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Chemical formula

Molar mass of CO 2 , carbon dioxide 44.0095 g/mol

12.0107+15.9994 2

Mass fractions of elements in the compound

Using the Molar Mass Calculator

• Chemical formulas must be entered case sensitive
• Indexes are entered as regular numbers
• The dot on the midline (multiplication sign), used, for example, in the formulas of crystalline hydrates, is replaced by a regular dot.
• Example: instead of CuSO₄ 5H₂O, the converter uses the spelling CuSO4.5H2O for ease of entry.

Molar mass calculator

mole

All substances are made up of atoms and molecules. In chemistry, it is important to accurately measure the mass of substances entering into a reaction and resulting from it. By definition, a mole is the amount of a substance that contains as many structural elements (atoms, molecules, ions, electrons and other particles or their groups) as there are atoms in 12 grams of a carbon isotope with a relative atomic mass of 12. This number is called a constant or number Avogadro is equal to 6.02214129(27)×10²³ mol⁻¹.

Avogadro's number N A = 6.02214129(27)×10²³ mol⁻¹

In other words, a mole is the amount of a substance equal in mass to the sum of the atomic masses of the atoms and molecules of the substance, multiplied by the Avogadro number. The mole is one of the seven basic units of the SI system and is denoted by the mole. Since the name of the unit and its symbol are the same, it should be noted that the symbol is not declined, unlike the name of the unit, which can be declined according to the usual rules of the Russian language. By definition, one mole of pure carbon-12 is exactly 12 grams.

Molar mass

Molar mass is a physical property of a substance, defined as the ratio of the mass of that substance to the amount of the substance in moles. In other words, it is the mass of one mole of a substance. In the SI system, the unit of molar mass is kilogram/mol (kg/mol). However, chemists are accustomed to using the more convenient unit g/mol.

molar mass = g/mol

Molar mass of elements and compounds

Compounds are substances made up of different atoms that are chemically bonded to each other. For example, the following substances, which can be found in the kitchen of any housewife, are chemical compounds:

• salt (sodium chloride) NaCl
• sugar (sucrose) C₁₂H₂₂O₁₁
• vinegar (acetic acid solution) CH₃COOH

The molar mass of chemical elements in grams per mole is numerically the same as the mass of the element's atoms expressed in atomic mass units (or daltons). The molar mass of compounds is equal to the sum of the molar masses of the elements that make up the compound, taking into account the number of atoms in the compound. For example, the molar mass of water (H₂O) is approximately 2 × 2 + 16 = 18 g/mol.

Molecular mass

Molecular weight (the old name is molecular weight) is the mass of a molecule, calculated as the sum of the masses of each atom that makes up the molecule, multiplied by the number of atoms in this molecule. The molecular weight is dimensionless a physical quantity numerically equal to the molar mass. That is, the molecular weight differs from the molar mass in dimension. Although the molecular mass is a dimensionless quantity, it still has a value called the atomic mass unit (amu) or dalton (Da), and is approximately equal to the mass of one proton or neutron. The atomic mass unit is also numerically equal to 1 g/mol.

Molar mass calculation

The molar mass is calculated as follows:

• determine the atomic masses of the elements according to the periodic table;
Post a question to TCTerms and within a few minutes you will receive an answer.

Instruction

Example 1: Determine the relative molecular weight of CO2. One molecule of carbon dioxide is made up of one carbon atom and two oxygen atoms. Find the atomic mass values ​​for these elements in the periodic table and write them down, rounding up to a whole number: Ar (C) \u003d 12; Ar(O) = 16.

Calculate the relative mass of the CO2 molecule by adding the masses of the atoms that make it up: Мr(CO2) = 12 + 2*16 = 44.

Example 2. How to express the mass of one gas molecule in grams, consider the example of the same carbon dioxide. Take 1 mole of CO2. The molar mass of CO2 is numerically equal to the molecular mass: М(СО2) = 44 g/mol. One mole of any contains 6.02 * 10^23 molecules. This is the number of Avogadro's constant and the symbol Na. Find the mass of one carbon dioxide molecule: m(CO2) = M(CO2)/Na = 44/6.02*10^23 = 7.31*10^(-23) .

Example 3. You are given a gas with a density of 1.34 g/l. It is required to find the mass of one gas molecule. According to Avogadro's law, under normal conditions, one mole of any gas occupies 22.4 liters. Having determined the mass of 22.4 liters, you will find the molar mass of the gas: Mg \u003d 22.4 * 1.34 \u003d 30 g / mol
Now, knowing the mass of one mole, calculate the mass of one molecule in the same way as in example 2: m = 30/6.02*10^23 = 5*10^(-23) grams.

Sources:

• molecular weight of the gas

You can calculate the mass of any molecule, knowing its chemical formula. For example, we calculate the relative mamolecular mass of an alcohol molecule.

You will need

• periodic table

Instruction

Consider the chemical formula of the molecule. Determine the atoms of which chemical elements are included in its composition.

The alcohol formula is C2H5OH. An alcohol molecule consists of 2 atoms, 6 hydrogen atoms and 1 oxygen atom.

Add up the atomic masses of all the elements by multiplying them by the atoms of the substance in the formula.

Thus, M (alcohol) \u003d 2 * 12 + 6 * 1 + 16 \u003d 24 + 6 + 16 \u003d 46 atomic masses. We found the molecular weight of the alcohol molecule.

If the mass of a molecule is in grams rather than in atomic mass units, remember that one atomic mass unit is the mass of 1/12 carbon atom. Numerically 1 a.m.u. \u003d 1.66 * 10 ^ -27 kg.

Then the mass of an alcohol molecule is 46*1.66*10^-27 kg = 7.636*10^-26 kg.

note

In Mendeleev's periodic table, the chemical elements are arranged in order of increasing atomic mass. Experimental methods for determining the molecular weight have been developed mainly for solutions of substances and for gases. There is also a method of mass spectrometry. The concept of molecular weight is of great practical importance for polymers. Polymers are substances consisting of repeating groups of atoms, but the number of these groups is not the same, so for polymers there is the concept of average molecular weight. According to the average molecular weight, one can speak about the degree of polymerization of a substance.

Useful advice

Molecular weight is an important quantity for physicists and chemists. Knowing the molecular weight of a substance, you can immediately determine the density of the gas, find out the molarity of the substance in solution, determine the composition and formula of the substance.

Sources:

• Molecular mass
• how to calculate the mass of a molecule

Mass is one of the most important physical characteristics of a body in space, characterizing the degree of its gravitational effect on the fulcrum. When it comes to calculating mass body, the so-called "rest mass" is implied. It is easy to calculate it.

You will need

• p is the density of the substance of which the given body consists (kg / m³);
• V is the volume of a given body, characterizing the amount of space it occupies (m³).

Instruction

Practical Approach:
For the masses of various bodies, they use one of the most ancient inventions of mankind - scales. The first scales were lever scales. On one was the reference weight, on the other -. Weights are used as indicators of the reference weight. When the weight of the kettlebell/weights coincided with the given body, the lever goes to rest without leaning to either side.

Related videos

In order to determine mass atom, find the molar mass of a monatomic substance using the periodic table. Then divide this mass by Avogadro's number (6.022 10^(23)). This will be the mass of the atom, in the units in which the molar mass was measured. The mass of an atom of a gas is found in terms of its volume, which is easy to measure.

You will need

• To determine the mass of an atom of a substance, take the periodic table, tape measure or ruler, pressure gauge, thermometer.

Instruction

Determining the mass of an atom of a solid body or To determine the mass of an atom of a substance, determine it (what it consists of). In the periodic table, find the cell that describes the corresponding element. Find the mass of one mole of this substance in grams per mole that is in this cell (this number corresponds to the mass of the atom in atomic mass units). Divide the molar mass of the substance by 6.022 10^(23) (Avogadro's number), the result is the given substance in grams. The mass of an atom can also be determined in another way. To do this, multiply the atomic mass of a substance in atomic mass units taken in the periodic table by the number 1.66 10^(-24). Get the mass of one atom in grams.

Determining the mass of an atom of a gas In the event that there is an unknown gas in the vessel, determine its mass in grams by weighing the empty vessel and the vessel with gas, and find the difference between their masses. After that, measure the volume of the vessel using a ruler or tape measure, followed by calculations or other methods. Express the result in . Use a manometer to measure the pressure of the gas inside the vessel, and measure its temperature with a thermometer. If the thermometer scale is calibrated in Celsius, determine the temperature value in Kelvin. To do this, add the number 273 to the temperature value on the thermometer scale.

To determine a gas, multiply the mass of a given volume of gas by its temperature and the number 8.31. Divide the result by the product of the gas, its volume and the Avogadro number 6.022 10 ^ (23) (m0 \u003d m 8.31 T / (P V NA)). The result will be the mass of the gas molecule in grams. In the event that it is known that the gas molecule is diatomic (the gas is not inert), divide the resulting number by 2. Multiplying the result by 1.66 10 ^ (-24) you can get its atomic mass in atomic mass units, and determine the chemical formula of the gas.

Related videos

The molecular weight of a substance refers to the total atomic mass of all the chemical elements that are part of that substance. To calculate the molecular mass substances, no special effort is required.

You will need

• periodic table.

Instruction

Now you need to take a closer look at any of the elements in this table. Under the name of any of the elements indicated in the table there is a numerical value. It is it and the atomic mass of this element.

Now it is worth considering a few examples of calculating the molecular weight, based on the fact that the atomic masses are now known. For example, you can calculate the molecular weight of a substance such as water (H2O). A water molecule contains one oxygen atom (O) and two hydrogens (H). Then, having found the atomic masses of hydrogen and oxygen from the periodic table, we can begin to calculate the molecular mass: 2 * 1.0008 (after all, there are two hydrogens) + 15.999 = 18.0006 amu (atomic mass units).

Another . The next substance, molecular mass which can be calculated, let it be ordinary table salt (NaCl). As can be seen from the molecular formula, the salt molecule contains one Na atom and one chlorine Cl atom. In this case, it is considered as follows: 22.99 + 35.453 = 58.443 a.m.u.

Related videos

note

I would like to note that the atomic masses of the isotopes of various substances differ from the atomic masses in the periodic table. This is due to the fact that the number of neutrons in the nucleus of an atom and inside an isotope of the same substance is different, so the atomic masses also differ markedly. Therefore, isotopes of various elements are usually denoted by the letter of the given element, while adding its mass number in the upper left corner. An example of an isotope is deuterium ("heavy hydrogen"), the atomic mass of which is not one, like an ordinary atom, but two.

One of the first concepts that a student encounters when studying a chemistry course is the mole. This value displays the amount of substance in which there is a certain number of particles of the Avogadro constant. The concept of "mole" was introduced in order to avoid complex mathematical calculations with large numbers of tiny particles.

Instruction

Determine the number of particles that are contained in 1 mol of a substance. This value is a constant and is called the Avogadro constant. It is equal to NA=6.02*1023 mol-1. If you want to make more accurate calculations, then the value of this value must be taken according to the information of the CODATA Data and Technology Committee, which recalculates the Avogadro constant and approves the most accurate values. For example, in 2011 it was accepted that NA = 6.022 140 78(18)×1023 mol-1.

Calculate the value of mole, which is equal to the ratio of the number of particles of a given substance to the value of Avogadro's constant.

Determine the value of a mole of a substance through its M. It has the dimension g / mol and is equal to the relative molecular mass Mr, which is determined from the periodic table for each element that is part of the substance. For example, the molar methane CH4 is equal to the sum of the relative atomic masses and four hydrogens: 12+ 4x1. As a result, you will get that M (CH4) \u003d 16 g / mol. Next, study the condition of the problem and find out for what mass m of the substance it is necessary to determine the number of moles. It will be equal to the ratio of mass to molar mass.

Remember that the molar mass of a substance is determined by the quantitative and qualitative characteristics of its composition, so substances can have the same mole values ​​​​at different masses.

Study the conditions of the problem, if it is necessary to determine the number of moles for a gaseous substance in it, then it can be calculated through volumes. In this case, it is necessary to find out the volume V of a given gas under the conditions. Then divide this value by the molar volume of the gas Vm, which is a constant and under normal conditions equals 22.4 l/mol.

Chemistry is an exact science, therefore, when mixing various substances, it is simply necessary to know their clear proportions. To do this, you need to be able to find mass substances. This can be done in various ways, depending on what quantities you know.

Instruction

If you know the meaning substances and its quantity, apply to determine the mass substances another formula by multiplying the quantity value substances to his molar mass(m(x) = n*M). If the quantity substances unknown, but given the number of molecules in it, then use Avogadro's number. Find quantity substances by dividing the number of molecules substances(N) by Avogadro's number (NA=6.022x1023): n=N/NA, and substitute into the formula above.

To find a molar mass complex substances, add up the atomic masses of all that are in it. Take the atomic masses from the table of D. I. Mendeleev in the notation of the corresponding elements (for convenience, round the atomic masses to the first digit after the decimal point). Then act in the formula, substituting the value of the molar mass there. Do not forget about indices: what is the index of the element in the chemical formula (i.e. how many atoms are in the substance), how much should you multiply the atomic mass.

If you have to deal with a solution, and you know the mass fraction of the desired substances, to determine the mass of this substances multiply the share substances on the mass the whole solution and divide the result by 100% (m(x) = w*m/100%).

Write an Equation substances, from it calculate the amount received or spent substances, and then the resulting amount substances plug into the formula given to you.

Apply the formula: yield=mp*100%/m(x). Then, depending on the mass that you want to calculate, find mp or m. If the product yield is not given, then it can be taken equal to 100% (it is extremely rare in real processes).

Related videos

Useful advice

Designations of quantities in the above formulas:
m(x) - mass of matter (calculated),
mp is the mass obtained in the real process,
V is the volume of the substance,
p is the density of matter,
P - pressure,
n is the amount of substance,
M is the molar mass of the substance,
w is the mass fraction of the substance,
N is the number of molecules,
NA - Avogadro's number
T is the temperature in Kelvin.

Write down these tasks briefly, indicating formulas using alphabetic and numerical designations.

Carefully check the condition and the data, the reaction equation can be given in the problem.

Sources:

• How to solve simple problems in chemistry

Molecular mass substances is the mass of a molecule, expressed in atomic units and numerically equal to the molar mass. In calculations in chemistry, physics and technology, the calculation of the values ​​​​of the molar mass of various substances is often used.

You will need

• - periodic table;
• - table of molecular weights;
• - table of cryoscopic constant values.

Instruction

Find the desired element in the periodic table. Pay attention to fractional numbers under its sign. For example, O has a cell value of 15.9994. This is the atomic mass of the element. nuclear mass must be multiplied by the index of the element. The index shows how much of the element is contained in the substance.

If a complex is given, then multiply the atomic mass of each element by its index (if there is one atom of one or another element and there is no index, respectively, then multiply by one) and add the resulting atomic masses. For example, water is calculated as follows - MH2O = 2 MH + MO ≈ 2 1 + 16 = 18 a. eat.

Calculate the molar mass using suitable formulas and equate it to the molecular one. Change units from g/mol to a.m.u. Given pressure, volume, absolute Kelvin temperature, and mass, calculate the molar mass gas according to the Mendeleev-Claiperon equation M=(m∙R∙T)/(P∙V), in which M is the molecular () in amu, R is the universal gas constant.

Calculate molar mass according to the formula M=m/n, where m is the mass of any given substances, n - chemical quantity substances. Express Quantity substances through the Avogadro number n=N/NA or using the volume n=V/VM. Plug into the formula above.

Find the molecular mass gas, if only the value of its volume is given. To do this, take a sealed container of known volume and pump out of it. Weigh it on the scales. Fill the cylinder with gas and measure again mass. The difference between the masses of the cylinder with the gas pumped into it and the empty cylinder is the mass of this gas.

Using a manometer, find the pressure inside the cylinder (in Pascals). Use a thermometer to measure the ambient air, it is equal to the temperature inside the cylinder. Convert Celsius to Kelvin. To do this, add 273 to the resulting value. Find the molar mass according to the Mendeleev-Clapeyron equation above. Convert it to molecular, replacing the units with a.m.u.

A substance with the chemical formula CO2 and a molecular weight of 44.011 g / mol, which can exist in four phase states - gaseous, liquid, solid and supercritical.

The gaseous state of CO2 is commonly known as carbon dioxide. At atmospheric pressure, it is a colorless gas without color and odor, at a temperature of +20? With a density of 1.839 kg / m? (1.52 times heavier than air), dissolves well in water (0.88 volume in 1 volume of water), partially interacting in it with the formation of carbonic acid. Included in the atmosphere on average 0.035% by volume. With a sharp cooling due to expansion (expanding), CO2 is able to desublimate - go immediately into a solid state, bypassing the liquid phase.

Gaseous carbon dioxide was previously often stored in stationary gas holders. Currently, this method of storage is not used; carbon dioxide in the required amount is obtained directly on site - by evaporating liquid carbon dioxide in the gasifier. Further, the gas can be easily pumped through any gas pipeline at a pressure of 2-6 atmospheres.

The liquid state of CO2 is technically called "liquid carbon dioxide" or simply "carbonic acid". It is a colorless, odorless liquid with an average density of 771 kg / m3, which exists only under a pressure of 3,482 ... 519 kPa at a temperature of 0 ... -56.5 degrees C (“low-temperature carbon dioxide”), or under a pressure of 3,482 ... at a temperature of 0 ... + 31.0 degrees C ("high-pressure carbon dioxide"). High-pressure carbon dioxide is most often obtained by compressing carbon dioxide to a condensation pressure, while cooling it with water. Low-temperature carbon dioxide, which is the main form of carbon dioxide for industrial consumption, is most often produced in a high-pressure cycle by three-stage cooling and throttling in special plants.

With a small and medium consumption of carbon dioxide (high pressure), tons, a variety of steel cylinders are used for its storage and transportation (from cans for household siphons to containers with a capacity of 55 liters). The most common is a 40 l cylinder with a working pressure of 15,000 kPa, containing 24 kg of carbon dioxide. Steel cylinders do not require additional care, carbon dioxide is stored without loss for a long time. High pressure carbon dioxide cylinders are painted black.

With significant consumption, for storage and transportation of low-temperature liquid carbon dioxide, isothermal tanks of the most diverse capacity, equipped with service refrigeration units, are used. There are accumulative (stationary) vertical and horizontal tanks with a capacity of 3 to 250 tons, transportable tanks with a capacity of 3 to 18 tons. Vertical tanks require the construction of a foundation and are used mainly in conditions of limited space for placement. The use of horizontal tanks makes it possible to reduce the cost of foundations, especially if there is a common frame with a carbon dioxide plant. The tanks consist of an internal welded vessel made of low-temperature steel and having polyurethane foam or vacuum thermal insulation; outer casing made of plastic, galvanized or stainless steel; pipelines, fittings and control devices. The inner and outer surfaces of the welded vessel are subjected to special treatment, due to which the probability of surface corrosion of the metal is reduced to a minimum. In expensive imported models, the outer sealed casing is made of aluminum. The use of tanks provides filling and discharge of liquid carbon dioxide; storage and transportation without loss of the product; visual control of weight and operating pressure during filling, storage and dispensing. All types of tanks are equipped with a multi-level security system. Safety valves allow inspection and repair without stopping and emptying the tank.

With an instantaneous decrease in pressure to atmospheric pressure, which occurs during injection into a special expansion chamber (throttling), liquid carbon dioxide instantly turns into gas and the thinnest snow-like mass, which is pressed and carbon dioxide is obtained in a solid state, which is commonly called "dry ice". At atmospheric pressure, it is a white vitreous mass with a density of 1,562 kg / m?, with a temperature of -78.5 ° C, which sublimates in the open air - gradually evaporates, bypassing the liquid state. Dry ice can also be obtained directly at high-pressure plants used to produce low-temperature carbon dioxide from gas mixtures containing CO2 in an amount of at least 75-80%. The volumetric cooling capacity of dry ice is almost 3 times greater than that of water ice and is 573.6 kJ/kg.

Solid carbon dioxide is usually produced in briquettes with a size of 200 × 100 × 20-70 mm, in granules with a diameter of 3, 6, 10, 12 and 16 mm, rarely in the form of the finest powder (“dry snow”). Briquettes, pellets and snow are stored for no more than 1-2 days in stationary underground mine-type storages, divided into small compartments; transported in special isothermal containers with a safety valve. Containers from different manufacturers with a capacity of 40 to 300 kg or more are used. Sublimation losses are, depending on the ambient temperature, 4-6% or more per day.

At pressures above 7.39 kPa and temperatures above 31.6 degrees C, carbon dioxide is in the so-called supercritical state, in which its density is like that of a liquid, and its viscosity and surface tension are like that of a gas. This unusual physical substance (fluid) is an excellent non-polar solvent. Supercritical CO2 is able to fully or selectively extract any non-polar constituents with a molecular weight of less than 2,000 daltons: terpene compounds, waxes, pigments, high molecular weight saturated and unsaturated fatty acids, alkaloids, fat-soluble vitamins and phytosterols. Insoluble substances for supercritical CO2 are cellulose, starch, high molecular weight organic and inorganic polymers, sugars, glycosidic substances, proteins, metals and many metal salts. Having similar properties, supercritical carbon dioxide is increasingly used in the processes of extraction, fractionation and impregnation of organic and inorganic substances. It is also a promising working fluid for modern heat engines.

• Specific gravity. The specific gravity of carbon dioxide depends on the pressure, temperature and state of aggregation in which it is located.
• The critical temperature of carbon dioxide is +31 degrees. The specific gravity of carbon dioxide at 0 degrees and a pressure of 760 mm Hg. is equal to 1.9769 kg/m3.
• The molecular weight of carbon dioxide is 44.0. The relative weight of carbon dioxide compared to air is 1.529.
• Liquid carbon dioxide at temperatures above 0 deg. much lighter than water and can only be stored under pressure.
• The specific gravity of solid carbon dioxide depends on the method of its production. Liquid carbon dioxide, when frozen, turns into dry ice, which is a transparent, glassy solid. In this case, solid carbon dioxide has the highest density (at normal pressure in a vessel cooled to minus 79 degrees, the density is 1.56). Industrial solid carbon dioxide is white, close to chalk in hardness,
• its specific gravity varies depending on the method of obtaining within 1.3 - 1.6.

• State equation. The relationship between the volume, temperature, and pressure of carbon dioxide is expressed by the equation
• V= R T/p - A, where
• V - volume, m3/kg;
• R - gas constant 848/44 = 19.273;
• T - temperature, K degrees;
• p pressure, kg/m2;
• A is an additional term characterizing the deviation from the equation of state for an ideal gas. It is expressed by the dependence A \u003d (0.0825 + (1.225) 10-7 p) / (T / 100) 10 / 3.

• Triple point of carbon dioxide. The triple point is characterized by a pressure of 5.28 ata (kg/cm2) and a temperature of minus 56.6 degrees.
• Carbon dioxide can exist in all three states (solid, liquid and gaseous) only at the triple point. At pressures below 5.28 ata (kg/cm2) (or at temperatures below minus 56.6 degrees), carbon dioxide can exist only in solid and gaseous states.
• In the vapor-liquid region, i.e. above the triple point, the following relations hold
• i "x + i" "y \u003d i,
• x + y = 1, where,
• x and y - the proportion of the substance in liquid and vapor form;
• i" is the enthalpy of the liquid;
• i"" - steam enthalpy;
• i is the enthalpy of the mixture.
• From these values ​​it is easy to determine the values ​​of x and y. Accordingly, for the region below the triple point, the following equations will be valid:
• i"" y + i"" z \u003d i,
• y + z = 1, where,
• i"" - enthalpy of solid carbon dioxide;
• z is the proportion of the substance in the solid state.
• At the triple point for three phases, there are also only two equations
• i"x + i""y + i"""z = i,
• x + y + z = 1.
• Knowing the values ​​of i," i"," i""" for the triple point and using the above equations, you can determine the enthalpy of the mixture for any point.

• Heat capacity. The heat capacity of carbon dioxide at a temperature of 20 degrees. and 1 ata is
• Ср = 0.202 and Сv = 0.156 kcal/kg*deg. Adiabatic exponent k = 1.30.
• The heat capacity of liquid carbon dioxide in the temperature range from -50 to +20 deg. characterized by the following values, kcal / kg * deg. :
• Deg.С -50 -40 -30 -20 -10 0 10 20
• Wed, 0.47 0.49 0.515 0.514 0.517 0.6 0.64 0.68

• Melting point. The melting of solid carbon dioxide occurs at temperatures and pressures corresponding to the triple point (t = -56.6 degrees and p = 5.28 atm) or above it.
• Below the triple point, solid carbon dioxide sublimates. The sublimation temperature is a function of pressure: at normal pressure it is -78.5 degrees, in vacuum it can be -100 degrees. and below.

• Enthalpy. The enthalpy of carbon dioxide vapor in a wide range of temperatures and pressures is determined by the Planck and Kupriyanov equation.
• i = 169.34 + (0.1955 + 0.000115t)t - 8.3724p(1 + 0.007424p)/0.01T(10/3), where
• I - kcal / kg, p - kg / cm2, T - deg. K, t - deg. C.
• The enthalpy of liquid carbon dioxide at any point can be easily determined by subtracting the latent heat of vaporization from the enthalpy of saturated steam. Similarly, by subtracting the latent heat of sublimation, one can determine the enthalpy of solid carbon dioxide.

• Thermal conductivity. Thermal conductivity of carbon dioxide at 0 deg. is 0.012 kcal / m * hour * deg. C, and at a temperature of -78 deg. it drops to 0.008 kcal/m*hour*deg.C.
• Data on the thermal conductivity of carbon dioxide in 10 4 tbsp. kcal/m*h*deg.С at above-zero temperatures are given in the table.
• Pressure, kg/cm2 10 deg. 20 deg. 30 deg. 40 deg.
• gaseous carbon dioxide
• 1 130 136 142 148
• 20 - 147 152 157
• 40 - 173 174 175
• 60 - - 228 213
• 80 - - - 325
• liquid carbonic acid
• 50 848 - - -
• 60 870 753 - -
• 70 888 776 - -
• 80 906 795 670
  The thermal conductivity of solid carbon dioxide can be calculated by the formula:
  236.5 / T1.216 st., kcal / m * hour * deg. C.

• Thermal expansion coefficient. The volume expansion coefficient a of solid carbon dioxide is calculated depending on the change in specific gravity and temperature. The linear expansion coefficient is determined by the expression b = a/3. In the temperature range from -56 to -80 degrees. the coefficients have the following values: a * 10 * 5st. \u003d 185.5-117.0, b * 10 * 5 st. = 61.8-39.0.

• Viscosity. Viscosity of carbon dioxide 10 * 6st. depending on pressure and temperature (kg*sec/m2)
• Pressure, ata -15 degrees. 0 deg. 20 deg. 40 deg.
• 5 1,38 1,42 1,49 1,60
• 30 12,04 1,63 1,61 1,72
• 75 13,13 12,01 8,32 2,30

• Dielectric constant. The dielectric constant of liquid carbon dioxide at 50 - 125 ati is in the range of 1.6016 - 1.6425.
• Dielectric constant of carbon dioxide at 15 deg. and pressure 9.4 - 39 atm 1.009 - 1.060.

• Moisture content of carbon dioxide. The content of water vapor in moist carbon dioxide is determined using the equation,
• X = 18/44 * p'/p - p' = 0.41 p'/p - p' kg/kg, where
• p' - partial pressure of water vapor at 100% saturation;
• p is the total pressure of the vapor-gas mixture.

• Solubility of carbon dioxide in water. The solubility of gases is measured by volumes of gas reduced to normal conditions (0 degrees, C and 760 mm Hg) per volume of solvent.
• The solubility of carbon dioxide in water at moderate temperatures and pressures up to 4 - 5 atm obeys Henry's law, which is expressed by the equation
• P \u003d H X, where
• P is the partial pressure of the gas above the liquid;
• X is the amount of gas in moles;
• H is Henry's coefficient.

• Liquid carbon dioxide as a solvent. The solubility of lubricating oil in liquid carbon dioxide at a temperature of -20 deg. up to +25 deg. is 0.388 g in 100 CO2,
• and increases to 0.718 g in 100 g of CO2 at a temperature of +25 degrees. FROM.
• The solubility of water in liquid carbon dioxide in the temperature range from -5.8 to +22.9 degrees. is not more than 0.05% by weight.

Safety

According to the degree of impact on the human body, gaseous carbon dioxide belongs to the 4th hazard class according to GOST 12.1.007-76 “Harmful substances. Classification and general safety requirements”. The maximum permissible concentration in the air of the working area has not been established; when assessing this concentration, one should be guided by the standards for coal and ozocerite mines, set within 0.5%.

When using dry ice, when using vessels with liquid low-temperature carbon dioxide, safety measures must be observed to prevent frostbite of the hands and other parts of the worker's body.

DEFINITION

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

The structure of the molecule is shown in fig. 1. Density - 1.997 g / l. Poorly soluble in water, partially reacting with it. Shows acidic properties. It is restored by active metals, hydrogen and carbon.

Rice. 1. The structure of the carbon dioxide molecule.

The gross formula of carbon dioxide is CO 2 . As you know, the molecular weight of a molecule is equal to the sum of the relative atomic masses of the atoms that make up the molecule (the values ​​​​of the relative atomic masses taken from the Periodic Table of D.I. Mendeleev are rounded to integers).

Mr(CO 2) = Ar(C) + 2×Ar(O);

Mr(CO 2) \u003d 12 + 2 × 16 \u003d 12 + 32 \u003d 44.

DEFINITION

Molar mass (M) is the mass of 1 mole of a substance.

It is easy to show that the numerical values ​​of the molar mass M and the relative molecular mass M r are equal, however, the first value has the dimension [M] = g/mol, and the second is dimensionless:

M = N A × m (1 molecules) = N A × M r × 1 a.m.u. = (N A ×1 amu) × M r = × M r .

It means that the molar mass of carbon dioxide is 44 g/mol.

The molar mass of a substance in the gaseous state can be determined using the concept of its molar volume. To do this, find the volume occupied under normal conditions by a certain mass of a given substance, and then calculate the mass of 22.4 liters of this substance under the same conditions.

To achieve this goal (calculation of the molar mass), it is possible to use the equation of state of an ideal gas (the Mendeleev-Clapeyron equation):

where p is the gas pressure (Pa), V is the gas volume (m 3), m is the mass of the substance (g), M is the molar mass of the substance (g / mol), T is the absolute temperature (K), R is the universal gas constant equal to 8.314 J / (mol × K).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2