Section 5. SOLUTIONS. THEORY OF ELECTROLYTIC DISSOCIATION

§ 5.2. Solubility of substances in water

Solubility is the property of a substance to dissolve in water or another solvent. Solid, liquid and gaseous substances can dissolve in water.

For solubility in water, all substances are divided into three groups: 1) highly soluble; 2) slightly soluble; and 3) practically insoluble. The latter are also called insoluble substances. However, it should be noted that there are no absolutely insoluble substances. If you immerse a glass rod or a piece of gold or silver in water, they still dissolve in water in negligible amounts. As you know, solutions of argentum or aurum in water kill microbes. Glass, silver, gold are examples of substances that are practically insoluble in water (solids). They also include kerosene, vegetable oil(liquid substances), noble gases (gas substances). Many substances dissolve quite well in water. Examples of such substances are sugar, copper sulphate, sodium hydroxide (solid substances), alcohol, acetone (liquid substances), chlorine water, ammonia (gas substances).

From the above examples it follows that solubility primarily depends on the nature of the substances, in addition, it depends on temperature and pressure. The dissolution process itself is due to the interaction of the particles of the solute and the solvent; it is a spontaneous process.

The process of dissolution of solids in liquids can be represented as follows: under the influence of a solvent, individual ions or molecules gradually detach from the surface of a solid and are evenly distributed throughout the volume of the solvent. If the solvent is in contact with a large amount of a substance, then after a while the solution becomes saturated.

A saturated solution is one that is in dynamic equilibrium with an excess of solute.

To prepare a saturated solution, you need to add a substance to water at a given temperature with stirring until a precipitate forms, that is, an excess of the substance remains insoluble. In this case, a dynamic equilibrium will be established between the solution and the excess of the substance, it dissolves: how many particles of the substance will pass into the solution, the same number will be released (crystallized) from the solution. A saturated solution at a given temperature contains the maximum amount of solute possible.

An unsaturated solution contains fewer substances, and a saturated solution contains more than a saturated solution. Supersaturated solutions are rather unstable. Gently shaking the vessel or adding a salt crystal to the solution causes the excess of the solute to precipitate. Saturated solutions form sucrose, Na 2 SO 4 ∙ 10H 2 O, Na 2 S 2 O 3 ∙ 5H 2 O, CH 3 COOHa, Na 2 B 4 O 7 ∙10H 2 O, etc.

Often poorly soluble and practically insoluble substances are combined by one name - slightly soluble. In this case, only soluble and poorly soluble substances are spoken of. Quantitatively, solubility is expressed by the concentration of a saturated solution. Most often, it is expressed as the maximum number of grams of a substance that can be dissolved in 100 g of a solvent at a given temperature. This amount of a substance is sometimes called the solubility coefficient or simply the solubility of the substance. For example, at 18 ° C, 51.7 g of lead(II) nitrate salt G will dissolve in 100 g of water. b (NO 3) 2 , that is, the solubility of this salt at 18°C ​​is 51.7. If, at the same temperature, in excess of this amount, more lead (II) nitrate salts are added, then it will not dissolve, but will precipitate in the form of a precipitate.

When talking about the solubility of a substance, the temperature of dissolution should be indicated. Most often, the solubility of solids with increasing temperature p amu p and c p remains. This is clearly illustrated by the solubility curves (Fig. 5.2). The temperature is plotted on the abscissa axis, and the solubility coefficient is plotted on the ordinate axis. However, the solubility of some substances increases slightly with increasing temperature (for example, NaCl, A l C l 3 ) or even decreases [for example, Ca( O H) 2, Li 2 SO 4 , Ca(CH 3 COO) 2]. On the solubility factor solid body in water, the pressure has little effect, since there is no noticeable change in the volume of the system during dissolution. With the help of solubility curves, it is easy to calculate how much salt will fall out of the solution when it is cooled. For example, if you take 100 g of water and prepare a saturated solution of potassium nitrate at 45 ° C, and then cool it to 0 ° C, then, as follows from the solubility curve (see Fig. 5.2), 60 g of salt crystals should fall out. Solubility curves are used to easily determine the solubility coefficient of substances at different temperatures.

The release of a substance from a solution with a decrease in temperature is called crystallization. If the solution contained impurities, then, due to crystallization, the substance is always obtained pure, since with respect to impurities the solution remains unsaturated even with a decrease in temperature, and impurities do not precipitate. This is the basis of the method of purification of substances, called recrystallization.

During the dissolution of gases in water, heat is released. Therefore, according to Le Chatelier's principle, with increasing

Rice. 5.2. Solubility curves for solids

temperature, the solubility of gases decreases, and as it decreases, it increases (Fig. 5.3). The solubility of gases increases with increasing pressure. Since the volume of gas that dissolves in a given volume of water does not depend on pressure, the solubility of a gas is usually expressed as the number of milliliters that dissolves in 100 g of solvent (see Fig. 5.3).

Rice. 5.3. Gas solubility curves

DISSOLUTION.

SOLUBILITY OF SUBSTANCES IN WATER.

I DISSOLUTION AND SOLUTIONS.

DISSOLUTION. SOLUTIONS.

Physical theory (van't Hoff,

Ostwald, Arrhenius).

Dissolution is a diffusion process

a solutions are homogeneous mixtures.

chemical theory (Mendeleev,

Kablukov, Kistyakovsky).

Dissolution is a chemical process

solute interactions

with water, - the process of hydration,

a solutions These compounds are hydrates.

Modern theory.

Dissolution- This is a physico-chemical process that occurs between the solvent and the particles of the solute and is accompanied by the process of diffusion.

Solutions- these are homogeneous (homogeneous) systems consisting of particles of a solute, a solvent and the products of their interaction - hydrates.

II SIGNS OF CHEMICAL INTERACTION DURING DISSOLUTION.

1. Thermal phenomena.

ü Exothermic - these are phenomena accompanied by the release of heat /dissolution of concentrated sulfuric acid H2SO4 in water/.

ü Endothermic- these are phenomena accompanied by the absorption of heat /dissolution of crystals of ammonium nitrate NH4NO3 in water/.

2. Color change.

CuSO4 + 5H2O → CuSO4∙ 5H2O

white blue crystals

crystals

3. Volume change.

III DEPENDENCE OF SOLID SUBSTANCES ON DISSOLUTION.

1. From the nature of substances:

ü highly soluble in water / more than 10 g of substance per 100 g of water /;

ü slightly soluble in water /less than 1g/;

ü practically insoluble in water /less than 0.01g/.

2. From temperature.

IV TYPES OF SOLUTIONS BY SOLUBILITY.

Ø According to the degree of solubility:

ü unsaturated solution - a solution in which, at a given temperature and pressure, further dissolution of the substance already contained in it is possible.

ü saturated solution - a solution that is in phase equilibrium with the solute.

ü Supersaturated solution - an unstable solution in which the content of a solute is greater than in a saturated solution of the same substance at those values ​​of temperature and pressure.

Ø According to the ratio of the solute to the solvent:

ü concentrated;

ü diluted.

THEORY OF ELECTROLYTIC DISSOCIATION (TED).

I. The theory of electrolytic dissociation (TED) was proposed by a Swedish scientist Svante Arrhenius in 1887

Later, TED developed and improved. The modern theory of aqueous solutions of electrolytes, in addition to the theory of electrolytic dissociation by S. Arrhenius, includes ideas about the hydration of ions (,), the theory of strong electrolytes (, 1923).

II. SUBSTANCES

electrolytes - substances, solutions

or whose melts conduct

electricity.

/acids, salts, bases/

Non-electrolytes Substances whose solutions or melts do not conduct electricity.

/simple substances/

IONS are charged particles.

ü cations /kat+/ are positively charged particles.

ü anions /an-/– negatively charged particles

III. MAIN PROVISIONS OF TED:

ü The spontaneous process of decomposition of an electrolyte into ions in a solution or in a melt is called electrolytic dissociation .

ü In aqueous solutions, ions are not in free, but in hydrated state, i.e., surrounded by dipoles of water and chemically associated with them. Ions in the hydrated state differ in properties from ions in the gaseous state of matter.

ü For the same solute, the degree of dissociation increases as the solution is diluted.

ü In solutions or melts of electrolytes, ions move randomly, but when passed through a solution or melt of electrolyte electric current, ions move in a direction: cations - to the cathode, anions - to the anode.

MECHANISM OF ELECTROLYTIC DISSOCIATION

1. ED of ionic substances:

ü Orientation of water dipoles relative to crystal ions.

ü The disintegration of the crystal into ions (proper dissociation).

ü Hydration of ions.

2. ED of substances with a covalent polar type of chemical bond.

ü Destruction of hydrogen bonds between water molecules, formation of water dipoles.

ü Orientation of water dipoles relative to the dipoles of a polar molecule.

ü Strong bond polarization, as a result of which the common electron pair is completely shifted to the atomic particle of a more electronegative element.

ü The disintegration of matter into ions (proper dissociation).

ü Hydration of ions.

DEGREE OF ELECTROLYTIC DISSOCIATION /α/

1. Degree of ED is the ratio of the number of decayed molecules to the total number of particles in the solution.

α = ─ ∙ 100%

Ntotal

2. According to the magnitude of the degree of ED, substances are divided:

ü strong electrolytes /HCl; H2SO4; NaOH; Na2CO3/

ü medium strength electrolytes /H3PO4/

ü weak electrolytes /H2CO3; H2SO3/.

CHEMICAL DICTATION

ON THE TOPIC: "ELETROLYTIC DISSOCIATION"

1. All water-soluble bases are strong electrolytes.

2. Only water-soluble salts undergo hydrolysis.

3. Dissociation is a reversible process.

4. The essence of the neutralization reaction, CH3COOH + KOH → CH3COOH + H2O, reflected in the form of a short ionic equation of a chemical reaction is: H++ OH- → H2O.

5. BaSO4 ; AgCl are water-insoluble salts, so they do not dissociate into ions.

6. Is the dissociation equation for the following salts correct:

ü Na2SO4 → 2Na+ + SO42-

ü KCl → K+ + Cl-

7. The dissociation equation for sulfurous acid has the following form: H2 SO3 → 2 H+ + SO3 2- .

8. The true degree of dissociation of a strong electrolyte is less than 100%.

9. As a result of the neutralization reaction, salt and water are always formed.

10. Only water-soluble bases - alkalis, are electrolytes.

11. The equations of chemical reactions presented below are ion exchange reactions:

ü 2KOH + SiO2 → K2SiO3 + H2O

ü Al2O3 + 2NaOH → 2NaAlO2 + H2O

ü CuO + 2HCl → CuCl2 + H2O

12. Sulfurous acid is a weak acid, so it decomposes into water (H2O) and sulfur dioxide (SO2).

H2SO3 → H2O + SO2.

THE CODE

1. No /excluding NH3∙H2O/

2. No: Al2S3 + 2H2O → 2AlOHS + H2S

3. No. /Dissociation of only weak electrolytes is a reversible process, strong electrolytes dissociate irreversibly/.

4. No: CH3COOH + OH - → CH3COO= + H2O.

5. No. /These salts are insoluble in relation to water, but they are able to dissociate/.

6. No. /These salts are strong electrolytes, so they dissociate irreversibly/.

7. No. /Polybasic acids dissociate stepwise/.

8. No. /The true degree of dissociation is equal to 100%/.

9. No: NH3(g.) + HCl(g.) → NH4Cl, water formation remains questionable.

10. No. /All bases are electrolytes/.

11. No. /These are exchange reactions, but ionic/.

12. No. /Decomposition of sulphurous acid occurs because it is a fragile acid/.

REGULATIONS

COMPILATION OF IONIC EQUATIONS OF CHEMICAL REACTIONS.

1. Simple substances, oxides, as well as insoluble acids, salts and bases do not decompose into ions.

2. Solutions are used for the ion exchange reaction, so even poorly soluble substances are in solutions in the form of ions. /If a poorly soluble substance is the original compound, then it is decomposed into ions when compiling ionic equations of chemical reactions/.

3. If the poorly soluble is formed as a result of the reaction, then when writing the ionic equation it is considered insoluble.

4. The sum of the electric charges on the left side of the equation must be equal to the sum of the electric charges on the right side.

TERMS

ION EXCHANGE REACTIONS

1. The formation of a low-dissociating substance of water - H2O:

ü HCl + NaOH → NaCl + H2O

H+ + Cl - + Na+ + OH- → Na+ + Cl - + H2O

H+ + OH - → H2O

ü Cu(OH)2 + H2SO4 → CuSO4 + 2H2O

Cu(OH)2 + 2H+ + SO42- → Cu2+ + SO42- + 2H2O

Cu(OH)2 + 2H+ → Cu2+ + 2H2O

2. Precipitation:

ü FeCl3 + 3NaOH → Fe(OH)3↓ + 3NaCl

Fe3++ 3Cl - + 3Na+ + 3OH- → Fe(OH)3↓ + 3Na++ 3Cl-

Fe3++ 3OH - → Fe(OH)3↓

ü BaCl2 + H2SO4 → BaSO4↓ + 2HCl

Ba2++ 2Cl - + 2H++ SO42- → BaSO4↓ + 2H++ 2Cl-

Ba2++ SO42- → BaSO4↓

ü AgNO3 + KBr → AgBr↓ + KNO3

Ag+ + NO3- + K++ Br - → AgBr↓ + K++ NO3-

Ag+ + Br - → AgBr↓

3. Gas release:

ü Na2CO3 + 2HCl → 2NaCl + H2O + CO2

2Na++ CO32-+ 2H++ 2Cl- → 2Na++ 2Cl - + H2O + CO2

CO32-+ 2H+ → H2O + CO2

ü FeS + H2SO4 → FeSO4 + H2S

FeS + 2H++ SO42-→ Fe2++ SO42-+ H2S

FeS + 2H+ → Fe2++ H2S

ü K2SO3 + 2HNO3 → 2KNO3 + H2O + SO2

2K++ SO32-+ 2H++ 2NO3- → 2K++ 2NO3- + H2O + SO2

Solubility (R, χ or k s) – this is a characteristic of a saturated solution, which shows what mass of a solute can be dissolved in 100 g of solvent as much as possible. The solubility dimension is g/ 100 g water. Since we are determining the mass of salt that falls on 100 g of water, we add a factor of 100 to the solubility formula:

here m r.v. is the mass of the dissolved substance, g

m r-la is the mass of the solvent, g

Sometimes the designation is used solubility factor k S .

Solubility tasks, as a rule, cause difficulties, since this physical quantity is not very familiar to schoolchildren.

The solubility of substances in various solvents varies widely.

The table shows the solubility of some substances in water at 20 o C:

What does the solubility of substances depend on? From a number of factors: from the nature of the solute and solvent, from temperature and pressure. The reference tables suggest substances are divided into highly soluble, slightly soluble and insoluble. This division is very conditional, since there are no absolutely insoluble substances. Even silver and gold are soluble in water, but their solubility is so low as to be negligible.

Dependence of solubility on the nature of the solute and solvent*

Solubility of solids in liquids depends on the structure of the solid (on the type of crystal lattice of the solid). For example, substances with metallic crystal lattices (iron, copper, etc.) are very slightly soluble in water. Substances with an ionic crystal lattice, as a rule, are highly soluble in water.

There is a wonderful rule: like dissolves in like". Substances with an ionic or polar type of bond dissolve well in polar solvents.For example salts are highly soluble in water. At the same time, non-polar substances, as a rule, dissolve well in non-polar solvents.

Most alkali metal and ammonium salts are highly soluble in water. Almost all nitrates, nitrites and many halides (except for silver, mercury, lead and thallium halides) and sulfates (except for alkaline earth metals, silver and lead sulfates) are highly soluble. Transition metals are characterized by a low solubility of their sulfides, phosphates, carbonates, and some other salts.

The solubility of gases in liquids also depends on their nature. For example, in 100 volumes of water at 20 o C dissolves 2 volumes of hydrogen, 3 volumes of oxygen. Under the same conditions, 700 volumes of ammonia dissolve in 1 volume of H 2 O.

Effect of temperature on the solubility of gases, solids and liquids*

The dissolution of gases in water due to the hydration of the dissolved gas molecules is accompanied by the release of heat. Therefore, as the temperature rises, the solubility of gases decreases.

Temperature affects the solubility of solids in water in various ways. In most cases solubility of solids increases with temperature. For example, the solubility of sodium nitrate NaNO 3 and potassium nitrate KNO 3 increases when heated (the dissolution process proceeds with the absorption of heat). The solubility of NaCl increases slightly with increasing temperature, which is due to the almost zero thermal effect of the dissolution of table salt.

Effect of pressure on the solubility of gases, solids and liquids*

The solubility of solid and liquid substances in liquids is practically not affected by pressure, since the change in volume during dissolution is small. When gaseous substances are dissolved in a liquid, the volume of the system decreases, therefore, an increase in pressure leads to an increase in the solubility of gases. In general, the dependence of the solubility of gases on pressure obeys W. Henry's law(England, 1803): the solubility of a gas at constant temperature is directly proportional to its pressure over the liquid.

Henry's law is valid only at low pressures for gases whose solubility is relatively low and provided there is no chemical interaction between the molecules of the dissolved gas and the solvent.

Influence of foreign substances on solubility*

In the presence of other substances (salts, acids and alkalis) in water, the solubility of gases decreases. The solubility of gaseous chlorine in a saturated aqueous solution of table salt is 10 times less. than pure water.

The effect of decreasing solubility in the presence of salts is called salting out. The decrease in solubility is due to the hydration of salts, which causes a decrease in the number of free water molecules. Water molecules associated with electrolyte ions are no longer a solvent for other substances.

Examples of problems for solubility

Task 1. The mass fraction of a substance in a saturated solution is 24% at a certain temperature. Determine the solubility coefficient of this substance at a given temperature.

Solution:

To determine the solubility of a substance, we take the mass of the solution equal to 100 g. Then the mass of salt is equal to:

m r.v. = m r-ra ⋅ω r.v. = 100⋅0.24 = 24 g

The mass of water is:

m water \u003d m solution - m r.v. = 100 - 24 = 76 g

Determine the solubility:

χ = m r.v. /m p-la ⋅100 = 24/76⋅100 = 31.6 g of substance per 100 g of water.

Answer: χ = 31.6 g

A few more similar issues:

2. The mass fraction of salt in a saturated solution at a certain temperature is 28.5%. Determine the solubility coefficient of the substance at this temperature.

3. Determine the solubility coefficient of potassium nitrate at a certain temperature, if the mass fraction of salt at this temperature is 0.48.

4. What mass of water and salt will be required to prepare 500 g of a solution of potassium nitrate saturated at a certain temperature, if its solubility coefficient at this temperature is 63.9 g of salt per 100 g of water?

Answer: 194.95 g

5. The solubility coefficient of sodium chloride at a certain temperature is 36g of salt in 100g of water. Determine molar concentration saturated solution of this salt, if the density of the solution is 1.2 g / ml.

Answer: 5.49M

6. What mass of salt and 5% of its solution will be required to prepare 450 g of a solution of potassium sulfate saturated at a certain temperature, if its solubility coefficient at this temperature is 439 g / 1000 g of water?

7. What mass of barium nitrate will be released from a solution saturated at 100ºС and cooled to 0ºС if there was 150 ml of water in the solution taken? The solubility coefficient of barium nitrate at temperatures of 0ºС and 100ºС is 50 g and 342 g in 100 g of water, respectively.

8. The solubility coefficient of potassium chloride at 90ºС is 500g/l of water. How many grams of this substance can be dissolved in 500 g of water at 90ºC and what is its mass fraction in a saturated solution at this temperature?

9. 300 g of ammonium chloride are dissolved in 500 g of water when heated. What mass of ammonium chloride will be released from the solution when it is cooled to 50ºС, if the solubility coefficient of the salt at this temperature is 50 g/l of water?

* Materials of the portal onx.distant.ru

Today we will talk about the substance - water!

Have any of you seen water?

Did the question seem ridiculous to you? But it refers to completely pure water, in which there are no impurities. To be honest and accurate in the answer, you will have to admit that neither I nor you have seen such water yet. That is why on a glass of water after the inscription "H 2 O" there is a question mark. So, there is not pure water in the glass, but what then?

Gases dissolved in this water: N 2, O 2, CO 2, Ar, salts from the soil, iron cations from water pipes. In addition, the smallest particles of dust are suspended in it. That's what we call h and s t o y water! Many scientists are working on solving the difficult problem of obtaining absolutely pure water. But so far it has not been possible to obtain such ultrapure water. However, you may object that there is distilled water. By the way, what is she?

In fact, we get such water when we sterilize the jars before canning. Turn the jar upside down and place it over boiling water. Droplets appear on the bottom of the jar, this is distilled water. But as soon as we turn the jar over, gases from the air enter it, and again there is a solution in the jar. Therefore, competent housewives try to fill the jars with the necessary contents immediately after sterilization. They say that the products in this case will be stored longer. Perhaps they are right. Feel free to experiment! Precisely because water is capable of dissolving various substances in itself, scientists still cannot obtain ideally pure water in large volumes. And it would be so useful, for example, in medicine for the preparation of medicines.

By the way, being in a glass, water "dissolves" the glass. Therefore, the thicker the glass, the longer the glasses will last. What is sea water?

This is a solution that contains many substances. For example, table salt. How can salt be isolated from sea ​​water?

Evaporation. By the way, this is exactly what our ancestors did. There were salt pans in Onega, where salt was evaporated from sea water. Salt was sold to Novgorod merchants, they bought expensive jewelry and chic fabrics for their brides and wives. Even the Moscow fashionistas did not have such outfits as the Pomoroks. And all only thanks to the knowledge of the properties of solutions! So, today we are talking about solutions and solubility. Write down the definition of the solution in your notebook.

A solution is a homogeneous system consisting of solvent and solute molecules, between which physical and chemical interactions occur.

Consider schemes 1–2 and analyze what solutions are.

Which solution would you prefer when making soup? Why?

Determine where is the dilute solution, where is the concentrated solution of copper sulphate?

If a certain volume of a solution contains little solute, then such a solution is called diluted, if a lot - concentrated .

Determine which solution is where?

Do not confuse the concepts of "saturated" and "concentrated" solution, "unsaturated" and "dilute" solution.

Some substances dissolve well in water, others little, and still others do not dissolve at all. Watch the video "SOLUBILITY OF SOLIDS IN WATER"

Complete the task in the notebook: Distribute the proposed substances -CO 2, H 2, O 2 , H 2 SO 4 , Vinegar, NaCl, Chalk, Rust, Vegetable oil, Alcoholinto the empty columns of table 1, using your life experience.

Table 1

Can you tell me about the solubility FeSO4?

How to be?

In order to determine the solubility of substances in water, we will use the table of the solubility of salts, acids and bases in water. It is in the attachments to the lesson.

In the top row of the table are cations, in the left column are anions; we are looking for an intersection point, we look at the letter - this is solubility.

Let's determine the solubility of salts: AgNO 3 , AgCl, CaSO 4 .

Solubility increases with increasing temperature (there are exceptions). You know perfectly well that it is more convenient and faster to dissolve sugar in hot, and not in cold water. See "Thermal Phenomena in Dissolution"

Try it yourself, using the table, to determine the solubility of substances.

Exercise. Determine the solubility of the following substances: AgNO 3 , Fe (OH) 2 , Ag 2 SO 3 , Ca (OH) 2 , CaCO 3 , MgCO 3 , KOH.

DEFINITIONS on the topic "Solutions"

Solution- a homogeneous system consisting of solvent and solute molecules, between which physical and chemical interactions occur.

saturated solution A solution in which a given substance no longer dissolves at a given temperature.

unsaturated solution A solution in which a substance can still dissolve at a given temperature.

suspensioncalled a suspension in which small particles of solid matter are evenly distributed among water molecules.

emulsioncalled a suspension in which small droplets of a liquid are distributed among the molecules of another liquid.

dilute solutions - solutions with a small content of dissolved substance.

concentrated solutions - solutions with a high content of solute.

ADDITIONALLY:

According to the ratio of the predominance of the number of particles passing into the solution or removed from the solution, solutions are distinguished saturated, unsaturated and supersaturated. According to the relative amounts of solute and solvent, solutions are divided into diluted and concentrated.

A solution in which a given substance at a given temperature no longer dissolves, i.e. a solution in equilibrium with a solute is called rich, and a solution in which an additional amount of a given substance can still be dissolved, - unsaturated.

A saturated solution contains the maximum possible (for given conditions) amount of solute. Therefore, a saturated solution is one that is in equilibrium with an excess of solute. The concentration of a saturated solution (solubility) for a given substance under strictly defined conditions (temperature, solvent) is a constant value.

A solution containing more solute than it should be under the given conditions in a saturated solution is called supersaturated. Supersaturated solutions are unstable, non-equilibrium systems in which a spontaneous transition to an equilibrium state is observed. In this case, an excess of the solute is released, and the solution becomes saturated.

Solubility of gases in liquids depends on a number of factors: the nature of the gas and liquid, pressure, temperature, the concentration of substances dissolved in the liquid (the concentration of electrolytes especially strongly affects the solubility of gases).

Biggest Influence the nature of substances affects the solubility of gases in liquids. So, in 1 liter of water at t = 18 ° C and P = 1 atm. dissolves 0.017 l. nitrogen, 748.8 l. ammonia or 427.8 l. hydrogen chloride. The abnormally high solubility of gases in liquids is usually due to their specific interaction with the solvent - the formation of a chemical compound (for ammonia) or dissociation into ions in solution (for hydrogen chloride). Gases whose molecules are non-polar tend to dissolve better in non-polar liquids, and vice versa. The dependence of gas solubility on pressure is expressed by the Henry-Dalton law:

The solubility of a gas in a liquid is directly proportional to its pressure over the liquid.

solubility of liquids - degree of mutual solubility of liquids. Some liquids can dissolve indefinitely in other liquids, that is, they can be mixed with each other in any proportions, for example, alcohol and water. Dr. they mutually dissolve only up to a certain limit (for example, when ether is shaken with water, 2 layers are formed: the upper one is a saturated solution of water in ether, and the lower one is a saturated solution of ether in water).

Dissolution of a solid in a liquid is essentially not much different from the dissolution of a liquid in a liquid. And in this case, the solute molecules are gradually distributed among the solvent molecules. The mass of the solute per unit volume of the solvent is called the concentration of the solution. A substance dissolves in a liquid up to a certain concentration, which depends on the nature of the solvent and the solute, as well as on the temperature.

Henry Dalton's law refers to the solubility of gases in a liquid as a function of the elasticity of that gas exerting pressure on the liquid.

At some specific pressure and constant temperature, a certain amount of gas dissolves in a liquid, which also depends on the properties of the liquid. With an increase or decrease in the pressure of the gas atmosphere on a liquid while maintaining the same temperature, the amount of dissolved gas increases or decreases in the same ratio.

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 this substance is in equilibrium state with a substance in solution.