The perception of cause-and-effect relationships underlies our models of the world. Effective analysis, research and modeling of any kind involves defining reasons observed phenomena. Causes are the basic elements responsible for the occurrence and existence of a particular phenomenon or situation. For example, successful problem solving is based on finding and working through the cause (or causes) of a particular symptom or set of symptoms of that problem. Having determined the cause of a particular desired or problematic state, you also determine the point of application of your efforts.

For example, if you believe that your allergy is caused by an external allergen, you try to avoid that allergen. Believing that the allergy is caused by a release of histamine, you begin taking antihistamines. If, in your opinion, the allergy is caused by stress, you will try to reduce this stress.

Our beliefs about cause and effect are reflected in a pattern of language that explicitly or implicitly describes the cause-and-effect relationship between two experiences or phenomena. As with complex equivalents, at the deep structure level such relationships can be precise or imprecise. For example, from the statement

"Criticism will make him respect the rules" It is not clear how exactly a critical remark can force the person in question develops respect for certain rules. Such criticism can just as easily have the opposite effect. This statement leaves out too many potentially significant links in the logical chain.

Of course, this does not mean that all claims about cause-and-effect relationships are unfounded. Some of them are quite reasonable, but not completed. Others make sense only under certain conditions. In fact, statements about cause-and-effect relationships are a form of indefinite verbs. The main danger is that such statements are overly simplified and or superficial.

But most phenomena arise from multiple causes rather than just one, since complex systems (such as the human nervous system) consist of many two-way cause-and-effect relationships.

In addition, elements of the cause-and-effect chain may have individual “additional energy.” That is, each of them is endowed with its own source of energy, and its reaction cannot be predicted. Due to this, the system becomes much more complex, since energy cannot spread through it automatically.

As Gregory Bateson pointed out, if you kick a ball, you can pretty accurately determine in advance where it will go by calculating the angle of impact, the amount of force applied to the ball, the friction of the surface, etc. If you kick a dog, at the same angle , with the same force, on the same surface, etc. - it is much more difficult to guess how the matter will end” since the dog has its own “additional energy”.

Often the causes are less obvious, broader and more systematic in nature than the phenomenon or symptom being studied. In particular, the reason for a decline in production or profits may be due to competition, management problems, leadership issues, changes in marketing strategies, changes in technology, communication channels, or something else.

The same is true for many of our beliefs about objective reality. We cannot see, hear or feel the interaction of molecular particles, gravitational or electromagnetic fields. We can only perceive and measure their manifestations. To explain such effects, we introduce the concept of “gravity”.

Concepts such as “gravity”, “electromagnetic field”, “atoms”, “cause-and-effect relationships”, “energy”, even “time” and “space” are largely arbitrarily created by our imagination (and not by the world around us) in order to to classify and organize our sensory experiences. Albert Einstein wrote:

Hume clearly saw that some concepts (for example, causality) cannot be logically deduced from the data of experience... All concepts, even those closest to our experience, from the point of view of logic are arbitrarily chosen conventions.

The meaning of Einstein's statement is that our senses cannot really perceive anything like "causes", they perceive only the fact that the first event happened first, and then the second. For example, the sequence of events can be perceived as follows:

“a man chops down a tree with an axe,” then “the tree falls,” or “a woman says something to a child,” then “a child begins to cry,” or “a solar eclipse occurs, and the next day an earthquake.”

According to Einstein, we can say that “a man caused a tree to fall,” “a woman caused a child to cry,” “a solar eclipse caused an earthquake.” However, we only perceive subsequence events, but not reason , which is an arbitrarily selected internal construct applied to a perceived relationship. With the same success we can say that

"The force of gravity caused the tree to fall"

“the reason that the child cried was his disappointed expectations” or

“The earthquake was caused by forces acting on the earth’s surface from within,”

– depending on the selected coordinate system.

According to Einstein, the fundamental laws of this world that we take into account when acting in it are not observable within the framework of our experience. In the words of Einstein, “a theory can be tested by experiment, but it is impossible to create a theory from experience.”

This dilemma applies equally to psychology, neuroscience, and probably every other field of scientific inquiry. The closer we get to the real primary relationships and laws that define and govern our experience, the further we move away from everything that is subject to direct perception. We can physically feel not the fundamental laws and principles that govern our behavior and our perception, but only their consequences. If the brain tries to perceive itself, the only and inevitable result will be blank spots.

Types of reasons

The ancient Greek philosopher Aristotle, in his work “Second Analytics,” identified four main types of causes that must be taken into account in any study and any analytical process:

1) “preceding”, “compelling” or “motivating” reasons;

2) “holding” or “driving” reasons;

3) “ultimate” causes;

4) “formal” reasons.

1. Reasons- these are events, actions or decisions related to the past that influence the present state of the system through the “action-reaction” chain.

2. Holding reasons- These are the present-day relationships, assumptions and limiting conditions that support the current state of the system (regardless of how it came to this state).

3. Final causes- these are future-related tasks or goals that guide and determine the current state of the system, giving actions meaning, importance or meaning (Fig. 26).

4. Formal reasons– these are basic definitions and images of something, i.e. basic assumptions and mental maps.

Looking for motivating reasons we consider a problem or its solution as a result of certain events and experiences of the past. Search holding reasons leads us to perceive a problem or its solution as a product of conditions corresponding to the current situation. Thinking about ultimate causes , we perceive a problem as a result of the motives and intentions of the people involved. Trying to find formal reasons problem, we view it as a function of those definitions and assumptions that apply to a given situation.

Of course, any of these reasons alone does not provide a complete explanation of the situation. In modern science it is customary to rely mainly on mechanical reasons , or preceding, motivating, according to Aristotle's classification. When considering a phenomenon from a scientific point of view, we tend to look for linear cause-and-effect chains that led to its occurrence. For example, we say: “The universe was created as a result of the “big bang”", which happened billions of years ago", or " AIDS is caused by a virus that enters the body and attacks the immune system.”, or “This organization succeeds because it took some action at some point.” Of course, these explanations are extremely important and useful, but they do not necessarily reveal all the details of the phenomena mentioned.

Establishment holding reasons will require an answer to the question: what preserves the integrity of the structure of a phenomenon, regardless of how it arose? For example, why do many people infected with HIV have no symptoms of the disease? If the Universe began expanding after the Big Bang, what determines the rate at which it is expanding now? What factors can stop the process of its expansion? The presence or absence of what factors can lead to an unexpected loss of profit or the complete collapse of an organization, regardless of the history of its creation?

Search final causes will require research into potential problems or outcomes of certain phenomena. For example

measures, is AIDS a punishment for humanity, an important lesson, or part of the evolutionary process? Is the universe just God's plaything, or does it have a definite future? What goals and perspectives bring to the organization; success?

Definition formal reasons for the Universe, a successful organization, or AIDS will require an examination of basic assumptions and intuitions about these phenomena. What exactly do we mean when we talk about “the Universe”, “success”, “organization”, “AIDS”? What assumptions do we make about their structure and nature? (Questions like these helped Albert Einstein in new ways formulate our perception of time, space and the structure of the Universe.)

Influence of formal reasons

In many ways, language, beliefs, and models of the world act as the “formal causes” of our reality. Formal causes are concerned with the basic definitions of certain phenomena or experiences. The concept of cause itself is a type of “formal cause.”

As the term implies, formal reasons are more associated with the form than with the content of something. The formal cause of a phenomenon is what defines its essence. We can say that the formal cause of a person, for example, is a deep structure of relationships encoded in the individual DNA molecule. Formal reasons are closely related to the language and mental maps from which we create our realities by interpreting and labeling our experiences.

For example, we say “horse” when referring to a bronze statue of an animal with four legs, hooves, a mane and a tail, because the object has the shape or formal characteristics that we associate in our minds with the word and concept “horse.” We say, “From an acorn grew an oak,” because we define something endowed with a trunk, branches, and leaves of a certain shape as an “oak.”

Thus, appeal to formal reasons is one of the main mechanisms of "Tricks of Language".

In fact, formal reasons can say more about who perceives the phenomenon than about the phenomenon itself. Identifying formal causes requires uncovering our own underlying assumptions and mental maps about the subject. When an artist, like Picasso, attaches a bicycle handlebar to a bicycle saddle to form a “bull’s head,” he is appealing to formal reasons, since he is dealing with the most important elements of the object’s form.

Aristotle called this type of reason “intuition.” In order to study something (such as “success”, “alignment” or “leadership”), it is necessary to have an idea that this phenomenon exists in principle. For example, trying to define an “effective leader” implies an intuitive belief that such people fit a certain mold.

In particular, searching for the formal causes of a problem or outcome involves examining our underlying definitions, assumptions, and intuitions about that problem or outcome.

Determining the formal causes of “leadership” or “successful organization” or “alignment” requires an examination of the underlying assumptions and intuitions about these phenomena. What exactly do we mean when we talk about “leadership,” “success,” “organization,” or “alignment”? What assumptions do we make about their structure and essence?

Here is a good example of the influence that formal reasons have. One researcher, hoping to find a pattern between treatments, decided to survey people in remission from terminal cancer. He secured permission from local authorities and went to collect data at the regional center for medical statistics.

However, in response to a request to find a list of people in remission on the computer, the center employee replied that she could not provide him with this information. The scientist explained that he had all the necessary papers on hand, but that was not the problem. It turns out that the computer did not have a “remission” category. Then the researcher asked for a list of all patients who had been diagnosed with terminal stage cancer ten to twelve years ago, as well as a list of those who had died from cancer in the intervening period.

He then compared both lists and identified several hundred people who had been diagnosed but were not reported to have died from cancer. Having excluded those who moved to another region or died for other reasons, the researcher finally received about two hundred names of people who were in remission, but were not included in the statistics. Since this group had no "formal reason", they simply did not exist for the computer.

Something similar happened to another group of researchers who were also interested in the phenomenon of remission. They interviewed doctors to find the names and medical histories of people who were in remission from terminal illness. However, doctors denied the existence of such patients. At first, the researchers decided that remission was much less common than they thought. At some point, one of them decided to change the wording. When asked whether there were any cases of “miraculous healing” in their memory, the doctors answered without hesitation: “Yes, of course, and more than one.”

Sometimes it is the formal reasons that are most difficult to establish, because they are part of our unconscious assumptions and premises, like water, which the fish swimming in it does not notice.

The tricks of language and the structure of beliefs

In general, complex equivalents and causal statements are the primary building blocks of our beliefs and belief systems. Based on them, we decide on further actions. Type statements "If X = Y, should do Z" involve action based on an understanding of this connection. Ultimately, such structures determine how we use and apply our knowledge.

According to the principles of Tricks of Language and NLP, in order for deep structures such as values ​​(as more abstract and subjective) to interact with the material environment in the form of concrete behavior, they must be linked to more specific cognitive processes and capabilities through beliefs . Each of the reasons identified by Aristotle must be involved at some level.

Thus, beliefs answer the following questions:

1. “How exactly do you define the quality (or essence) that you value?” “What other qualities, criteria and values ​​is it associated with?” (Formal reasons)

2. “What causes or shapes this quality?” (Pushing reasons)

3. “What consequences or results will this value lead to?” “What is it aimed at?” (Final causes)

4. “How exactly do you determine that a given behavior or experience meets a certain criterion or value?” “What specific behaviors or experiences are associated with this criterion or this value?” (Holding reasons)

For example, a person defines success as “achievement” and “satisfaction.” This person may believe that “success” comes from “doing your best” and also entails “security” and “recognition from others.” At the same time, a person determines the degree of his own success by “a special feeling in the chest and stomach.”

In order to be guided by a certain value, it is necessary to at least outline a belief system that corresponds to it. For example, in order for such a value as “professionalism” to be realized in behavior, it is necessary to create beliefs about what professionalism is (“criteria” of professionalism), how you will know that it has been achieved (criteria compliance), what leads to the formation of professionalism and what he can lead. When choosing actions, these beliefs play no less important role than the values ​​themselves.

For example, two people share the common value “security.” However, one of them is convinced that security means “being stronger than your enemies.” Another believes that the reason for safety is “understanding the positive intentions of those who threaten us and responding to these intentions.” These two will seek security in very different ways. It may even seem that their approaches contradict each other. The first will seek security by strengthening its power. The second will use the communication process for the same purpose, collecting information and searching for possible options.

Obviously, a person's beliefs about his core values ​​determine both the place that these values ​​will occupy on his mental map and the ways in which he will declare them. Successfully internalizing values ​​or creating new values ​​requires working with each of the belief questions above. In order for people within the same system to act in accordance with core values, they must, to a certain extent, share the same beliefs and values.

Tricks of Language patterns can be viewed as verbal operations that allow one to change or place in a new frame the various elements and connections that make up the complex equivalents and cause-and-effect relationships that form beliefs and their formulations. In all of these patterns, language is used to relate and connect various aspects of our experiences and “world maps” to core values.

In the Tricks of Language model, a complete belief statement must contain at least one complex equivalent or cause-and-effect statement. For example, a statement such as “Nobody cares about me” is not a complete statement of belief. This generalization refers to the value of caring, but does not reveal the associated self-beliefs. In order to identify beliefs, The following questions need to be asked: "How do you know that no one cares about you?”, “What forces people don't care about you?", "What are consequences that no one cares about you?” So what Means that people don't care about you?

Such beliefs are often revealed through “connecting” words such as “because”, “whenever”, “if”, “after”, “therefore”, etc. For example, “People don’t care about me.” because…", "People won't care about me if..." « People don't care about me, therefore... Indeed, from the point of view of NLP, the problem is not so much whether a person manages to find the “correct” belief associated with cause-and-effect relationships, but rather what practical results he is able to achieve by acting as if this or that another correspondence or cause-and-effect relationship did exist.

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>> Chemistry: Why chemical reactions occur

Predicting the possibility of carrying out a particular reaction is one of the main tasks facing chemists.

You can write the equation of any chemical reaction on paper (“paper will endure anything”), but is such a reaction practically possible?

In some cases (for example, when calcining limestone: CaCO3 -> CaO + CO2), it is enough to increase the temperature for the reaction to begin, but in others (for example, the reduction of calcium from its oxide with hydrogen: CaO + H2 -> Ca + H20) the reaction cannot be carried out under no circumstances!

Experimental testing of the possibility of a particular reaction occurring under different conditions is labor-intensive and ineffective. But you can theoretically answer this question based on the laws of chemical thermodynamics (which you learned in physics lessons).

One of the most important laws of nature (the first law of thermodynamics) is the law of conservation of energy: energy does not arise from nothing and does not disappear without a trace, but only transfers from one form to another.

In general, the energy of an object consists of three main types: kinetic, potential, internal. Which of these types is most important when considering chemical reactions? Of course, internal energy (e)! After all, it consists of the kinetic energy of movement of atoms, molecules, ions; from the energy of their mutual attraction and repulsion; from the energy associated with the movement of electrons in an atom, their attraction to the nucleus, mutual repulsion of electrons and nuclei, as well as intranuclear energy.

You know that during chemical reactions some chemical bonds are destroyed, while others are formed; in this case, the electronic state of the atoms and their relative positions change, and therefore the internal energy of the reaction products differs from the internal energy of the reactants.

Let's consider two possible cases.

1. E reactants > E products. Based on the law of conservation of energy, as a result of such a reaction, energy should be released into the environment: air, a test tube, a car engine, and reaction products are heated.

Reactions in which energy is released and the environment is heated are called exothermic (Fig. 23).

2. E reagents< Е продуктов. Исходя из закона сохранения энергии, следует предположить, что исходные вещества при таких процессах должны поглощать энергию из окружающей среды, температура реагирующей системы должна понижаться.

Reactions during which energy is absorbed from the environment are called endothermic.

The energy that is released or absorbed in a chemical reaction is called, as you know, the thermal effect of this reaction. This term is used everywhere, although it would be more accurate to talk about the energetic effect of the reaction.

The thermal effect of a reaction is expressed in energy units. The energy of individual atoms and molecules is insignificant. Therefore, the thermal effects of reactions are usually attributed to those quantities of substances that are determined by the equation and are expressed in J or kJ.

The equation of a chemical reaction in which the thermal effect is indicated, as you already know, is called a thermochemical equation.

For example, the thermochemical equation:

2H2 + 02 = 2H20 + 484 kJ

Knowledge of the thermal effects of chemical reactions is of great practical importance. For example, when designing a chemical reactor, it is important to provide for either an influx of energy to maintain the reaction by heating the reactor, or, conversely, removal of excess heat so that there is no overheating of the reactor with all the ensuing consequences, including an explosion.

If the reaction takes place between simple molecules, then calculating the thermal effect of the reaction is quite simple.

For example:

H 2 + Cl 2 -> 2HCl

Energy is spent on breaking two chemical bonds H-H and Cl-Cl, energy is released when two chemical bonds H-Cl are formed. It is in chemical bonds that the most important component of the internal energy of a compound is concentrated. Knowing the energies of these bonds, one can determine the thermal effect of the reaction (Fr) from the difference.

En-n = 436 kJ/mol, Ecl-cl = 240 kJ/mol,

Enсl = 430 kJ/mol,

Q p = 2,430 - 1,436 - 1,240 = 184 kJ.

Therefore, this reaction is exothermic.

How, for example, can we calculate the thermal effect of the decomposition reaction of calcium carbonate? After all, this is a compound of non-molecular structure. How to determine exactly which bonds and how many of them are destroyed, what their energy is, what bonds and how many of them are formed in calcium oxide?

To calculate the thermal effects of reactions, the values ​​of the heats of formation of all chemical compounds participating in the reaction (initial and products) are used.

The heat of formation of a compound (Qbr) is the thermal effect of the reaction of the formation of one mole of a compound from simple substances that are stable under standard conditions (25 °C, 1 atm.).

Under these conditions, the heat of formation of simple substances is zero by definition.

C + 02 = C02 + 394 kJ

0.5T2 + 0.502 = N0 - 90 kJ,

where 394 kJ and -90 kJ are the heats of formation of CO2 and N0, respectively.

If a given chemical compound can be directly obtained from simple substances, and the reaction occurs quantitatively (100% yield of products), it is enough to carry out the reaction and measure its thermal effect using a special device - a calorimeter. This is how the heats of formation of many oxides, chlorides, sulfides, etc. are determined. However, the vast majority of chemical compounds are difficult or impossible to obtain directly from simple substances.

For example, when burning coal in oxygen, it is impossible to determine the Qrev of carbon monoxide CO, since the process of complete oxidation always occurs. In this case, the law formulated in the last century by St. Petersburg academician G.I. Hess comes to the rescue.

The thermal effect of a chemical reaction does not depend on the intermediate stages (provided that the starting materials and reaction products are the same).

Knowing the heats of formation of compounds allows us to evaluate their relative stability, as well as calculate the thermal effects of reactions.

The thermal effect of a chemical reaction is equal to the sum of the heats of formation of all reaction products minus the sum of the heats of formation of all reactants (taking into account the coefficients in the reaction equation).

The human body is a unique “chemical reactor” in which many different chemical reactions take place. Their main difference from the processes occurring in a test tube, flask, or industrial plant is that in the body all reactions occur under “mild” conditions (atmospheric pressure, low temperature), and few harmful by-products are formed.

The process of oxidation of organic substances with oxygen is the main source of energy, and its main end products are CO2 and H20.

This released energy is a large quantity, and if food were oxidized quickly and completely in the body, then just a few pieces of sugar eaten would cause the body to overheat. But biochemical processes, the total thermal effect of which, according to Hess’s law, does not depend on the mechanism and is a constant value, proceed stepwise, as if extended in time. Therefore, the body does not “burn out”, but economically spends this energy on vital processes. But does this always happen?

Every person should have at least an approximate idea of ​​how much energy enters his body with food and how much is consumed during the day.

One of the principles of rational nutrition is this: the amount of energy supplied from food should not exceed energy consumption (or be less) by more than 5%, otherwise metabolism is disrupted and a person becomes fat or loses weight.

The energy equivalent of food is its calorie content, expressed in kilocalories per 100 g of product (often indicated on the packaging, can also be found in special reference books and cookbooks). And energy consumption in the body depends on age, gender, and intensity of work. For example, a woman (secretary, accountant) needs about 2100 kcal per day, and a man (lumberjack, concrete worker, miner) needs approximately 4300 kcal per day.

The most beneficial diet is low in calories, but contains all the components in the food (proteins, fats, carbohydrates, minerals, vitamins, microelements).

The energy value of food and the calorific value of fuel are associated with exothermic reactions of their oxidation. The driving force of such reactions is the “striving” of the system towards a state with the lowest internal energy.

Exothermic reactions begin spontaneously, or require only a small “push”—an initial supply of energy.

What then is the driving force behind endothermic reactions, during which thermal energy comes from the environment and is stored in the reaction products, turning into their internal energy? This “force” is associated with the tendency of any system to the most probable state, which is characterized by maximum disorder; it is called entropy. For example, the molecules that make up the air do not fall to the Earth, although the minimum potential energy of each molecule corresponds to its lowest position, since the desire for the most probable state causes the molecules to be randomly distributed in space.

Imagine that you poured different nuts into a glass. It is almost impossible to achieve separation and order by shaking them, since in this case the system will tend to the most probable state in which disorder in the system increases, so the nuts will always be mixed. Moreover, the more particles we have, the greater the likelihood of disorder. The greatest order in chemical systems is in an ideal crystal at absolute zero temperature. They say that entropy in this case is zero. With increasing temperature in the crystal, random vibrations of atoms (molecules, ions) begin to intensify. Entropy increases. This occurs especially sharply at the moment of melting during the transition from a solid to a liquid, and even more so at the moment of evaporation during the transition from liquid to gas.

The entropy of gases significantly exceeds the entropy of liquids and, especially, solids. If you spill a little gasoline in an enclosed space, such as a garage, you will soon smell it throughout the entire room. Evaporation (endothermic process) and diffusion occur, a random distribution of gasoline vapor throughout the entire volume. Gasoline vapor has greater entropy compared to liquid.

The process of boiling water from an energy point of view is also an endothermic process, but it is beneficial from the point of view of an increase in entropy when the liquid transforms into vapor. At a temperature of 100 °C, the entropy factor “outweighs” the energy factor - water begins to boil - water vapor has greater entropy compared to liquid water.

Table 11 Some values ​​of standard molar entropy

As you analyze the data in Table 11, notice how low the entropy value is for a diamond that has a very regular structure. Substances formed more

Standard molar entropy is the entropy value for 1 mole of a substance at a temperature of 298 K and a pressure of 10 5 Pa.

complex particles have very high entropy values. For example, the entropy of ethane is greater than the entropy of methane. Endothermic reactions are precisely those reactions in which a fairly strong increase in entropy is observed, for example, due to the formation of gaseous products from liquid or solid substances or due to an increase in the number of particles. For example:

CaC03 -> CaO + C02 - Q

Let's draw conclusions:

1. The direction of a chemical reaction is determined by two factors: the desire to reduce internal energy with the release of energy and the desire for maximum disorder, that is, to increase entropy.

2. An endothermic reaction can be made to proceed if it is accompanied by an increase in entropy.

3. Entropy increases with increasing temperature and especially strongly during phase transitions: solid - liquid, solid - gaseous.

4. The higher the temperature at which the reaction is carried out, the greater the importance of the entropy factor compared to the energy factor.

There are experimental and theoretical methods for determining the entropy of various chemical compounds. Using these methods, it is possible to quantify the changes in entropy during a particular reaction, in a similar way to the thermal effect of a reaction. As a result, it becomes possible to predict the direction of a chemical reaction (Table 12).

Special reference data have been compiled, which include a comparative description of these quantities taking into account temperature.

Let's return to case No. 2 (see Table 12).

All life on our planet - from viruses and bacteria to humans - consists of highly organized matter, which is more ordered compared to the surrounding world. For example, protein. Remember its structures: primary, secondary, tertiary. You are already well acquainted with the “substance of heredity” - DNA, the molecules of which consist of structural units arranged in a strictly defined sequence. This means that protein or DNA synthesis is accompanied by a huge decrease in entropy.

Table 12 Possibility of chemical reactions occurring depending on changes in energy and entropy

In addition, the initial building material for the growth of plants and animals is formed in the plants themselves from water H20 and carbon dioxide C02 during the process of photosynthesis:

6Н20 + 6С02(g) -> С6Н1206 + 602(g)

In this reaction, entropy decreases and a reaction occurs with the absorption of light energy. This means the process is endothermic! Thus, the reactions to which we owe our lives turn out to be thermodynamically forbidden. But they are coming! And this uses the energy of light quanta in the visible region of the spectrum, which is much greater than thermal energy (infrared quanta). In nature, endothermic reactions with a decrease in entropy, as you can see, occur under certain conditions. Chemists cannot yet create such conditions artificially.

1. When 7 g of ethylene is burned, 350 kJ of heat is released. Determine the thermal effect of the reaction.

2. Thermochemical equation for the reaction of complete combustion of acetylene:

2C2H2 + 502 = 4C02 + 2H20 + 2610 kJ How much heat is released when using 1.12 liters of acetylene?

3. When 18 g of aluminum combines with oxygen, 547 kJ of heat is released. Write a thermochemical equation for this reaction.

4. Based on the fact that the combustion of 6.5 g of zinc releases heat equal to 34.8 kJ, determine the heat of formation of zinc oxide.

5*. Determine the thermal effect of the reaction:

2С2Н6(g) + 702(g) -> 4С02(g) + 6Н20(g), if

Qrev (H20)(g) = 241.8 kJ/mol;

Qrev (CO2)(g) = 393.5 kJ/mol;

Qsamp (C2H6)(g) = 89.7 kJ/mol.

6*. Determine the heat of formation of ethylene if

C(s) + 02(g) = C02(g) +393.5 kJ,

H2(g) + 0.502(g) = H20 + 241.8 kJ,

С2Н4(g) + 302(g) = 2С02(g) + 2Н20(g) + 1323 kJ.

7*. Calculate the thermal effects of reactions occurring in the body:

a) C6H1206(s) -> 2C2H5OH(l) + 2C02(g);

b) C6H1206(s) + 602(g) -> 6С02(g) + 6H20 (l), if Qarr (H20)(l) = 285.8 kJ/mol;

Q arr (C02)(g) (see problems 5 and 6); Q arr (C2H50H)(l) = 277.6 kJ/mol; Q arr (C6H1206)(t) = 1273 kJ/mol.

8*. Based on the following data:

FeO(s) + CO(g) -> Fe(s) + CO2(g) + 18.2 kJ, 2СО(g) + 02(g) -> 2С02(g) + 566 kJ, Q arr(H2O) (g) = 241.8 kJ/mol, calculate the thermal effect of the reaction:

FeO(s) + H2(g) -> Fe(s) + H20(g).

lesson presentation

Meet Christina Gepting. A young prose writer from Veliky Novgorod. Winner of the Lyceum literary award 2017 for the story “Plus Life.” She is also a philologist and mother of two girls. We met with Christina over a cup of coffee to talk about the writing process itself and the influence of the writer's personality on it.

Photo from the personal archive of Christina Gepting.

Are you writing here?

It's not here. In general, sometimes I write in a cafe. But still, nowhere does one write as well as at home. I recently went to a sanatorium in the Caucasus - I thought, without work, without children, I would do nothing but write for a whole week. But no.

How do you write in general? Do you set aside an hour a day or in between work on the run?

I write most often at night. Almost like Bukowski: “Writing during the day is like running naked down the street.” Although during the day I can enter some thoughts into my phone or a successful phrase that suddenly came to me... It turns out that I write most productively when I literally find a few hours for it - after coming home from work and putting my daughters to bed...

In the age of modern technology, do you write directly using gadgets or the old fashioned way, on paper? Do you think through the plot in advance or do the characters lead you on their own?

I always write in Google Docs: this allows you to return to the text at any time and see the history of edits. I write by hand only a certain plan, a synopsis of a future story or novella. For some reason it’s easier to work with the text further.

Your typical reader – how do you imagine him?

And when you write, do you think about the reader’s reactions?

No, I don't think so. After all, it is impossible to predict the reader’s reactions. Everyone perceives the style of the text differently, so there is no point in thinking about it.

Having received the Lyceum Award, you went through the entire process from the first lines to the publication of the book and the award on Red Square. You have already had negotiations regarding the film adaptation of the story. There are many events. What moment along this journey was the most emotional?

I wrote the story for exactly two months, and for another six months I polished the text. These were very happy days for me: I was immersed in the text to such an extent that I was even upset when I finished writing it - it was such a pity to part with the main character. By the way, perhaps I’m most looking forward to the film version of “Plus Life” precisely because for me it will be an opportunity to meet “my boy” again, albeit in a different form...

Returning to the question - there is nothing more joyful for me than the feeling that the text is taking shape, so I remember the process of working on the story as one of the most fulfilling periods of life. If we highlight the most emotionally striking moment, then, perhaps, this is the episode in the text when the hero forgives his deceased mother, who, in general, became the main culprit of his troubles. By the way, I didn’t initially come up with this scene, but I revived the hero, first of all, for myself. Therefore, I believe that he himself led me to the understanding that there should be such a moment in the text, that it is psychologically justified.

Do you write “because” or “in order to”?...

When I write, I just feel better. If I don’t write, I get depressed and don’t sleep well.

I often hear from writers that school literature lessons did not leave any warm memories at all. But this is such an opportunity to captivate the kids! What would you add to the school literature curriculum or what would you definitely remove?

It seems to me that the question is not what to read, but how to present it in class. And this is the problem at school. I think it is necessary for a schoolchild to be able to correlate what is said in the book with his own personal experience: and both a 13-year-old and, even more so, a 17-year-old have it.

You said that there were many strong candidates on the shortlist for the award. Unfortunately, modern young Russian writers are usually known only in their own literary circle. Which of today's 25-30 year olds do you think is strong?

Indeed, the Lyceum shortlist was very strong. I definitely don’t consider the texts of Konstantin Kupriyanov, Aida Pavlova, Sergei Kubrin inferior to mine. In general, I follow the work of my literary peers - I always look forward to new prose by Zhenya Dekina, Olga Breininger, yours too, Lena... I won’t name all the names now - otherwise the list will be too long.

And as for the fact that “nobody knows us.” Actually, this is normal. And writers of established, recognized masters, you know, are not accompanied by great fame now... One can argue whether this is fair, but the fact is: there are many different kinds of entertainment today, and it is not always the case that a smart reader will prefer high-quality prose to a high-quality series. This is a given that you just have to accept.

This philosophical approach probably makes the life of a young writer easier in many ways! And now a quick survey, answer without hesitation. According to the principle “I name the emotion, and you name the author or his work, which you associate with this emotion.” Are you ready?

Let's try it!

Let's go. Dejection?

Roman Senchin, “The Eltyshevs.”

Ease?

Alexander Pushkin, "Blizzard".

Confusion?

Patrick Suskind, "Dove". Although there is, perhaps, a spectrum of emotions.

Horror?

Lives of Christian saints.

Obsessiveness?

Chekhov's plays.

Tenderness?

Patrick Suskind, "Double Bass". There is a lot of Süskind, but, for some reason, it’s true that his texts are the first to emerge on these emotions.

This is an interesting list! Thank you for the conversation! If you are in Moscow, stop by our faculty.

Elena Tulusheva

The article published here is not popular science. This is the text of the first message about a remarkable discovery: a periodically operating, oscillatory chemical reaction. This text was not printed. The author sent his manuscript in 1951 to a scientific journal. The editors sent the article for review and received a negative review. Reason: the reaction described in the article is impossible... Only in 1959 was a short abstract published in a little-known collection. The editors of "Chemistry and Life" provide the reader with the opportunity to get acquainted with the text and the unusual fate of the first message about the great discovery.

Academician I.V. Petryanov

INTERMITTENT REACTION
AND ITS MECHANISM

B.P. Belousov

As is known, slowly occurring redox reactions can be very noticeably accelerated, for example, by introducing relatively small amounts of a third substance - a catalyst. The latter is usually sought empirically and is to a certain extent specific for a given reaction system.

Some help in finding such a catalyst can be provided by the rule according to which its normal potential is selected as the average between the potentials of the substances reacting in the system. Although this rule simplifies the selection of a catalyst, it does not yet allow us to predict in advance and with certainty whether the substance thus selected will actually be a positive catalyst for a given redox system, and if it is suitable, it is still unknown, in to what extent it will manifest its active action in the chosen system.

It must be assumed that one way or another the exquisite catalyst will have an effect both in its oxidative form and in its reduced form. Moreover, the oxidized form of the catalyst should obviously react easily with the reducing agent of the main reaction, and its reduced form with the oxidizing agent.

In the system of bromate with citrate, cerium ions fully meet the above conditions, and therefore, at a suitable pH of the solution, they can be good catalysts. Note that in the absence of cerium ions, bromate itself is practically unable to oxidize citrate, while tetravalent cerium does this quite easily. If we take into account the ability of bromate to oxidize Ce III to Ce IV, the catalytic role of cerium in such a reaction becomes clear.

Experiments carried out in this direction confirmed the catalytic role of cerium in the chosen system, and in addition, revealed a striking feature of the course of this reaction.

Indeed, the reaction described below is remarkable in that when it is carried out in the reaction mixture, a number of hidden redox processes occur, ordered in a certain sequence, one of which is periodically revealed by a distinct temporary change in the color of the entire reaction mixture taken. Such an alternating change in color, from colorless to yellow and vice versa, is observed indefinitely (an hour or more) if the constituent parts of the reaction solution were taken in certain quantities and in the appropriate general dilution.

For example, a periodic change in color can be observed in 10 ml of an aqueous solution of the following composition *:

If the specified solution, at room temperature, is well mixed, then in the solution at the first moment the appearance of several rapid changes in color from yellow to colorless and vice versa, which after 2-3 minutes acquire the correct rhythm.

* If you want to change the pulsation rate, the given recipe for the composition of the reaction solution can be changed to a certain extent. The quantitative ratios of the ingredients included in the described reaction indicated in the text were experimentally developed by A.P. Safronov. He also proposed an indicator for this reaction - phenanthroline / iron. For which the author is very grateful to him.

Under experimental conditions, the duration of one color change has an average value of approximately 80 s. However, this interval after some time (10-15 minutes) tends to increase and from 80 s gradually reaches 2-3 minutes or more. At the same time, a thin white suspension appears in the solution, which over time partially sediments and falls to the bottom of the vessel in the form of a white precipitate. Its analysis shows the formation of pentabromoacetone as a product of oxidation and bromination of citric acid. An increase in the concentration of hydrogen or cerium ions greatly accelerates the reaction rate; at the same time, the intervals between pulses (color changes) become shorter; at the same time, a rapid release of significant amounts of pentabromacetone and carbon dioxide occurs, which entails a sharp decrease in citric acid and bromate in the solution. In such cases, the reaction noticeably approaches the end, which is evident from the sluggishness of the rhythm and the absence of clear changes in color. Depending on the product consumed, the addition of bromate or citric acid again excites the intensity of the decaying pulses and noticeably prolongs the entire reaction. The course of the reaction is also greatly influenced by an increase in the temperature of the reaction mixture, which greatly accelerates the rhythm of the pulses; on the contrary, cooling slows down the process.

Some disturbance in the course of the reaction, and with this the uniformity of the rhythm, observed after some time from the beginning of the process, probably depends on the formation and accumulation of the solid phase, a suspension of pentabromacetone.

In fact, due to the ability of acetone pentabromide to sorb and retain a small part of the free bromine released during pulses (see below), the latter will obviously be partially eliminated from this part of the reaction; on the contrary, at the next change of pulse, when the solution becomes colorless, the sorbed bromine will slowly desorb into the solution and react in a disorderly manner, thereby disrupting the overall synchronicity of the process that was created at the beginning.

Thus, the more suspension of pentabromacetone accumulates, the more disturbances in the duration of the rhythm are observed: the burden between scenes of solution colors increases, and the changes themselves become unclear.

Comparison and analysis of experimental data indicate that this reaction is based on the peculiar behavior of citric acid in relation to certain oxidizing agents.

If we have an aqueous solution of citric acid acidified with sulfuric acid, to which KBrO 3 and a cerium salt are added, then, obviously, the following reaction should occur first:

1) HOOC-CH 2 -C(OH)(COOH)-CH 2 -COOH + Ce 4+ ® HOOC-CH 2 -CO-CH 2 -COOH + Ce 3+ + CO 2 + H 2 O

This reaction is quite slow, and one can see in it (by the disappearance of the yellow color characteristic of Ce 4+ ions) a gradual accumulation of trivalent cerium ion.

The resulting trivalent cerium will react with bromate:

2) Ce 3+ + BrО 3 - ® Ce 4+ + Br - .

This reaction is slower than the previous one (1), since all the formed Ce 4+ has time to return to reaction 1 for the oxidation of citric acid, and therefore no color (from Ce 4+ ) is observed.

3) Br - + BrО 3 - ® BrO - + BrО 2 - .

The reaction is relatively fast due to the high concentration of H +; it is followed by even faster processes:

a) Br - + BrO - ® Br 2

b) 3Br - + BrО 2 - ® 2 Br 2

However, the release of free bromine has not yet been observed, although it is being formed. This is obviously because in reaction 2 the bromide accumulates slowly; Thus, there is little “free” bromine, and it has time to be consumed in the rapid reaction 4 with acetone dicarboxylic acid (formed in reaction 1).

4) HOOC-CH 2 -CO-CH 2 -COOH + 5Br 2 ® Br 3 C-CO-CHBr 2 + 5Br - + 2CO 2 + 5H +

Here, obviously, the color of the solution will also be absent; Moreover, the solution may become slightly cloudy from the resulting poorly soluble acetonepentabromide. The release of gas (CO 2 ) is not yet noticeable.

Finally, after a sufficient amount of Br - has accumulated (reactions 2 and 4), the moment of interaction of bromide with bromate comes, now with the visible release of some portion of free bromine. It is clear that by this moment acetone dicarboxylic acid (which previously “blocked” free bromine) will have time to be consumed due to the low rate of its accumulation in reaction 1.

The release of free bromine occurs spontaneously, and this causes a sudden coloration of the entire solution, which will probably intensify due to the simultaneous appearance of yellow ions of tetravalent cerium. The free bromine released will be gradually, but at a noticeable rate, consumed for the formation of Ce 4+ ions (consumed by reaction 1), and therefore for reaction 3. Perhaps bromine will also be consumed for interaction with citric acid in the presence of BrO 3 - * , since this does not exclude the role of emerging side processes that induce this reaction.

*If in aqueous solution H 2 SO 4 (1:3) there are only citric acid and bromate, then when such a solution is slightly heated (35-40°) and bromine water is added, the solution quickly becomes cloudy and bromine disappears. Subsequent extraction of the suspension with ether shows the formation of acetonepentabromide. Traces of cerium salts greatly accelerate this process with the rapid release of CO.

After the disappearance of free bromine and Ce 3+ ions, inactive acetone pentabromide, excess citric acid and bromate, as well as tetravalent cerium catalyzing the process, will obviously remain in the reaction solution. There is no doubt that in this case the above-described reactions will begin again and will be repeated until one of the ingredients of the taken reaction mixture is used up, i.e. citric acid or bromate*.

* In the event that the reaction has stopped due to the consumption of one of the ingredients, the addition of the spent substance will again resume the periodic processes.

Since of the numerous processes taking place, only a few are determined visually in the form of a change in color, an attempt was made to identify hidden reactions using an oscilloscope.

Indeed, a number of periodic processes are visible in oscillographic images, which, obviously, must correspond to visible and hidden reactions (see figure). However, the latter require further detailed analysis.

One of the first oscillograms of a periodic response obtained by B.P. Belousov (published for the first time)

In conclusion, we note that a more distinct change in the color of the periodic reaction is observed with the use of an indicator for redox processes. As such, ironphenanthroline turned out to be the most convenient, recommended for determining the transition of Ce 4+ to Ce 3+. We used 0.1-0.2 ml of reagent (1.0 g) per 10 ml of reaction mixture O-phenanthroline, 5 ml H 2 SO 4 (1:3) and 0.8 g Mohr's salt in 50 ml water). In this case, the colorless color of the solution (Ce 3+ ) corresponded to the red form of the indicator, and the yellow form (Ce 4+ ) corresponded to the blue form.

This indicator was especially valuable for demonstration purposes. For example, this reaction is extremely effective in demonstrating that its rate varies with temperature.

If a vessel with a reaction liquid showing a normal number of pulses (1-2 per minute) is heated, then a rapid change in the rate of alternation of color changes is observed, reaching the complete disappearance of the intervals between pulses. Upon cooling, the rhythm of the reaction slows down again and the change in colors again becomes clearly visible.

Another unique picture of a pulsating reaction using an indicator can be observed if the reaction solution, located in a cylindrical vessel and “tuned” to a fast pace, is carefully diluted with water (by layering) so that the concentration of the reacting substances gradually decreases from the bottom of the vessel to the upper level liquids.

With this dilution, the highest pulsation rate will be in the more concentrated lower (horizontal) layer, decreasing from layer to layer towards the surface of the liquid level. Thus, if in any layer at some time there was a change in color, then at the same time in the above or underlying layer one can expect the absence of such or a different color. This consideration undoubtedly applies to all layers of pulsating fluid. If we take into account the ability of the suspension of precipitating pentabromacetone to selectively sorb and retain the reduced red form of the indicator for a long time, then the red color of pentabromacetone will be fixed in the layer. It is not violated even with a subsequent change in the redox potential of the environment. As a result, all the liquid in the vessel after some time becomes permeated with horizontal red layers.

It should be pointed out that the introduction of another redox couple into our system: Fe 2+ + Fe 3+ - cannot, of course, fail to affect the first one.

In this case, a faster release of acetone pentabromide and, accordingly, a faster completion of the entire process are noted.

RESULTS

A periodic, long-lasting (pulsating) reaction has been discovered.

Based on observation of the reaction pattern and analysis of factual material, considerations are proposed about the key points of the mechanism of its action.

1951-1957

The reviewer's indifferent pen

Very few, even among chemists, can boast that they had the opportunity to read this article. The fate of the only publicly read publication by Boris Pavlovich Belousov is as unusual as the fate of its author, the 1980 Lenin Prize laureate. Recognition of the merits of this remarkable scientist did not find him alive - Belousov died in 1970, at the age of 77 years.

They say that only young people can make discoveries of revolutionary significance for science - and Boris Pavlovich discovered the first oscillatory reaction at the age of 57. But he discovered it not by chance, but quite deliberately, trying to create a simple chemical model of some stages of the Krebs cycle*. An experienced researcher, he immediately appreciated the significance of his observations. Belousov repeatedly emphasized that the reaction he discovered has direct analogies with the processes occurring in a living cell.

* The Krebs cycle is a system of key biochemical transformations of carboxylic acids in the cell.

In 1951, deciding that the first stage of the research was completed, Belousov tried to publish a report about this reaction in one of the chemical journals. However, the article was not accepted, as it received negative feedback from the reviewer. The review stated that it should not be published because the reaction described in it was impossible.

If only this reviewer knew that the existence of oscillatory reactions was predicted back in 1910 by A. Lotka, that since then there has been a mathematical theory of this kind of periodic processes. And it was not necessary to know these intricacies - the chemist reviewer could, after all, pick up a test tube and mix in it the simple components described in the article. However, the custom of verifying the messages of colleagues by experiment has long been forgotten - as well as (unfortunately!) the custom of trusting their scientific integrity. They simply didn’t believe Belousov, and he was very offended by this. The reviewer wrote that a message about an “allegedly discovered” phenomenon could be published only if it had a theoretical explanation. It was implied that such an explanation was impossible. And just at that time, the works of A. Lotka and V. Volterra, who developed Lotka’s theory in relation to biological processes (the “predator-prey” model with undamped fluctuations in the numbers of species), to the experimental and theoretical studies of D.A. Frank-Kamenetsky (1940) was supplemented by the work of I. Christiansen, who directly called for the search for periodic chemical reactions in view of their complete scientific probability.

Despite refusing to publish the work, Belousov continued to study the periodic reaction. This is how the part of his article appeared that uses a loopback oscilloscope. Changes in the emf of the system during the reaction cycle were recorded, and fast periodic processes were discovered that occurred against the background of slower ones observed with the naked eye.

A second attempt to publish an article about these phenomena was made in 1957. And again the reviewer - this time from another chemical journal - rejected the article. This time the indifferent pen of the reviewer gave rise to the following version. The reaction scheme, the review stated, was not confirmed by kinetic calculations. It can be published, but only if it is reduced to the length of a letter to the editor.

Both demands were unrealistic. The substantiation of the kinetic scheme of the process subsequently required ten years of work by many researchers. To reduce the article to 1-2 typewritten pages meant making it simply unintelligible.

The second review put Belousov in a gloomy mood. He decided to refuse to publish his discovery altogether. This created a paradoxical situation. The discovery was made, vague rumors circulated among Moscow chemists, but no one knew what it was or who made it.

One of us had to start a “Sherlock Holmes” manhunt. For a long time, the searches were fruitless, until at one of the scientific seminars it was possible to establish that the author of the work being sought was Belousov. Only after this did the opportunity open up to contact Boris Pavlovich and begin to persuade him to publish his observations in some form. After much persuasion, it was finally possible to force Boris Pavlovich to publish a short version of the article in the “Collection of Abstracts on Radiation Medicine,” published by the Institute of Biophysics of the USSR Ministry of Health. The article was published in 1959, but the small circulation of the collection and its low prevalence made it almost inaccessible to colleagues.

Meanwhile, periodic reactions were intensively studied. The work involved the Department of Biophysics of the Physics Faculty of Moscow State University, and then the Laboratory of Physical Biochemistry at the Institute of Biophysics of the USSR Academy of Sciences in Pushchino. Significant progress in understanding the reaction mechanism began with the appearance of the works of A.M. Jabotinsky. However, the fact that Belousov’s message was published in a truncated form hampered the progress of research to some extent. His followers sometimes had to rediscover many details of the experiment. This was the case, for example, with the indicator - a complex of iron with phenanthroline, which remained forgotten until 1968, as well as with “waves” of color.

A.M. Zhabotinsky showed that bromine is not formed in noticeable quantities in the oscillatory reaction, and established the key role of the bromide ion, which provides “feedback” in this system. He and his collaborators found eight different reducing agents capable of supporting an oscillatory reaction, as well as three catalysts. The kinetics of some stages that together make up this very complex process, which is still unclear in detail to this day, was studied in detail.

Over the past since the discovery of B.P. Belousov 30 years, a large class of oscillatory reactions of oxidation of organic substances with bromate was discovered. In general terms, their mechanism is described as follows.

During the reaction, bromate oxidizes the reducing agent (B.P. Belousov used citric acid as a reducing agent). However, this does not happen directly, but with the help of a catalyst (B.P. Belousov used cerium). In this case, two main processes occur in the system:

1) oxidation of the reduced form of the catalyst with bromate:

HBrO 3 + Cat n+ ® Cat (n+1)+ + ...

2) reduction of the oxidized form of the catalyst with a reducing agent:

Cat (n+1)+ + Red ® Cat"+ Cat n+ + Br - + ...

During the second process, bromide is released (from the original reducing agent or from its bromine derivatives formed in the system). Bromide is an inhibitor of the first process. Thus, the system has feedback and the possibility of establishing a regime in which the concentration of each of the catalyst forms periodically fluctuates. Currently, about ten catalysts and more than twenty reducing agents are known that can support an oscillatory reaction. Among the latter, the most popular are malonic and bromomalonic acids.

When studying the Belousov reaction, complex periodic regimes and regimes close to stochastic were discovered.

When carrying out this reaction in a thin layer without stirring, A.N. Zaikin and A.M. Zhabotinsky discovered autowave regimes with sources such as the leading center and reverberator (see "Chemistry and Life", 1980, No. 4). A fairly complete understanding of the process of catalyst oxidation with bromate has been achieved. What seems least clear now is the mechanism of bromide production and feedback.

In recent years, in addition to the discovery of new reducing agents for vibrational reactions, a new interesting class of vibrational reactions has been discovered that do not contain transition metal ions as a catalyst. The mechanism of these reactions is assumed to be similar to that described above. In this case, it is believed that one of the intermediate compounds acts as a catalyst. Autowave regimes have also been discovered in these systems.

The class of Belousov reactions is interesting not only because it represents a nontrivial chemical phenomenon, but also because it serves as a convenient model for studying vibrational and wave processes in active media. These include periodic processes of cellular metabolism; waves of activity in cardiac tissue and brain tissue; processes occurring at the level of morphogenesis and at the level of ecological systems.

The number of publications devoted to the Belousov-Zhabotinsky reactions (this is the now generally accepted name for this class of chemical vibrational processes) is measured in the hundreds, and a considerable part of it consists of monographs and fundamental theoretical studies. The logical result of this story was the award of B.P. Belousov, G.R. Ivanitsky, V.I. Krinsky, A.M. Zhabotinsky and A.N. Zaikin Lenin Prize.

In conclusion, we cannot help but say a few words about the responsible work of reviewers. No one disputes that reports of the discovery of fundamentally new, previously unseen phenomena should be treated with caution. But is it possible, in the heat of the “fight against pseudoscience,” to go to the other extreme: without giving oneself the trouble to check an unusual message in all good faith, but, guided only by intuition and prejudice, rejecting it outright? Doesn't such reviewer haste slow down the development of science? It is apparently necessary to react with greater caution and tact to reports of “strange” but not experimentally and theoretically refuted phenomena.

Doctor of Biological Sciences S.E. Shnol,
Candidate of Chemical Sciences B.R. Smirnov,
Candidate of Physical and Mathematical Sciences G.I. Zadonsky,
Candidate of Physical and Mathematical Sciences A.B. Rovinsky

WHAT TO READ ABOUT VIBRATIONAL REACTIONS

A. M. Zhabotinsky. Periodic course of oxidation of malonic acid in solution (Study of the Belousov reaction). - Biophysics, 1964, vol. 9, issue. 3, p. 306-311.

A.N. Zaikin, A.M. Zhabotinskii. Concentrational Wave Propagation in Two-Dimensional liquid-phase Self-oscillating System. - Nature, 1970, v. 225, p. 535-537.

A.M. Jabotinsky. Concentration self-oscillations. M., "Science", 1974.

G.R. Ivanitsky, V.I. Krinsky, E.E. Selkov. Mathematical biophysics of cells. M., "Science", 1977.

R.M. Noyes. Oscillations in Homogeneous Systems. - Ber. Bunsenges. Phys. Chem., 1980, V. 84, S. 295-303.

A.M. Zhabotinskii. Oscillating Bromate Oxidative Reactions. - I bid. S. 303-308.

At ΔG< 0 реакция термодинамически разрешена и система стремится к достижению условия ΔG = 0, при котором наступает равновесное состояние обратимого процесса; ΔG >0 indicates that the process is thermodynamically prohibited.

Figure 3

Change in Gibbs energy: a – reversible process; b – irreversible process.

Having written equation (1) in the form ΔH = ΔG + TΔS, we find that the enthalpy of the reaction includes the free Gibbs energy and the “unfree” energy ΔS · T. The Gibbs energy, which is the decrease in the isobaric (P = const) potential, is equal to the maximum useful work. Decreasing with the course of the chemical process, ΔG reaches a minimum at the moment of equilibrium (ΔG = 0). The second term ΔS · T (entropy factor) represents that part of the energy of the system that at a given temperature cannot be converted into work. This bound energy can only be dissipated into the environment in the form of heat (increasing chaoticity of the system).

So, in chemical processes, the energy reserve of the system (enthalpy factor) and the degree of its disorder (entropy factor, energy that does not do work) simultaneously change.

Analysis of equation (1) allows us to establish which of the factors that make up the Gibbs energy is responsible for the direction of the chemical reaction, enthalpy (ΔH) or entropy (ΔS · T).

· If ΔH< 0 и ΔS >0, then always ΔG< 0 и реакция возможна при любой температуре.

· If ΔH > 0 and ΔS< 0, то всегда ΔG >0, and a reaction with the absorption of heat and a decrease in entropy is impossible under any conditions.

· In other cases (ΔH< 0, ΔS < 0 и ΔH >0, ΔS > 0) the sign of ΔG depends on the ratio of ΔH and TΔS. A reaction is possible if it is accompanied by a decrease in the isobaric potential; at room temperature, when the value of T is small, the value of TΔS is also small, and usually the enthalpy change is greater than TΔS. Therefore, most reactions occurring at room temperature are exothermic. The higher the temperature, the greater the TΔS, and even endothermic reactions become feasible.

Let us illustrate these four cases with the corresponding reactions:

	ΔH< 0 ΔS >0ΔG< 0	C2H5–O–C2H5 + 6O2 = 4CO2 + 5H2O (reaction possible at any temperature)
	ΔH > 0 ΔS< 0 ΔG > 0	reaction is impossible
	ΔH< 0 ΔS < 0 ΔG >0.ΔG< 0	N2 + 3H2 = 2NH3 (possible at low temperature)
	ΔH > 0 ΔS > 0 ΔG > 0, ΔG< 0	N2O4(g) = 2NO2(g) (possible at high temperature).

To assess the sign of the ΔG reaction, it is important to know the values ​​ΔH and ΔS of the most typical processes. ΔH of formation of complex substances and ΔH of reaction are in the range of 80–800 kJ∙mol-1. The enthalpy of the combustion reaction ΔH0combustion is always negative and amounts to thousands of kJ∙mol-1. The enthalpies of phase transitions are usually less than the enthalpies of formation and chemical reaction ΔHvapor - tens of kJ∙mol-1, ΔHcryst and ΔHmelt are 5–25 kJ∙mol-1.

The dependence of ΔH on temperature is expressed by the relation ΔHT = ΔH° + ΔCp · ΔT, where ΔCp is the change in the heat capacity of the system. If in the temperature range 298 K – T the reagents do not undergo phase transformations, then ΔCp = 0, and ΔH° values ​​can be used for calculations.

The entropy of individual substances is always greater than zero and ranges from tens to hundreds of J∙mol–1K–1 (Table 4.1). The sign of ΔG determines the direction of the actual process. However, to assess the feasibility of a process, the values ​​of the standard Gibbs energy ΔG° are usually used. The ΔG° value cannot be used as a probability criterion in endothermic processes with a significant increase in entropy (phase transitions, thermal decomposition reactions with the formation of gaseous substances, etc.). Such processes can be carried out due to the entropy factor, provided:

Entropy.

ENTROPY (from the Greek entropia - rotation, transformation) (usually denoted S), a function of the state of a thermodynamic system, the change in which dS in an equilibrium process is equal to the ratio of the amount of heat dQ imparted to the system or removed from it to the thermodynamic temperature T of the system. Nonequilibrium processes in an isolated system are accompanied by an increase in entropy; they bring the system closer to an equilibrium state in which S is maximum. The concept of “entropy” was introduced in 1865 by R. Clausius. Statistical physics considers entropy as a measure of the probability of a system being in a given state (Boltzmann principle). The concept of entropy is widely used in physics, chemistry, biology and information theory. Entropy is a function of state, that is, any state can be associated with a completely definite (up to a constant - this uncertainty is removed by agreement that at absolute zero entropy is also zero) entropy value. For reversible (equilibrium) processes, the following mathematical equality holds (a consequence of the so-called Clausius equality) , where δQ is the supplied heat, is the temperature, and are the states, SA and SB are the entropy corresponding to these states (the process of transition from state to state is considered here). For irreversible processes, the inequality following from the so-called Clausius inequality is satisfied , where δQ is the supplied heat, is the temperature, and are the states, SA and SB are the entropy corresponding to these states. Therefore, the entropy of an adiabatically isolated (no heat supply or removal) system can only increase during irreversible processes. Using the concept of entropy, Clausius (1876) gave the most general formulation of the 2nd law of thermodynamics: in real (irreversible) adiabatic processes, entropy increases, reaching a maximum value in a state of equilibrium (the 2nd law of thermodynamics is not absolute, it is violated during fluctuations).