Shift in equilibrium when heated. Shift in chemical equilibrium. Le Chatelier's principle

Chemical reactions can be reversible or irreversible.

those. if some reaction A + B = C + D is irreversible, this means that the reverse reaction C + D = A + B does not occur.

i.e., for example, if a certain reaction A + B = C + D is reversible, this means that both the reaction A + B → C + D (direct) and the reaction C + D → A + B (reverse) occur simultaneously ).

Essentially, because Both direct and reverse reactions occur; in the case of reversible reactions, both the substances on the left side of the equation and the substances on the right side of the equation can be called reagents (starting substances). The same goes for products.

For anyone reversible reaction a situation is possible when the rates of forward and reverse reactions are equal. This condition is called state of balance.

At equilibrium, the concentrations of both all reactants and all products are constant. The concentrations of products and reactants at equilibrium are called equilibrium concentrations.

Shift in chemical equilibrium under the influence of various factors

Due to external influences on the system such as changes in temperature, pressure or concentration starting materials or products, the balance of the system may be disturbed. However, after the cessation of this external influence, the system will, after some time, move to a new state of equilibrium. Such a transition of a system from one equilibrium state to another equilibrium state is called displacement (shift) of chemical equilibrium .

In order to be able to determine how the chemical equilibrium shifts under a particular type of influence, it is convenient to use Le Chatelier’s principle:

If any external influence is exerted on a system in a state of equilibrium, then the direction of the shift in chemical equilibrium will coincide with the direction of the reaction that weakens the effect of the influence.

The influence of temperature on the state of equilibrium

When the temperature changes, the equilibrium is any chemical reaction shifts. This is due to the fact that any reaction has a thermal effect. Moreover, the thermal effects of the forward and reverse reactions are always directly opposite. Those. if the forward reaction is exothermic and proceeds with a thermal effect equal to +Q, then the reverse reaction is always endothermic and has a thermal effect equal to –Q.

Thus, in accordance with Le Chatelier’s principle, if we increase the temperature of some system that is in a state of equilibrium, then the equilibrium will shift towards the reaction during which the temperature decreases, i.e. towards an endothermic reaction. And similarly, if we lower the temperature of the system in a state of equilibrium, the equilibrium will shift towards the reaction, as a result of which the temperature will increase, i.e. towards an exothermic reaction.

For example, consider the following reversible reaction and indicate where its equilibrium will shift as the temperature decreases:

As can be seen from the equation above, the forward reaction is exothermic, i.e. As a result of its occurrence, heat is released. Consequently, the reverse reaction will be endothermic, that is, it occurs with the absorption of heat. According to the condition, the temperature is reduced, therefore, the equilibrium will shift to the right, i.e. towards direct reaction.

Effect of concentration on chemical equilibrium

An increase in the concentration of reagents in accordance with Le Chatelier’s principle should lead to a shift in equilibrium towards the reaction as a result of which the reagents are consumed, i.e. towards direct reaction.

And vice versa, if the concentration of the reactants is reduced, then the equilibrium will shift towards the reaction as a result of which the reactants are formed, i.e. side of the reverse reaction (←).

A change in the concentration of reaction products also has a similar effect. If the concentration of products is increased, the equilibrium will shift towards the reaction as a result of which the products are consumed, i.e. towards the reverse reaction (←). If, on the contrary, the concentration of products is reduced, then the equilibrium will shift towards the direct reaction (→), so that the concentration of products increases.

Effect of pressure on chemical equilibrium

Unlike temperature and concentration, changes in pressure do not affect the equilibrium state of every reaction. In order for a change in pressure to lead to a shift in chemical equilibrium, the sums of the coefficients for gaseous substances on the left and right sides of the equation must be different.

Those. of two reactions:

a change in pressure can affect the equilibrium state only in the case of the second reaction. Since the sum of the coefficients in front of the formulas of gaseous substances in the case of the first equation on the left and right is the same (equal to 2), and in the case of the second equation it is different (4 on the left and 2 on the right).

From here, in particular, it follows that if there are no gaseous substances among both reactants and products, then a change in pressure will not affect the current state of equilibrium in any way. For example, pressure will not affect the equilibrium state of the reaction:

If, on the left and right, the amount of gaseous substances differs, then an increase in pressure will lead to a shift in equilibrium towards the reaction during which the volume of gases decreases, and a decrease in pressure will lead to a shift in the equilibrium, as a result of which the volume of gases increases.

Effect of a catalyst on chemical equilibrium

Since a catalyst equally accelerates both forward and reverse reactions, its presence or absence has no effect to a state of equilibrium.

The only thing a catalyst can affect is the rate of transition of the system from a nonequilibrium state to an equilibrium one.

The impact of all the above factors on chemical equilibrium is summarized below in a cheat sheet, which you can initially look at when performing equilibrium tasks. However, it will not be possible to use it in the exam, therefore, after analyzing several examples with its help, you should learn it and practice solving equilibrium problems without looking at it:

Designations: T - temperature, p - pressure, With – concentration, – increase, ↓ – decrease

1. Among all known reactions, a distinction is made between reversible and irreversible reactions. When studying ion exchange reactions, the conditions under which they proceed to completion were listed. ().

There are also known reactions that, under given conditions, do not proceed to completion. So, for example, when sulfur dioxide is dissolved in water, the reaction occurs: SO 2 + H 2 O→ H2SO3. But it turns out that only a certain amount of sulfurous acid can form in an aqueous solution. This is explained by sulfurous acid fragile, and a reverse reaction occurs, i.e. decomposition into sulfur oxide and water. Consequently, this reaction does not go to completion because two reactions occur simultaneously - straight(between sulfur oxide and water) and reverse(decomposition of sulfurous acid). SO 2 +H 2 O↔ H 2 SO 3 .

Chemical reactions occurring under given conditions in mutually opposite directions are called reversible.

2. Since the rate of chemical reactions depends on the concentration of the reactants, at first the rate of the direct reaction( υ pr) must be maximum and speed reverse reaction ( υ arr.) is equal to zero. The concentration of reactants decreases over time, and the concentration of reaction products increases. Therefore, the rate of the forward reaction decreases and the rate of the reverse reaction increases. At a certain point in time, the rates of forward and reverse reactions become equal:

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

υ pr =υ arr.

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

In a state of chemical equilibrium, the quantitative ratio between the reactants and reaction products remains constant: how many molecules of the reaction product are formed per unit time, so many of them decompose. However, the state of chemical equilibrium is maintained as long as the reaction conditions remain unchanged: concentration, temperature and pressure.

The state of chemical equilibrium is described quantitatively law of mass action.

At equilibrium, the ratio of the product of concentrations of reaction products (in powers of their coefficients) to the product of concentrations of reactants (also in powers of their coefficients) is a constant value, independent of the initial concentrations of substances in the reaction mixture.

This constant is called equilibrium constant - k

So for the reaction: N 2 (G) + 3 H 2 (G) ↔ 2 NH 3 (G) + 92.4 kJ the equilibrium constant is expressed as follows:

υ 1 =υ 2

v 1 (direct reaction) = k 1 [ N 2 ][ H 2 ] 3 , where– equilibrium molar concentrations, = mol/l

υ 2 (backlash) = k 2 [ N.H. 3 ] 2

k 1 [ N 2 ][ H 2 ] 3 = k 2 [ N.H. 3 ] 2

Kp = k 1 / k 2 = [ N.H. 3 ] 2 / [ N 2 ][ H 2 ] 3 – equilibrium constant.

Chemical equilibrium depends on concentration, pressure, temperature.

Principledetermines the direction of equilibrium mixing:

If an external influence is exerted on a system that is in equilibrium, then the equilibrium in the system will shift in the direction opposite to this influence.

1) Effect of concentration – if the concentration of the starting substances is increased, the equilibrium shifts towards the formation of reaction products.

For example,Kp = k 1 / k 2 = [ N.H. 3 ] 2 / [ N 2 ][ H 2 ] 3

When added to the reaction mixture, for example nitrogen, i.e. the concentration of the reagent increases, the denominator in the expression for K increases, but since K is a constant, then to fulfill this condition the numerator must also increase. Thus, the amount of reaction product in the reaction mixture increases. In this case, they speak of a shift in chemical equilibrium to the right, towards the product.

Thus, an increase in the concentration of reactants (liquid or gaseous) shifts towards the products, i.e. towards direct reaction. An increase in the concentration of products (liquid or gaseous) shifts the equilibrium towards the reactants, i.e. towards the opposite reaction.

Changing the mass of a solid does not change the equilibrium position.

2) Effect of temperature – an increase in temperature shifts the equilibrium towards an endothermic reaction.

A)N 2 (G) + 3H 2 (G) ↔ 2N.H. 3 (G) + 92.4 kJ (exothermic - heat release)

As the temperature increases, the equilibrium will shift towards the ammonia decomposition reaction (←)

b)N 2 (G) +O 2 (G) ↔ 2NO(G) – 180.8 kJ (endothermic - heat absorption)

As the temperature increases, the equilibrium will shift towards the formation reaction NO (→)

3) Influence of pressure (only for gaseous substances) – with increasing pressure, the equilibrium shifts towards the formationI substances occupying less o I eat.

N 2 (G) + 3H 2 (G) ↔ 2N.H. 3 (G)

1 V - N 2

3 V - H 2

2 V – N.H. 3

With increasing pressure ( P): before reaction4 V gaseous substances → after the reaction2 Vgaseous substances, therefore, the equilibrium shifts to the right ( → )

When the pressure increases, for example, by 2 times, the volume of gases decreases by the same amount, and therefore, the concentrations of all gaseous substances will increase by 2 times. Kp = k 1 / k 2 = [ N.H. 3 ] 2 / [ N 2 ][ H 2 ] 3

In this case, the numerator of the expression for K will increase by 4 times, and the denominator is 16 times, i.e. equality will be violated. To restore it, the concentration must increase ammoniaand concentrations decrease nitrogenAndwaterkind. The balance will shift to the right.

So, when the pressure increases, the equilibrium shifts towards a decrease in volume, and when the pressure decreases, towards an increase in volume.

A change in pressure has virtually no effect on the volume of solid and liquid substances, i.e. does not change their concentration. Consequently, the equilibrium of reactions in which gases do not participate is practically independent of pressure.

! The course of a chemical reaction is influenced by substances - catalysts. But when using a catalyst, the activation energy of both the forward and reverse reactions decreases by the same amount and therefore the balance does not shift.

Solve problems:

No. 1. Initial concentrations of CO and O 2 in the reversible reaction

2CO (g) + O 2 (g)↔ 2 CO 2 (g)

Equal to 6 and 4 mol/l, respectively. Calculate the equilibrium constant if the concentration of CO 2 at the moment of equilibrium is 2 mol/l.

No. 2. The reaction proceeds according to the equation

2SO 2 (g) + O 2 (g) = 2SO 3 (g) + Q

Indicate where the equilibrium will shift if

a) increase the pressure

b) increase the temperature

c) increase the oxygen concentration

d) introduction of a catalyst?

The equilibrium state for a reversible reaction can last indefinitely (without outside intervention). But if an external influence is exerted on such a system (change the temperature, pressure or concentration of final or initial substances), then the state of equilibrium will be disrupted. The speed of one of the reactions will become greater than the speed of the other. Over time, the system will again occupy an equilibrium state, but the new equilibrium concentrations of the initial and final substances will differ from the original ones. In this case, they talk about a shift in chemical equilibrium in one direction or another.

If, as a result of an external influence, the rate of the forward reaction becomes greater than the rate of the reverse reaction, this means that the chemical equilibrium has shifted to the right. If, on the contrary, it becomes more speed reverse reaction, this means that the chemical equilibrium has shifted to the left.

When the equilibrium shifts to the right, the equilibrium concentrations of the starting substances decrease and the equilibrium concentrations of the final substances increase compared to the initial equilibrium concentrations. Accordingly, the yield of reaction products also increases.

A shift of chemical equilibrium to the left causes an increase in the equilibrium concentrations of the starting substances and a decrease in the equilibrium concentrations of the final products, the yield of which will decrease.

The direction of the shift in chemical equilibrium is determined using Le Chatelier’s principle: “If an external influence is exerted on a system in a state of chemical equilibrium (change temperature, pressure, concentration of one or more substances participating in the reaction), this will lead to an increase in the rate of that reaction, the occurrence of which will compensate (reduce) the impact."

For example, as the concentration of starting substances increases, the rate of the forward reaction increases and the equilibrium shifts to the right. When the concentration of the starting substances decreases, on the contrary, the rate of the reverse reaction increases, and the chemical equilibrium shifts to the left.

When the temperature increases (i.e. when the system is heated), the equilibrium shifts towards the endothermic reaction, and when it decreases (i.e. when the system cools) - towards the exothermic reaction. (If the forward reaction is exothermic, then the reverse reaction will necessarily be endothermic, and vice versa).

It should be emphasized that an increase in temperature, as a rule, increases the rate of both forward and reverse reactions, but the rate of an endothermic reaction increases to a greater extent than the rate of an exothermic reaction. Accordingly, when the system is cooled, the rates of forward and reverse reactions decrease, but also not to the same extent: for an exothermic reaction it is significantly less than for an endothermic one.

A change in pressure affects the shift in chemical equilibrium only if two conditions are met:

it is necessary that at least one of the substances participating in the reaction be in a gaseous state, for example:

CaCO 3 (s) CaO (s) + CO 2 (g) - a change in pressure affects the displacement of the equilibrium.

CH 3 COOH (liquid) + C 2 H 5 OH (liquid) CH 3 COOC 2 H 5 (liquid) + H 2 O (liquid) – a change in pressure does not affect the shift in chemical equilibrium, because none of the starting or final substances is in a gaseous state;

if several substances are in the gaseous state, it is necessary that the number of gas molecules on the left side of the equation for such a reaction is not equal to the number of gas molecules on the right side of the equation, for example:

2SO 2 (g) + O 2 (g) 2SO 3 (g) – pressure changes affect the equilibrium shift

I 2(g) + H 2(g) 2НI (g) – pressure change does not affect the equilibrium shift

When these two conditions are met, an increase in pressure leads to a shift in equilibrium towards a reaction, the occurrence of which reduces the number of gas molecules in the system. In our example (catalytic combustion of SO 2) this will be a direct reaction.

A decrease in pressure, on the contrary, shifts the equilibrium towards the reaction that occurs with the formation more gas molecules. In our example, this will be the opposite reaction.

An increase in pressure causes a decrease in the volume of the system, and therefore an increase in the molar concentrations of gaseous substances. As a result, the rate of forward and reverse reactions increases, but not to the same extent. A decrease in pressure according to a similar scheme leads to a decrease in the rates of forward and reverse reactions. But at the same time, the reaction rate, towards which the equilibrium shifts, decreases to a lesser extent.

The catalyst does not affect the equilibrium shift, because it speeds up (or slows down) both the forward and reverse reactions to the same extent. In its presence, chemical equilibrium is only established faster (or slower).

If a system is affected by several factors simultaneously, then each of them acts independently of the others. For example, in the synthesis of ammonia

N 2(gas) + 3H 2(gas) 2NH 3(gas)

the reaction is carried out by heating and in the presence of a catalyst to increase its speed. But the effect of temperature leads to the fact that the equilibrium of the reaction shifts to the left, towards the reverse endothermic reaction. This causes a decrease in the output of NH 3. To compensate for this undesirable effect of temperature and increase the yield of ammonia, the pressure in the system is simultaneously increased, which shifts the equilibrium of the reaction to the right, i.e. towards the formation of fewer gas molecules.

In this case, the most optimal conditions for the reaction (temperature, pressure) are selected experimentally, at which it would proceed at a sufficiently high speed and give an economically viable yield of the final product.

Le Chatelier's principle is similarly used in the chemical industry in the production of large number various substances of great importance for the national economy.

Le Chatelier's principle is applicable not only to reversible chemical reactions, but also to various other equilibrium processes: physical, physicochemical, biological.

The adult human body is characterized by the relative constancy of many parameters, including various biochemical indicators, including the concentrations of biologically active substances. However, such a state cannot be called equilibrium, because it is not applicable to open systems.

The human body, like any living system, constantly exchanges various substances with the environment: it consumes food and releases products of their oxidation and decay. Therefore, it is typical for an organism steady state, defined as the constancy of its parameters at a constant rate of exchange of matter and energy with the environment. To a first approximation, a stationary state can be considered as a series of equilibrium states interconnected by relaxation processes. In a state of equilibrium, the concentrations of substances participating in the reaction are maintained due to the replenishment of the initial products from the outside and the removal of the final products to the outside. A change in their content in the body does not lead, unlike closed systems, to a new thermodynamic equilibrium. The system returns to its original state. Thus, the relative dynamic constancy of the composition and properties of the internal environment of the body is maintained, which determines the stability of its physiological functions. This property of a living system is called differently homeostasis.

During the life of an organism in a stationary state, in contrast to a closed equilibrium system, an increase in entropy occurs. However, along with this, the reverse process also occurs simultaneously - a decrease in entropy due to consumption from the environment nutrients with a low entropy value (for example, high-molecular compounds - proteins, polysaccharides, carbohydrates, etc.) and the release of decomposition products into the environment. According to the position of I.R. Prigogine, the total production of entropy for an organism in a stationary state tends to a minimum.

A major contribution to the development of nonequilibrium thermodynamics was made by I. R. Prigozhy, laureate Nobel Prize 1977, who argued that “in any nonequilibrium system there are local areas that are in an equilibrium state. In classical thermodynamics, equilibrium refers to the entire system, but in nonequilibrium, only to its individual parts.”

It has been established that entropy in such systems increases during embryogenesis, during regeneration processes and the growth of malignant neoplasms.

Main article: Le Chatelier-Brown principle

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 the pattern that was expressed in general view in 1885 by the French scientist Le Chatelier.

Factors influencing chemical equilibrium:

1) temperature

As the temperature increases, the chemical equilibrium shifts towards the endothermic (absorption) reaction, and when it decreases, towards the exothermic (release) reaction.

CaCO 3 =CaO+CO 2 -Q t →, t↓ ←

N 2 +3H 2 ↔2NH 3 +Q t ←, t↓ →

2) pressure

As pressure increases, the chemical equilibrium shifts towards a smaller volume of substances, and as pressure decreases towards a larger volume. This principle only applies to gases, i.e. If solids are involved in the reaction, they are not taken into account.

CaCO 3 =CaO+CO 2 P ←, P↓ →

1mol=1mol+1mol

3) concentration of starting substances and reaction products

With an increase in the concentration of one of the starting substances, the chemical equilibrium shifts towards the reaction products, and with an increase in the concentration of the reaction products, towards the starting substances.

S 2 +2O 2 =2SO 2 [S],[O] →, ←

Catalysts do not affect the shift of chemical equilibrium!

Basic quantitative characteristics of chemical equilibrium: chemical equilibrium constant, degree of conversion, degree of dissociation, equilibrium yield. Explain the meaning of these quantities using the example of specific chemical reactions.

In chemical thermodynamics, the law of mass action relates the equilibrium activities of the starting substances and reaction products, according to the relationship:

Activity of substances. Instead of activity, concentration (for a reaction in an ideal solution), partial pressures (a reaction in a mixture of ideal gases), fugacity (a reaction in a mixture of real gases) can be used;

Stoichiometric coefficient (negative for starting substances, positive for products);

Chemical equilibrium constant. The subscript "a" here means the use of the activity value in the formula.

The efficiency of a reaction is usually assessed by calculating the yield of the reaction product (section 5.11). At the same time, the efficiency of the reaction can also be assessed by determining what part of the most important (usually the most expensive) substance was converted into the target reaction product, for example, what part of SO 2 was converted into SO 3 during the production of sulfuric acid, that is, find degree of conversion original substance.

Let a brief diagram of the ongoing reaction

Then the degree of conversion of substance A into substance B (A) is determined by the following equation

Where n proreact (A) – the amount of substance of reagent A that reacted to form product B, and n initial (A) – initial amount of reagent A.

Naturally, the degree of transformation can be expressed not only through the amount of a substance, but also through any quantities proportional to it: the number of molecules (formula units), mass, volume.

If reagent A is taken in short supply and the loss of product B can be neglected, then the degree of conversion of reagent A is usually equal to the yield of product B

The exception is reactions in which the starting substance is obviously consumed to form several products. So, for example, in the reaction

Cl 2 + 2KOH = KCl + KClO + H 2 O

chlorine (reagent) is converted equally into potassium chloride and potassium hypochlorite. In this reaction, even with a 100% yield of KClO, the degree of conversion of chlorine into it is 50%.

The quantity you know - the degree of protolysis (section 12.4) - is a special case of the degree of conversion:

Within the framework of TED, similar quantities are called degree of dissociation acids or bases (also designated as the degree of protolysis). The degree of dissociation is related to the dissociation constant according to Ostwald's dilution law.

Within the framework of the same theory, the hydrolysis equilibrium is characterized by degree of hydrolysis (h), and the following expressions are used that relate it to the initial concentration of the substance ( With) and dissociation constants of weak acids (K HA) and weak bases formed during hydrolysis ( K MOH):

The first expression is valid for the hydrolysis of a salt of a weak acid, the second - salts of a weak base, and the third - salts of a weak acid and a weak base. All these expressions can only be used for dilute solutions with a degree of hydrolysis of no more than 0.05 (5%).

Typically, the equilibrium yield is determined by a known equilibrium constant, with which it is related in each specific case by a certain ratio.

The yield of the product can be changed by shifting the equilibrium of the reaction in reversible processes, under the influence of factors such as temperature, pressure, concentration.

In accordance with Le Chatelier's principle, the equilibrium degree of conversion increases with increasing pressure during simple reactions, and in other cases the volume of the reaction mixture does not change and the yield of the product does not depend on pressure.

The effect of temperature on the equilibrium yield, as well as on the equilibrium constant, is determined by the sign of the thermal effect of the reaction.

For a more complete assessment of reversible processes, the so-called yield from the theoretical (yield from the equilibrium) is used, equal to the ratio of the actually obtained product to the amount that would be obtained in a state of equilibrium.

THERMAL DISSOCIATION chemical

a reaction of reversible decomposition of a substance caused by an increase in temperature.

With Etc., several (2H2H+ OCaO + CO) or one simpler substance are formed from one substance

Equilibrium etc. is established according to the law of mass action. It

can be characterized either by an equilibrium constant or by the degree of dissociation

(the ratio of the number of decayed molecules to the total number of molecules). IN

In most cases, etc. is accompanied by the absorption of heat (increase

enthalpy

DN>0); therefore, in accordance with Le Chatelier-Brown principle

heating enhances it, the degree of displacement etc. with temperature is determined

absolute value of DN. The pressure interferes with etc., the more strongly, the greater

change (increase) in the number of moles (Di) of gaseous substances

the degree of dissociation does not depend on pressure. If solids are not

form solid solutions and are not in a highly dispersed state,

then the pressure etc. is uniquely determined by the temperature. To implement T.

d. solids (oxides, crystalline hydrates, etc.)

It is important to know

temperature at which the dissociation pressure becomes equal to the external one (in particular,

atmospheric) pressure. Since the gas released can overcome

ambient pressure, then upon reaching this temperature the decomposition process

immediately intensifies.

Dependence of the degree of dissociation on temperature: the degree of dissociation increases with increasing temperature (increasing temperature leads to an increase in the kinetic energy of dissolved particles, which promotes the disintegration of molecules into ions)

The degree of conversion of starting substances and the equilibrium yield of the product. Methods for their calculation at a given temperature. What data is needed for this? Give a scheme for calculating any of these quantitative characteristics of chemical equilibrium using an arbitrary example.

The degree of conversion is the amount of reacted reagent divided by its original amount. For the simplest reaction, where is the concentration at the inlet to the reactor or at the beginning of the periodic process, is the concentration at the outlet of the reactor or the current moment of the periodic process. For a voluntary response, for example, , in accordance with the definition, the calculation formula is the same: . If there are several reagents in a reaction, then the degree of conversion can be calculated for each of them, for example, for the reaction The dependence of the degree of conversion on the reaction time is determined by the change in the concentration of the reagent over time. At the initial moment of time, when nothing has transformed, the degree of transformation is zero. Then, as the reagent is converted, the degree of conversion increases. For an irreversible reaction, when nothing prevents the reagent from being completely consumed, its value tends (Fig. 1) to unity (100%). Fig. 1 The greater the rate of consumption of the reagent, determined by the value of the rate constant, the faster the degree of conversion increases, as shown in the figure. If the reaction is reversible, then as the reaction tends to equilibrium, the degree of conversion tends to the equilibrium value, the value of which depends on the ratio of the rate constants of the forward and reverse reactions (on the equilibrium constant) (Fig. 2). Fig. 2 Yield of the target product Yield of the product is the amount of the target product actually obtained, divided by the amount of this product that would have been obtained if all the reagent had passed into this product (to the maximum possible amount of the resulting product). Or (through the reagent): the amount of the reagent actually converted into the target product, divided by the initial amount of the reagent. For the simplest reaction, the yield is , and keeping in mind that for this reaction, , i.e. For the simplest reaction, the yield and the degree of conversion are the same value. If the transformation takes place with a change in the amount of substances, for example, then, in accordance with the definition, the stoichiometric coefficient must be included in the calculated expression. In accordance with the first definition, the imaginary amount of product obtained from the entire initial amount of the reagent will be for this reaction two times less than the initial amount of the reagent, i.e. , and the calculation formula. In accordance with the second definition, the amount of the reagent actually transferred into the target product will be twice as large as this product was formed, i.e. , then the calculation formula is . Naturally, both expressions are the same. For a more complex reaction, the calculation formulas are written in exactly the same way in accordance with the definition, but in this case the yield is no longer equal to the degree of conversion. For example, for the reaction, . If there are several reagents in a reaction, the yield can be calculated for each of them; if there are also several target products, then the yield can be calculated for any target product for any reagent. As can be seen from the structure of the calculation formula (the denominator contains a constant value), the dependence of the yield on the reaction time is determined by the time dependence of the concentration of the target product. So, for example, for the reaction this dependence looks like in Fig. 3. Fig.3

The degree of conversion as a quantitative characteristic of chemical equilibrium. How will an increase in total pressure and temperature affect the degree of conversion of the reagent ... in a gas-phase reaction: ( the equation is given)? Give reasons for your answer and appropriate mathematical expressions.