The study of the parameters of the system, including the initial substances and reaction products, allows us to find out what factors shift the chemical equilibrium and lead to the desired changes. Based on the conclusions of Le Chatelier, Brown and other scientists about the methods of carrying out reversible reactions, industrial technologies are based that make it possible to carry out processes that previously seemed impossible and obtain economic benefits.

Variety of chemical processes

According to the characteristics of the thermal effect, many reactions are classified as exothermic or endothermic. The former go with the formation of heat, for example, the oxidation of carbon, the hydration of concentrated sulfuric acid. The second type of changes is associated with the absorption of thermal energy. Examples of endothermic reactions: the decomposition of calcium carbonate with the formation of slaked lime and carbon dioxide, the formation of hydrogen and carbon during the thermal decomposition of methane. In the equations of exo- and endothermic processes, it is necessary to indicate the thermal effect. The redistribution of electrons between the atoms of the reacting substances occurs in redox reactions. Four types of chemical processes are distinguished according to the characteristics of the reactants and products:

To characterize the processes, the completeness of the interaction of the reacting compounds is important. This feature underlies the division of reactions into reversible and irreversible.

Reversibility of reactions

Reversible processes make up the majority of chemical phenomena. The formation of end products from reactants is a direct reaction. In the reverse, the initial substances are obtained from the products of their decomposition or synthesis. In the reacting mixture, a chemical equilibrium arises, in which as many compounds are obtained as the initial molecules decompose. In reversible processes, instead of the "=" sign between the reactants and products, the symbols "↔" or "⇌" are used. Arrows can be unequal in length, which is associated with the dominance of one of the reactions. In chemical equations, aggregate characteristics of substances can be indicated (g - gases, w - liquids, m - solids). Scientifically substantiated methods of influencing reversible processes are of great practical importance. Thus, the production of ammonia became profitable after the creation of conditions that shift the equilibrium towards the formation of the target product: 3H 2 (g) + N 2 (g) ⇌ 2NH 3 (g). Irreversible phenomena lead to the appearance of an insoluble or slightly soluble compound, the formation of a gas that leaves the reaction sphere. These processes include ion exchange, decomposition of substances.

Chemical equilibrium and conditions for its displacement

Several factors influence the characteristics of the forward and reverse processes. One of them is time. The concentration of the substance taken for the reaction gradually decreases, and the final compound increases. The reaction of the forward direction is slower and slower, the reverse process is gaining speed. In a certain interval, two opposite processes go synchronously. The interaction between substances occurs, but the concentrations do not change. The reason is the dynamic chemical equilibrium established in the system. Its retention or modification depends on:

• temperature conditions;
• compound concentrations;
• pressure (for gases).

Shift in chemical equilibrium

In 1884, A. L. Le Chatelier, an outstanding scientist from France, proposed a description of ways to bring a system out of a state of dynamic equilibrium. The method is based on the principle of leveling the action of external factors. Le Chatelier drew attention to the fact that processes arise in the reacting mixture that compensate for the influence of extraneous forces. The principle formulated by the French researcher says that a change in conditions in a state of equilibrium favors the course of a reaction that weakens an extraneous influence. Equilibrium shift obeys this rule, it is observed when the composition, temperature conditions and pressure change. Technologies based on the findings of scientists are used in industry. Many chemical processes that were considered impracticable are carried out using methods of shifting the equilibrium.

Influence of concentration

A shift in equilibrium occurs if certain components are removed from the interaction zone or additional portions of a substance are introduced. The removal of products from the reaction mixture usually causes an increase in the rate of their formation, while the addition of substances, on the contrary, leads to their predominant decomposition. In the esterification process, sulfuric acid is used for dehydration. When it is introduced into the reaction sphere, the yield of methyl acetate increases: CH 3 COOH + CH 3 OH ↔ CH 3 COOSH 3 + H 2 O. If you add oxygen that interacts with sulfur dioxide, then the chemical equilibrium shifts towards the direct reaction of the formation of sulfur trioxide. Oxygen binds to SO 3 molecules, its concentration decreases, which is consistent with Le Chatelier's rule for reversible processes.

Temperature change

Processes that go with the absorption or release of heat are endo- and exothermic. To shift the equilibrium, heating or heat removal from the reacting mixture is used. An increase in temperature is accompanied by an increase in the rate of endothermic phenomena in which additional energy is absorbed. Cooling leads to the advantage of exothermic processes that release heat. During the interaction of carbon dioxide with coal, heating is accompanied by an increase in the concentration of monoxide, and cooling leads to the predominant formation of soot: CO 2 (g) + C (t) ↔ 2CO (g).

Pressure influence

The change in pressure is an important factor for reacting mixtures that include gaseous compounds. You should also pay attention to the difference in the volumes of the initial and resulting substances. A decrease in pressure leads to a predominant occurrence of phenomena in which the total volume of all components increases. The increase in pressure directs the process in the direction of reducing the volume of the entire system. This pattern is observed in the reaction of ammonia formation: 0.5N 2 (g) + 1.5H 2 (g) ⇌ NH 3 (g). A change in pressure will not affect the chemical equilibrium in those reactions that take place at a constant volume.

Optimal conditions for the implementation of the chemical process

The creation of conditions for shifting the equilibrium largely determines the development of modern chemical technologies. The practical use of scientific theory contributes to obtaining optimal production results. The most striking example is the production of ammonia: 0.5N 2 (g) + 1.5H 2 (g) ⇌ NH 3 (g). An increase in the content of N 2 and H 2 molecules in the system is favorable for the synthesis of a complex substance from simple ones. The reaction is accompanied by the release of heat, so a decrease in temperature will cause an increase in the concentration of NH 3. The volume of the initial components is greater than the volume of the target product. An increase in pressure will provide an increase in the yield of NH 3 .

Under production conditions, the optimal ratio of all parameters (temperature, concentration, pressure) is selected. In addition, the contact area between the reactants is of great importance. In solid heterogeneous systems, an increase in surface area leads to an increase in the reaction rate. Catalysts increase the rate of forward and reverse reactions. The use of substances with such properties does not lead to a shift in chemical equilibrium, but accelerates its onset.

Chemical equilibrium is inherent reversible reactions and is not typical for irreversible chemical reactions.

Often, during the implementation of a chemical process, the initial reactants completely pass into the reaction products. For example:

Cu + 4HNO 3 \u003d Cu (NO 3) 2 + 2NO 2 + 2H 2 O

It is impossible to obtain metallic copper by carrying out the reaction in the opposite direction, because. given the reaction is irreversible. In such processes, the reactants are completely converted into products, i.e. the reaction proceeds to completion.

But most of the chemical reactions reversible, i.e. the parallel flow of the reaction in the forward and reverse directions is likely. In other words, the reactants are only partially converted into products, and the reaction system will consist of both reactants and products. The system in this case is in the state chemical equilibrium.

In reversible processes, at first the direct reaction has a maximum rate, which gradually decreases due to a decrease in the amount of reagents. The reverse reaction, on the contrary, initially has a minimum rate, which increases as the products accumulate. In the end, there comes a moment when the rates of both reactions become equal - the system comes to a state of equilibrium. When an equilibrium state is reached, the concentrations of the components remain unchanged, but the chemical reaction does not stop. That. This is a dynamic (moving) state. For clarity, we present the following figure:

Let's say there is some reversible chemical reaction:

a A + b B = c C + d D

then, based on the law of mass action, we write the expressions for straightυ 1 and reverseυ 2 reactions:

υ1 = k 1 [A] a [B] b

υ2 = k 2 [C] c [D] d

In condition chemical equilibrium, the rates of the forward and reverse reactions are equal, i.e.:

k 1 [A] a [B] b = k 2 [C] c [D] d

we get

To= k1 / k 2 = [C] c [D] d ̸ [A] a [B] b

Where K =k 1 / k 2 – equilibrium constant.

For any reversible process, under given conditions k is a constant value. It does not depend on the concentrations of substances, since when the amount of one of the substances changes, the amounts of other components also change.

When the conditions for the course of a chemical process change, a shift in equilibrium is possible.

Factors affecting the shift in equilibrium:

• change in the concentrations of reactants or products,
• pressure change,
• temperature change,
• introducing a catalyst into the reaction medium.

Le Chatelier's principle

All of the above factors affect the shift in chemical equilibrium, which is subject to Le Chatelier principle: if you change one of the conditions under which the system is in equilibrium - concentration, pressure or temperature - then the equilibrium will shift in the direction of the reaction that counteracts this change. Those. the equilibrium tends to shift in the direction, leading to a decrease in the influence of the impact that led to the violation of the equilibrium state.

So, we will consider separately the influence of each of their factors on the state of equilibrium.

Influence changes in reactant or product concentrations let's show by example Haber process:

N 2 (g) + 3H 2 (g) \u003d 2NH 3 (g)

If, for example, nitrogen is added to an equilibrium system consisting of N 2 (g), H 2 (g) and NH 3 (g), then the equilibrium should shift in the direction that would contribute to a decrease in the amount of hydrogen towards its original value, those. in the direction of formation of an additional amount of ammonia (to the right). At the same time, a decrease in the amount of hydrogen will also occur. When hydrogen is added to the system, the equilibrium will also shift towards the formation of a new amount of ammonia (to the right). Whereas the introduction of ammonia into the equilibrium system, according to Le Chatelier principle , will cause a shift in equilibrium towards the process that is favorable for the formation of the starting substances (to the left), i.e. the concentration of ammonia should be reduced by decomposing some of it into nitrogen and hydrogen.

A decrease in the concentration of one of the components will shift the equilibrium state of the system towards the formation of this component.

Influence pressure changes it makes sense if gaseous components take part in the process under study and, in this case, there is a change in the total number of molecules. If the total number of molecules in the system remains permanent, then the change in pressure does not affect on its balance, for example:

I 2 (g) + H 2 (g) \u003d 2HI (g)

If the total pressure of an equilibrium system is increased by decreasing its volume, then the equilibrium will shift in the direction of decreasing volume. Those. towards decreasing number gas in system. In reaction:

N 2 (g) + 3H 2 (g) \u003d 2NH 3 (g)

from 4 gas molecules (1 N 2 (g) and 3 H 2 (g)) 2 gas molecules are formed (2 NH 3 (g)), i.e. the pressure in the system decreases. As a result, an increase in pressure will contribute to the formation of an additional amount of ammonia, i.e. the equilibrium will shift in the direction of its formation (to the right).

If the temperature of the system is constant, then a change in the total pressure of the system will not lead to a change in the equilibrium constant TO.

Temperature change system affects not only the displacement of its equilibrium, but also the equilibrium constant TO. If an equilibrium system, at constant pressure, is given additional heat, then the equilibrium will shift in the direction of heat absorption. Consider:

N 2 (g) + 3H 2 (g) \u003d 2NH 3 (g) + 22 kcal

So, as you can see, the forward reaction proceeds with the release of heat, and the reverse reaction with absorption. With an increase in temperature, the equilibrium of this reaction shifts towards the reaction of ammonia decomposition (to the left), because it is and weakens the external influence - the rise in temperature. On the contrary, cooling leads to a shift in the equilibrium in the direction of ammonia synthesis (to the right), since the reaction is exothermic and resists cooling.

Thus, an increase in temperature favors a shift chemical equilibrium in the direction of an endothermic reaction, and the temperature drop is in the direction of an exothermic process . Equilibrium constants of all exothermic processes with increasing temperature decrease, and endothermic processes - increase.

Most chemical reactions are reversible, that is, they proceed simultaneously in opposite directions. In cases where the forward and reverse reactions proceed at the same rate, chemical equilibrium occurs.

When chemical equilibrium is reached, the number of molecules of the substances that make up the system ceases to change and remains constant in time under unchanged external conditions.

The state of a system in which the rate of the forward reaction is equal to the rate of the reverse reaction is called chemical equilibrium.

For example, the equilibrium of the reaction H 2 (g) + I 2 (g) ⇆ 2HI (g) occurs when exactly as many hydrogen iodide molecules are formed in a unit of time in a direct reaction as they decay in a reverse reaction into iodine and hydrogen.

The ability of a reaction to proceed in opposite directions is called kinetic reversibility..

In a reaction equation, reversibility is indicated by two opposite arrows (⇆) instead of an equals sign between the left and right sides of the chemical equation.

Chemical equilibrium is dynamic (mobile). When external conditions change, the equilibrium shifts and returns to its original state if the external conditions acquire constant values. The influence of external factors on the chemical balance causes its shift.

The position of chemical equilibrium depends on the following reaction parameters:

Temperatures;

pressure;

Concentrations.

The influence that these factors have on a chemical reaction follows a pattern that was expressed in general terms in 1884 by the French scientist Le Chatelier (Fig. 1).

Rice. 1. Henri Louis Le Chatelier

Modern formulation of Le Chatelier's principle

If an external influence is exerted on a system in equilibrium, then the equilibrium shifts in the direction that weakens this influence.

1. Effect of temperature

In each reversible reaction, one of the directions corresponds to an exothermic process, and the other to an endothermic one.

Example: industrial production of ammonia. Rice. 2.

Rice. 2. Plant for the production of ammonia

Ammonia synthesis reaction:

N 2 + 3H 2 ⇆ 2NH 3 + Q

The forward reaction is exothermic and the reverse reaction is endothermic.

The effect of temperature change on the position of chemical equilibrium obeys the following rules.

As the temperature rises, the chemical equilibrium shifts in the direction of the endothermic reaction, and as the temperature decreases, in the direction of the exothermic reaction.

To shift the equilibrium in the direction of obtaining ammonia, the temperature must be lowered.

2. Influence of pressure

In all reactions involving gaseous substances, accompanied by a change in volume due to a change in the amount of substance in the transition from the starting substances to the products, the equilibrium position is affected by the pressure in the system.

The influence of pressure on the equilibrium position obeys the following rules.

With an increase in pressure, the equilibrium shifts in the direction of the formation of substances (initial or products) with a smaller volume; as the pressure decreases, the equilibrium shifts in the direction of the formation of substances with a large volume.

In an ammonia synthesis reaction, with increasing pressure, the equilibrium shifts towards the formation of ammonia, because the reaction proceeds with a decrease in volume.

3. Effect of concentration

The influence of concentration on the state of equilibrium obeys the following rules.

With an increase in the concentration of one of the starting substances, the equilibrium shifts in the direction of the formation of reaction products; with an increase in the concentration of one of the reaction products, the equilibrium shifts in the direction of the formation of the starting substances.

In the ammonia production reaction, in order to shift the equilibrium towards ammonia production, it is necessary to increase the concentration of hydrogen and nitrogen.

Summing up the lesson

In the lesson, you learned about the concept of “chemical equilibrium” and how to shift it, what conditions affect the shift in chemical equilibrium, and how the “Le Chatelier principle” works.

Bibliography

1. Novoshinsky I.I., Novoshinskaya N.S. Chemistry. Textbook for grade 10 general. inst. profile level. - M .: LLC "TID "Russian Word - RS", 2008. (§§ 24, 25)
2. Kuznetsova N.E., Litvinova T.N., Lyovkin A.N. Chemistry: Grade 11: A textbook for students in general. inst. (profile level): in 2 hours. Part 2. M.: Ventana-Graf, 2008. (§ 24)
3. Rudzitis G.E. Chemistry. Fundamentals of General Chemistry. Grade 11: textbook. for general institution: basic level / G.E. Rudzitis, F.G. Feldman. - M .: Education, JSC "Moscow textbooks", 2010. (§ 13)
4. Radetsky A.M. Chemistry. didactic material. 10-11 grades. - M.: Enlightenment, 2011. (p. 96-98)
5. Khomchenko I.D. Collection of problems and exercises in chemistry for high school. - M.: RIA "New Wave": Publisher Umerenkov, 2008. (p. 65-68)

1. Hemi.nsu.ru ().
2. Alhimikov.net ().
3. Prosto-o-slognom.ru ().

Homework

1. with. 65-66 No. 12.10-12.17 from the Collection of tasks and exercises in chemistry for secondary school (Khomchenko I.D.), 2008.
2. In what case will a change in pressure not cause a shift in the chemical equilibrium in reactions involving gaseous substances?
3. Why does the catalyst not contribute to shifting the chemical equilibrium?

The state in which the rates of the forward and reverse reactions are equal is called chemical equilibrium. Reversible reaction equation in general form:

Forward reaction rate v 1 =k 1 [A] m [B] n , rate of reverse reaction v 2 =k 2 [С] p [D] q , where in square brackets are the equilibrium concentrations. By definition, at chemical equilibrium v 1 =v 2, from where

K c \u003d k 1 / k 2 \u003d [C] p [D] q / [A] m [B] n,

where K c is the chemical equilibrium constant expressed in terms of molar concentrations. The above mathematical expression is often called the law of mass action for a reversible chemical reaction: the ratio of the product of the equilibrium concentrations of the reaction products to the product of the equilibrium concentrations of the starting materials.

The position of chemical equilibrium depends on the following reaction parameters: temperature, pressure and concentration. The influence that these factors have on a chemical reaction is subject to a pattern that was expressed in general terms in 1884 by the French scientist Le Chatelier. The modern formulation of Le Chatelier's principle is as follows:

If an external influence is exerted on a system that is in a state of equilibrium, then the system will move to another state in such a way as to reduce the effect of external influence.

Factors affecting chemical equilibrium.

1. Effect of temperature. In each reversible reaction, one of the directions corresponds to an exothermic process, and the other to an endothermic one.

As the temperature rises, the chemical equilibrium shifts in the direction of the endothermic reaction, and as the temperature decreases, in the direction of the exothermic reaction.

2. Influence of pressure. In all reactions involving gaseous substances, accompanied by a change in volume due to a change in the amount of substance in the transition from the starting substances to the products, the equilibrium position is affected by the pressure in the system.
The influence of pressure on the equilibrium position obeys the following rules:

With increasing pressure, the equilibrium shifts in the direction of the formation of substances (initial or products) with a smaller volume.

3. Influence of concentration. The influence of concentration on the state of equilibrium obeys the following rules:

With an increase in the concentration of one of the starting substances, the equilibrium shifts in the direction of the formation of reaction products;
with an increase in the concentration of one of the reaction products, the equilibrium shifts in the direction of the formation of the starting substances.

Questions for self-control:

1. What is the rate of a chemical reaction and what factors does it depend on? On what factors does the rate constant depend?

2. Write an equation for the reaction rate of the formation of water from hydrogen and oxygen and show how the rate changes if the hydrogen concentration is tripled.

3. How does the reaction rate change over time? What reactions are called reversible? What is the state of chemical equilibrium? What is called the equilibrium constant, on what factors does it depend?

4. What external influences can disturb the chemical balance? In which direction will the equilibrium shift as the temperature changes? Pressure?

5. How can a reversible reaction be shifted in a certain direction and completed?

Lecture No. 12 (problem)

Solutions

Target: Give qualitative conclusions about the solubility of substances and a quantitative assessment of solubility.

Keywords: Solutions - homogeneous and heterogeneous; true and colloidal; solubility of substances; concentration of solutions; solutions of nonelectroyls; laws of Raoult and van't Hoff.

Plan.

1. Classification of solutions.

2. Concentration of solutions.

3. Solutions of non-electrolytes. Raoult's laws.

Classification of solutions

Solutions are homogeneous (single-phase) systems of variable composition, consisting of two or more substances (components).

According to the nature of the state of aggregation, solutions can be gaseous, liquid and solid. Usually, a component that under given conditions is in the same state of aggregation as the resulting solution is considered a solvent, the remaining components of the solution are solutes. In the case of the same aggregate state of the components, the solvent is the component that prevails in the solution.

Depending on the size of the particles, solutions are divided into true and colloidal. In true solutions (often referred to simply as solutions), the solute is dispersed to the atomic or molecular level, the particles of the solute are not visible either visually or under a microscope, they move freely in the solvent medium. True solutions are thermodynamically stable systems, infinitely stable over time.

The driving forces for the formation of solutions are the entropy and enthalpy factors. When dissolving gases in a liquid, the entropy always decreases ΔS< 0, а при растворении кристаллов возрастает (ΔS >0). The stronger the interaction between the solute and the solvent, the greater the role of the enthalpy factor in the formation of solutions. The sign of the change in the enthalpy of dissolution is determined by the sign of the sum of all thermal effects of the processes accompanying dissolution, of which the main contribution is made by the destruction of the crystal lattice into free ions (ΔH > 0) and the interaction of the formed ions with solvent molecules (solvation, ΔH< 0). При этом независимо от знака энтальпии при растворении (абсолютно нерастворимых веществ нет) всегда ΔG = ΔH – T·ΔS < 0, т. к. переход вещества в раствор сопровождается значительным возрастанием энтропии вследствие стремления системы к разупорядочиванию. Для жидких растворов (расплавов) процесс растворения идет самопроизвольно (ΔG < 0) до установления динамического равновесия между раствором и твердой фазой.

The concentration of a saturated solution is determined by the solubility of the substance at a given temperature. Solutions with a lower concentration are called unsaturated.

Solubility for various substances varies considerably and depends on their nature, the interaction of the particles of the solute with each other and with solvent molecules, as well as on external conditions (pressure, temperature, etc.)

In chemical practice, solutions prepared on the basis of a liquid solvent are most important. It is liquid mixtures in chemistry that are simply called solutions. The most widely used inorganic solvent is water. Solutions with other solvents are called non-aqueous.

Solutions are of extremely great practical importance; many chemical reactions take place in them, including those underlying the metabolism in living organisms.

Solution concentration

An important characteristic of solutions is their concentration, which expresses the relative amount of components in the solution. There are mass and volume concentrations, dimensional and dimensionless.

To dimensionless concentrations (shares) include the following concentrations:

Mass fraction of solute W(B) expressed as a fraction of a unit or as a percentage:

where m(B) and m(A) are the mass of the solute B and the mass of the solvent A.

The volume fraction of a dissolved substance σ(B) is expressed in fractions of a unit or volume percent:

where V i is the volume of the component of the solution, V(B) is the volume of the dissolved substance B. Volume percentages are called degrees *) .

*) Sometimes the volume concentration is expressed in thousandths (ppm, ‰) or in parts per million (ppm), ppm.

The mole fraction of a solute χ(B) is expressed by the relation

The sum of the mole fractions of the k components of the solution χ i is equal to one

To dimensional concentrations include the following concentrations:

The molality of the dissolved substance C m (B) is determined by the amount of substance n (B) in 1 kg (1000 g) of the solvent, the unit is mol/kg.

Molar concentration of substance B in solution C(B) - the content of the amount of dissolved substance B per unit volume of the solution, mol/m 3, or more often mol/liter:

where μ(B) is the molar mass of B, V is the volume of the solution.

Molar concentration equivalents of substance B C E (B) (normality - obsolete.) is determined by the number of equivalents of a solute per unit volume of the solution, mol / liter:

where n E (B) is the amount of substance equivalents, μ E is the molar mass of the equivalent.

The titer of a solution of substance B( T B) is determined by the mass of the solute in g contained in 1 ml of the solution:

g/ml or g/ml.

Mass concentrations (mass fraction, percentage, molal) do not depend on temperature; volumetric concentrations refer to a specific temperature.

All substances are capable of solubility to some extent and are characterized by solubility. Some substances are infinitely soluble in each other (water-acetone, benzene-toluene, liquid sodium-potassium). Most compounds are sparingly soluble (water-benzene, water-butyl alcohol, water-table salt), and many are slightly soluble or practically insoluble (water-BaSO 4 , water-gasoline).

The solubility of a substance under given conditions is its concentration in a saturated solution. In such a solution, equilibrium is reached between the solute and the solution. In the absence of equilibrium, the solution remains stable if the concentration of the solute is less than its solubility (unsaturated solution), or unstable if the solution contains substances greater than its solubility (supersaturated solution).

All chemical reactions are, in principle, reversible.
This means that both the interaction of the reactants and the interaction of the products proceed in the reaction mixture. In this sense, the distinction between reactants and products is arbitrary. The direction of a chemical reaction is determined by the conditions of its implementation (temperature, pressure, concentration of substances).
Many reactions have one predominant direction and extreme conditions are required to carry out such reactions in the opposite direction. In such reactions, almost complete conversion of reactants into products occurs.

Example. Iron and sulfur react with each other under moderate heating to form iron (II) sulfide, FeS is stable under such conditions and practically does not decompose into iron and sulfur:

At 200 atm and 400 0C, the maximum and equal to 36% (by volume) content of NH3 in the reaction mixture is achieved. With a further increase in temperature, due to the enhanced flow of the reverse reaction, the volume fraction of ammonia in the mixture decreases.
The forward and reverse reactions proceed simultaneously in opposite directions.

In all reversible reactions, the rate of the forward reaction decreases and the rate of the reverse reaction increases until both rates become equal and an equilibrium state is established.

In a state of equilibrium, the rates of the forward and reverse reactions become equal.

THE PRINCIPLE OF LE CHATELIER. SHIFT OF CHEMICAL EQUILIBRIUM.

The position of chemical equilibrium depends on the following reaction parameters: temperature, pressure and concentration. The influence that these factors have on a chemical reaction is subject to a pattern that was expressed in general terms in 1884 by the French scientist Le Chatelier. The modern formulation of Le Chatelier's principle is as follows:

1. Effect of temperature. In each reversible reaction, one of the directions corresponds to an exothermic process, and the other to an endothermic one.

2. Influence of pressure. In all reactions involving gaseous substances, accompanied by a change in volume due to a change in the amount of a substance when moving from starting substances to products, the pressure in the system affects the equilibrium position.
The influence of pressure on the equilibrium position obeys the following rules:

Thus, during the transition from the starting substances to the products, the volume of gases decreased by half. This means that with an increase in pressure, the equilibrium shifts towards the formation of NH3, as evidenced by the following data for the ammonia synthesis reaction at 400 0C:

3. Influence of concentration. The influence of concentration on the state of equilibrium obeys the following rules: