How to find mole in chemistry formula. Mole fractions of matter and the number of atoms
This physical quantity is used to measure macroscopic quantities of substances in cases where, for a numerical description of the processes under study, it is necessary to take into account the microscopic structure of the substance, for example, in chemistry, when studying electrolysis processes, or in thermodynamics, when describing the equations of state of an ideal gas.
When describing chemical reactions, the amount of a substance is a more convenient quantity than the mass, since the molecules interact regardless of their mass in quantities that are multiples of integers.
For example, the combustion reaction of hydrogen (2H 2 + O 2 → 2H 2 O) requires twice as much hydrogen substance as oxygen. In this case, the mass of hydrogen involved in the reaction is approximately 8 times less than the mass of oxygen (since the atomic mass of hydrogen is approximately 16 times less than the atomic mass of oxygen). Thus, the use of the amount of a substance facilitates the interpretation of the reaction equations: the ratio between the amounts of reacting substances is directly reflected by the coefficients in the equations.
Since it is inconvenient to use the number of molecules directly in calculations, because this number is too large in real experiments, instead of measuring the number of molecules "in pieces", they are measured in moles. The actual number of units of a substance in 1 mole is called the Avogadro number (N A \u003d 6.022 141 79 (30) 10 23 mol −1) (more correctly - Avogadro's constant, since, unlike a number, this quantity has units of measurement).
The amount of a substance is denoted by the Latin n (en) and is not recommended to be denoted by the Greek letter (nu), since this letter in chemical thermodynamics denotes the stoichiometric coefficient of a substance in a reaction, and it, by definition, is positive for reaction products and negative for reactants. However, it is the Greek letter (nu) that is widely used in the school course.
To calculate the amount of a substance based on its mass, the concept of molar mass is used: where m is the mass of the substance, M is the molar mass of the substance. Molar mass is the mass per mole of a given substance. The molar mass of a substance can be obtained by multiplying the molecular weight of that substance by the number of molecules in 1 mole - by Avogadro's number. Molar mass (measured in g/mol) is numerically the same as relative molecular weight.
According to Avogadro's law, the amount of a gaseous substance can also be determined based on its volume: \u003d V / V m, where V is the volume of gas (under normal conditions), V m is the molar volume of gas at N. W., equal to 22.4 l /mol.
Thus, a formula is valid that combines the basic calculations with the amount of substance:
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amount of substance- medžiagos kiekis statusas T sritis Standartizacija ir metrologija apibrėžtis Dydis, išreiškiamas medžiagos masės ir jos molio masės dalmeniu. atitikmenys: engl. amount of substance vok. Molmenge, f; Stoffmenge, f rus. amount of substance, n;… … Penkiakalbis aiskinamasis metrologijos terminų žodynas
amount of substance- medžiagos kiekis statusas T sritis fizika atitikmenys: engl. amount of substance vok. Stoffmenge, f rus. amount of substance, n pranc. quantite de matiere, f … Fizikos terminų žodynas
Phys. a quantity determined by the number of structural elements (atoms, molecules, ions, and other particles or their groups) contained in a ve (see Mole) ...
amount of substance retained in the body- rus content (c) of a harmful substance in the body, amount (c) of a substance retained in the body eng body burden fra charge (f) corporelle deu inkorporierte Noxe (f) spa carga (f) corporal … Occupational safety and health. Translation into English, French, German, Spanish
a small amount (of a substance)- very small amount of substance - Topics oil and gas industry Synonyms very small amount of substance EN trace ...
The minimum amount of a substance in production at a time, which defines the boundary between technological processes and technological processes of increased fire hazard. Source: GOST R 12.3.047 98 EdwART. Dictionary… … Emergencies Dictionary
threshold amount of a substance- The minimum amount of a substance in production at a time, which defines the boundary between technological processes and technological processes of increased fire hazard. [GOST R 12.3.047 98] Fire topics ... ... Technical Translator's Handbook
threshold amount of a substance- 3.1.17. threshold amount of a substance: The minimum amount of a substance in production at a time that defines the boundary between technological processes and technological processes of increased fire hazard. A source … Dictionary-reference book of terms of normative and technical documentation
Phys. a value equal to the element kolva in va, which combines with atomic hydrogen or replaces it in chem. connections. Unit E, k.v. (in SI) mol. E. to. in. for k you is equal to the count in va divided by the basicity of k you (the number of hydrogen ions), ... ... Big encyclopedic polytechnic dictionary
Quantity is a category that expresses the external, formal relationship of objects or their parts, as well as properties, connections: their size, number, degree of manifestation of a particular property. Contents 1 History of the concept ... Wikipedia
Books
- Chemistry. Grade 9 Textbook. GEF (number of volumes: 2), Zhilin D.M.. A textbook for grade 9 is part of the teaching materials for chemistry for secondary schools. The textbook outlines the basic concepts and laws of chemistry, as well as the basics of general, inorganic and organic chemistry. ...
Target:
To acquaint students with the concepts of "amount of substance", "molar mass" to give an idea of the Avogadro constant. Show the relationship between the amount of a substance, the number of particles and the Avogadro constant, as well as the relationship between the molar mass, mass and amount of a substance. Learn to do calculations.
1) What is the amount of substance?
2) What is a mole?
3) How many structural units are contained in 1 mole?
4) Through what quantities can the amount of a substance be determined?
5) What is the molar mass, what does it numerically coincide with?
6) What is molar volume?
The amount of a substance is a physical quantity that means a certain number of structural elements (molecules, atoms, ions) Denoted n (en) measured in the international system of units (Ci) mol
Avogadro's number - shows the number of particles in 1 mol of a substance Denoted by NA measured in mol-1 has a numerical value of 6.02*10^23
The molar mass of a substance is numerically equal to its relative molecular mass. Molar mass - a physical quantity that shows the mass in 1 mole of a substance. It is denoted by M measured in g / mol M \u003d m / n
Molar volume - a physical quantity that shows the volume that any gas occupies with an amount of substance 1 mol. It is denoted by Vm measured in l / mol Vm \u003d V / n Vm=22.4l/mol
A MOLE is a QUANTITY of SUBSTANCE equal to 6.02. 10 23 structural units of a given substance - molecules (if the substance consists of molecules), atoms (if it is an atomic substance), ions (if the substance is an ionic compound).
1 mole (1 M) water = 6 .
10 23 H 2 O molecules,
1 mole (1 M) iron = 6 . 10 23 Fe atoms,
1 mole (1 M) chlorine = 6 . 10 23 Cl 2 molecules,
1 mol (1 M) chloride ion Cl - = 6 . 10 23 ions Cl - .
1 mol (1 M) electrons e - = 6 . 10 23 electrons e - .
Tasks:
1) How many moles of oxygen are contained in 128 g of oxygen?
2) During lightning discharges in the atmosphere, the following reaction occurs: N 2 + O 2 ® NO 2. Equalize the response. How many moles of oxygen will be required to completely convert 1 mole of nitrogen into NO 2? How many grams of oxygen will that be? How many grams of NO 2 is formed?
3) 180 g of water is poured into a glass. How many water molecules are in a glass? How many moles of H 2 O is this?
4) Mixed 4 g of hydrogen and 64 g of oxygen. The mixture was blown up. How many grams of water did you get? How many grams of oxygen are left unused?
Homework: paragraph 15, ex. 1-3.5
Molar volume of gaseous substances.
Target: educational - to systematize students' knowledge about the concepts of the amount of a substance, Avogadro's number, molar mass, on their basis to form an idea of the molar volume of gaseous substances; reveal the essence of Avogadro's law and its practical application;
developing - to form the ability for adequate self-control and self-esteem; develop the ability to think logically, put forward hypotheses, draw reasoned conclusions.
During the classes:
1. Organizational moment.
2. Announcement of the topic and objectives of the lesson.
3.Updating basic knowledge
4. Problem solving
Avogadro's law- this is one of the most important laws of chemistry (formulated by Amadeo Avogadro in 1811), stating that "in equal volumes of different gases, which are taken at the same pressure and temperature, the same number of molecules is contained."
Molar volume of gases is the volume of gas containing 1 mol of particles of this gas.
Normal conditions– temperature 0 С (273 K) and pressure 1 atm (760 mm Hg or 101 325 Pa).
Answer the questions:
1. What is called an atom? (Atom is the smallest chemically indivisible part of a chemical element, which is the carrier of its properties).
2. What is a mole? (A mole is the amount of a substance, which is equal to 6.02.10 ^ 23 structural units of this substance - molecules, atoms, ions. This is the amount of a substance containing as many particles as there are atoms in 12 g of carbon).
3. How is the amount of a substance measured? (In moles).
4. How is the mass of a substance measured? (The mass of a substance is measured in grams).
5. What is molar mass and how is it measured? (Molar mass is the mass of 1 mol of a substance. It is measured in g/mol).
Consequences of Avogadro's law.
Two consequences follow from Avogadro's law:
1. One mole of any gas occupies the same volume under the same conditions. In particular, under normal conditions, i.e. at 0 ° C (273 K) and 101.3 kPa, the volume of 1 mole of gas is 22.4 liters. This volume is called the molar volume of the gas Vm. This value can be recalculated to other temperatures and pressures using the Mendeleev-Clapeyron equation (Figure 3).
The molar volume of a gas under normal conditions is a fundamental physical constant widely used in chemical calculations. It allows you to use the volume of gas instead of its mass. The value of the molar volume of gas at n.o. is the coefficient of proportionality between the Avogadro and Loschmidt constants
2. The molar mass of the first gas is equal to the product of the molar mass of the second gas and the relative density of the second of the first gas. This position was of great importance for the development of chemistry, because. it made it possible to determine the partial weight of bodies that are capable of passing into a vapor or gaseous state. Therefore, the ratio of the mass of a certain volume of one gas to the mass of the same volume of another gas, taken under the same conditions, is called the density of the first gas according to the second
1. Fill in the blanks:
Molar volume is a physical quantity that shows ..............., denoted by .............. .., measured in ............... .
2. Write down the formula by the rule.
The volume of a gaseous substance (V) is equal to the product of the molar volume
(Vm) by the amount of substance (n) ............................. .
3. Using the material of task 3, derive formulas for calculation:
a) the volume of a gaseous substance.
b) molar volume.
Homework: paragraph 16, ex. 1-5
Solving problems for calculating the amount of matter, mass and volume.
Generalization and systematization of knowledge on the topic "Simple substances"
Target: generalize and systematize students' knowledge about the main classes of compounds
Working process:
1) Organizational moment
2) Generalization of the studied material:
a) Oral survey on the topic of the lesson
b) Completion of task 1 (finding oxides, bases, acids, salts among the given substances)
c) Completion of task 2 (compilation of formulas for oxides, bases, acids, salts)
3. Consolidation (independent work)
5. Homework
2)
but)
What two groups can substances be divided into?
What substances are called simple?
What two groups are simple substances divided into?
What substances are called complex?
What complex substances are known?
What substances are called oxides?
What substances are called bases?
What substances are called acids?
What substances are called salts?
b)
Write out oxides, bases, acids, salts separately:
KOH, SO 2, HCI, BaCI 2, P 2 O 5,
NaOH, CaCO 3 , H 2 SO 4 , HNO 3 ,
MgO, Ca (OH) 2, Li 3 PO 4
Name them.
in)
Write formulas for oxides corresponding to bases and acids:
Potassium Hydroxide-Potassium Oxide
Iron(III) hydroxide-iron(III) oxide
Phosphoric acid-phosphorus(V) oxide
Sulfuric acid-sulfur(VI) oxide
Write the formula for barium nitrate salt; by ion charges, oxidation states of elements write down
formulas of the corresponding hydroxides, oxides, simple substances.
1. The oxidation state of sulfur is +4 in the compound:
2. Oxides include a substance:
3. Sulfurous acid formula:
4. The basis is the substance:
5. Salt K 2 CO 3 is called:
1- potassium silicate
2-potassium carbonate
3-potassium carbide
4- calcium carbonate
6. In a solution of what substance will litmus change color to red:
2- in alkali
3- in acid
Homework: repeat paragraphs 13-16
Examination No. 2
"Simple Substances"
Oxidation state: binary compounds
Purpose: to teach how to make molecular formulas of substances consisting of two elements according to the degree of oxidation. continue to consolidate the skill of determining the degree of oxidation of an element by the formula.
1. The oxidation state (s. o.) is conditional charge of the atoms of a chemical element in a complex substance, calculated on the basis of the assumption that it consists of simple ions.
Should know!
1) In connections with. about. hydrogen = +1, except for hydrides.
2) In compounds with. about. oxygen = -2, except for peroxides 
and fluorides
3) The oxidation state of metals is always positive.
For metals of the main subgroups of the first three groups from. about. constant:
Group IA metals - p. about. = +1,
Group IIA metals - p. about. = +2,
Group IIIA metals - p. about. = +3.
4) For free atoms and simple substances p. about. = 0.
5) Total s. about. all elements in the compound = 0.
2. Method of formation of names two-element (binary) compounds.
3. 
Tasks:
Make formulas of substances by name.
How many molecules are contained in 48 g of sulfur oxide (IV)?
The oxidation state of manganese in the K2MnO4 compound is:
Chlorine exhibits the maximum oxidation state in a compound whose formula is:
Homework: paragraph 17, ex. 2,5,6
Oxides. Volatile hydrogen compounds.
Target: the formation of students' knowledge about the most important classes of binary compounds - oxides and volatile hydrogen compounds.
Questions:
What substances are called binary?
What is the degree of oxidation?
What oxidation state will the elements have if they donate electrons?
What oxidation state will the elements have if they accept electrons?
– How to determine how many electrons will give or receive elements?
– What oxidation state will single atoms or molecules have?
- What will the compounds be called if sulfur is in second place in the formula?
- What will the compounds be called if chlorine is in second place in the formula?
- What will the compounds be called if hydrogen is in second place in the formula?
- What will the compounds be called if nitrogen is in second place in the formula?
- What will the compounds be called if oxygen is in second place in the formula?
Exploring a new topic:
What do these formulas have in common?
– What will be the name of such substances?
SiO 2, H 2 O, CO 2, AI 2 O 3, Fe 2 O 3, Fe 3 O 4, CO.
oxides- a class of substances of inorganic compounds widespread in nature. Oxides include such well-known compounds as:
Sand (silicon dioxide SiO2 with a small amount of impurities);
Water (hydrogen oxide H2O);
Carbon dioxide (carbon dioxide CO2 IV);
Carbon monoxide (CO II carbon monoxide);
Clay (aluminum oxide AI2O3 with a small amount of other compounds);
Most ferrous ores contain oxides, such as red iron ore - Fe2O3 and magnetic iron ore - Fe3O4.
Volatile hydrogen compounds- the most practically important group of compounds with hydrogen. These include substances commonly found in nature or used in industry, such as water, methane and other hydrocarbons, ammonia, hydrogen sulfide, hydrogen halides. Many of the volatile hydrogen compounds are in the form of solutions in soil waters, in the composition of living organisms, as well as in gases formed during biochemical and geochemical processes, therefore their biochemical and geochemical role is very large.
Depending on the chemical properties, there are:
Salt-forming oxides:
o basic oxides (for example, sodium oxide Na2O, copper (II) oxide CuO): metal oxides, the oxidation state of which is I-II;
o acidic oxides (for example, sulfur oxide (VI) SO3, nitric oxide (IV) NO2): metal oxides with an oxidation state of V-VII and oxides of non-metals;
o amphoteric oxides (for example, zinc oxide ZnO, aluminum oxide Al2O3): metal oxides with oxidation states III-IV and exceptions (ZnO, BeO, SnO, PbO);
Non-salt-forming oxides: carbon monoxide (II) CO, nitric oxide (I) N2O, nitric oxide (II) NO, silicon oxide (II) SiO.
Homework: paragraph 18, exercise 1,4,5
Foundations.
Target:
to introduce students to the composition, classification and representatives of the base class
continue the formation of knowledge about ions on the example of complex hydroxide ions
continue the formation of knowledge about the degree of oxidation of elements, chemical bonds in substances;
give the concept of qualitative reactions and indicators;
to form skills in handling chemical glassware and reagents;
develop a caring attitude towards your health.
In addition to binary compounds, there are complex substances, such as bases, which consist of three elements: metal, oxygen, and hydrogen.
Hydrogen and oxygen are included in them in the form of a hydroxo group OH -. Therefore, the hydroxo group OH- is an ion, but not simple, like Na + or Cl-, but complex - OH- - hydroxide ion.
Foundations
- These are complex substances consisting of metal ions and one or more hydroxide ions associated with them.
If the charge of the metal ion is 1+, then, of course, one hydroxo group OH- is associated with the metal ion, if 2+, then two, etc. Therefore, the composition of the base can be written by the general formula: M (OH) n, where M is the metal , m - the number of OH groups and at the same time the charge of the ion (oxidation state) of the metal.
The names of the bases consist of the word hydroxide and the name of the metal. For example, Na0H is sodium hydroxide. Ca(OH)2 - calcium hydroxide.
If the metal exhibits a variable degree of oxidation, then its value, just as for binary compounds, is indicated by a Roman numeral in brackets and pronounced at the end of the name of the base, for example: CuOH - copper (I) hydroxide, read "copper hydroxide one"; Cr (OH), - copper (II) hydroxide, reads "copper hydroxide two."
In relation to water, the bases are divided into two groups: soluble NaOH, Ca (OH) 2, K0H, Ba (OH)? and insoluble Cr(OH)7, Re(OH)2. Soluble bases are also called alkalis. You can find out whether a base is soluble or insoluble in water using the table "Solubility of bases, acids and salts in water."
Sodium hydroxide NaOH- solid white substance, hygroscopic and therefore deliquescent in air; dissolves well in water, and heat is released. A solution of sodium hydroxide in water is soapy to the touch and very caustic. It corrodes leather, textiles, paper and other materials. For this property, sodium hydroxide is called caustic soda. Sodium hydroxide and its solutions must be handled with care, being careful not to get them on clothes, shoes, and even more so on hands and face. On the skin from this substance, wounds that do not heal for a long time are formed. NaOH is used in soap making, leather and pharmaceutical industries.
Potassium hydroxide KOH- also a solid white substance, highly soluble in water, with the release of a large amount of heat. A solution of potassium hydroxide, like a solution of caustic soda, is soapy to the touch and very caustic. Therefore, potassium hydroxide is otherwise called caustic potash. It is used as an additive in the production of soap, refractory glass.
Calcium hydroxide Ca (OH) 2 or slaked lime is a loose white powder, slightly soluble in water (in the solubility table against the formula Ca (OH) a there is the letter M, which means a poorly soluble substance). It is obtained by the interaction of quicklime CaO with water. This process is called quenching. Calcium hydroxide is used in construction during masonry and plastering of walls, for whitewashing trees, to obtain bleach, which is a disinfectant.
A clear solution of calcium hydroxide is called lime water. When CO2 is passed through lime water, it becomes cloudy. This experience serves to recognize carbon dioxide.
Reactions by which certain chemicals are recognized are called qualitative reactions.
For alkalis, there are also qualitative reactions, with the help of which solutions of alkalis can be recognized among solutions of other substances. These are reactions of alkalis with special substances - indicators (lat. "pointers"). If a few drops of an indicator solution are added to an alkali solution, it will change its color.
Homework: paragraph 19, exercises 2-6, table 4
Mole, molar mass
The smallest particles - molecules, atoms, ions, electrons - participate in chemical processes. The number of such particles, even in a small portion of matter, is very large. Therefore, in order to avoid mathematical operations with large numbers, a special unit is used to characterize the amount of a substance participating in a chemical reaction - mole.
mole- this is such an amount of a substance that contains a certain number of particles (molecules, atoms, ions) equal to the Avogadro constant
The Avogadro constant N A is defined as the number of atoms contained in 12 g of the 12 C isotope:
Thus, 1 mole of any substance contains 6.02 10 23 particles of this substance.
1 mole of oxygen contains 6.02 10 23 O 2 molecules.
1 mole of sulfuric acid contains 6.02 10 23 H 2 SO 4 molecules.
1 mole of iron contains 6.02 10 23 Fe atoms.
1 mole of sulfur contains 6.02 10 23 S atoms.
2 moles of sulfur contains 12.04 10 23 S atoms.
0.5 mol sulfur contains 3.01 10 23 S atoms.
Based on this, any amount of a substance can be expressed by a certain number of moles ν
(nude). For example, a sample of a substance contains 12.04 10 23 molecules. Therefore, the amount of substance in this sample is:
In general:
where Nis the number of particles of a given substance;
N a- the number of particles that contains 1 mol of a substance (Avogadro's constant).
Molar mass of a substance (M)
is the mass that 1 mole of a given substance has.
This value, equal to the ratio of the mass m substance to amount of substance ν
, has dimension kg/mol or g/mol. The molar mass, expressed in g / mol, is numerically equal to the relative relative molecular mass M r (for substances of atomic structure - the relative atomic mass Ar r).
For example, the molar mass of methane CH 4 is defined as follows:
M r (CH 4) \u003d A r (C) + 4 A r (H) \u003d 12 + 4 \u003d 16
M(CH 4) \u003d 16 g / mol, i.e. 16 g of CH 4 contains 6.02 10 23 molecules.
The molar mass of a substance can be calculated if its mass is known m and quantity (number of moles) ν
, according to the formula:
Accordingly, knowing the mass and molar mass of a substance, we can calculate the number of its moles:
or find the mass of a substance by the number of moles and the molar mass:
m = ν M
It should be noted that the value of the molar mass of a substance is determined by its qualitative and quantitative composition, i.e. depends on M r and A r . Therefore, different substances with the same number of moles have different masses. m.
Example
Calculate the masses of methane CH 4 and ethane C 2 H 6 taken in the amount ν
= 2 moles each.
Solution
The molar mass of methane M(CH 4) is 16 g/mol;
molar mass of ethane M (C 2 H 6) \u003d 2 12 + 6 \u003d 30 g / mol.
From here:
m(CH 4) \u003d 2 mol 16 g / mol \u003d 32 g;
m(C 2 H 6) \u003d 2 mol 30 g / mol \u003d 60 g.
Thus, a mole is a portion of a substance containing the same number of particles, but having a different mass for different substances, since particles of matter (atoms and molecules) are not the same in mass.
n(CH 4) = n(C 2 H 6), but m(CH 4) < m (C 2 H 6)
calculation ν used in almost every computational problem.
Relationship:
Problem Solving Samples
|
Task number 1. Calculate the mass (g) of iron taken by the amount of substance 0.5 mol? Given: ν (Fe) \u003d 0.5 mol To find: m(Fe) - ? Solution: m = M ν M (Fe) \u003d Ar (Fe) \u003d 56 g / mol (From the periodic system) m (Fe) \u003d 56 g / mol 0.5 mol \u003d 28 g Answer: m (Fe) \u003d 28 g |
|
Task number 2. Calculate mass (g) 12.04 10 23 oxide moleculescalciumCaABOUT? Given: N (CaO) \u003d 12.04 * 10 23 molecules To find: m (CaO) - ? Solution: m \u003d M ν, ν \u003d N /N a, therefore, the formula for calculating m = M (N/N a) M(CaO) = Ar(Ca) + Ar(O) = 40 + 16 = 56 g/mol m \u003d 56 g / mol (12.04 * 10 23 / 6.02 10 23 1 / mol) \u003d 112 g |
The amount of substance. A mole is a unit of quantity of a substance. Avogadro's number
In addition to the absolute and relative masses of atoms and molecules considered earlier, a special quantity is of great importance in chemistry - the amount of substance. The amount of a substance is determined by the number of structural units (atoms, molecules, ions or other particles) of this substance. The amount of substance is denoted by the letter ν. You already know that any physical quantity has its own unit of measurement. For example, the length of a body is measured in meters, the mass of a substance is measured in kilograms. How is the amount of a substance measured? To measure the amount of a substance, there is a special unit - the mole.
mole- this is the amount of a substance containing as many particles (atoms, molecules or others) as there are carbon atoms in 0.012 kg (i.e. 12 g of carbon. This means that one mole of zinc, one mole of aluminum, one mole of carbon contain one and the same number of atoms. It also means that one mole of molecular oxygen, one mole of water contain the same number of molecules. Both in the first and in the second cases, the number of particles (atoms, molecules) that is contained in one mole is equal to number of atoms in one mole of carbon.It has been experimentally established that one mole of a substance contains 6.02 1023 particles (atoms, molecules, or others). substance.If a substance consists of atoms (for example, zinc, aluminum, etc.), then one mole of this substance is 6.02 1023 of its atoms.If a substance consists of molecules (for example, oxygen, water, etc.), then one a mole of this substance is 6.02 1023 of its molecules. ina 6.02 1023 is named after the famous Italian scientist Amedeo Avogadro "Avogadro's constant" and is designated NA. Avogadro's number shows the number of particles in one mole of a substance, so it could have the dimension "particles / mole". However, since the particles can be different, the word “particles” is omitted and instead a unit is written in the dimension of the Avogadro number: “1/mol” or “mol-1”. Thus: NA = 6.02 1023.
Avogadro's number very large. Compare: if you collect 6.02 1023 balls with a radius of 14 centimeters, then their total volume will be approximately the same volume that our entire planet Earth occupies.
To determine the number of atoms (molecules) in a certain amount of a substance, you must use the following formula: N = ν NA,
where N is the number of particles (atoms or molecules).
For example, let's determine the number of aluminum atoms contained in 2 mol of aluminum substance: N (Al) = ν (Al) · NA.
N (Al) \u003d 2 mol 6.02 1023 \u003d 12.04 1023 (atoms).
In addition, you can determine the amount of a substance by a known number of atoms (molecules): 
One of the basic units in the International System of Units (SI) is the unit of quantity of a substance is the mole.
mole – this is such an amount of a substance that contains as many structural units of a given substance (molecules, atoms, ions, etc.) as there are carbon atoms in 0.012 kg (12 g) of a carbon isotope 12 FROM .
Given that the value of the absolute atomic mass for carbon is m(C) \u003d 1.99 10 26 kg, you can calculate the number of carbon atoms N BUT contained in 0.012 kg of carbon.
A mole of any substance contains the same number of particles of this substance (structural units). The number of structural units contained in a substance with an amount of one mole is 6.02 10 23 and called Avogadro's number (N BUT ).
For example, one mole of copper contains 6.02 10 23 copper atoms (Cu), and one mole of hydrogen (H 2) contains 6.02 10 23 hydrogen molecules.
molar mass(M) is the mass of a substance taken in an amount of 1 mol.
The molar mass is denoted by the letter M and has the unit [g/mol]. In physics, the dimension [kg/kmol] is used.
In the general case, the numerical value of the molar mass of a substance numerically coincides with the value of its relative molecular (relative atomic) mass.
For example, the relative molecular weight of water is:
Mr (H 2 O) \u003d 2Ar (H) + Ar (O) \u003d 2 ∙ 1 + 16 \u003d 18 a.m.u.
The molar mass of water has the same value, but is expressed in g/mol:
M (H 2 O) = 18 g/mol.
Thus, a mole of water containing 6.02 10 23 water molecules (respectively 2 6.02 10 23 hydrogen atoms and 6.02 10 23 oxygen atoms) has a mass of 18 grams. 1 mole of water contains 2 moles of hydrogen atoms and 1 mole of oxygen atoms.
1.3.4. The relationship between the mass of a substance and its quantity
Knowing the mass of a substance and its chemical formula, and hence the value of its molar mass, one can determine the amount of a substance and, conversely, knowing the amount of a substance, one can determine its mass. For such calculations, you should use the formulas:
where ν is the amount of substance, [mol]; m is the mass of the substance, [g] or [kg]; M is the molar mass of the substance, [g/mol] or [kg/kmol].
For example, to find the mass of sodium sulfate (Na 2 SO 4) in the amount of 5 mol, we find:
1) the value of the relative molecular weight of Na 2 SO 4, which is the sum of the rounded values of the relative atomic masses:
Mr (Na 2 SO 4) \u003d 2Ar (Na) + Ar (S) + 4Ar (O) \u003d 142,
2) the value of the molar mass of the substance numerically equal to it:
M (Na 2 SO 4) = 142 g/mol,
3) and, finally, a mass of 5 mol of sodium sulfate:
m = ν M = 5 mol 142 g/mol = 710 g
Answer: 710.
1.3.5. The relationship between the volume of a substance and its quantity
Under normal conditions (n.o.), i.e. at pressure R , equal to 101325 Pa (760 mm Hg), and temperature T, equal to 273.15 K (0 С), one mole of various gases and vapors occupies the same volume, equal to 22.4 l.
The volume occupied by 1 mole of gas or vapor at n.o. is called molar volumegas and has the dimension of a liter per mole.
V mol \u003d 22.4 l / mol.
Knowing the amount of gaseous substance (ν ) And molar volume value (V mol) you can calculate its volume (V) under normal conditions:
V = ν V mol,
where ν is the amount of substance [mol]; V is the volume of the gaseous substance [l]; V mol \u003d 22.4 l / mol.
Conversely, knowing the volume ( V) of a gaseous substance under normal conditions, you can calculate its amount (ν) :
