The state of equilibrium for a reversible reaction can last for an indefinitely long time (without outside intervention). But if an external influence is applied to such a system (to change the temperature, pressure or concentration of the final or initial substances), then the state of equilibrium will be disturbed. The rate of one of the reactions will become greater than the rate of the other. Over time, the system will again take an equilibrium state, but the new equilibrium concentrations of the initial and final substances will differ from the initial ones. In this case, one speaks of a shift in the 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, then this means that the chemical equilibrium has shifted to the right. If, on the contrary, the rate of the reverse reaction becomes greater, this means that the chemical equilibrium has shifted to the left.
When the equilibrium shifts to the right, the equilibrium concentrations of the initial substances decrease and the equilibrium concentrations of the final substances increase in comparison with the initial equilibrium concentrations. Accordingly, the yield of reaction products also increases.
The shift of the chemical equilibrium to the left causes an increase in the equilibrium concentrations of the starting substances and a decrease in the equilibrium concentrations final products, the output of which will then decrease.
The direction of the chemical equilibrium shift is determined using the Le Chatelier principle: “If an external effect is exerted on a system that is in a state of chemical equilibrium (change the temperature, pressure, concentration of one or more substances participating in the reaction), then this will lead to an increase in the rate of that reaction, the course of which will compensate (reduce) the impact.
For example, with an increase in the concentration of the starting substances, the rate of the direct reaction increases and the equilibrium shifts to the right. With a decrease in the concentration of the starting substances, on the contrary, the rate of the reverse reaction increases, and the chemical equilibrium shifts to the left.
With an increase in temperature (i.e., when the system is heated), the equilibrium shifts towards the occurrence of an endothermic reaction, and when it decreases (i.e., when the system is cooled), it shifts towards the occurrence of an 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 the forward and reverse reactions, but the rate of the endothermic reaction increases to a greater extent than the rate of the 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 much 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 (t) CaO (t) + CO 2 (g) - a change in pressure affects the displacement of equilibrium.
CH 3 COOH (l.) + C 2 H 5 OH (l.) CH 3 COOS 2 H 5 (l.) + H 2 O (l.) - a change in pressure does not affect the shift in chemical equilibrium, because none of the starting or end 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 change affects the equilibrium shift
I 2 (g) + Н 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 the equilibrium towards the reaction, the course 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 in the direction of the reaction proceeding with the formation more gas molecules. In our example, this will be the reverse reaction.
An increase in pressure causes a decrease in the volume of the system, and hence 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. Lowering the same pressure in a similar way 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 equally. In its presence, the chemical equilibrium is only more quickly (or more slowly) established.
If the system is affected by several factors at the same time, 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 with heating and in the presence of a catalyst to increase its rate. But at the same time, the effect of temperature leads to the fact that the reaction equilibrium is shifted to the left, towards the reverse endothermic reaction. This causes a decrease in the output of NH 3 . In order to compensate for this undesirable effect of temperature and increase the ammonia yield, at the same time the pressure in the system is increased, which shifts the reaction equilibrium to the right, i.e. towards the formation of a smaller number of gas molecules.
At the same time, the most optimal conditions for the reaction (temperature, pressure) are selected empirically, under which it would proceed at a sufficiently high rate 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 a large number of different 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 body of an adult is characterized by the relative constancy of many parameters, including various biochemical indicators, including the concentration of biologically active substances. However, such a state cannot be called equilibrium, because it does not apply to open systems.
The human body, like any living system, constantly exchanges various substances with the environment: it consumes food and releases the products of their oxidation and decay. Therefore, the body is characterized steady state, defined as the constancy of its parameters at a constant rate of exchange of matter and energy with the environment. In the first approximation, the 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 by replenishing the initial products from the outside and removing the final products to the outside. Changing their content in the body does not lead, in contrast to 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.
In the course of the life of an organism in a stationary state, in contrast to a closed equilibrium system, there is an increase in entropy. However, along with this, the reverse process simultaneously proceeds - a decrease in entropy due to the consumption of nutrients with a low entropy value from the environment (for example, high-molecular compounds - proteins, polysaccharides, carbohydrates, etc.) and the release of decay products into the environment. According to the position of I.R. Prigozhin, the total production of entropy for an organism in a stationary state tends to a minimum.
A great contribution to the development of nonequilibrium thermodynamics was made by I. R. Prigozhy, laureate Nobel Prize 1977, who stated that “in any non-equilibrium system, there are local areas that are in an equilibrium state. In classical thermodynamics, equilibrium refers to the whole system, and in non-equilibrium - only to its individual parts.
It has been established that entropy in such systems increases during the period of embryogenesis, during the processes of regeneration and the growth of malignant neoplasms.
Chemical equilibrium is maintained as long as the conditions in which the system is located remain unchanged. Changing conditions (concentration of substances, temperature, pressure) causes an imbalance. After some time, the chemical equilibrium is restored, but in new, different from the previous conditions. Such a transition of a system from one equilibrium state to another is called displacement(shift) of balance. The direction of displacement is subject to Le Chatelier's principle.
With an increase in the concentration of one of the starting substances, the equilibrium shifts towards a greater consumption of this substance, and the direct reaction increases. A decrease in the concentration of the starting substances shifts the equilibrium in the direction of the formation of these substances, since the reverse reaction is enhanced. An increase in temperature shifts the equilibrium towards an endothermic reaction, while a decrease in temperature shifts it towards an exothermic reaction. An increase in pressure shifts the equilibrium in the direction of decreasing quantities gaseous substances, that is, in the direction of smaller volumes occupied by these gases. On the contrary, with a decrease in pressure, the equilibrium shifts in the direction of increasing amounts of gaseous substances, that is, in the direction of large volumes formed by gases.
EXAMPLE 1.
How will an increase in pressure affect the equilibrium state of the following reversible gas reactions:
a) SO 2 + C1 2 \u003d SO 2 CI 2;
b) H 2 + Br 2 \u003d 2HBr.
Solution:
We use the Le Chatelier principle, according to which the increase in pressure in the first case (a) shifts the equilibrium to the right, towards a smaller amount of gaseous substances occupying a smaller volume, which weakens the external effect of the increased pressure. In the second reaction (b), the amount of gaseous substances, both the initial and the reaction products, are equal, as are the volumes occupied by them, so the pressure has no effect and the equilibrium is not disturbed.
EXAMPLE 2.
In the reaction of ammonia synthesis (–Q) 3Н 2 + N 2 = 2NH 3 + Q, the direct reaction is exothermic, the reverse is endothermic. How should the concentration of reactants, temperature and pressure be changed to increase the yield of ammonia?
Solution:
To shift the equilibrium to the right, it is necessary:
a) increase the concentration of H 2 and N 2;
b) lower the concentration (removal from the reaction sphere) of NH 3 ;
c) lower the temperature;
d) increase the pressure.
EXAMPLE 3.
The homogeneous reaction of the interaction of hydrogen chloride and oxygen is reversible:
4HC1 + O 2 \u003d 2C1 2 + 2H 2 O + 116 kJ.
1. What effect will the equilibrium of the system have:
a) increase in pressure;
b) temperature increase;
c) the introduction of a catalyst?
Solution:
a) In accordance with Le Chatelier's principle, an increase in pressure leads to a shift in equilibrium towards a direct reaction.
b) An increase in t° leads to a shift in the equilibrium in the direction of the reverse reaction.
c) The introduction of a catalyst does not shift the equilibrium.
2. In what direction will the chemical equilibrium shift if the concentration of reactants is doubled?
Solution:
υ → = k → 0 2 0 2 ; υ 0 ← = k ← 0 2 0 2
After increasing the concentrations, the rate of the forward reaction became:
υ → = k → 4 = 32 k → 0 4 0
that is, it increased by 32 times compared to the initial speed. Similarly, the rate of the reverse reaction increases 16 times:
υ ← = k ← 2 2 = 16k ← [Н 2 O] 0 2 [С1 2 ] 0 2 .
The increase in the rate of the forward reaction is 2 times higher than the increase in the rate of the reverse reaction: the equilibrium shifts to the right.
EXAMPLE 4
AT which direction will the equilibrium of a homogeneous reaction shift:
PCl 5 \u003d PC1 3 + Cl 2 + 92 KJ,
if the temperature is increased by 30 °C, knowing that the temperature coefficient of the forward reaction is 2.5, and the reverse reaction is 3.2?
Solution:
Since the temperature coefficients of the forward and reverse reactions are not equal, an increase in temperature will have a different effect on the change in the rates of these reactions. Using the van't Hoff rule (1.3), we find the rates of forward and reverse reactions when the temperature rises by 30 °C:
υ → (t 2) = υ → (t 1)=υ → (t 1)2.5 0.1 30 = 15.6υ → (t 1);
υ ← (t 2) = υ ← (t 1) = υ → (t 1)3.2 0.1 30 = 32.8υ ← (t 1)
An increase in temperature increased the rate of the forward reaction by 15.6 times, and the reverse reaction by 32.8 times. Consequently, the equilibrium will shift to the left, towards the formation of PCl 5 .
EXAMPLE 5.
How will the rates of forward and reverse reactions change in an isolated system C 2 H 4 + H 2 ⇄ C 2 H 6 and where will the equilibrium shift when the volume of the system increases by 3 times?
Solution:
The initial rates of the forward and reverse reactions are as follows:
υ 0 = k 0 0; υ 0 = k 0 .
An increase in the volume of the system causes a decrease in the concentrations of reactants by 3 times, hence the change in the rate of forward and reverse reactions will be as follows:
υ 0 = k = 1/9υ 0
υ = k = 1/3υ 0
The decrease in the rates of forward and reverse reactions is not the same: the rate of the reverse reaction is 3 times (1/3: 1/9 = 3) higher than the rate of the reverse reaction, so the equilibrium will shift to the left, to the side where the system occupies a larger volume, that is, towards the formation of C 2 H 4 and H 2 .
Equilibrium is usually understood as a special state of a system or body, when all the influences exerted on it compensate each other. Or absent altogether. In chemistry, the concept of equilibrium is applied to reactions occurring between different substances, or rather, to the conditions for their occurrence.
The concept of balance
Chemical reactions have many classifications according to various criteria, but speaking of chemical equilibrium, what are reversible and irreversible reactions should be remembered.
If, as a result of a reaction, products are formed that do not interact with each other, they speak of irreversible reactions, that is, they only go in the forward direction. Usually, one of the products in them is a gaseous, slightly dissociating or insoluble compound. For example:
Pb(NO 3) 2 + 2ΗCl<―>PbCl 2 ↓ + 2HNO 3
Na 2 CO 3 + 2ΗCl<―>2NaCl + CO 2 + Η 2 O
NaOΗ + ΗCl<―>NaCl + Η 2 O
The products of reversible reactions are able to interact with each other, thus forming the starting substances, that is, two oppositely directed reactions occur simultaneously. If at some point in time, under certain conditions, the rate of the forward reaction will be equal to the rate of the reverse, then chemical equilibrium is established.
It should be mentioned that such an equilibrium is characterized as dynamic. In other words, both reactions continue, but the values of the concentrations of all its participants remain unchanged and are called equilibrium.
Mathematically, this state is expressed using the equilibrium constant (Kp). Let there be an interaction of substances described by the equation аΑ + bB<―>cc + dD. For opposite reactions, one can write formulas for calculating their velocities through the law of acting masses. Since these rates will be equal in the state of equilibrium, it is possible to express the ratio of the rate constants of two opposite reactions. Here it will be numerically equal to the equilibrium constant.
The value of K p helps to determine the completeness of the ongoing reactions. If K r<1, то реакция в прямом направлении почти не протекает. Если К р >1, then the equilibrium is shifted to products.
Types of balance
Chemical equilibrium is true, apparent and false. For true balance there are signs:
- If there is no external influence, then it is unchanged in time.
- If external influences change (this applies to temperature, pressure, etc.), then the state of the system also changes. But one has only to return the initial values of the conditions, the balance is immediately restored.
- The state of true equilibrium can be achieved both from the side of products chemical reaction, as well as from the starting materials.
If at least one of these conditions is not met, then such an equilibrium is said to be apparent (metastable). If the state of the system begins to change irreversibly when changing external conditions, then this equilibrium is called false (or inhibited). An example of the latter is the reaction of iron with oxygen.
The concept of equilibrium is somewhat different in terms of thermodynamics and kinetics. Under thermodynamic equilibrium is understood as the minimum value of the Gibbs energy for a particular system. True equilibrium is characterized by ΔG \u003d 0. And about the state for which the rates of direct and reverse reactions are equalized, that is, v 1 \u003d v 2, they say that such an equilibrium is - kinetic.
Le Chatelier's principle
Henri Le Chatelier studied the patterns of equilibrium shift in the 19th century, but later Karl Brown summarized all these works and formulated the principle of moving equilibrium:
if an equilibrium system is acted upon from the outside, then the equilibrium will shift in the direction of reducing the effect produced
In other words, if there is any impact on the equilibrium system, it tends to change in such a way that this impact is minimal.
Equilibrium shift
Consider the consequences of the Le Chatelier principle using the reaction equation as an example:
N 2 + 3H 2<―>2NΗ 3 + Q.
If the temperature is increased, the equilibrium will shift towards an endothermic reaction. AT this example heat is released, which means that the direct reaction is exothermic, and the equilibrium will shift to the starting substances.
If the pressure is increased, this will lead to a shift in equilibrium to smaller volumes of gaseous substances. In the above example, there are 4 moles of gaseous starting materials and 2 moles of gaseous products, which means that the equilibrium will shift to the reaction products.
If the concentration of the starting substance is increased, then the equilibrium will shift in the direction of the direct reaction and vice versa. Thus, if the concentration of N 2 or Η 2 is increased, then the equilibrium will shift in the forward direction, and if ammonia, then in the opposite direction.
The chemical equilibrium corresponding to the equality of the rates of direct and reverse reactions ( = ) and the minimum value of the Gibbs energy (∆ G р,т = 0) is the most stable state of the system under given conditions and remains unchanged as long as the parameters are kept constant, at which balance has been established.
When conditions change, the equilibrium is disturbed and shifted in the direction of a direct or reverse reaction. The shift in equilibrium is due to the fact that the external influence to a different extent changes the speed of two mutually opposite processes. After some time, the system again becomes equilibrium, i.e. it moves from one equilibrium state to another. The new equilibrium is characterized by a new equality of the rates of forward and reverse reactions and new equilibrium concentrations of all substances in the system.
The direction of equilibrium shift in the general case is determined by the Le Chatelier principle: if an external influence is exerted on a system in a state of stable equilibrium, then the equilibrium shift occurs in the direction of a process that weakens the effect of external influence.
A shift in equilibrium can be caused by a change in temperature, concentration (pressure) of one of the reagents.
Temperature is the parameter on which the value of the equilibrium constant of a chemical reaction depends. The issue of shifting the equilibrium with a change in temperature, depending on the conditions for using the reaction, is solved by using the isobar equation (1.90) - =
1. For an isothermal process ∆ r H 0 (t)< 0, в правой части выражения (1.90) R >0, T > 0, hence the first derivative of the logarithm of the equilibrium constant with respect to temperature is negative< 0, т.е. ln Kp (и сама константа Кр) являются убывающими функциями температуры. При увеличении температуры константа химического равновесия (Кр) уменьшается и что согласно закону действующих масс (2.27), (2.28)соответствует смещению химического равновесия в сторону обратной (эндотермической) реакции. Именно в этом проявляется противодействие системы оказанному воздействию.
2. For an endothermic process ∆ r H 0 (t) > 0, the derivative of the logarithm of the equilibrium constant with respect to temperature is positive (> 0), the theme is ln Kp and Kp are increasing functions of temperature, i.e. in accordance with the law of mass action, with increasing temperature, the equilibrium shifts towards a straight line (endothermic reaction). However, it must be remembered that the rate of both isothermal and endothermic processes increases with increasing temperature, and decreases with decreasing, but the change in rates is not the same with a change in temperature, therefore, by varying the temperature, it is possible to shift the equilibrium in a given direction. A shift in equilibrium can be caused by a change in the concentration of one of the components: the addition of a substance to the equilibrium system or the removal from the system.
According to the Le Chatelier principle, when the concentration of one of the participants in the reaction changes, the equilibrium shifts towards the compensating change, i.e. with an increase in the concentration of one of the starting substances - in right side, and as the concentration increases, one of the reaction products moves to the left. If gaseous substances participate in a reversible reaction, then when the pressure changes, all their concentrations change equally and simultaneously. The rates of processes also change, and, consequently, a shift in chemical equilibrium can also occur. So, for example, with an increase in pressure (compared to the equilibrium one) on the CaCO 3 (K) CO (c) + CO 2 (g) system, the rate of the reverse reaction increases \u003d which will lead to a shift in equilibrium in left side. When the pressure on the same system decreases, the rate of the reverse reaction decreases, and the equilibrium shifts to the right side. With an increase in pressure on the 2HCl H 2 +Cl 2 system, which is in equilibrium, the equilibrium will not shift, because both speeds and will increase equally.
For the 4HCl + O 2 2Cl 2 + 2H 2 O (g) system, an increase in pressure will increase the rate of the direct reaction and shift the equilibrium to the right.
And so, in accordance with the principle of Le Chatelier, with increasing pressure, the equilibrium shifts towards the formation of a smaller number of moles of gaseous substances in the gas mixture and, accordingly, towards a decrease in pressure in the system.
And vice versa, under an external influence that causes a decrease in pressure, the equilibrium shifts towards the formation more moles of gaseous substances, which will cause an increase in pressure in the system and will counteract the effect produced.
Le Chatelier's principle has a great practical value. On its basis, it is possible to choose such conditions for the implementation of chemical interaction that will ensure the maximum yield of reaction products.
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, allowing to carry out processes that previously seemed impossible, to 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 action 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 a French researcher states 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 changes, temperature conditions and pressure. Technologies based on the findings of scientists are used in industry. Many chemical processes, which were considered practically impracticable, are carried out thanks to 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
Change in pressure - important factor for reacting mixtures, including 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
Creating conditions for shifting the balance largely determines the development of modern chemical technologies. Practical use scientific theory contributes to 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.