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Energy of chemical reactions. Energy in the chemical industry

The entire history of the development of civilization is the search for energy sources. This is still very relevant today. After all, energy is an opportunity for further development of industry, obtaining sustainable harvests, improving cities and helping nature heal the wounds inflicted on it by civilization. Therefore, solving the energy problem requires global efforts. Chemistry makes its considerable contribution as a link between modern natural science and modern technology.

Energy supply is the most important condition for the socio-economic development of any country, its industry, transport, agriculture, cultural and everyday life.

But in the next decade, energy workers will not yet discount wood, coal, oil, or gas. And at the same time, they must intensively develop new ways of producing energy.

The chemical industry is characterized by close ties with all sectors of the national economy due to the wide range of products it produces. This area of production is characterized by high material intensity. Material and energy costs in production can range from 2/3 to 4/5 of the cost of the final product.

The development of chemical technology follows the path of integrated use of raw materials and energy, the use of continuous and waste-free processes, taking into account the environmental safety of the environment, the use of high pressures and temperatures, and advances in automation and cybernetization.

The chemical industry consumes especially a lot of energy. Energy is spent on endothermic processes, transporting materials, crushing and grinding solids, filtering, compressing gases, etc. Significant energy expenditures are required in the production of calcium carbide, phosphorus, ammonia, polyethylene, isoprene, styrene, etc. Chemical production, together with petrochemical production, are energy-intensive areas of the industry. Producing almost 7% of industrial products, they consume between 13-20% of the energy used by the entire industry.

Energy sources are most often traditional non-renewable natural resources - coal, oil, natural gas, peat, shale. Lately they have been depleting very quickly. Oil and natural gas reserves are decreasing at a particularly accelerated pace, but they are limited and irreparable. Not surprisingly, this creates an energy problem.

Over the course of 80 years, some main sources of energy were replaced by others: wood was replaced by coal, coal by oil, oil by gas, hydrocarbon fuel by nuclear fuel. By the beginning of the 80s, about 70% of the world's energy demand was met by oil and natural gas, 25% by coal and brown coal, and only about 5% by other energy sources.

In different countries, the energy problem is solved differently, however, chemistry makes a significant contribution to its solution everywhere. Thus, chemists believe that in the future (about another 25-30 years) oil will retain its leading position. But its contribution to energy resources will noticeably decrease and will be compensated by the increased use of coal, gas, hydrogen energy from nuclear fuel, solar energy, energy from the earth’s depths and other types of renewable energy, including bioenergy.

Already today, chemists are concerned about the maximum and comprehensive energy-technological use of fuel resources - reducing heat losses to the environment, recycling heat, maximizing the use of local fuel resources, etc.

Since among the types of fuel the most scarce is liquid, many countries have allocated large funds to create a cost-effective technology for processing coal into liquid (as well as gaseous) fuel. Scientists from Russia and Germany are collaborating in this area. The essence of the modern process of processing coal into synthesis gas is as follows. A mixture of water vapor and oxygen is supplied to the plasma generator, which is heated to 3000°C. And then coal dust enters the hot gas torch, and as a result of a chemical reaction a mixture of carbon monoxide (II) and hydrogen is formed, i.e. synthesis gas. Methanol is obtained from it: CO+2H2CH3OH. Methanol can replace gasoline in internal combustion engines. In terms of solving environmental problems, it compares favorably with oil, gas, and coal, but, unfortunately, its heat of combustion is 2 times lower than that of gasoline, and, in addition, it is aggressive towards some metals and plastics.

Chemical methods have been developed for the removal of binder oil (contains high molecular weight hydrocarbons), a significant part of which remains in underground pits. To increase the yield of oil, surfactants are added to the water that is injected into the formations; their molecules are placed at the oil-water interface, which increases the mobility of the oil.

Future replenishment of fuel resources is combined with sustainable coal processing. For example, crushed coal is mixed with oil, and the extracted paste is exposed to hydrogen under pressure. This produces a mixture of hydrocarbons. To produce 1 ton of artificial gasoline, about 1 ton of coal and 1,500 m of hydrogen are spent. So far, artificial gasoline is more expensive than that produced from oil, however, the fundamental possibility of its extraction is important.

Hydrogen energy, which is based on the combustion of hydrogen, during which no harmful emissions are generated, seems very promising. However, for its development it is necessary to solve a number of problems related to reducing the cost of hydrogen, creating reliable means of storing and transporting it, etc. If these problems are solvable, hydrogen will be widely used in aviation, water and land transport, industrial and agricultural production.

Nuclear energy contains inexhaustible possibilities; its development for the production of electricity and heat makes it possible to release a significant amount of fossil fuel. Here, chemists are faced with the task of creating complex technological systems for covering the energy costs that occur during endothermic reactions using nuclear energy. Now nuclear energy is developing along the path of widespread introduction of fast neutron reactors. Such reactors use uranium enriched in the 235U isotope (by at least 20%), and do not require a neutron moderator.

Currently, nuclear energy and reactor building is a powerful industry with a large amount of capital investment. For many countries it is an important export item. Reactors and auxiliary equipment require special materials, including high frequencies. The task of chemists, metallurgists and other specialists is to create such materials. Chemists and representatives of other related professions are also working on uranium enrichment.

Nowadays, nuclear energy is faced with the task of displacing fossil fuels not only from the sphere of electricity production, but also from heat supply and, to some extent, from the metallurgical and chemical industries by creating reactors of energy technological significance.

Nuclear power plants will find another application in the future - for the production of hydrogen. Part of the hydrogen produced will be consumed by the chemical industry, the other part will be used to power gas turbine units switched on at peak loads.

For the manufacture of solar cells, the main semiconductor material is silicon and silicon compounds. Chemists are now working on developing new materials that convert energy. These can be different systems of salts as energy storage devices. Further successes of solar energy depend on the materials that chemists offer for energy conversion.

In the new millennium, an increase in electricity production will occur due to the development of solar energy, as well as methane fermentation of household waste and other non-traditional sources of energy production.

Along with giant power plants, there are also autonomous chemical current sources that convert the energy of chemical reactions directly into electrical energy. Chemistry plays a major role in resolving this issue. In 1780, the Italian doctor L. Galvani, observing the contraction of the cut off leg of a frog after touching it with wires of different metals, decided that there was electricity in the muscles, and called it “animal electricity.” A. Volta, continuing the experience of his compatriot, suggested that the source of electricity is not the animal’s body: the electric current arises from the contact of different metal wires. The “ancestor” of modern galvanic cells can be considered the “electric pole” created by A. Volta in 1800. This invention looks like a layer cake made of several pairs of metal plates: one plate is made of zinc, the second is made of copper, stacked on top of each other, and between They are placed with a felt pad soaked in dilute sulfuric acid. Before its invention in Germany by W. Siemens in 1867. Galvanic dynamos were the only source of electric current. Nowadays, when aviation, the submarine fleet, rocketry, and electronics need autonomous energy sources, the attention of scientists is again drawn to them.

Essay

The role of chemistry in solving energy problems

Introduction

1. The origins of modern chemistry and its problems in the 21st century

chemistry society energy

The end of the Middle Ages was marked by a gradual retreat from the occult, a decline in interest in alchemy and the spread of a mechanistic view of the structure of nature.

Iatrochemistry.

Paracelsus held completely different views on the goals of alchemy. The Swiss physician Philip von Hohenheim went down in history under this name, chosen by him. Paracelsus, like Avicenna, believed that the main task of alchemy was not the search for ways to obtain gold, but the production of medicines. He borrowed from the alchemical tradition the doctrine that there are three main parts of matter - mercury, sulfur, salt, which correspond to the properties of volatility, flammability and hardness. These three elements form the basis of the macrocosm and are associated with the microcosm formed by spirit, soul and body. Moving on to determining the causes of diseases, Paracelsus argued that fever and plague occur from an excess of sulfur in the body, with an excess of mercury paralysis occurs, etc. The principle that all iatrochemists adhered to was that medicine is a matter of chemistry, and everything depends on the ability of the doctor to isolate pure principles from impure substances. Within this scheme, all body functions were reduced to chemical processes, and the alchemist's task was to find and prepare chemical substances for medical purposes.

The main representatives of the iatrochemical direction were Jan Helmont, a doctor by profession; Francis Sylvius, who enjoyed great fame as a physician and eliminated “spiritual” principles from iatrochemical teaching; Andreas Libavi, doctor from Rothenburg.

Their research greatly contributed to the formation of chemistry as an independent science.

Mechanistic philosophy.

With the decrease in the influence of iatrochemistry, natural philosophers again turned to the teachings of the ancients about nature. To the fore in the 17th century. atomistic views emerged. One of the most prominent scientists - the authors of the corpuscular theory - was the philosopher and mathematician Rene Descartes. He outlined his views in 1637 in the essay Discourse on Method. Descartes believed that all bodies “consist of numerous small particles of various shapes and sizes, which do not fit each other so exactly that there are no gaps around them; these gaps are not empty, but filled with... rarefied matter.” Descartes did not consider his “little particles” to be atoms, i.e. indivisible; he stood on the point of view of the infinite divisibility of matter and denied the existence of emptiness.

One of Descartes' most prominent opponents was the French physicist and philosopher Pierre Gassendi.

Gassendi's atomism was essentially a retelling of the teachings of Epicurus, however, unlike the latter, Gassendi recognized the creation of atoms by God; he believed that God created a certain number of indivisible and impenetrable atoms, of which all bodies are composed; There must be absolute emptiness between the atoms.

In the development of chemistry in the 17th century. a special role belongs to the Irish scientist Robert Boyle. Boyle did not accept the statements of ancient philosophers who believed that the elements of the universe could be established speculatively; this is reflected in the title of his book, The Skeptical Chemist. Being a supporter of the experimental approach to determining chemical elements, he did not know about the existence of real elements, although he almost discovered one of them - phosphorus - himself. Boyle is usually credited with introducing the term "analysis" into chemistry. In his experiments on qualitative analysis, he used various indicators and introduced the concept of chemical affinity. Based on the works of Galileo Galilei Evangelista Torricelli, as well as Otto Guericke, who demonstrated the “Magdeburg hemispheres” in 1654, Boyle described the air pump he designed and experiments to determine the elasticity of air using a U-shaped tube. As a result of these experiments, the well-known law of inverse proportionality between air volume and pressure was formulated. In 1668, Boyle became an active member of the newly organized Royal Society of London, and in 1680 he was elected its president.

Biochemistry. This scientific discipline, which studies the chemical properties of biological substances, was first one of the branches of organic chemistry. It became an independent region in the last decade of the 19th century. as a result of studies of the chemical properties of substances of plant and animal origin. One of the first biochemists was the German scientist Emil Fischer. He synthesized substances such as caffeine, phenobarbital, glucose, and many hydrocarbons, and made a great contribution to the science of enzymes - protein catalysts, first isolated in 1878. The formation of biochemistry as a science was facilitated by the creation of new analytical methods.

In 1923, Swedish chemist Theodor Svedberg designed an ultracentrifuge and developed a sedimentation method for determining the molecular weight of macromolecules, mainly proteins. Svedberg's assistant Arne Tiselius in the same year created the method of electrophoresis - a more advanced method for separating giant molecules, based on the difference in the speed of migration of charged molecules in an electric field. At the beginning of the 20th century. Russian chemist Mikhail Semenovich Tsvet described a method for separating plant pigments by passing their mixture through a tube filled with an adsorbent. The method was called chromatography.

In 1944, English chemists Archer Martini Richard Singh proposed a new version of the method: they replaced the tube with the adsorbent with filter paper. This is how paper chromatography appeared - one of the most common analytical methods in chemistry, biology and medicine, with the help of which in the late 1940s - early 1950s it was possible to analyze mixtures of amino acids resulting from the breakdown of different proteins and determine the composition of proteins. As a result of painstaking research, the order of amino acids in the insulin molecule was established, and by 1964 this protein was synthesized. Nowadays, many hormones, medicines, and vitamins are obtained using biochemical synthesis methods.

Quantum chemistry. In order to explain the stability of the atom, Niels Bohr combined classical and quantum concepts of electron motion in his model. However, the artificiality of such a connection was obvious from the very beginning. The development of quantum theory led to a change in classical ideas about the structure of matter, motion, causality, space, time, etc., which contributed to a radical transformation of the picture of the world.

In the late 20s - early 30s of the 20th century, fundamentally new ideas about the structure of the atom and the nature of chemical bonds were formed on the basis of quantum theory.

After Albert Einstein created the photon theory of light (1905) and his derivation of the statistical laws of electronic transitions in the atom (1917), the wave-particle problem became more acute in physics.

If in the 18th-19th centuries there were discrepancies between various scientists who used either the wave or corpuscular theory to explain the same phenomena in optics, now the contradiction has become fundamental: some phenomena were interpreted from a wave position, and others from a corpuscular one. A solution to this contradiction was proposed in 1924 by the French physicist Louis Victor Pierre Raymond de Broglie, who attributed wave properties to the particle.

Based on de Broglie's idea of matter waves, the German physicist Erwin Schrödinger in 1926 derived the basic equation of the so-called. wave mechanics, containing the wave function and allowing one to determine the possible states of a quantum system and their change in time. Schrödinger gave a general rule for converting classical equations into wave equations. Within the framework of wave mechanics, an atom could be represented as a nucleus surrounded by a stationary wave of matter. The wave function determined the probability density of finding an electron at a given point.

In the same 1926, another German physicist Werner Heisenberg developed his own version of the quantum theory of the atom in the form of matrix mechanics, starting from the correspondence principle formulated by Bohr.

According to the correspondence principle, the laws of quantum physics should transform into classical laws when the quantum discreteness tends to zero as the quantum number increases. More generally, the principle of correspondence can be formulated as follows: a new theory that claims a wider range of applicability than the old one must include the latter as a special case. Heisenberg's quantum mechanics made it possible to explain the existence of stationary quantized energy states and to calculate the energy levels of various systems.

Friedrich Hund, Robert Sanderson Mulliken and John Edward Lennard-Jones in 1929 create the foundations of the molecular orbital method. The basis of MMO is the idea of the complete loss of individuality of atoms united into a molecule. The molecule, therefore, does not consist of atoms, but is a new system formed by several atomic nuclei and electrons moving in their field. Hund also created a modern classification of chemical bonds; in 1931 he came to the conclusion that there are two main types of chemical bonds - simple, or ?-communications, and ?-communications. Erich Hückel extended the MO method to organic compounds, formulating in 1931 the rule of aromatic stability (4n+2), which establishes whether a substance belongs to the aromatic series.

Thus, in quantum chemistry, two different approaches to understanding chemical bonds are immediately distinguished: the method of molecular orbitals and the method of valence bonds.

Thanks to quantum mechanics, by the 30s of the 20th century, the method of forming bonds between atoms had been largely clarified. In addition, within the framework of the quantum mechanical approach, Mendeleev’s doctrine of periodicity received a correct physical interpretation.

Probably the most important stage in the development of modern chemistry was the creation of various research centers that, in addition to fundamental research, also carried out applied research.

At the beginning of the 20th century. a number of industrial corporations created the first industrial research laboratories. The DuPont chemical laboratory and the Bell laboratory were founded in the USA. After the discovery and synthesis of penicillin in the 1940s, and then other antibiotics, large pharmaceutical companies emerged, staffed by professional chemists. Work in the field of chemistry of macromolecular compounds was of great practical importance.

One of its founders was the German chemist Hermann Staudinger, who developed the theory of the structure of polymers. Intensive searches for methods for producing linear polymers led in 1953 to the synthesis of polyethylene, and then other polymers with desired properties. Today, polymer production is the largest branch of the chemical industry.

Not all advances in chemistry have been beneficial to humans. In the production of paints, soap, and textiles, hydrochloric acid and sulfur were used, which posed a great danger to the environment. In the 21st century The production of many organic and inorganic materials will increase due to the recycling of used substances, as well as through the processing of chemical wastes that pose a risk to human health and the environment.

2. The role of chemistry in solving energy problems

Energy supply is the most important condition for the socio-economic development of any country, its industry, transport, agriculture, cultural and everyday life.

But in the next decade, energy workers will not yet discount wood, coal, oil, or gas. And at the same time, they must intensively develop new ways of producing energy.

The chemical industry consumes especially a lot of energy. Energy is spent on endothermic processes, transporting materials, crushing and grinding solids, filtering, compressing gases, etc. The production of calcium carbide, phosphorus, ammonia, polyethylene, isoprene, styrene, etc. requires significant energy expenditure. Chemical production, together with petrochemical production, are energy-intensive areas of the industry. Producing almost 7% of industrial products, they consume between 13-20% of the energy used by the entire industry.

Since among the types of fuel the most scarce is liquid, many countries have allocated large funds to create a cost-effective technology for processing coal into liquid (as well as gaseous) fuel. Scientists from Russia and Germany are collaborating in this area. The essence of the modern process of processing coal into synthesis gas is as follows. A mixture of water vapor and oxygen is supplied to the plasma generator, which is heated to 3000°C. And then coal dust enters the hot gas torch, and as a result of a chemical reaction a mixture of carbon monoxide (II) and hydrogen is formed, i.e. synthesis gas. Methanol is obtained from it: CO+2H2?СH3OH. Methanol can replace gasoline in internal combustion engines. In terms of solving environmental problems, it compares favorably with oil, gas, and coal, but, unfortunately, its heat of combustion is 2 times lower than that of gasoline, and, in addition, it is aggressive towards some metals and plastics.

Hydrogen energy, which is based on the combustion of hydrogen, during which no harmful emissions are generated, seems very promising. However, for its development, it is necessary to solve a number of problems related to reducing the cost of hydrogen, creating reliable means of storing and transporting it, etc. If these problems are solvable, hydrogen will be widely used in aviation, water and land transport, industrial and agricultural production.

Great hopes are placed on the use of solar radiation (solar energy). In Crimea, there are solar panels whose photovoltaic cells convert sunlight into electricity. Solar thermal units, which convert solar energy into heat, are widely used for desalination of water and heating homes. Solar panels have long been used in navigation structures and on spacecraft. IN
Unlike nuclear energy, the cost of energy produced using solar panels is constantly decreasing. For the manufacture of solar cells, the main semiconductor material is silicon and silicon compounds. Chemists are now working on developing new materials that convert energy. These can be different systems of salts as energy storage devices. Further successes of solar energy depend on the materials that chemists offer for energy conversion.

Along with giant power plants, there are also autonomous chemical current sources that convert the energy of chemical reactions directly into electrical energy. Chemistry plays a major role in resolving this issue. In 1780, the Italian doctor L. Galvani, observing the contraction of the cut off leg of a frog after touching it with wires of different metals, decided that there was electricity in the muscles, and called it “animal electricity.” A. Volta, continuing the experience of his compatriot, suggested that the source of electricity is not the animal’s body: the electric current arises from the contact of different metal wires. The “ancestor” of modern galvanic cells can be considered the “electric pole” created by A. Volta in 1800. This invention looks like a layer cake made of several pairs of metal plates: one plate is made of zinc, the second is made of copper, stacked on top of each other, and between They are placed with a felt pad soaked in dilute sulfuric acid. Before the invention of dynamos in Germany by W. Siemens in 1867, galvanic cells were the only source of electric current. Nowadays, when aviation, the submarine fleet, rocketry, and electronics need autonomous energy sources, the attention of scientists is again drawn to them.

Conclusion

The use of nuclear energy makes it possible to abandon natural coal and oil. As a result, emissions of combustion products are reduced, which could possibly lead to a “greenhouse effect” on Earth. It would seem that an insignificantly small (compared to coal and oil) amount of fuel for nuclear power plants should be safe, but this is far from the case; a striking example is the accident at the Chernobyl nuclear power plant. In my opinion, any method of extracting energy (in any form) from the bowels of the Earth is a combination of positive and negative features, and it seems to me that the non-positive ones predominate.

I did not talk about all the directions of solving the energy problem by scientists around the world, but only about the main ones. In each country it has its own characteristics: socio-economic and geographical conditions, provision of natural resources, level of development of science and technology.

indicating the topic right now to find out about the possibility of obtaining a consultation.

Ministry of Education of the Republic of Belarus

Ministry of Education of the Russian Federation

STATE INSTITUTION OF HIGHER

PROFESSIONAL EDUCATION

BELARUSIAN-RUSSIAN UNIVERSITY

Department of Metal Technologies

Energy of chemical processes.

CHEMICAL AFFINANCY

Guidelines for independent work of students and practical classes in chemistry

Mogilev 2003

UDC 54 Compiled by: dr. tech. sciences, prof. Lovshenko F.G.,

Ph.D. tech. Sciences, Associate Professor Lovshenko G.F.

Energy of chemical processes. Chemical affinity. Methodological instructions for independent work of students and conducting practical classes in chemistry. - Mogilev: Belarusian-Russian University, 2003. - 28 p.

The guidelines provide the basic principles of thermodynamics. Examples of solving typical problems are presented. The conditions for tasks for independent work are given.

Approved by the Department of Metal Technologies of the Belarusian-Russian University (minutes of meeting No. 1 dated September 1, 2003).

Reviewer Art. Rev. Patsey V.F.

Responsible for the release is Lovshenko G.F.

ENERGY OF CHEMICAL PROCESSES. CHEMICAL AFFINANCY

Signed for printing Format 60x84 1/16. Offset paper. Screen printing

Conditional oven l. Uch. from. L. Circulation 215 copies. Order No. _______

Publisher and printing:

State institution of higher professional education

"Belarusian-Russian University"

License LV No.

212005, Mogilev, Mira Ave., 43

Republic

Energy of chemical processes

Chemical thermodynamics studies the transitions of chemical energy into other forms - thermal, electrical, etc., establishes the quantitative laws of these transitions, as well as the direction and limits of the spontaneous occurrence of chemical reactions under given conditions.

The object of study in thermodynamics is a system.

System is called a collection of people in mutualaction of substances, mentally(oractually) separate fromenvironment.

Phase - Thispart of a system that is homogeneous in composition and properties at all pointsand separated from other parts of the system by an interface.

Distinguish homogeneous And heterogeneous systems. Homogeneous systems consist of one phase, heterogeneous systems consist of two or more phases.

The same system can be in different states. Each state of the system is characterized by a certain set of values of thermodynamic parameters. Thermodynamic parameters include temperature, pressure, raftspeed, concentration, etc.. A change in at least one thermodynamic parameter leads to a change in the state of the system as a whole. Thermodynamic state of the nasal systemvayutequilibrium , if it is characterized by constant termodynamic parameters at all points of the system and without changingoccurs spontaneously (without the cost of work). In chemical thermodynamics, the properties of a system are considered in its equilibrium states.

Depending on the conditions for the transition of a system from one state to another, thermodynamics distinguishes between isothermal, isobaric, isochoric and adiabatic processes. The first ones occur at a constant temperature ( T= const), the second – at constant pressure (p = const), others - at constant volume (V= const), fourth – in conditions of absence of heat exchange between the system and the environment ( q = 0).

Chemical reactions often occur under isobaric-isothermal conditions ( p= const, T= const). Such conditions are met when interactions between substances are carried out in open vessels without heating or at a higher but constant temperature.

Internal energy of the system.

When a system transitions from one state to another, some of its properties change, in particular internal energy U.

Internal energy systems represents withfight her full energy, which consists of kineticand potential energies of molecules, atoms, atomic nuclei, electronsRonov and others. Internal energy includes the energy of translational, rotational and vibrational motions, as well as potential energy due to the forces of attraction and repulsion acting between molecules, atoms and intra-atomic particles. It does not include the potential energy of the system’s position in space and the kinetic energy of the system’s motion as a whole.

The absolute internal energy of a system cannot be determined, but its change can be measured  U during the transition from one state to another. Magnitude  U is considered positive (  U>0), if in any process the internal energy of the system increases.

Internal energy is thermodynamicfunktion state systems. This means that whenever the system finds itself in a given state, its internal energy takes on a certain value inherent in this state. Consequently, the change in internal energy does not depend on the path and method of transition of the system from one state to another and is determined by the difference in the values of the internal energy of the system in these two states:

U = U 2 -U 1 , (1)

Where U 1 And U 2 – internal energy of the system in the final and initial states, respectively.

Complied with in any process law of energy conservation , expressed by equality

q = U+A, (2)

which means that heat q, supplied to the system is spent on increasing its internal energy  U and for the system to perform work A above the external environment. Equation (2) – mathematical expression first law of thermodynamics .

From the first law of thermodynamics it follows that the increase in the internal energy of the system  U in any process is equal to the amount of heat imparted to the system q minus the amount of perfect system work A; since the quantities q And A can be directly measured, using equation (2) you can always calculate the value  U .

In the first law of thermodynamics, work A means the sum of all types of work against the forces acting on the system from the external environment. This amount may include work against the forces of an external electric field, and work against the forces of a gravitational field, and work of expansion against external pressure forces, and other types of work.

Due to the fact that the work of expansion is most characteristic of chemical interactions, it is usually separated from the total:

A = A’ + p V, (p =const), (3)

Where A' - all types of work, except expansion work;

R - external pressure;

V– change in the volume of the system equal to the difference V 2 – V 1 (V 2 – volume of reaction products, a V 1 – volume of starting materials).

If, during the course of a particular process, the work of expansion is the only type of work, equation (3) takes the form

A = p V, (4)

Then the mathematical expression of the first law of thermodynamics (2) will be written as follows:

q p =  U+R V, (5)

Where q p– heat supplied to the system at constant pressure.

Considering that  U = U 2 – U 1 And  V = V 2 – V 1 , equation (5) can be transformed by grouping the values U And V by indices related to the final and initial states of the system:

q p = (U 2 -U t ) + p(V 2 -V t ) = (U 2 +pV 2 ) - (U 1 +pV 1 ). (6)

Amount (U + pV) are calledenthalpy (heat content) of the system and denoteletterH :

H=U + pV.(7)

Substituting the enthalpy H into equation (6), we obtain

q p = N 2 – N 1 =  N, (8)

i.e. heat supplied to the system at constant pressure,is spent on increasing the enthalpy of the system.

Just as for internal energy, the absolute value of the enthalpy of the system cannot be determined experimentally, but it is possible by measuring the value q p , find the enthalpy change  N when a system transitions from one state to another. Size  N considered positive (  N>0) if the enthalpy of the system increases. Because the value  N is determined by the difference ( N 2 – N 1 ) and does not depend on the path and method of carrying out the process, enthalpy, like internal energy, is referred to thermodynamic functions of the system state.

Thermal effects of chemical reactions.

Algebraic summu of the heat absorbed during the reaction and the work done minus the work against external pressure forces (R V) namesvayutthermal effect of a chemical reaction .

Thermochemical laws. Independence of the heat of a chemical reaction from the process path at p= const and T= const was established in the first half of the 19th century. Russian scientist G.I. Hess: the thermal effect of a chemical reaction does not depend on its pathflow, but depends only on the nature and physical conditionstarting materials and reaction products (Hess's law ).

The branch of chemical thermodynamics that studies thermalthe effects of chemical reactions are calledthermochemistry . Thermochemistry uses a simplified idea of the thermal effect of a chemical reaction, which meets the conditions for its independence from the process path. It's warmth q T , supplied to the system during the reaction (or released as a result of the reaction) at a constant temperature.

If heat is supplied to the system ( q T> 0), the reaction is called endothermic, if heat is released into the environment ( q T < 0), реакцию называют экзотермической.

Thermochemistry, first of all, studies isobaric-isothermal reactions, as a result of which only expansion work is performed  V. The thermal effect of such reactions q p , T equal to the change in enthalpy of the system  H.

Equations of chemical reactions, which indicate their heathigh effects are calledthermochemical equations . Since the state of the system as a whole depends on the aggregate states of substances, in thermochemical equations the states of substances (crystalline, liquid, dissolved and gaseous) are indicated using letter indices (k), (g), (p) or (d). The allotropic modification of the substance is also indicated if several such modifications exist. If the state of aggregation of a substance or its modification under given conditions is obvious, letter indices may be omitted. So, for example, at atmospheric pressure and room temperature, hydrogen and oxygen are gaseous (this is obvious), and the reaction product H 2 O formed during their interaction can be liquid and gaseous (water vapor). Therefore, the thermochemical reaction equation must indicate the aggregate state of H 2 O:

H 2 + ½O 2 = H 2 O (l) or H 2 + ½O 2 = H 2 O (g).

Currently, it is customary to indicate the thermal effect of a reaction in the form of a change in enthalpy  H, equal to the heat of the isobaric-isothermal process q p , T . Often the enthalpy change is written as  H or  H . Superscript 0 means the standard value of the thermal effect of the reaction, and the lower one means the temperature at which the interaction occurs. Below are examples of thermochemical equations for several reactions:

2C 6 H 6 (l) + 15O 2 = 12CO 2 + 6H 2 O (l),  H = -6535.4 kJ, (a)

2C (graphite) + H 2 = C 2 H 2,  H = 226.7 kJ, (b)

N 2 + 3H 2 = 2NH 3 (g),  H = -92.4 kJ. (V)

In reactions (a) and (c), the enthalpy of the system decreases (  H <0). Эти реакции экзотермические. В реакции (б) энтальпия увеличивается ( H >0); the reaction is endothermic. In all three examples the value  H refers to the number of moles of substances determined by the reaction equation. In order for the thermal effect of a reaction to be expressed in kilojoules per mole (kJ/mol) of one of the starting substances or reaction products, fractional coefficients are allowed in thermochemical equations:

C 6 H 6(g) + 7 O 2 = 6CO 2 + 3H 2 O (l),  H = -3267.7 kJ,

N2+ =NH 3 (g),  H = -46.2 kJ.

Enthalpy of formation of chemical compounds.

Enthalpy (heat) of formation chemical compound N T calledchange in enthalpy in the process of obtaining one mole of this compoundof simple substances that are stable at a given temperature.

Standard enthalpy (warmth) obra calling chemical compound N , arr. call changeenthalpy in the process of formation of one mole of this compound,being in the standard state (T = 298 K and = 101.3 kPa), from simple substances,phases and modifications also in standard states and thermodynamically stable at a given temperature(Table A.1).

The standard enthalpies of formation of simple substances aretoil as equalszero , if their states of aggregation and modificationcation is stable under standard conditions. For example, the standard heat of formation of liquid bromine (not gaseous) and graphite (not diamond) are equal to zero.

Standard enthalpythe formation of a compound is its measurethermodynamic stability,strength, quantitative expressionthe energy properties of the compoundopinions.

Thermochemical calculations. Most thermochemical calculations are based on corollary of Hess's law : thermal effectThe effect of a chemical reaction is equal to the sum of the heats (enthalpies) of the reactionformation of reaction products minus the sum of heats (enthalpii) formation of starting substances, taking into account their stoichiometric coefficients in the reaction equation.

N h.r. =   N arr. (cont. district) -  N arr. (ref. in.) (9)

Equation (9) allows you to determine both the thermal effect of the reaction from the known enthalpies of formation of the substances participating in the reaction, and one of the enthalpies of formation if the thermal effect of the reaction and all other enthalpies of formation are known.

The thermal effect of a chemical reaction is the energy effect of a process occurring at a constant temperature. Using reference data that relates to 298 K, it is possible to calculate the thermal effects of reactions occurring at this temperature. However, when performing thermochemical calculations, usually allowing for a slight error, you can use standard values of the heat of formation even when the process conditions differ from the standard ones.

Thermal effects of phase transformations. Phase transformations often accompany chemical reactions. However, the thermal effects of phase transformations are usually less than the thermal effects of chemical reactions. Below are examples of thermochemical equations for some phase transformations:

H 2 O (l)  H 2 O (g),  H = 44.0 kJ/mol,

H 2 O (k)  H 2 O (l),  H = 6.0 kJ/mol,

I 2(k)  I 2(g) ,  H = 62.24 kJ/mol.

Based on the above data, it can be noted that a phase transition from a more to a less condensed state leads to an increase in the enthalpy of the system (heat is absorbed - the process is endothermic).

T
AND
G

The transition of a substance from an amorphous state to a crystalline state is always accompanied by the release of heat (  H <0) – процесс экзотермический:

Sb (amorphous)  Sb (k) ,  H = -10.62 kJ/mol,

B 2 O 3 (amorphous)  B 2 O 3 (k),  H = -25.08 kJ/mol.

Spontaneous and non-spontaneous processes. Many processes are carried out spontaneously, that is, without the expenditure of external work. As a result, work can be obtained against external forces, proportional to the change in the energy of the system that has occurred. Thus, water spontaneously flows down an inclined chute or heat is transferred from a more heated body to a less heated one. During a spontaneous process, the system loses its ability to produce useful work.

A spontaneous process cannot proceed in the opposite direction as spontaneously as in the forward direction.. Thus, water cannot flow up an inclined chute on its own, and heat cannot on its own move from a cold body to a hot one. To pump water upward or transfer heat from the cold part of the system to the hot part, it is necessary to perform work on the system. For processes that are reverse to spontaneous ones, the term “ non-spontaneous».

When studying chemical interactions, it is very important to assess the possibility or impossibility of their spontaneous occurrence under given conditions, to find out chemical typequantity of substances. There must be a criterion with the help of which it would be possible to establish the fundamental feasibility, direction and limits of the spontaneous course of the reaction at certain temperatures and pressures. The first law of thermodynamics does not provide such a criterion. The thermal effect of a reaction does not determine the direction of the process: both exothermic and endothermic reactions can occur spontaneously.

The criterion for the spontaneous occurrence of a process in isolationbathroom systems givessecond law of thermodynamics . Before moving on to consider this law, let us introduce an idea of the thermodynamic function of the state of the system, called entropy.

Entropy. To characterize the state of a certain amount of a substance, which is a collection of a very large number of molecules, you can either indicate the temperature, pressure and other thermodynamic parameters of the state of the system, or indicate the instantaneous coordinates of each molecule ( x i , y i , z i) and speed of movement in all three directions (v xi , v yi , v zi ). In the first case, the macrostate of the system is characterized, in the second, the microstate. Each macrostate is associated with a huge number of microstates. The number of microstates with the help of which a given macrostate is realized is called termoddynamic probability of the system state and denote W.

The thermodynamic probability of the state of a system consisting of only 10 gas molecules is approximately 1000, but only 1 cm 3 of gas contains 2.710 19 molecules (n.s.). To move on to numbers that are more convenient for perception and calculations, in thermodynamics they use not the quantity W, and its logarithm lnW. The latter can be given the dimension (J/K) by multiplying by the Boltzmann constant k:

klnW = S. (10)

Size S called entropy systems.

Entropy is a thermodynamic function of the state of a system and its value depends on the amount of the substance in question. Therefore, it is advisable to relate the entropy value to one mole of a substance (J/(molK)) and express it as

RlnW = S. (11)

Where R = kN A – molar gas constant;

N A– Avogadro’s constant.

From equation (11) it follows that the entropy of the system increases in proportion to the logarithm of the thermodynamic probability of the state W. This relationship underlies modern statistical thermodynamics.

At p =const entropy is a function of temperature T, Moreover, the freezing point and boiling point are those points at which entropy changes especially sharply, abruptly.

So, entropy Sis a measure of the disorder of the system. The “carriers” of entropy are gases. If the number of moles of gaseous substances increases during a reaction, then the entropy also increases. Those. Without making calculations, you can, if necessary, determine the sign of the change in the entropy of the system:

C (k) + O 2 (g) = CO 2 (g), S  0;

2C (k) + O 2 (g) = 2СО (g), S > 0;

N 2(g) + 3H 2(g) = 2NH 3(g) , S< 0.

Table A.1 shows the values S some substances (note that the absolute values of the entropy of substances are known, while the absolute values of the function U And H not known).

Because entropy is a function of the state of the system, then entropy change ( S) in a chemical reaction is equal to the sum of the entropies of the reaction products minus the sum of the entropies of the starting substancestaking into account their stoichiometric coefficients in the reaction equation.

S h.r. =  S arr. (cont. district) - S arr. (ref. in.) (12)

Direction and limit of processes in isolatedsystems. Second law of thermodynamics. Isolated systems do not exchange heat or work with the external environment. Based on equation (9), it can be argued that when q = 0 And A = 0 magnitude  U is also zero, i.e. the internal energy of an isolated system is constant (U= const); its volume is also constant (V = const). In isolated systemsOnly those processes that are accompanied byincrease in the entropy of the system: S>0 ; in this case, the limit for the spontaneous course of the process is to achieve the maximum entropy S max for the given conditions.

The considered provision represents one of the formulations second law of thermodynamics (the law is statistical in nature, i.e. it is applicable only to systems consisting of a very large number of particles). The requirement of constancy of the internal energy and volume of the system excludes the use of entropy as a criterion for the direction and limit of the occurrence of chemical reactions, in which the internal energy of substances inevitably changes, and also the work of expansion is performed against external pressure.

Entropy and enthalpy factors of chemical reactions,occurring under isobaric-isothermal conditions. The driving force of a process occurring under isobaric-isothermal conditions can be either the desire of the system to transition to a state with the lowest energy, i.e., release heat into the environment, reduce enthalpy ( H<0), or the desire of the system to transition to a state with the highest thermodynamic probability, i.e., to increase entropy ( S>0). If the process proceeds in such a way that  H=0 , then the growth of entropy becomes its only driving force. And, conversely, provided  S = 0 the only driving force of the process is the loss of enthalpy. In this regard, we can talk about enthalpy  H and entropy T S process factors.

Maximum work. The Dutch physical chemist Van't Hoff proposed a new theory of chemical affinity, which, without explaining the nature of chemical affinity, is limited to indicating the method of its measurement, i.e., it gives a quantitative assessment of chemical affinity.

Van't Hoff uses maximum work as a measure of chemical affinity A or A for reactions occurring at V, T= const or p, T = const accordingly.

The maximum work is equal to the energy that must be applied to the system to stop the reaction, that is, to overcome the forces of chemical affinity. Since the reaction proceeds in the direction of doing positive maximum work, the sign A or A determines the direction of the spontaneous flow of chemical interaction.

Maximum work at constant volume is

A = -  U+T S(13)

A = -(U 2 -U 1 ) + T(S 2 – S 1 ) = -[(U 2 – T.S. 2 ) – (U 1 – T.S. 1 )] (14)

where U 1, S 1 and U 2, S 2 are the values of the internal energy and entropy of the system in the initial and final states, respectively.

Difference (U - T.S.) called Helmholtz energy systems and are designated by the letter F. Thus,

A = -  F. (15)

Purpose of the work: Familiarization with the technology of water preparation for nuclear power plants using the ion exchange method and comparison of water quality: for the technological needs of nuclear power plants, drinking and lake water. Familiarization with the technology of water preparation for nuclear power plants using the ion exchange method and comparison of water quality: for the technological needs of nuclear power plants, drinking and lake water.

Objectives of the work Objectives of the work: to study the requirements for water used for technological needs at a modern nuclear power plant using the example of the Kalinin NPP. study the requirements for water used for technological needs at a modern nuclear power plant using the example of the Kalinin NPP. get acquainted with the theory of the ion exchange method, get acquainted with the theory of the ion exchange method, visit the water intake station of Udomlya and become familiar with the chemical composition of drinking water and lake water. visit the water intake station of Udomlya and get acquainted with the chemical composition of drinking water and lake water. compare the indicators of chemical analysis of drinking water and water of the second circuit of a nuclear power plant. compare the indicators of chemical analysis of drinking water and water of the second circuit of a nuclear power plant.

Objectives of the work Objectives of the work: visit the chemical shop of the Kalinin NPP and get acquainted: visit the chemical shop of the Kalinin NPP and get acquainted with: the process of water preparation at chemical water treatment; with the process of water purification at a block desalting plant; visit the express laboratory of the second circuit; visit the express laboratory of the second circuit; get acquainted theoretically with the work of special water treatment. get acquainted theoretically with the work of special water treatment. draw conclusions about the importance of ion exchange in water preparation. draw conclusions about the importance of ion exchange in water preparation.

NPP equipment is subject to strict requirements for safety, reliability and operating efficiency. NPP equipment is subject to strict requirements for safety, reliability and operating efficiency. The water chemistry regime of a nuclear power plant must be organized so that corrosion and other impacts on equipment and pipelines of nuclear power plant systems do not lead to violation of the limits and conditions of its safe operation. The water chemistry regime of a nuclear power plant must be organized so that corrosion and other impacts on equipment and pipelines of nuclear power plant systems do not lead to violation of the limits and conditions of its safe operation. Relevance

Comparative characteristics of drinking water and water from the 2nd circuit of a nuclear power plant Indicator Unit of measurement Drinking water MPC Water from the 2nd circuit Control values Femg/l0.0945.00.005

Schematic diagram of the desalting part of chemical water treatment (ionization) To make up BSN FSD 14 OH II BCHOV OH I 10 H I H II 78 Pre-purified (clarified) water

100% of condensate is passed through electromagnetic filters; through mixed-action filters it is possible to pass both 100% of water and part of it. So, with one working mixed filter (purification of 20% condensate), the specific electrical conductivity decreased: χ = 0.23 µS/cm - before the block desalting plant and χ = 0.21 µS/cm - after the block desalting plant.

A power unit with VVER-1000 type reactors has four closed circuits for collecting and processing wastewater: organized leaks and primary circuit purge water; boron concentrate; steam generator purge water; drain water and special laundry water. These installations include: mechanical filters, H-cation and OH-anion filters.

Conclusion All drainage from pre-treatment and chemical water treatment equipment is collected in an underground drainage water tank. After neutralization, the water is supplied to the filter block of the deep burial site. The settled water is pumped into wells to a depth of about 1.5 km. Thus, the commissioning of a deep disposal site eliminates the possibility of discharging industrial non-radioactive wastewater into the environment.

Conclusion Water preparation using the ion exchange method allows you to achieve the required values necessary for safe, reliable and economical operation of the equipment. However, this is a rather expensive process: the cost of 1 m 3 of drinking water is 6.19 rubles, and the cost of 1 m 3 of chemically desalted water is 20.4 rubles. (2007 data) - why closed water circulation cycles are used.

Currently, it is difficult to overestimate the development of various branches of the chemical industry, as well as the achievements of chemical science. The chemicalization of the national economy is integral to technical progress and is closely related to it. There are more than 7,000 scientific journals around the world that publish new scientific materials on chemistry. On average, more than 100,000 articles are published per year. The improvement of chemical production facilities producing a wide variety of products has led to the accelerated development of the chemical industry over the past 30-40 years. Over the past 70 years, new industries have been created: in particular, synthetic rubber, chemical fibers and plastics, mineral fertilizers, plant protection products, vitamins, antibiotics, etc. Many polymers and rubber are widely used in the manufacture of various machine parts. Oil, coal, natural gas, water, wood, etc. are the most important sources of raw materials for the chemical industry.

Chemicalization of the national economy is one of the areas of technical progress that contributes to the intensification and accelerated development of industry and agriculture. There is not a single industry that does not use oil and natural gas products. The production capacity of petrochemical and chemical industries has increased many times. In addition, many new technological processes have emerged designed for large-scale production, and the rapid growth of polymers has stimulated the accelerated development of petrochemistry, which, along with energy, metallurgy and mechanical engineering, ensures technical progress in many industries.

A special feature of the chemical industry is the production of a wide range of diverse products. Only by processing benzene can one obtain hexachlorane, chlorobenzene, benzenesulfonyl chloride, nitrobenzene, phenol, etc. Modern chemistry is distinguished by a variety of synthesis routes. There are from 20 to 80 theoretical schemes per technological scheme. At the same time, all existing technological process schemes are constantly being improved. At the same time, technological methods are constantly being developed to protect the environment from pollution by industrial chemical emissions. A big role in this is played by the creation and implementation of waste-free technology for obtaining raw materials, semi-finished products and finished products. Keeping the environment clean is a big social problem related to maintaining people's health. At the same time, it is combined with an important economic task - the recycling and return to production of valuable products, raw materials, materials and water. It is necessary to create processes, equipment, technological schemes that would prevent environmental pollution. Technology changes should follow the path of reducing the amount of emissions and waste, reducing the cost of purifying gases and water circulating in production systems, and becoming enterprises for the integrated use of raw materials that operate without waste. To create waste-free industrial production on a nationwide scale, scientific and technical foundations are needed for planning and designing regional territorial-industrial complexes, in which waste from some enterprises could serve as raw materials for others. The introduction of such complexes requires the restructuring of connections between enterprises and sectors of the national economy, at great expense. On the basis of existing scientific and practical developments, it is already possible today to create regional production and economic systems with a high level of closure when using material resources.

Chemical processes can be easily automated and optimized. Therefore, in the near future, automated process control systems, computers for conducting experiments, automation and rationalization of information retrieval will become commonplace.

Chemical processes require less cost than other processes and are highly productive. Syntheses of chemicals using high-voltage magnetic fields are not currently carried out under production conditions. These syntheses, like electrosyntheses, require further study. Already today, tests are being carried out on some reduction reactions, oxidation of hydrocarbons, production of organometallic compounds with the participation of the electrode metal, anodic fluorination, production of propylene oxide dimethyl sebacate for production; plastics and artificial fibers, electrochemical initiation of polymerization, etc.

The last of these processes are of great interest for the possible protection of metals from corrosion, since polymer compounds can be applied to the surface of metals.

Chemistry plays an extremely important role in the creation of synthetic food products. Some of them can already be obtained today in laboratory conditions. Revealing the secrets of the chemical form of the movement of matter will contribute to the development of the chemical industry.

The most important aspect of the problem of interaction between energy and the environment in new conditions is the ever-increasing reverse influence - the determining role of environmental conditions in solving practical energy problems (choosing the type of energy installations, location of enterprises, choosing unit capacities of energy equipment, etc.).

Thus, at the present stage, the problem of interaction between energy and the environment is very multifaceted, is at the forefront of scientific and technical thought and requires special attention. A large number of heterogeneous studies to determine the individual impacts of energy facilities on rivers, on air purity in cities, on vegetation, etc. are carried out by hydrologists, climatologists, geographers, geologists, biologists, etc. Although a significant number of studies on individual issues could not give a general description state of the problem, the accumulation of a volume of materials contributed to the preparation of a qualitatively new stage in the approach to its consideration.

Modern energy industry consists of large associations with a high concentration of energy production, centralization of its distribution, wide possibilities for the interchangeability of energy resources and developed internal and external connections. These features give energy the characteristics of large systems, for the study of which, at the current level of knowledge, system analysis is productively used. Energy development has an impact on various components of the natural environment: the atmosphere (oxygen consumption, emissions of gases, vapors and solid particles), the hydrosphere (water consumption, wastewater transfer, the creation of new reservoirs, discharges of polluted and heated waters, liquid waste) and the lithosphere (consumption of fossil fuels, changes in water balance, changes in landscape, emissions of solid, liquid and gaseous toxic substances on the surface and into the depths). Currently, this impact is becoming global, affecting all structural components of our planet. The variety of structures, properties and phenomena, existing as a single whole with developed internal and external connections, allows us to characterize the environment as a complex large system. From a human point of view, the main goal of this large system is to ensure equilibrium, or close to it, functioning.

It is obvious that the tasks of developing energy and maintaining the equilibrium natural functioning of the natural environment involve an objective contradiction. The interaction of energy with the environment occurs at all stages of the hierarchy of the fuel and energy complex: production, processing, transportation, transformation and use of energy. This interaction is due to both the methods of extraction, processing and transportation of resources associated with the impact on the structure and landscape of the lithosphere, the consumption and pollution of waters of seas, rivers, lakes, changes in the balance of groundwater, the release of heat, solid, liquid and gaseous substances into all environments, and and the use of electrical and thermal energy from general networks and autonomous sources. The current stage of the problem of interaction between energy and the environment should be considered as the result of the complex historical development of these interacting large systems. At the same time, there are fundamental differences in their development: fundamental changes in the natural environment occur on a geological time scale, and changes in the scale of energy development occur in historically short periods of time.

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