2.1: 3.17: 2.1: 1.1 = 2: 3: 2: 1.

This means that the simplest formula for a compound of carbon, hydrogen, oxygen and chlorine will be C2H3O2Cl.