Alcohol is a liquid or gaseous substance. How and when do liquids turn into a gaseous state? Complex compounds of a gaseous nature

To date, more than 3 million different substances are known to exist. And this figure is growing every year, as synthetic chemists and other scientists are constantly making experiments to obtain new compounds that have some useful properties.

Some of the substances are natural inhabitants that form naturally. The other half are artificial and synthetic. However, in both the first and second cases, a significant part is made up of gaseous substances, examples and characteristics of which we will consider in this article.

Aggregate states of substances

Since the 17th century, it has been generally accepted that all known compounds are capable of existing in three states of aggregation: solid, liquid, gaseous substances. However, careful research in recent decades in the field of astronomy, physics, chemistry, space biology and other sciences has proven that there is another form. This is plasma.

What does she represent? This is partially or completely And it turns out that the overwhelming majority of such substances in the Universe. So, it is in the plasma state that there are:

interstellar matter;
space matter;
the upper layers of the atmosphere;
nebulae;
composition of many planets;
stars.

Therefore, today they say that there are solid, liquid, gaseous substances and plasma. By the way, each gas can be artificially transferred to such a state if it is subjected to ionization, that is, forced to turn into ions.

Gaseous substances: examples

There are many examples of substances under consideration. After all, gases have been known since the 17th century, when van Helmont, a naturalist, first obtained carbon dioxide and began to study its properties. By the way, he also gave the name to this group of compounds, since, in his opinion, gases are something disordered, chaotic, associated with spirits and something invisible, but tangible. This name has taken root in Russia.

It is possible to classify all gaseous substances, then it will be easier to give examples. After all, it is difficult to cover all the diversity.

The composition is distinguished:

simple,
complex molecules.

The first group includes those that consist of the same atoms in any number. Example: oxygen - O 2, ozone - O 3, hydrogen - H 2, chlorine - CL 2, fluorine - F 2, nitrogen - N 2 and others.

hydrogen sulfide - H 2 S;
hydrogen chloride - HCL;
methane - CH 4;
sulfur dioxide - SO 2;
brown gas - NO 2;
freon - CF 2 CL 2;
ammonia - NH 3 and others.

Classification by the nature of substances

You can also classify the types of gaseous substances according to belonging to the organic and inorganic world. That is, by the nature of the constituent atoms. Organic gases are:

the first five representatives (methane, ethane, propane, butane, pentane). General formula C n H 2n+2 ;
ethylene - C 2 H 4;
acetylene or ethyne - C 2 H 2;
methylamine - CH 3 NH 2 and others.

Another classification that can be subjected to the compounds in question is division based on the particles that make up the composition. It is from atoms that not all gaseous substances consist. Examples of structures in which ions, molecules, photons, electrons, Brownian particles, plasma are present also refer to compounds in such a state of aggregation.

Properties of gases

The characteristics of substances in the considered state differ from those for solid or liquid compounds. The thing is that the properties of gaseous substances are special. Their particles are easily and quickly mobile, the substance as a whole is isotropic, that is, the properties are not determined by the direction of movement of the constituent structures.

It is possible to designate the most important physical properties of gaseous substances, which will distinguish them from all other forms of the existence of matter.

These are connections that cannot be seen and controlled, felt in ordinary human ways. To understand the properties and identify a particular gas, they rely on four parameters that describe them all: pressure, temperature, amount of substance (mol), volume.
Unlike liquids, gases are able to occupy the entire space without a trace, limited only by the size of the vessel or room.
All gases are easily mixed with each other, while these compounds do not have an interface.
There are lighter and heavier representatives, so under the influence of gravity and time, it is possible to see their separation.
Diffusion is one of the most important properties of these compounds. The ability to penetrate other substances and saturate them from the inside, while making completely disordered movements within its structure.
Real gases cannot conduct electric current, but if we talk about rarefied and ionized substances, then the conductivity increases dramatically.
The heat capacity and thermal conductivity of gases is low and varies from species to species.
Viscosity increases with increasing pressure and temperature.
There are two options for the interphase transition: evaporation - the liquid turns into vapor, sublimation - the solid, bypassing the liquid, becomes gaseous.

A distinctive feature of vapors from true gases is that the former, under certain conditions, are able to pass into a liquid or solid phase, while the latter are not. It should also be noted the ability of the compounds under consideration to resist deformation and be fluid.

Similar properties of gaseous substances allow them to be widely used in various fields of science and technology, industry and the national economy. In addition, specific characteristics are strictly individual for each representative. We have considered only features common to all real structures.

Compressibility

At different temperatures, as well as under the influence of pressure, gases are able to compress, increasing their concentration and reducing the volume occupied. At elevated temperatures they expand, at low temperatures they shrink.

Pressure also changes. The density of gaseous substances increases and, upon reaching a critical point, which is different for each representative, a transition to another state of aggregation may occur.

The main scientists who contributed to the development of the doctrine of gases

There are many such people, because the study of gases is a laborious and historically long process. Let us dwell on the most famous personalities who managed to make the most significant discoveries.

made a discovery in 1811. It doesn't matter what gases, the main thing is that under the same conditions they are contained in one volume of them in an equal amount by the number of molecules. There is a calculated value named after the name of the scientist. It is equal to 6.03 * 10 23 molecules for 1 mole of any gas.
Fermi - created the doctrine of an ideal quantum gas.
Gay-Lussac, Boyle-Marriott - the names of scientists who created the basic kinetic equations for calculations.
Robert Boyle.
John Dalton.
Jacques Charles and many other scientists.

The structure of gaseous substances

The most important feature in the construction of the crystal lattice of the substances under consideration is that at its nodes there are either atoms or molecules that are connected to each other by weak covalent bonds. There are also van der Waals forces when it comes to ions, electrons, and other quantum systems.

Therefore, the main types of lattice structures for gases are:

atomic;
molecular.

The bonds inside break easily, so these compounds do not have a permanent shape, but fill the entire spatial volume. This also explains the lack of electrical conductivity and poor thermal conductivity. But the thermal insulation of gases is good, because, thanks to diffusion, they are able to penetrate solids and occupy free cluster spaces inside them. At the same time, air is not passed, heat is retained. This is the basis for the use of gases and solids in combination for construction purposes.

Simple substances among gases

Which gases belong to this category in terms of structure and structure, we have already discussed above. These are the ones that are made up of the same atoms. There are many examples, because a significant part of non-metals from the entire periodic system under normal conditions exists in this state of aggregation. For example:

white phosphorus - one of this element;
nitrogen;
oxygen;
fluorine;
chlorine;
helium;
neon;
argon;
krypton;
xenon.

The molecules of these gases can be both monatomic (noble gases) and polyatomic (ozone - O 3). The type of bond is covalent non-polar, in most cases it is rather weak, but not in all. The crystal lattice of the molecular type, which allows these substances to easily move from one state of aggregation to another. So, for example, iodine under normal conditions - dark purple crystals with a metallic sheen. However, when heated, they sublimate into clubs of bright purple gas - I 2.

By the way, any substance, including metals, under certain conditions can exist in a gaseous state.

Complex compounds of a gaseous nature

Such gases, of course, are the majority. Various combinations of atoms in molecules, united by covalent bonds and van der Waals interactions, allow the formation of hundreds of different representatives of the aggregate state under consideration.

Examples of precisely complex substances among gases can be all compounds consisting of two or more different elements. This may include:

propane;
butane;
acetylene;
ammonia;
silane;
phosphine;
methane;
carbon disulfide;
sulphur dioxide;
brown gas;
freon;
ethylene and others.

Crystal lattice of molecular type. Many of the representatives easily dissolve in water, forming the corresponding acids. Most of these compounds are an important part of chemical syntheses carried out in industry.

Methane and its homologues

Sometimes the general concept of "gas" denotes a natural mineral, which is a whole mixture of gaseous products of a predominantly organic nature. It contains substances such as:

methane;
ethane;
propane;
butane;
ethylene;
acetylene;
pentane and some others.

In industry, they are very important, because it is the propane-butane mixture that is the household gas on which people cook food, which is used as a source of energy and heat.

Many of them are used for the synthesis of alcohols, aldehydes, acids and other organic substances. The annual consumption of natural gas is estimated at trillions of cubic meters, and this is quite justified.

Oxygen and carbon dioxide

What gaseous substances can be called the most widespread and known even to first graders? The answer is obvious - oxygen and carbon dioxide. After all, they are the direct participants in the gas exchange that occurs in all living beings on the planet.

It is known that it is thanks to oxygen that life is possible, since without it only certain types of anaerobic bacteria can exist. And carbon dioxide is a necessary "nutrition" product for all plants that absorb it in order to carry out the process of photosynthesis.

From a chemical point of view, both oxygen and carbon dioxide are important substances for synthesizing compounds. The first is a strong oxidizing agent, the second is more often a reducing agent.

Halogens

This is such a group of compounds in which atoms are particles of a gaseous substance connected in pairs to each other due to a covalent non-polar bond. However, not all halogens are gases. Bromine is a liquid under ordinary conditions, while iodine is a highly sublimable solid. Fluorine and chlorine are poisonous substances hazardous to the health of living beings, which are the strongest oxidizing agents and are widely used in synthesis.

Mixtures can differ from each other not only in composition, but also by appearance. In accordance with how this mixture looks and what properties it has, it can be attributed either to homogeneous (homogeneous), or to heterogeneous (heterogeneous) mixtures.

Homogeneous (homogeneous) called such mixtures in which even with the help of a microscope it is impossible to detect particles of other substances.

The composition and physical properties in all parts of such a mixture are the same, since there are no interfaces between its individual components.

To homogeneous mixtures relate:

mixtures of gases;
solutions;
alloys.

Gas mixtures

An example of such a homogeneous mixture is air.

Clean air contains various gaseous substances:

nitrogen (its volume fraction in clean air is \(78\)%);
oxygen (\(21\)%);
noble gases - argon and others (\ (0.96 \)%);
carbon dioxide (\(0.04\)%).

The gaseous mixture is natural gas and associated petroleum gas. The main components of these mixtures are gaseous hydrocarbons: methane, ethane, propane and butane.

Also, a gaseous mixture is such a renewable resource as biogas formed during the processing of organic residues by bacteria in landfills, in the tanks of treatment facilities and in special installations. The main component of biogas is methane, which contains an admixture of carbon dioxide, hydrogen sulfide and a number of other gaseous substances.

Gas mixtures: air and biogas. Air can be sold to inquisitive tourists, and biogas obtained from green mass in special containers can be used as fuel

Solutions

This is usually called liquid mixtures of substances, although this term in science has a broader meaning: it is customary to call a solution any(including gaseous and solid) homogeneous mixture substances. So, about liquid solutions.

An important solution found in nature is oil. Liquid products obtained during its processing: gasoline, kerosene, diesel fuel, fuel oil, lubricating oils- are also a mixture of different hydrocarbons.

Pay attention!

To prepare a solution, you need to mix a gaseous, liquid or solid substance with a solvent (water, alcohol, acetone, etc.).

For example, ammonia obtained by dissolving the input gas ammonia. In turn, to prepare iodine tinctures crystalline iodine is dissolved in ethyl alcohol (ethanol).

Liquid homogeneous mixtures (solutions): oil and ammonia

An alloy (solid solution) can be obtained based on any metal, and it can include many different substances.

The most important at present are iron alloys- cast iron and steel.

Iron alloys containing more than \(2\)% carbon are called cast irons, and iron alloys with a lower carbon content are called steels.

What is commonly referred to as "iron" is actually low carbon steel. Except carbon iron alloys may contain silicon, phosphorus, sulfur.

single-phase systems consisting of two or more components. According to their state of aggregation, solutions can be solid, liquid or gaseous. Thus, air is a gaseous solution, a homogeneous mixture of gases; vodka- liquid solution, a mixture of several substances forming one liquid phase; sea water- liquid solution, a mixture of solid (salt) and liquid (water) substances forming one liquid phase; brass- solid solution, a mixture of two solids (copper and zinc) forming one solid phase. A mixture of gasoline and water is not a solution, since these liquids do not dissolve in each other, remaining in the form of two liquid phases with an interface. The components of the solutions retain their unique properties and do not enter into chemical reactions with each other with the formation of new compounds. So, when mixing two volumes of hydrogen with one volume of oxygen, a gaseous solution is obtained. If this gas mixture is ignited, then a new substance is formed- water, which by itself is not a solution. The component present in the solution in a larger amount is called the solvent, the remaining components- dissolved substances.

However, sometimes it is difficult to draw a line between the physical mixing of substances and their chemical interaction. For example, when mixing gaseous hydrogen chloride HCl with water

H2O H ions are formed 3 O + and Cl - . They attract neighboring water molecules to themselves, forming hydrates. Thus, the initial components - HCl and H 2 O - undergo significant changes after mixing. Nevertheless, ionization and hydration (in the general case, solvation) are considered as physical processes occurring during the formation of solutions.

One of the most important types of mixtures that represent a homogeneous phase are colloidal solutions: gels, sols, emulsions and aerosols. The particle size in colloidal solutions is 1-1000 nm, in true solutions

~ 0.1 nm (on the order of molecular size).Basic concepts. Two substances that dissolve in each other in any proportions with the formation of true solutions are called completely mutually soluble. Such substances are all gases, many liquids (for example, ethyl alcohol- water, glycerin - water, benzene - gasoline), some solids (for example, silver - gold). To obtain solid solutions, it is first necessary to melt the starting materials, then mix them and allow to solidify. With their complete mutual solubility, one solid phase is formed; if the solubility is partial, then small crystals of one of the initial components remain in the resulting solid.

If two components form one phase when mixed only in certain proportions, and in other cases two phases occur, then they are called partially mutually soluble. Such, for example, are water and benzene: true solutions are obtained from them only by adding a small amount of water to a large volume of benzene, or a small amount of benzene to a large volume of water. If you mix equal amounts of water and benzene, then a two-phase liquid system is formed. Its lower layer is water with a small amount of benzene, and the upper

- benzene with a small amount of water. There are also substances that do not dissolve one in the other at all, for example, water and mercury. If two substances are only partially mutually soluble, then at a given temperature and pressure, there is a limit to the amount of one substance that can form a true solution with the other under equilibrium conditions. A solution with a limiting concentration of a solute is called saturated. You can also prepare the so-called supersaturated solution, in which the concentration of the solute is even greater than in the saturated one. However, supersaturated solutions are unstable, and with the slightest change in conditions, such as stirring, dust particles, or the addition of solute crystals, an excess of the solute precipitates.

Any liquid begins to boil at the temperature at which the pressure of its saturated vapor reaches the value of the external pressure. For example, water under a pressure of 101.3 kPa boils at 100

° C because at this temperature the water vapor pressure is exactly 101.3 kPa. If, however, some non-volatile substance is dissolved in water, then its vapor pressure will decrease. To bring the vapor pressure of the resulting solution to 101.3 kPa, you need to heat the solution above 100° C. It follows that the boiling point of a solution is always higher than the boiling point of a pure solvent. The decrease in the freezing point of solutions is explained similarly.Raoult's Law. In 1887, the French physicist F. Raul, studying solutions of various non-volatile liquids and solids, established a law relating the decrease in vapor pressure over dilute solutions of non-electrolytes with concentration: the relative decrease in the pressure of a saturated vapor of a solvent over a solution is equal to the mole fraction of a solute. It follows from Raoult's law that an increase in the boiling point or a decrease in the freezing point of a dilute solution compared to a pure solvent is proportional to the molar concentration (or mole fraction) of the solute and can be used to determine its molecular weight.

A solution whose behavior obeys Raoult's law is called ideal. The closest to ideal solutions are non-polar gases and liquids (the molecules of which do not change orientation in an electric field). In this case, the heat of dissolution is zero, and the properties of solutions can be directly predicted, knowing the properties of the initial components and the proportions in which they are mixed. For real solutions, such a prediction cannot be made. During the formation of real solutions, heat is usually released or absorbed. Processes with the release of heat are called exothermic, and those with absorption are called endothermic.

Those characteristics of a solution that depend mainly on its concentration (the number of molecules of a solute per unit volume or mass of the solvent), and not on the nature of the solute, are called

colligative . For example, the boiling point of pure water at normal atmospheric pressure is 100° C, and the boiling point of a solution containing 1 mole of a dissolved (non-dissociating) substance in 1000 g of water is already 100.52° C regardless of the nature of this substance. If the substance dissociates, forming ions, then the boiling point increases in proportion to the growth of the total number of particles of the solute, which, due to dissociation, exceeds the number of molecules of the substance added to the solution. Other important colligative quantities are the freezing point of the solution, the osmotic pressure and the partial vapor pressure of the solvent.Solution concentration is a value that reflects the proportions between a solute and a solvent. Such qualitative concepts as "diluted" and "concentrated" only say that the solution contains little or a lot of solute. To quantify the concentration of solutions, percentages (mass or volume) are often used, and in the scientific literature - the number of moles or chemical equivalents (cm . EQUIVALENT WEIGHT)solute per unit mass or volume of the solvent or solution. Concentration units should always be specified accurately to avoid confusion. Consider the following example. A solution consisting of 90 g of water (its volume is 90 ml, since the density of water is 1 g / ml) and 10 g of ethyl alcohol (its volume is 12.6 ml, since the density of alcohol is 0.794 g / ml), has a mass of 100 g , but the volume of this solution is 101.6 ml (and would be equal to 102.6 ml if, when mixing water and alcohol, their volumes simply added up). The percentage concentration of a solution can be calculated in different ways: or

The concentration units used in the scientific literature are based on such concepts as mole and equivalent, since all chemical calculations and equations of chemical reactions must be based on the fact that substances react with each other in certain ratios. For example, 1 eq. NaCl, equal to 58.5 g, interacts with 1 eq. AgNO 3 equal to 170 g. It is clear that solutions containing 1 equiv. these substances have completely different percentage concentrations.Molarity (M or mol / l) - the number of moles of solute contained in 1 liter of solution.molality (m) is the number of moles of solute contained in 1000 g of solvent.Normality (n.) - the number of chemical equivalents of a solute contained in 1 liter of solution.Mole fraction (dimensionless value) - the number of moles of a given component, referred to the total number of moles of a solute and a solvent. (mole percent is the mole fraction multiplied by 100.)

The most common unit is molarity, but some ambiguities must be taken into account when calculating it. For example, in order to obtain a 1M solution of a given substance, its exact weight, equal to the mol. mass in grams, and bring the volume of the solution to 1 liter. The amount of water needed to prepare this solution may vary slightly depending on temperature and pressure. Therefore, two one-molar solutions prepared under different conditions do not actually have exactly the same concentration. The molality is calculated from a certain mass of solvent (1000 g), which is independent of temperature and pressure. In laboratory practice, it is much more convenient to measure certain volumes of liquids (there are burettes, pipettes, volumetric flasks for this) than to weigh them, therefore, in the scientific literature, concentrations are often expressed in moles, and molality is usually used only for very accurate measurements.

Normality is used to simplify calculations. As we have already said, substances interact with each other in quantities corresponding to their equivalents. Having prepared solutions of different substances of the same normality and taking their equal volumes, we can be sure that they contain the same number of equivalents.

Where it is difficult (or not necessary) to distinguish between solvent and solute, the concentration is measured in mole fractions. Mole fractions, like molality, do not depend on temperature and pressure.

Knowing the densities of a solute and a solution, one can convert one concentration to another: molarity to molality, mole fraction, and vice versa. For dilute solutions of a given solute and solvent, these three quantities are proportional to each other.

Solubility of a given substance is its ability to form solutions with other substances. Quantitatively, the solubility of a gas, liquid, or solid is measured by the concentration of their saturated solution at a given temperature. This is an important characteristic of a substance that helps to understand its nature, as well as to influence the course of reactions in which this substance participates.Gases. In the absence of chemical interaction, gases mix with each other in any proportions, and in this case it makes no sense to talk about saturation. However, when a gas dissolves in a liquid, there is a certain limiting concentration that depends on pressure and temperature. The solubility of gases in some liquids correlates with their ability to liquefy. Most easily liquefied gases such as NH 3 , HCl, SO 2 , are more soluble than gases that are difficult to liquefy, such as O 2 , H 2 and He. In the presence of a chemical interaction between the solvent and the gas (for example, between water and NH 3 or HCl) solubility increases. The solubility of a given gas varies with the nature of the solvent, but the order in which the gases are arranged in accordance with the increase in their solubility remains approximately the same for different solvents.

The dissolution process obeys the principle of Le Chatelier (1884): if a system in equilibrium is subjected to any impact, then as a result of the processes occurring in it, the equilibrium will shift in such a direction that the impact will decrease. The dissolution of gases in liquids is usually accompanied by the release of heat. In this case, in accordance with the principle of Le Chatelier, the solubility of gases decreases. This decrease is the more noticeable, the higher the solubility of gases: such gases have and b

higher heat of solution. The “soft” taste of boiled or distilled water is due to the absence of air in it, since its solubility at high temperatures is very small.

With increasing pressure, the solubility of gases increases. According to Henry's law (1803), the mass of a gas that can dissolve in a given volume of liquid at a constant temperature is proportional to its pressure. This property is used for the preparation of carbonated drinks. Carbon dioxide is dissolved in a liquid at a pressure of 3-4 atm.; under these conditions, 3-4 times more gas (by mass) can dissolve in a given volume than at 1 atm. When a container with such a liquid is opened, the pressure in it drops, and part of the dissolved gas is released in the form of bubbles. A similar effect is observed when opening a bottle of champagne or when underground waters, saturated at great depths with carbon dioxide, come to the surface.

When a mixture of gases is dissolved in one liquid, the solubility of each of them remains the same as in the absence of other components at the same pressure as in the case of a mixture (Dalton's law).

Liquids. The mutual solubility of two liquids is determined by how similar the structure of their molecules (“like dissolves like”). Non-polar liquids, such as hydrocarbons, are characterized by weak intermolecular interactions; therefore, the molecules of one liquid easily penetrate between the molecules of another, i.e. liquids mix well. In contrast, polar and non-polar liquids, such as water and hydrocarbons, do not mix well with each other. Each water molecule must first escape from the environment of other similar molecules, which strongly attract it to itself, and penetrate between hydrocarbon molecules, which weakly attract it. Conversely, hydrocarbon molecules, in order to dissolve in water, must squeeze between water molecules, overcoming their strong mutual attraction, and this requires energy. As the temperature rises, the kinetic energy of the molecules increases, the intermolecular interaction weakens, and the solubility of water and hydrocarbons increases. With a significant increase in temperature, their complete mutual solubility can be achieved. This temperature is called the upper critical solution temperature (UCST).

In some cases, the mutual solubility of two partially miscible liquids increases with decreasing temperature. This effect is observed when heat is released during mixing, usually as a result of a chemical reaction. With a significant decrease in temperature, but not below the freezing point, it is possible to reach the lower critical dissolution temperature (LCST). It can be assumed that all systems that have LCTS also have UCTS (the converse is not necessary). However, in most cases one of the miscible liquids boils below the VCTR. The nicotine-water system has an LCTR of 61

° C, and the VCTR is 208° C. Between 61-208° C these liquids are limitedly soluble, and outside this interval they have complete mutual solubility.Solids. All solids exhibit limited solubility in liquids. Their saturated solutions have a certain composition at a given temperature, which depends on the nature of the solute and solvent. So, the solubility of sodium chloride in water is several million times higher than the solubility of naphthalene in water, and when they are dissolved in benzene, the opposite picture is observed. This example illustrates the general rule that a solid dissolves easily in a liquid that has similar chemical and physical properties to it, but does not dissolve in a liquid with opposite properties.

Salts are usually readily soluble in water and worse in other polar solvents, such as alcohol and liquid ammonia. However, the solubility of salts also varies significantly: for example, ammonium nitrate has millions of times greater solubility in water than silver chloride.

The dissolution of solids in liquids is usually accompanied by the absorption of heat, and according to Le Chatelier's principle, their solubility should increase with heating. This effect can be used to purify substances by recrystallization. To do this, they are dissolved at high temperature until a saturated solution is obtained, then the solution is cooled and, after precipitation of the solute, is filtered. There are substances (for example, calcium hydroxide, sulfate and acetate), the solubility of which in water decreases with increasing temperature.

Solids, like liquids, can also dissolve completely in each other, forming a homogeneous mixture - a true solid solution, similar to a liquid solution. Substances partially soluble in each other form two equilibrium conjugated solid solutions whose compositions change with temperature.

Distribution coefficient. If a solution of a substance is added to an equilibrium system of two immiscible or partially miscible liquids, then it is distributed between the liquids in a certain proportion, independent of the total amount of the substance, in the absence of chemical interactions in the system. This rule is called the distribution law, and the ratio of the concentrations of a solute in liquids is called the distribution coefficient. The distribution coefficient is approximately equal to the ratio of the solubility of a given substance in two liquids, i.e. the substance is distributed between liquids according to its solubility. This property is used to extract a given substance from its solution in one solvent using another solvent. Another example of its use is the process of extracting silver from ores, in which it is often included together with lead. To do this, zinc is added to the molten ore, which does not mix with lead. Silver is distributed between molten lead and zinc, mainly in the upper layer of the latter. This layer is collected and the silver is separated by zinc distillation.Solubility product (ETC ). Between excess (precipitation) of solid M x B y and its saturated solution establishes a dynamic equilibrium described by the equationThe equilibrium constant of this reaction is

and is called the solubility product. It is constant at given temperature and pressure and is the value from which the solubility of the precipitate is calculated and changed. If a compound is added to the solution that dissociates into ions of the same name as the ions of a sparingly soluble salt, then, in accordance with the expression for PR, the solubility of the salt decreases. When adding a compound that reacts with one of the ions, it, on the contrary, will increase.On some properties of solutions of ionic compounds see also ELECTROLYTES. LITERATURE Shakhparonov M.I. Introduction to the molecular theory of solutions . M., 1956
Remy I. Course of inorganic chemistry , tt. 1-2. M., 1963, 1966

3. Hydrocarbons

HYDROCARBONS, organic compounds whose molecules consist only of carbon and hydrogen atoms.

The simplest representative is methane CH 4 . Hydrocarbons are the progenitors of all other organic compounds, a huge variety of which can be obtained by introducing functional groups into the hydrocarbon molecule; therefore, organic chemistry is often defined as the chemistry of hydrocarbons and their derivatives.

Hydrocarbons, depending on the molecular weight, can be gaseous, liquid or solid (but plastic) substances. Compounds containing up to four carbon atoms in a molecule, under normal conditions - gases, such as methane, ethane, propane, butane, isobutane; these hydrocarbons are part of the combustible natural and associated petroleum gases. Liquid hydrocarbons are part of oil and oil products; they typically contain up to sixteen carbon atoms. Some waxes, paraffin, asphalts, bitumen, and tar contain even heavier hydrocarbons; Thus, the composition of paraffin includes solid hydrocarbons containing from 16 to 30 carbon atoms.

Hydrocarbons are divided into open chain compounds - aliphatic, or non-cyclic, compounds with a closed cyclic structure - alicyclic (do not have the property of aromaticity) and aromatic (their molecules contain a benzene ring or fragments built from fused benzene rings). Aromatic hydrocarbons are separated into a separate class, because due to the presence of a closed conjugated system of r-bonds, they have specific properties.

Non-cyclic hydrocarbons can have a non-branched chain of carbon atoms (normal structure molecules) and branched (isostructure molecules). Depending on the type of bonds between carbon atoms, both aliphatic and cyclic hydrocarbons are divided into saturated, containing only simple bonds (alkanes, cycloalkanes) , and unsaturated, containing along with simple multiple bonds (alkenes, cycloalkenes, dienes, alkynes, cyclo-alkynes).

The classification of hydrocarbons is reflected in the diagram (see p. 590), which also gives examples of the structures of representatives of each class of hydrocarbons.

Hydrocarbons are indispensable as an energy source, since the main common property of all these compounds is the release of a significant amount of heat during combustion (for example, the calorific value of methane is 890 kJ / mol). Mixtures of hydrocarbons are used as fuel at thermal stations and boiler houses (natural gas, fuel oil, boiler fuel), as fuel for engines of cars, aircraft and other vehicles (gasoline, kerosene and diesel fuel). Complete combustion of hydrocarbons produces water and carbon dioxide.

In terms of reactivity, various classes of hydrocarbons differ greatly from each other: saturated compounds are relatively inert, for unsaturated compounds, addition reactions by multiple bonds are characteristic, for aromatic compounds, substitution reactions (for example, nitration, sulfonation).

Hydrocarbons are used as initial and intermediate products in organic synthesis. In the chemical and petrochemical industry, not only hydrocarbons of natural origin are used, but also synthetic ones. Methods for obtaining the latter are based on the processing of natural gas (production and use of synthesis gas - a mixture of CO and H2), oil (cracking), coal (hydrogenation), and more recently biomass, in particular agricultural waste, wood processing and other productions.

3.1 Limit hydrocarbons. Alkanes CnH3n+2

Features of the chemical structure

Main physical and chemical properties:

CH4 gas, colorless and odorless, lighter than air, insoluble in water

С-С4 - gas;

C5-C16 - liquid;

C16 and more - solid

Examples of hydrocarbons used in cosmetology, their composition and properties (paraffin, vaseline).

In cosmetics, hydrocarbons are used to create a film that provides a sliding effect (for example, in massage creams) and as structure-forming components of various preparations.

Gaseous hydrocarbons

Methone and ethane are constituents of natural gas. Propane and butane (in liquefied form) - fuel for transport.

Liquid hydrocarbons

Petrol. Transparent, flammable liquid with a typical odor, easily soluble in organic solvents (alcohol, ether, carbon tetrachloride). A mixture of gasoline and air is a strong explosive. Special gasoline is sometimes used to degrease and clean the skin, for example, from the remnants of the patch.

Vaseline oil. Liquid, viscous hydrocarbon with a high boiling point and low viscosity. In cosmetics, it is used as hair oil, skin oil, and is part of creams. Paraffin oil. Transparent, colorless, colorless, odorless, thick, oily substance, high viscosity, insoluble in water, almost insoluble in ethanol, soluble in ether and other organic solvents. Solid hydrocarbons

Paraffin. A mixture of solid hydrocarbons obtained by distillation of the paraffin fraction of oil. Paraffin is a crystalline mass with a specific odor and a neutral reaction. Paraffin is used in thermotherapy. Molten paraffin, which has a high heat capacity, cools slowly and, gradually giving off heat, maintains uniform warming of the body for a long time. Cooling down, the paraffin passes from a liquid state to a solid state and, decreasing in volume, compresses the underlying tissues. Preventing hyperemia of superficial vessels, molten paraffin increases the temperature of tissues and sharply increases sweating. Indications for paraffin therapy are facial seborrhea, acne, especially indurated acne, infiltrated chronic eczema. It is advisable to prescribe facial skin cleansing after a paraffin mask.

Ceresin. A mixture of hydrocarbons obtained during the processing of ozocerite. It is used in decorative cosmetics as a thickening agent, since cook mixes well with fats.

Petrolatum is a mixture of hydrocarbons. It is a good basis for ointments, does not decompose the medicinal substances that make up their composition, mixes with oils and fats in any quantities. All hydrocarbons are not saponified, they cannot penetrate directly through the skin, therefore they are used in cosmetics as a surface protective agent. All liquid, semi-solid and solid hydrocarbons are non-rancid (not attacked by microorganisms).

The considered hydrocarbons are called acyclic. They are contrasted with cyclic (having a benzene ring in the molecule) hydrocarbons that are obtained by distillation of coal tar - benzene (solvent), naphthalene, which was previously used as an anti-moth agent, anthracene and other substances.

3.2 Unsaturated hydrocarbons

Alkenes (ethylene hydrocarbons) - unsaturated hydrocarbons, in the molecules of which there is one double bond

Features of the chemical structure

With 2 H 4 ethylene is a colorless gas with a faint sweet smell, lighter than air, slightly soluble in water.

Principles for naming hydrocarbons:

Hydrocarbons containing a double bond end in -ene.

Ethane C 2 H 6 ethene C 2 H 4

3.3 Cyclic and aromatic hydrocarbons, principles of chemical structure, examples

Arenes (aromatic hydrocarbons), the molecules of which contain stable cyclic structures - benzene nuclei, with a special nature of bonds.

There are no single (C - O and double (C \u003d C)) bonds in the benzene molecule. All bonds are equivalent, their lengths are equal. This is a special type of bond - circular p-conjugation.

Hybridization - ;s p 2 Valence angle -120°

Six non-hybrid bonds form a single -electron system (aromatic nucleus), which is located perpendicular to the plane of the benzene ring.

Chemical properties:

Benzene occupies an intermediate position between saturated and unsaturated hydrocarbons, because. enters into a substitution reaction (it proceeds easily) and addition (it proceeds difficultly).

Azulene. This is a cyclic hydrocarbon obtained synthetically (the natural analogue of chamazulene is obtained from chamomile and yarrow flowers). Azulene has anti-allergic and anti-inflammatory properties, relieves spasm of smooth muscles, accelerates the processes of tissue regeneration and healing. means, as well as in resins for biomechanical depilation.

4. Alcohols

4.1 Definition

Alcohols are organic compounds in which one hydrogen atom (H) has been replaced by a hydroxyl group (OH).

4.2 Functional groups. Classification of alcohols into monohydric and polyhydric alcohols, examples. Principles for naming alcohols

In accordance with the number of OH groups, mono- and polyhydric alcohols are distinguished.

Depending on the location of the OH group, alcohols are divided into primary, secondary and tertiary. Unlike paraffin hydrocarbons, they have a relatively high boiling point. All polyhydric alcohols have a sweetish aftertaste.

Short chain alcohols are hydrophilic, i.e. they are miscible with water and readily dissolve hydrophilic substances. Monohydric alcohols with long chains are almost or completely insoluble in water, i.e. hydrophobic.

Alcohols with a large mass of molecules (fatty alcohols) are solid at room temperature (for example, myristyl or cetyl alcohol). Alcohol containing more than 24 carbon atoms is called waxed alcohol.

With an increase in the number of hydroxyl groups, the sweet taste and the solubility of alcohol in water increase. Therefore, glycerol (3-atomic alcohol), similar to oil, dissolves well in water. Solid 6-atomic alcohol sorbitol is used as a sugar substitute for diabetic patients.

4.3 Basic chemical and physical properties of alcohols, their use in cosmetology (methanol, ethanol, isopropanol, glycerin)

Monohydric alcohols

Methanol (methyl alcohol, wood alcohol) is a clear, colorless liquid, easily miscible with water, alcohol and ether. This highly toxic substance is not used in cosmetics.

Ethanol (ethyl alcohol, wine alcohol, food alcohol) is a transparent, colorless, volatile liquid, can be mixed with water and organic solvents, is much less toxic than methanol, is widely used in medicine and cosmetics as a solvent for biologically active substances (essential oils). , resins, iodine, etc.). Ethanol is obtained from the fermentation of substances containing sugar and starch. The fermentation process occurs due to yeast enzymes. After fermentation, alcohol is isolated by distillation. Then purification from undesirable impurity substances (rectification) is carried out. Ethanol enters pharmacies mainly with a strength of 96 °. Other mixtures of ethanol with water contain 90, 80, 70, 40% alcohol. Almost pure alcohol (with very small amounts of water) is called absolute alcohol.

Depending on the purpose of the use of alcohol, it is flavored with various additives (essential oils, camphor). Ethanol promotes the expansion of subcutaneous capillaries, has a disinfectant effect.

Eau de toilette for the face can contain from 0 to 30% alcohol, hair lotion - about 50%, cologne - at least 70%. Lavender water contains about 3% essential oil. Perfumes contain from 12 to 20% essential oils and a fixative, colognes contain about 9% essential oils and a little fixative. Isopropanol (isopropyl alcohol) - a complete and inexpensive substitute for ethanol, refers to secondary alcohols. Even purified isopropyl alcohol has a characteristic odor that cannot be eliminated. The disinfectant and degreasing properties of isopropanol are stronger than those of ethyl alcohol. It is used only externally, as part of eau de toilette for hair, in fixatives, etc. Vodka should not contain isopropanol, and a small amount of it is allowed in alcohol tincture on coniferous needles (coniferous concentrate).

Polyhydric alcohols

Dihydric alcohols have the standard ending of the name - glycol. In cosmetic preparations, propylene glycol, which has low toxicity, is used as a solvent and moisturizer. Dihydric alcohols, or glycols, are called diols according to substitutional nomenclature. Trihydric alcohol - glycerol - is widely used in medicine and pharmaceuticals. The consistency of glycerin is similar to syrup, almost odorless, hygroscopic, has a sweet aftertaste, soluble in all other substances containing an OH group, insoluble in ether, gasoline, chloroform, fatty and essential oils. 86 - 88% glycerin and dehydrated 98% glycerin enter the trade. In diluted form, glycerin is found in skin creams, facial toilet water, toothpastes, shaving soaps, and hand gels. Diluted in the appropriate proportion, it softens the skin, makes it supple, replacing the skin's natural moisture factor. In its pure form, it is not used in skin care preparations, as it dries it out. and human health organic chemistry Academy of Sciences of the USSR, one of the organizers ... to several areas organic chemistry - chemistry alicyclic compounds, chemistry heterocycles, organic catalysis chemistry protein and amino acids. ...

Ionic association effects in organic chemistry

Abstract >> Chemistry

Stereochemical orientation of the process. AT organic chemistry interest in ion pairs arose ... the most striking achievements of physical organic chemistry. Reaction studies, in ... then the concept of ion pairs in organic chemistry has undergone significant changes; were...

I remember how the definition of the aggregate state of matter was explained to us back in elementary school. The teacher gave a good example about the tin soldier and then everything became clear to everyone. Below I will try to refresh my memories.

Determine the state of matter

Well, everything is simple here: if the substance is taken in hand, you can feel it and when you press it, it retains its volume and shape - this is a solid state. In a liquid state, a substance does not retain its shape, but retains its volume. For example, there is water in a glass, at the moment it has the shape of a glass. And if it is poured into a cup, it will take the form of a cup, but the amount of water itself will not change. This means that a substance in a liquid state can change shape, but not volume. In the gaseous state, neither the shape nor the volume of the substance is preserved, but it tries to fill all the available space.

And in relation to the table, it is worth mentioning that sugar and salt may seem like liquid substances, but in fact they are loose substances, their entire volume consists of small solid crystals.

States of matter: liquid, solid, gaseous

All substances in the world are in a certain state: solid, liquid or gas. And any substance can go from one state to another. Surprisingly, even a tin soldier can be liquid. But for this it is necessary to create certain conditions, namely, to place it in a very, very hot room, where the tin will melt and turn into liquid metal.

But the easiest way to consider the state of aggregation on the example of water.

If liquid water is frozen, it will turn into ice - this is its solid state.
If liquid water is strongly heated, then it will begin to evaporate - this is its gaseous state.
And if you heat the ice, it will begin to melt and again turn into water - this is called the liquid state.

It is especially worth highlighting the process of condensation: if you concentrate and cool the evaporated water, then the gaseous state will turn into a solid one - this is called condensation, and this is how snow forms in the atmosphere.