What is called a solution in chemistry. How to prepare chemical solutions. Solutions, mechanical mixtures and chemical compounds

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Solution- homogeneous (homogeneous) mixtureconsisting of particles of the dissolved substance, solvent and products of their interaction. “Homogeneous” means that each of the components is distributed in the mass of the other in the form of its particles, that is, atoms, molecules or ions. .

Solution- a single-phase system of variable, or heterogeneous, composition, consisting of two or more components.

The formation of one or another type of solution is determined by the intensity of the intermolecular, interatomic, interionic or other type of interaction, that is, the same forces that determine the occurrence of one or another state of aggregation. Differences: the formation of a solution depends on the nature and intensity of the interaction of particles different substances.

Compared to individual substances, solutions are more complex in structure.

The chemical interaction of a solute with water leads to the formation of compounds called hydrates. Their formulas are expressed using the formulas of the solute and water, connected by the sign "."

The hydrate theory of solutions was proposed by the Russian scientist D. I. Mendeleev.

Hydration- the process of interaction of a solute with water.

Crystal hydrates- crystals, which include water molecules; water contained in crystalline hydrates - crystallization.

Solid, liquid, gaseous solutions

Most often, a solution means a liquid substance, such as a solution of salt or alcohol in water (or even a solution of gold in amalgam).

Dissolution

Dissolution is the transition of molecules of a substance from one phase to another ( solution, dissolved state). Occurs as a result of the interaction of atoms (molecules) of the solvent and the solute and is accompanied by an increase in entropy during the dissolution of solids and its decrease during the dissolution of gases. When dissolved, the interfacial boundary disappears, while many of the physical properties of the solution (for example, density, viscosity, sometimes color, and others) change.

In the case of a chemical interaction between a solvent and a solute, the chemical properties also change greatly - for example, when hydrogen chloride gas dissolves in water, liquid hydrochloric acid is formed.

When crystalline substances are dissolved, the solubility of which increases with increasing temperature, the solution cools down due to the fact that the solution has more internal energy than the crystalline substance and solvent taken separately. For example, boiling water, in which sugar is dissolved, is strongly cooled.

Solutions of electrolytes and non-electrolytes

Electrolytes are substances that conduct electric current in melts or aqueous solutions. In melts or aqueous solutions, they dissociate into ions. Non-electrolytes are substances whose aqueous solutions and melts do not conduct electric current, since their molecules do not dissociate into ions. Electrolytes, when dissolved in suitable solvents (water, other polar solvents), dissociate into ions. A strong physicochemical interaction during dissolution leads to a strong change in the properties of the solution (chemical theory of solutions).

Substances that do not decompose into ions under the same conditions and do not conduct electric current are called non-electrolytes.

Electrolytes include acids, bases, and almost all salts; non-electrolytes include most organic compounds, as well as substances in whose molecules there are only covalent non-polar or low-polar bonds.

Polymer solutions

Solutions of high-molecular substances IUDs - proteins, carbohydrates, etc. simultaneously have many properties of true and colloidal solutions.

Solution concentration

Depending on the purpose, different physical quantities are used to describe the concentration of solutions.

• unsaturated solution- a solution in which the concentration of a solute is less than in a saturated solution, and in which, under given conditions, some more of it can be dissolved.
• saturated solution A solution in which the solute has reached its maximum concentration under given conditions and is no longer soluble. The precipitate of a given substance is in equilibrium with the substance in solution.
• Supersaturated solution- a solution containing under given conditions more solute than in a saturated solution, the excess of the substance easily precipitates. Typically, a supersaturated solution is obtained by cooling a solution saturated at a higher temperature (supersaturation).
• concentrated solution A solution with a high content of solute as opposed to a dilute solution containing a small amount of solute. The division of solutions into concentrated and dilute is not related to the division into saturated and unsaturated. So a saturated 0.0000134 solution of silver chloride is very dilute, and a 4 solution of potassium bromide, being very concentrated, is not saturated.
• diluted solution- a solution with a low solute content. Note that a dilute solution is not always unsaturated - for example, a saturated 0.0000134 M solution of practically insoluble silver chloride is very dilute. The boundary between dilute and concentrated solutions is very conditional.

see also

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Notes

Literature

• Shakhparonov M.I. Introduction to the molecular theory of solutions. - M .: State publishing house of technical and theoretical literature, 1956. - 508 p.
• Remy G. Course of inorganic chemistry. - M .: Publishing house of foreign literature, 1963, 1966. - T. 1-2.
• Streitwieser Andrew. Introduction to Organic Chemistry. - 4th ed.. - Macmillan Publishing Company, New York, 1992. - ISBN ISBN 0-02-418170-6.

Links

• - article from the encyclopedia "Round the World"
• . xumuk.ru. Retrieved March 11, 2015.

Solid Liquid Gas Plasma Disperse systems Phase transitions see also

An excerpt characterizing the Solution

- Eh bien, qu "est ce qu" il y a? [Well, what else?] - Napoleon said in the tone of a man annoyed by the incessant interference.
- Sire, le prince ... [Sovereign, Duke ...] - began the adjutant.
"Requesting reinforcements?" Napoleon spoke with an angry gesture. The adjutant bowed his head affirmatively and began to report; but the emperor turned away from him, took two steps, stopped, turned back and called Berthier. “We need to give reserves,” he said, spreading his arms slightly. - Whom to send there, what do you think? - he turned to Berthier, to this oison que j "ai fait aigle [the caterpillar that I made an eagle], as he later called him.
- Sovereign, send Claparede's division? - said Berthier, who remembered by heart all the divisions, regiments and battalions.
Napoleon nodded his head in the affirmative.
The adjutant galloped to Claparede's division. And after a few minutes the young guards, standing behind the mound, moved from their place. Napoleon silently looked in that direction.
“No,” he suddenly turned to Berthier, “I cannot send Claparède. Send Friant's division, he said.
Although there was no advantage in sending Friant's division instead of Claparède, and there was even an obvious inconvenience and delay in stopping Claparede now and sending Friant, the order was carried out with precision. Napoleon did not see that in relation to his troops he played the role of a doctor who interferes with his medicines - a role that he so correctly understood and condemned.
Friant's division, like the others, disappeared into the smoke of the battlefield. Adjutants continued to jump up from different sides, and all, as if by agreement, said the same thing. Everyone asked for reinforcements, everyone said that the Russians were holding their positions and were producing un feu d "enfer [hell fire], from which the French army was melting.
Napoleon sat thoughtfully in a folding chair.
Hungry in the morning, Mr de Beausset, who loved to travel, approached the emperor and dared to respectfully offer breakfast to his majesty.
“I hope that now I can already congratulate Your Majesty on your victory,” he said.
Napoleon silently shook his head. Believing that denial refers to victory and not breakfast, mr de Beausset allowed himself to playfully respectfully remark that there is no reason in the world that could prevent breakfast when it can be done.
- Allez vous ... [Get out to ...] - Napoleon suddenly said gloomily and turned away. A blissful smile of regret, repentance and delight shone on the face of Monsieur Bosse, and he walked with a floating step to the other generals.
Napoleon experienced a heavy feeling, similar to that experienced by an always happy player who madly threw his money, always winning, and suddenly, just when he calculated all the chances of the game, feeling that the more deliberate his move, the more sure he loses.
The troops were the same, the generals were the same, the preparations were the same, the disposition was the same, the same proclamation courte et energique [short and energetic proclamation], he himself was the same, he knew it, he knew that he was even much more experienced and more skillful now than he was before, even the enemy was the same as near Austerlitz and Friedland; but the terrible swing of the hand fell magically powerless.
All those former methods, which used to be invariably crowned with success: both the concentration of batteries on one point, and the attack of reserves to break through the line, and the attack of the des hommes de fer [iron men] cavalry - all these methods have already been used, and not only were not victory, but the same news came from all sides about the dead and wounded generals, about the need for reinforcements, about the impossibility of knocking down the Russians and about the disorder of the troops.
Previously, after two or three orders, two or three phrases, marshals and adjutants galloped with congratulations and cheerful faces, declaring the corps of prisoners of war as trophies, des faisceaux de drapeaux et d "aigles ennemis, [bunches of enemy eagles and banners,] and cannons, and carts, and Murat he asked only for permission to send cavalry to pick up the baggage trains.So it was near Lodi, Marengo, Arcole, Jena, Austerlitz, Wagram, etc., etc. Now something strange was happening to his troops.
Despite the news of the capture of the flushes, Napoleon saw that it was not the same, not at all what had been in all his previous battles. He saw that the same feeling that he experienced was experienced by all the people around him, experienced in the matter of battles. All faces were sad, all eyes avoided each other. Only Bosse could not understand the meaning of what was happening. Napoleon, after his long experience of the war, knew well what it meant in the course of eight hours, after all the efforts expended, a battle not won by the attacker. He knew that this was an almost lost battle, and that the slightest chance could now - on that tense point of hesitation on which the battle stood - destroy him and his troops.
When he went over in his imagination all this strange Russian campaign, in which not a single battle was won, in which neither banners, nor cannons, nor corps of troops were taken in two months, when he looked at the covertly sad faces of those around him and listened to reports that that the Russians are still standing, - a terrible feeling, similar to the feeling experienced in dreams, seized him, and all the unfortunate accidents that could destroy him occurred to him. The Russians could attack his left wing, they could tear his middle apart, a stray cannonball could kill him himself. All this was possible. In his previous battles, he considered only the chances of success, but now countless accidents seemed to him, and he expected them all. Yes, it was like in a dream, when a villain is advancing on him, and in a dream the man swung and hit his villain with that terrible effort, which, he knows, should destroy him, and feels that his hand, powerless and soft, falls like a rag, and the horror of irresistible doom seizes the helpless man.
The news that the Russians were attacking the left flank of the French army aroused this horror in Napoleon. He sat silently on a folding chair under the barrow, his head bowed and his elbows on his knees. Berthier approached him and offered to drive along the line to see what the situation was.
- What? What are you talking about? Napoleon said. - Yes, tell me to give me a horse.
He mounted and rode to Semyonovsky's.
In the slowly dispersing powder smoke throughout the space through which Napoleon rode, horses and people lay in pools of blood, singly and in heaps. Napoleon and none of his generals had ever seen such a horror, such a number of people killed in such a small space. The rumble of guns, which did not stop for ten hours in a row and exhausted the ear, gave special significance to the spectacle (like music in live pictures). Napoleon rode out to the height of Semenovsky and through the smoke he saw rows of people in uniforms of colors unusual for his eyes. These were Russians.
The Russians stood in tight ranks behind Semyonovsky and the kurgan, and their guns ceaselessly hummed and smoked along their line. There was no more fighting. There was a continuing murder, which could lead neither the Russians nor the French to anything. Napoleon stopped his horse and fell back into that thoughtfulness from which Berthier had led him; he could not stop the deed that was being done before him and around him and which was considered to be led by him and dependent on him, and for the first time this deed, due to failure, seemed to him unnecessary and terrible.
One of the generals who approached Napoleon allowed himself to suggest that he bring the old guard into action. Ney and Berthier, who were standing beside Napoleon, exchanged glances and smiled contemptuously at the general's senseless proposal.
Napoleon lowered his head and was silent for a long time.
- A huit cent lieux de France je ne ferai pas demolir ma garde, [Three thousand two hundred miles from France, I can not let my guards be defeated.] - he said and, turning his horse, rode back to Shevardin.

Kutuzov was sitting with his gray head bowed and his heavy body lowered on a bench covered with a carpet, in the very place where Pierre had seen him in the morning. He did not make any orders, but only agreed or disagreed with what was offered to him.

Solutions called homogeneous (homogeneous) systems that consist of two or more components, the relative amount of which can vary over a wide range without violating homogeneity.

The components of a solution are the solvent and the substances dissolved in it. Solvent is a medium in which solutes are evenly distributed in the form of molecules or ions. Of the two or more components of the solution, the solvent is the one that is taken in a larger amount and has the same state of aggregation as the solution as a whole.

The most common solvent in nature is water. Solutions are classified according to a number of criteria:

According to the state of aggregation, solutions can be:

- liquid (liquid solutions can be obtained by dissolving a gas in a liquid, for example, carbonated water is a solution of carbon monoxide (IV) in water; liquids in a liquid, for example, a solution of alcohol in water; a solid in a liquid, for example, a solution of salt in water, etc. .d.).

- gaseous (an example of gaseous solutions is air, consisting of oxygen, nitrogen, carbon monoxide, noble gases and water vapor; the molecules of these substances behave like gas molecules, that is, air is a homogeneous system);

- solid (most metal alloys belong to such solutions; steel, for example, is a crystalline solution of carbon in iron).

Typically, the term solutions refers to liquid systems.

Depending on the nature of the solvent solutions can be:

- water;

- non-aqueous (alcohol, benzene, etc.).

By type of substance in solution solutions are divided into:

― electrolytes (substances which in a solution or melt decompose into ions and conduct electric current);

- non-electrolytes.

― diluted (solute content does not exceed 30%;

― concentrated (the mass fraction of the dissolved substance makes over 30%).

However, the boundaries between diluted and concentrated solutions are conditional. For example, for sulfuric acid, a solution containing 96 g of H 2 SO 4 is considered concentrated, for nitric acid - 63 g of HNO 3, for hydrochloric acid - 37 g of HCI in 100 g of water.

Depending on the concentration of hydrogen ions solutions can be:

- acidic (pH<7);

— neutral (рН=7);

- alkaline (pH>7).

According to the ability of substances to dissolve under given conditions in a certain mass of solvent solutions are:

Unsaturated (a solution in which, under given conditions, some more solute can be dissolved);

Saturated (a solution in which the solute under the given conditions has reached its maximum concentration and no longer dissolves); the precipitate of a given substance is in equilibrium with the substance in solution;

Supersaturated (a solution containing, under given conditions, more solute than in a saturated solution, the excess of the substance easily precipitates). Typically, a supersaturated solution is obtained by cooling a solution saturated at a higher temperature (supersaturation). Supersaturated solutions are very unstable. Stirring, shaking, adding grains of salt can cause the excess salt to crystallize and transition to a saturated stable state.

Basic concepts

Solution called a homogeneous system consisting of two or more components.

One of the components of the solution is solvent, the rest - solutes. A solvent is usually considered to be that component whose state of aggregation does not change when a solution is formed. If both components are in the same state of aggregation, then the solvent is the component that is in a larger amount.

Solutions are saturated, unsaturated and supersaturated.

saturated solution is a solution that is in equilibrium with the solid phase of the solute, i.e. contains the maximum amount of solute possible at a given temperature.

unsaturated solution is a solution whose concentration is less than the concentration of a saturated solution.

Supersaturated solution A solution that contains more solute than a saturated solution at a given temperature.

Solubility called the ability of one substance to dissolve in another. Quantitatively, the solubility of solids and liquids is determined by the solubility coefficient. Solubility factor expressed by the mass of a substance that dissolves under given conditions in 100 g of solvent to form a saturated solution. The substance is usually considered soluble (R), if the value of the solubility coefficient exceeds 1. With a solubility coefficient from 1 to 0.01, the substance slightly soluble (m). When the solubility coefficient is less than 0.01, the substance practically insoluble (n).

The dissolution of substances is often accompanied by the release or absorption of heat. What is the consequence of the chemical interaction of the solute with the solvent. This process is called hydration if the solvent is water, or solvation if a non-aqueous solvent is taken. In this case, compounds are formed, which are respectively called hydrates and solvates.

Hydrates are generally not persistent substances. But some of them are so strong that water is part of the solute crystals. Such substances are called crystalline hydrates , and the water they contain is called crystallization .

The composition of the crystalline hydrate is represented by a formula that shows how much water of crystallization is contained in the crystalline hydrate:

· blue vitriol(crystal hydrate of copper sulfate) - CuSO 4 5H 2 O;

· Glauber's salt(crystal hydrate of sodium sulfate) - Na 2 SO 4 10H 2 O.

Topic 7. Solutions and disperse systems Table of contents

Topic 7. Solutions and disperse systems 1

7.1 Basic concepts and definitions. Topic structure 3

7.1.1 Classification of solutions 3

7.1.2 Structure of topic 4

7.2. Disperse systems (mixtures) their types 5

7.2.1 Coarse systems 6

7.2.2. Finely dispersed systems (colloidal solutions) 6

7.2.3. Highly dispersed systems (true solutions) 9

7.3. Concentration, ways of expressing it 10

7.3.1 Solubility of substances. ten

7.3.2. Methods for expressing the concentration of solutions. eleven

7.3.2.1 Interest 12

7.3.2.2 Molar 12

7.3.2.3 Normal 12

7.3.2.4 Molar 12

7.3.2.5 Mole fraction 12

7.4. Physical laws of solutions 13

7.4.1 Raoult's law 13

7.4.1.1 Changing freezing temperatures 14

7.4.1.2 Changing boiling points 15

7.4.2 Henry's Law 15

7.4.3 Van't Hoff's law. Osmotic pressure 15

7.4.4 Ideal and real solutions. sixteen

7.4.4.1. Activity - concentration for real systems 17

7.5.Theory of solutions 17

7.5.1 Physical theory 18

7.5.2 Chemical theory 18

7.6 Theory of electrolytic dissociation 19

7.6.1 Electrolyte solutions 20

7.6.1.1 Dissociation constant 20

7.6.1.2 Degree of dissociation. Strong and weak electrolytes 24

7.6.1.3 Ostwald's Dilution Law 27

7.6.2 Electrolytic dissociation of water 27

7.6.2.1 Ionic product of water 28

7.6.2.2. Hydrogen index. Acidity and basicity of solutions 29

7.6.2.3 Acid-base indicators 29

7.7. Ion exchange reactions. 31

7.7.1 Formation of a weak electrolyte 32

7.7.2 Gas evolution 34

7.7.3 Precipitation formation 34

7.7.3.1 Precipitation condition. Solubility product 34

7.7.4. Hydrolysis of salts 36

7.7.4.1. Equilibrium shift during hydrolysis 38

1. Basic concepts and definitions. Theme Structure

Dispersed systems or mixtures are multicomponent systems in which one or more substances are uniformly distributed in the form of particles in the medium of another substance.

In dispersed systems, a dispersed phase is distinguished - a finely divided substance and a dispersion medium - a homogeneous substance in which the dispersed phase is distributed. For example, in muddy water containing clay, the dispersed phase is solid particles of clay, and the dispersion medium is water; in fog, the dispersed phase is liquid particles, the dispersion medium is air; in smoke, the dispersed phase is solid particles of coal, the dispersion medium is air; in milk - dispersed phase - fat particles, dispersion medium - liquid, etc. Disperse systems can be both homogeneous and heterogeneous.

A homogeneous dispersed system is a solution.

1. Classification of solutions

According to the size of the dissolved substances, all multicomponent solutions are divided into:

coarse systems (mixtures);

finely dispersed systems (colloidal solutions);

highly dispersed systems (true solutions).

According to the phase state, solutions are:

According to the composition of dissolved substances, liquid solutions are considered as:

electrolytes;

non-electrolytes.

1. Theme Structure

1. Dispersed systems (mixtures) their types

Disperse system - a mixture of two or more substances that do not mix at all or practically and do not chemically react with each other. The first of the substances dispersed phase) is finely distributed in the second ( dispersion medium). The phases are separated by an interface and can be physically separated from each other (centrifuged, separated, etc.).

The main types of disperse systems: aerosols, suspensions, emulsions, sols, gels, powders, fibrous materials such as felt, foams, latexes, composites, microporous materials; in nature - rocks, soils, precipitation.

By kinetic properties dispersed phase, dispersed systems can be divided into two classes:

Freely dispersed systems in which the dispersed phase is mobile;

Cohesive-dispersed systems, the dispersion medium of which is solid, and the particles of their dispersed phase are interconnected and cannot move freely.

By particle size dispersed phase are distinguished coarse systems(suspensions) with a particle size of more than 500 nm and finely dispersed(colloidal solutions or colloids) with particle sizes from 1 to 500 nm.

Table 7.1. Variety of disperse systems.

Dispersion medium	Dispersed phase	Name of the disperse system	Examples of dispersed systems
	Liquid	Spray can	Fog, clouds, carburetor mixture of gasoline and air in a car engine.
	Solid	Spray can	Smoke, smog, dust in the air
Liquid			Carbonated drinks, whipped cream
	Liquid	emulsions	Milk, mayonnaise, body fluids (blood plasma, lymph), liquid contents of cells (cytoplasm, karyoplasm)
	Solid	Sol, suspension	River and sea silt, mortars, pastes.
Solid		hard foam	Ceramics, foam plastics, polyurethane, foam rubber, aerated chocolate.
	Liquid		Jelly, gelatin, cosmetic and medical products (ointments, mascara, lipstick)
	Solid	solid sol	Rocks, colored glass, some alloys.

Non-aqueous solutions, definition, characterization

NON-AQUEOUS SOLUTIONS. SOLVENTS, CHARACTERISTICS. TECHNOLOGICAL SCHEME OF PRODUCTION IN PHARMACEUTICAL AND FACTORY CONDITIONS. NOMENCLATURE

Plan:

1. Non-aqueous solutions, definition, characterization.

2. Features of the technology of solutions on non-aqueous volatile solvents.

3. Features of the technology of solutions on non-aqueous non-volatile solvents.

4. Assessment of the quality of non-aqueous solutions.

Prospects for improving the quality and technology of non-aqueous solutions.

Non-aqueous solutions, definition, characterization.

Non-aqueous solutions - These are liquid dosage forms, which are homogeneous dispersed systems, the structural units of which are ions and molecules. These solutions are intended mainly for external use (lubrication, rubbing, lotions, nose drops, ear drops, etc.). Much less often they are used orally, for injections and for inhalations.

Causes non-aqueous solvent applications:

1. The need to obtain solutions from medicinal substances that are difficult to dissolve in water;

2. To eliminate the hydrolysis of medicinal substances;

3. The possibility of prolonging the action;

4. To increase the stability of medicinal substances in solution.

For non-aqueous solutions are presented requirements, similar to the requirements for aqueous solutions, that is:

Compliance with the medical purpose to achieve the desired therapeutic effect;

Completeness of dissolution of medicinal substances;

No mechanical inclusions;

Compliance of concentrations of medicinal substances, volume or mass of solutions prescribed;

Storage stability.

Virtues non-aqueous solutions are:

Prostate manufacturing;

Variety of appointment methods;

Stability of non-aqueous solutions (they are more stable than aqueous solutions).

Disadvantages:

The impossibility of filtering solutions on viscous solvents;

Some volatile solvents are flammable. Therefore, work with them must be carried out away from sources of fire.

Solvents, which are part of non-aqueous solutions, are divided into two groups:

Þ volatile (ethanol, diethyl ether, chloroform);

Þ non-volatile (glycerin, mineral oils (vaseline), silicones (esilon 4, 5), polyethylene oxides (PEO - 400), dimexide).

The preparation of solutions based on non-aqueous solvents is characterized by the same steps as for aqueous solutions, i.e. weighing or measuring medicinal substances and solvents, dissolving and mixing, filtering, packaging, processing. At the same time, each of these stages in the technology of non-aqueous solutions has its own characteristics, mainly due to the physicochemical properties of solvents.

What are Solutions? Solvent? and Solubility? Define terms!

Ekaterina Murenko

A solution is a homogeneous (homogeneous) mixture formed by at least two components, one of which is called a solvent and the other a soluble substance; it is also a system of variable composition in a state of chemical equilibrium.

A chemical solution is a mixture of one or more acids with water.

A solution is a single-phase system of variable composition, consisting of two or more components. Solutions are homogeneous (homogeneous) systems, that is, each of the components is distributed in the mass of the other in the form of molecules, atoms or ions

Solvent - a component whose state of aggregation does not change during the formation of a solution. In the case of solutions formed by mixing a gas with a gas, a liquid with a liquid, a solid with a solid, the solvent is the component whose amount in the solution prevails

Solubility - the ability of a substance to form homogeneous systems with other substances - solutions in which the substance is in the form of individual atoms, ions, molecules or particles.

Olka

SOLUTIONS - homogeneous mixtures of variable composition. R. is divided into gas, liquid and solid. Gas R. include air, natural combustible gases, etc.; they are more commonly referred to as mixtures.

SOLUTIONS - homogeneous systems consisting of two or more components, the composition of which, within certain limits, can continuously change

SOLUBILITY, the ability of a substance to form homogenous with other substance (or substances). mixtures with dispersed distribution

Solvents - an individual chemical compound or a mixture thereof capable of dissolving various substances, that is, forming with them homogeneous systems of variable composition of two or more components

Solutions are a homogeneous mass or mixture consisting of two or more substances, in which one substance acts as a solvent, and the other as soluble particles.

There are two theories of interpretation of the origin of solutions: chemical, the founder of which is D. I. Mendeleev, and physical, proposed by the German and Swiss physicists Ostwald and Arrhenius. According to Mendeleev's interpretation, the components of the solvent and the solute become participants in a chemical reaction with the formation of unstable compounds of these same components or particles.

The physical theory denies the chemical interaction between the molecules of the solvent and the dissolved substances, explaining the process of formation of solutions as a uniform distribution of particles (molecules, ions) of the solvent between the particles of the dissolved substance due to a physical phenomenon called diffusion.

Classification of solutions according to various criteria

Today there is no unified classification system for solutions, however, conditionally, the types of solutions can be grouped according to the most significant criteria, namely:

I) According to the state of aggregation, they distinguish: solid, gaseous and liquid solutions.

II) By the size of the particles of the dissolved substance: colloidal and true.

III) According to the degree of concentration of the particles of the dissolved substance in the solution: saturated, unsaturated, concentrated, diluted.

IV) According to the ability to conduct electric current: electrolytes and non-electrolytes.

V) By purpose and scope: chemical, medical, building, special solutions, etc.

Types of solutions by state of aggregation

The classification of solutions according to the state of aggregation of the solvent is given in the broad sense of the meaning of this term. It is customary to consider liquid substances as solutions (moreover, both a liquid and a solid element can act as a solute), but if we take into account the fact that a solution is a homogeneous system of two or more substances, then it is quite logical to recognize also solid solutions, and gaseous. Solid solutions are considered to be mixtures of, for example, several metals, better known in everyday life as alloys. Gaseous types of solutions are mixtures of several gases, an example is the air around us, which is presented as a combination of oxygen, nitrogen and carbon dioxide.

Solutions by size of dissolved particles

The types of solutions in terms of the size of the dissolved particles include true (ordinary) solutions and B. The solute breaks down into small molecules or atoms, which are close in size to the molecules of the solvent. At the same time, the true types of solutions retain the original properties of the solvent, only slightly transforming it under the influence of the physicochemical properties of the element added to it. For example: when salt or sugar is dissolved in water, the water remains in the same state of aggregation and the same consistency, almost the same color, only its taste changes.

Colloidal solutions differ from conventional ones in that the added component does not completely decompose, retaining complex molecules and compounds, the dimensions of which are much larger than the solvent particles, exceeding the value of 1 nanometer.

Types of concentration solutions

In the same amount of solvent, you can add a different amount of the dissolved element, at the output we will have solutions with different concentrations. We list the main ones:

1. Saturated solutions are characterized by the degree at which the dissolved component, under the influence of a constant value of temperature and pressure, no longer decomposes into atoms and molecules, and the solution reaches phase equilibrium. Saturated solutions can also be conditionally divided into concentrated ones, in which the dissolved component is comparable to the solvent, and dilute ones, where the solute is several times less than the solvent.
2. Unsaturated are those solutions in which the solute can still decompose into small particles.
3. Supersaturated solutions are obtained when the parameters of the influencing factors (temperature, pressure) change, as a result of which the process of "crushing" of the dissolved substance continues, it becomes more than it was under normal (usual) conditions.

Electrolytes and non-electrolytes

Some substances in solution decompose into ions that can conduct electricity. Such homogeneous systems are called electrolytes. This group includes acids, most salts. And solutions that do not conduct electric current are commonly called non-electrolytes (almost all organic compounds).

Groups of solutions by purpose

Solutions are indispensable in all sectors of the national economy, the specificity of which has created such types of special solutions as medical, construction, chemical and others.

Medical solutions are a set of drugs in the form of ointments, suspensions, mixtures, solutions for infusions and injections and other dosage forms used for medical purposes for the treatment and prevention of various diseases.

Types of chemical solutions include a huge variety of homogeneous compounds used in chemical reactions: acids, salts. These solutions can be of organic or inorganic origin, aqueous (sea water) or anhydrous (based on benzene, acetone, etc.), liquid (vodka) or solid (brass). They have found their application in various sectors of the national economy: chemical, food, textile industry.

Types of mortars are distinguished by a viscous and thick consistency, which is why the name of the mixture is more suitable for them.

Due to their ability to quickly harden, they are successfully used as masonry for walls, ceilings, load-bearing structures, as well as for finishing work. They are aqueous solutions, most often three-component (solvent, cement of various markings, aggregate), where sand, clay, crushed stone, lime, gypsum and other building materials are used as a filler.

Simple chemical solutions can be easily prepared in a variety of ways at home or at work. Whether you are making a solution from a powder material or diluting a liquid, the correct amount of each component can be easily determined. When preparing chemical solutions, remember to use personal protective equipment to avoid injury.

Steps

Calculation of percentages using the weight/volume formula

1. Determine percentage content by weight/volume of solution. Percentages show how many parts of a substance are in one hundred parts of a solution. When applied to chemical solutions, this means that if the concentration is 1 percent, then 100 milliliters of the solution contains 1 gram of the substance, that is, 1 ml / 100 ml.

   • For example, by weight: A 10% solution by weight contains 10 grams of the substance dissolved in 100 milliliters of the solution.
   • For example, by volume: A 23% solution by volume contains 23 milliliters of the liquid compound for every 100 milliliters of solution.

2. Determine the volume of solution you want to prepare. To find out the required mass of a substance, you must first determine the final volume of the solution you need. This volume depends on how much solution you need, how often you will use it, and on the stability of the finished solution.

   • If it is necessary to use a fresh solution each time, prepare only the amount needed for one use.
   • If the solution retains its properties for a long time, you can prepare a larger amount to use it in the future.

3. Calculate the number of grams of substance required to prepare the solution. To calculate the required number of grams, use the following formula: number of grams = (required percentages)(required volume / 100 ml). In this case, the required percentages are expressed in grams, and the required volume is in milliliters.

   • Example: you need to prepare a 5% NaCl solution with a volume of 500 milliliters.
   • number of grams = (5g)(500ml/100ml) = 25 grams.
   • If NaCl is given as a solution, simply take 25 milliliters of NaCl instead of grams of powder and subtract that volume from the final volume: 25 milliliters of NaCl per 475 milliliters of water.

4. Weigh the substance. After you calculate the required mass of the substance, you should measure this amount. Take a calibrated scale, place the bowl on it and set it to zero. Weigh the required amount of the substance in grams and pour it out.

   • Before continuing to prepare the solution, be sure to clear the weighing pan of powder residue.
   • In the example above, 25 grams of NaCl needs to be weighed.

5. Dissolve the substance in the required amount of liquid. Unless otherwise specified, water is used as the solvent. Take a measuring beaker and measure out the required amount of liquid. After that, dissolve the powder material in the liquid.

   • Sign the container in which you will store the solution. Clearly indicate on it the substance and its concentration.
   • Example: Dissolve 25 grams of NaCl in 500 milliliters of water to make a 5% solution.
   • Remember that if you are diluting a liquid substance, to obtain the required amount of water, you must subtract the volume of the substance added from the final volume of the solution: 500 ml - 25 ml \u003d 475 ml of water.

   Preparation of a molecular solution

   1. Determine the molecular weight of the substance used by the formula. The formula molecular weight (or simply molecular weight) of a compound is written in grams per mole (g/mol) on the side of the bottle. If you can't find the molecular weight on the bottle, look it up online.

      • The molecular weight of a substance is the mass (in grams) of one mole of that substance.
      • Example: The molecular weight of sodium chloride (NaCl) is 58.44 g/mol.

   2. Determine the volume of the required solution in liters. It is very easy to prepare one liter of the solution, as its molarity is expressed in moles/liter, however it may be necessary to make more or less than a liter, depending on the purpose of the solution. Use the final volume to calculate the required number of grams.

      • Example: it is necessary to prepare 50 milliliters of a solution with a molar fraction of NaCl 0.75.
      • To convert milliliters to liters, divide them by 1000 and get 0.05 liters.

   3. Calculate the number of grams needed to prepare the required molecular solution. To do this, use the following formula: number of grams = (required volume) (required molarity) (molecular weight according to the formula). Remember that the required volume is expressed in liters, the molarity is in moles per liter, and the molecular weight of the formula is in grams per mole.

      • Example: if you want to prepare 50 milliliters of a solution with a NaCl mole fraction of 0.75 (molecular weight formula: 58.44 g/mol), you should calculate the number of grams of NaCl.
      • number of grams = 0.05 L * 0.75 mol/L * 58.44 g/mol = 2.19 grams of NaCl.
      • By reducing the units of measurement, you get grams of a substance.

   4. Weigh the substance. Using a properly calibrated balance, weigh out the required amount of the substance. Place the bowl on the balance and zero before weighing. Add the substance to the bowl until you get the desired mass.

      • Clean the weighing pan after use.
      • Example: Weigh 2.19 grams of NaCl.

   5. Dissolve the powder in the required amount of liquid. Unless otherwise noted, water is used to prepare most solutions. In this case, the same volume of liquid is taken, which was used in calculating the mass of the substance. Add the substance to the water and stir it until completely dissolved.

      • Sign the container with the solution. Clearly label the solute and molarity so that the solution can be used later.
      • Example: Using a beaker (a volume measuring instrument), measure 50 milliliters of water and dissolve 2.19 grams of NaCl in it.
      • Stir the solution until the powder is completely dissolved.

   Dilution of solutions with a known concentration

   1. Determine the concentration of each solution. When diluting solutions, you need to know the concentration of the original solution and the solution that you want to receive. This method is suitable for diluting concentrated solutions.

      • Example: 75 ml of a 1.5 M NaCl solution is to be prepared from a 5 M solution. The stock solution is 5 M and needs to be diluted to 1.5 M.

   2. Determine the volume of the final solution. You need to find the volume of the solution that you want to get. You will have to calculate the amount of solution that will be required to dilute this solution to obtain the required concentration and volume.

      • Example: 75 milliliters of a 1.5 M NaCl solution are to be prepared from a 5 M initial solution. In this example, the final volume of the solution is 75 milliliters.