Reaction of water with a simple substance. II

Water is the most common solvent on planet Earth, which largely determines the nature of terrestrial chemistry as a science. Most of chemistry, at its inception as a science, began precisely as the chemistry of aqueous solutions of substances. It is sometimes considered as an ampholyte - both an acid and a base at the same time (cation H+ anion OH−). In the absence of foreign substances in water, the concentration of hydroxide ions and hydrogen ions (or hydronium ions) is the same, pKa ≈ approx. 16.

Water is a chemically quite active substance. Highly polar water molecules solvate ions and molecules and form hydrates and crystalline hydrates. Solvolysis, and in particular hydrolysis, occurs in living and nonliving nature, and is widely used in the chemical industry.

Water reacts at room temperature:

WITH active metals(sodium, potassium, calcium, barium, etc.)

With halogens (fluorine, chlorine) and interhalogen compounds

With salts formed by a weak acid and a weak base, causing their complete hydrolysis

With anhydrides and acid halides of carboxylic and inorganic acids

With active metal organic compounds(diethylzinc, Grignard reagents, methyl sodium, etc.)

With carbides, nitrides, phosphides, silicides, hydrides of active metals (calcium, sodium, lithium, etc.)

With many salts, forming hydrates

With boranes, silanes

With ketenes, carbon dioxide

With noble gas fluorides

Water reacts when heated:

With iron, magnesium

With coal, methane

With some alkyl halides

Water reacts in the presence of a catalyst:

With amides, esters of carboxylic acids

With acetylene and other alkynes

With alkenes

With nitriles

The chemical properties of water are determined by the features of its structure. Water is a fairly stable substance; it begins to decompose into hydrogen and oxygen when heated to at least 1000 ° C (thermal dissociation occurs) or under the influence of ultraviolet radiation (photochemical dissociation).

Water is a chemically active compound. For example, it reacts with fluorine. Chlorine, when heated or exposed to light, decomposes water releasing atomic oxygen:

H2O + Cl2 = HCl + HClO (HClO = HCl + O)

Under normal conditions, it interacts with active metals:

2H2O + Ca = Ca(OH) 2 + H2

2H2O + 2Na = 2NaOH + H2

Water also reacts with many non-metals. For example, when interacting with atomic oxygen, hydrogen peroxide is formed:

H2O + O = H2O2

Many oxides react with water to form bases and acids:

CO2 + H2O = H2CO3

CaO + H2O = Ca(OH)2

When interacting with some salts, crystalline hydrates are formed. When heated, they lose water of crystallization:

Na2CO3 + 10H2O = Na2CO3*10H2O

Water also decomposes most salts (called hydrolysis).

Noble metals do not react with water.

In addition to the main ions, the content of which in water is quite high, a number of elements: nitrogen, phosphorus, silicon, aluminum, iron, fluorine are present in it in concentrations from 0.1 to 10 mg/l. They are called mesoelements (from the Greek “mesos” - “average”, “intermediate”).

Nitrogen in the form of nitrates NO3- enters reservoirs with rainwater, and in the form of amino acids, urea (NH2)2CO and ammonium salts NH4+ during the decomposition of organic residues.

Phosphorus exists in water in the form of hydrogen phosphates HPO32- and dihydrogen phosphates H2PO3-, formed as a result of the decomposition of organic residues.

Silicon is a constant component of the chemical composition natural waters. This is facilitated, in contrast to other components, by the ubiquity of silicon compounds in rocks, and only the low solubility of the latter explains the low silicon content in water. The concentration of silicon in natural waters is usually several milligrams per liter. In underground waters it increases and often reaches tens of milligrams per liter, and in hot thermal waters - even hundreds. In addition to temperature, the solubility of silicon is strongly influenced by an increase in the pH of the solution. The relatively low silicon content in surface waters, inferior to the solubility of silicon dioxide (125 mg/l at 26 °C, 170 mg/l at 38 °C), indicates the presence of processes in water that reduce its concentration. These include the consumption of silicon by aquatic organisms, many of which, such as diatoms, build their skeletons from silicon. In addition, silicic acid, being weaker, is displaced from the solution by carbonic acid:

Na4SiO4 + 4CO2 + 4H2O = H4SiO4 + 4NaHCO3

The instability of silicon in solution also contributes to the tendency of silicic acid to turn into a gel under certain conditions. In very lightly mineralized waters, silicon constitutes a significant and sometimes predominant part of the chemical composition of the water, despite its low absolute content. The presence of silicon in water is a serious hindrance in technology, since when water is boiled for a long time, silicon forms a very hard silicate scale in boilers.

Aluminum enters water bodies as a result of the action of acids on clays (kaolin):

Al2(OH)4 + 6H+ = 2SiO2 + 5H2O + 2Al3+

The main source of iron is iron-containing clays. Organic residues (hereinafter referred to as “C”) in contact with them reduce iron to divalent, which is slowly washed out in the form of bicarbonate or salts of humic acids:

2Fe2O3 + "C" + 4H2O + 7CO2 = 4Fe(HCO3)2

When water with Fe2+ ions dissolved in it comes into contact with air, iron quickly oxidizes, forming a brown precipitate of Fe(OH)3 hydroxide. Over time, it turns into swamp ore - brown iron ore (limonite) FeO(OH). Karelian bog ore was used in the 18th-19th centuries to obtain iron.

The bluish film on the surface of the water is Fe(OH)3, which forms when groundwater containing Fe2+ ions comes into contact with air. It is often confused with an oil film, but it is very easy to distinguish them: the iron hydroxide film has jagged edges. If the surface of the water is slightly agitated, the hydroxide film, unlike the oil film, will not overflow.

The chemical composition of natural water is determined by the history preceding it, i.e. the path taken by water during its cycle. The amount of dissolved substances in such water will depend, on the one hand, on the composition of the substances with which it came into contact, and on the other, on the conditions under which these interactions occurred. influence chemical composition water can be caused by the following factors: rocks, soils, living organisms, human activities, climate, relief, water regime, vegetation, hydrogeological and hydrodynamic conditions, etc. Let's consider just some of the factors influencing the composition of water.

Soil solution and atmospheric precipitation filtered through the soil can enhance the dissolution of rocks and minerals. This is one of the most important properties of the soil, influencing the formation of the composition of natural waters, and is the result of an increase in the concentration of carbon dioxide in the soil solution, released during the respiration of living organisms and the root system in soils and the biochemical decomposition of organic residues. As a result, the concentration of CO2 in soil air increases from 0.033% typical atmospheric air, up to 1% or more in the soil air (in heavy clay soils, the concentration of CO2 in the soil air sometimes reaches 5-10%, thereby giving the solution a strong aggressive effect towards rocks). Another factor that enhances the aggressive effect of water filtered through the soil is organic matter - soil humus, which is formed in soils during the transformation of plant residues. In the composition of humus, humic and fulvic acids and simpler compounds, for example organic acids (citric, oxalic, acetic, malic, etc.), amines, etc., should be mentioned first of all as active reagents. The soil solution, enriched with organic acids and CO2, greatly accelerates the chemical weathering of aluminosilicates contained in soils. Likewise, water filtering through the soil accelerates the chemical weathering of aluminosilicates and carbonate rocks underlying the soil. Limestone easily forms soluble (up to 1.6 g/l) calcium bicarbonate:

CaCO3 + H2O + CO2 ↔ Ca(HCO3)2

In almost the entire European part of Russia (except for Karelia and the Murmansk region), limestones, as well as dolomites MgCO3 CaCO3, occur quite close to the surface. Therefore, the water here contains mainly calcium and magnesium bicarbonates. In rivers such as the Volga, Don, Northern Dvina, and their main tributaries, calcium and magnesium bicarbonates make up from 3/4 to 9/10 of all dissolved salts.

Salts also enter water bodies as a result of human activity. So, sodium and calcium chlorides are sprinkled on roads in winter to melt the ice. In spring, chlorides flow into rivers along with meltwater. A third of the chlorides in the rivers of the European part of Russia were brought there by humans. In the rivers on which they stand major cities, this share is much larger.

The terrain indirectly affects the composition of water, contributing to the leaching of salts from the rock mass. The depth of the erosional incision of the river facilitates the entry of more mineralized groundwater from the lower horizons into the river. This is also facilitated by other types of depressions (river valleys, ravines, ravines), which improve the drainage of the catchment area.

The climate creates the general background against which most processes occur that influence the formation of the chemical composition of natural waters. Climate primarily determines the balance of heat and moisture, which determines the moisture content of the area and the volume of water flow, and, consequently, the dilution or concentration of natural solutions and the possibility of substances dissolving or precipitating.

The chemical composition of water and its changes over time are greatly influenced by the power sources of a water body and their ratio. During the period of snow melting, the water in rivers, lakes and reservoirs has a lower mineralization than during the period when most of the nutrition comes from groundwater and groundwater. This circumstance is used to regulate the filling of reservoirs and the discharge of water from them. As a rule, reservoirs are filled during the spring flood, when the inflow water has less mineralization.

WATER

A water molecule consists of an oxygen atom and two hydrogen atoms attached to it at an angle of 104.5°.

The angle of 104.5° between the bonds in a water molecule determines the friability of ice and liquid water and, as a consequence, the anomalous dependence of density on temperature. This is why large bodies of water do not freeze to the bottom, which makes life possible in them.

Physical properties

WATER, ICE AND STEAM,respectively liquid, solid and gaseous states chemical compound molecular formula H 2 O.

Due to the strong attraction between molecules, water has high melting points (0C) and boiling points (100C). A thick layer of water has a blue color, which is determined not only by its physical properties, but also by the presence of suspended particles of impurities. The water of mountain rivers is greenish due to the suspended particles of calcium carbonate it contains. Pure water is a poor conductor of electricity. The density of water is maximum at 4C; it is equal to 1 g/cm3. Ice has a lower density than liquid water and floats to its surface, which is very important for the inhabitants of reservoirs in winter.

Water has an extremely high heat capacity, so it heats up slowly and cools down slowly. Thanks to this, water pools regulate the temperature on our planet.

Chemical properties of water

Water is a highly reactive substance. Under normal conditions, it reacts with many basic and acidic oxides, as well as with alkali and alkaline earth metals. Water forms numerous compounds - crystalline hydrates.

Under the influence electric current water decomposes into hydrogen and oxygen:

2H2O electric current= 2 H 2 + O 2

Video "Electrolysis of water"

Magnesium reacts with hot water to form an insoluble base:

Mg + 2H 2 O = Mg(OH) 2 + H 2

Beryllium with water forms an amphoteric oxide: Be + H 2 O = BeO + H 2

1. Active metals are:

Li, Na, K, Rb, Cs, Fr– 1 group “A”

Ca, Sr, Ba, Ra– 2nd group “A”

2. Metal activity series

3. Alkali is a water-soluble base, a complex substance which includes an active metal and a hydroxyl group OH ( I).

4. Medium activity metals in the voltage range range from MgtoPb(aluminum in special position)

Video "Interaction of sodium with water"

Remember!!!

Aluminum reacts with water like active metals to form a base:

2Al + 6H 2 O = 2Al( OH) 3 + 3H 2

Video "Interaction of acid oxides with water"

Using the sample, write down the interaction reaction equations:

WITHO2 + H2O =

SO 3 + H 2 O =

Cl 2 O 7 + H 2 O =

P 2 O 5 + H 2 O (hot) =

N 2 O 5 + H 2 O =

Remember! Only oxides of active metals react with water. Metal oxides average activity and metals that come after hydrogen in the activity series do not dissolve in water, for example, CuO + H 2 O = reaction is not possible.

Video "Interaction of metal oxides with water"

Li + H 2 O =

Cu + H2O =

ZnO + H2O =

Al + H 2 O =

Ba + H 2 O =

K 2 O + H 2 O =

Mg + H2O =

N 2 O 5 + H 2 O =

The most important substance of our planet, unique in its properties and composition, is, of course, water. After all, it is thanks to her that there is life on Earth, while on other objects known today solar system she's not there. Solid, liquid, in the form of steam - any of it is needed and important. Water and its properties are the subject of study of a whole scientific discipline- hydrology.

The amount of water on the planet

If we consider the indicator of the amount of this oxide in all states of aggregation, then it is about 75% of the total mass on the planet. In this case, one should take into account bound water in organic compounds, living things, minerals and other elements.

If we take into account only the liquid and solid states of water, the figure drops to 70.8%. Let's consider how these percentages are distributed, where the substance in question is contained.

There is 360 million km 2 of salt water in the oceans and seas, and saline lakes on Earth.
Fresh water is distributed unevenly: 16.3 million km 2 of it is encased in ice in the glaciers of Greenland, the Arctic, and Antarctica.
5.3 million km 2 of hydrogen oxide is concentrated in fresh rivers, swamps and lakes.
Groundwater amounts to 100 million m3.

That is why astronauts from distant outer space can see the Earth in the shape of a blue ball with rare inclusions of land. Water and its properties, knowledge of the structural features are important elements science. In addition, recently humanity has begun to experience a clear shortage of fresh water. Perhaps such knowledge will help in solving this problem.

Composition of water and molecular structure

If we consider these indicators, the properties that this amazing substance exhibits will immediately become clear. Thus, a water molecule consists of two hydrogen atoms and one oxygen atom, therefore it has the empirical formula H 2 O. In addition, the electrons of both elements play an important role in the construction of the molecule itself. Let's see what the structure of water and its properties are.

It is obvious that each molecule is oriented around the other, and together they form a common crystal lattice. It is interesting that the oxide is built in the shape of a tetrahedron - an oxygen atom in the center, and two pairs of electrons and two hydrogen atoms around it asymmetrically. If you draw lines through the centers of the nuclei of atoms and connect them, you will get exactly a tetrahedral geometric shape.

The angle between the center of the oxygen atom and the hydrogen nuclei is 104.5 0 C. Length O-N connections= 0.0957 nm. The presence of electron pairs of oxygen, as well as its greater electron affinity compared to hydrogen, ensures the formation of a negatively charged field in the molecule. In contrast, the hydrogen nuclei form the positively charged part of the compound. Thus, it turns out that the water molecule is a dipole. This determines what water can be, and its physical properties also depend on the structure of the molecule. For living beings, these features play a vital role.

Basic physical properties

These usually include the crystal lattice, boiling and melting points, and special individual characteristics. Let's consider all of them.

The structure of the crystal lattice of hydrogen oxide depends on the state of aggregation. It can be solid - ice, liquid - basic water under normal conditions, gaseous - steam when the water temperature rises above 100 0 C. Ice forms beautiful patterned crystals. The lattice as a whole is loose, but the connection is very strong and the density is low. You can see it in the example of snowflakes or frosty patterns on glass. In ordinary water, the lattice does not have a constant shape; it changes and passes from one state to another.
Water molecule in outer space has the correct shape of a ball. However, under the influence earthly power gravity it is distorted and in liquid state takes the form of a vessel.
The fact that hydrogen oxide is a dipole in structure determines the following properties: high thermal conductivity and heat capacity, which can be seen in the rapid heating and long cooling of the substance, the ability to orient both ions and individual electrons and compounds around itself. This makes water a universal solvent (both polar and neutral).
The composition of water and the structure of the molecule explain the ability of this compound to form multiple hydrogen bonds, including with other compounds that have lone electron pairs (ammonia, alcohol, and others).
The boiling point of liquid water is 100 0 C, crystallization occurs at +4 0 C. Below this indicator there is ice. If you increase the pressure, the boiling point of water will increase sharply. Yes, when high atmospheres You can melt lead in it, but it won’t even boil (over 300 0 C).
The properties of water are very significant for living beings. For example, one of the most important is surface tension. This is the formation of a thin protective film on the surface of hydrogen oxide. It's about about liquid water. It is very difficult to break this film by mechanical action. Scientists have found that you will need strength, equal to weight 100 tons. How to spot it? The film is obvious when water drips slowly from the faucet. It can be seen that it is as if in some kind of shell, which is stretched to a certain limit and weight and comes off in the form of a round droplet, slightly distorted by gravity. Thanks to surface tension many objects can be on the surface of the water. Insects with special adaptations can move freely along it.
Water and its properties are anomalous and unique. According to organoleptic indicators, this compound is a colorless liquid without taste or odor. What we call the taste of water is the minerals and other components dissolved in it.
The electrical conductivity of hydrogen oxide in the liquid state depends on how many and what salts are dissolved in it. Distilled water, which does not contain any impurities, does not conduct electric current.

Ice is a special state of water. In the structure of this state, the molecules are connected to each other by hydrogen bonds and form a beautiful crystal lattice. But it is quite unstable and can easily split, melt, that is, become deformed. There are many voids between the molecules, the dimensions of which exceed the dimensions of the particles themselves. Due to this, the density of ice is less than that of liquid hydrogen oxide.

It has great value for rivers, lakes and other fresh water bodies. Indeed, in winter, the water in them does not freeze completely, but only becomes covered with a dense crust more light ice, floating to the top. If this property were not characteristic of the solid state of hydrogen oxide, then the reservoirs would freeze through. Life under water would be impossible.

In addition, the solid state of water is of great importance as a source of huge amounts of fresh drinking water. These are glaciers.

A special property of water can be called the triple point phenomenon. This is a state in which ice, steam and liquid can exist simultaneously. This requires the following conditions:

high pressure - 610 Pa;
temperature 0.01 0 C.

Water clarity varies depending on foreign matter. The liquid can be completely transparent, opalescent, or cloudy. Waves of yellow and red colors are absorbed, violet rays penetrate deeply.

Chemical properties

Water and its properties are an important tool in understanding many life processes. Therefore they have been studied very well. Thus, hydrochemistry is interested in water and its chemical properties. Among them are the following:

Rigidity. This is a property that is explained by the presence of calcium and magnesium salts and their ions in solution. It is divided into permanent (salts of the named metals: chlorides, sulfates, sulfites, nitrates), temporary (bicarbonates), which is eliminated by boiling. In Russia, water is softened before use. chemically for better quality.
Mineralization. A property based on the dipole moment of hydrogen oxide. Thanks to its presence, molecules are able to attach to themselves many other substances, ions and hold them. This is how associates, clathrates and other associations are formed.
Redox properties. As a universal solvent, catalyst, and associate, water is capable of interacting with many simple and complex compounds. With some it acts as an oxidizing agent, with others - vice versa. As a reducing agent it reacts with halogens, salts, some less active metals, and with many organic substances. Studies the latest transformations organic chemistry. Water and its properties, in particular chemical ones, show how universal and unique it is. As an oxidizing agent, it reacts with active metals, some binary salts, many organic compounds, carbon, and methane. At all chemical reactions with the participation of this substance require the selection of certain conditions. The outcome of the reaction will depend on them.
Biochemical properties. Water is an integral part of all biochemical processes in the body, being a solvent, catalyst and medium.
Interaction with gases to form clathrates. Ordinary liquid water can absorb even chemically inactive gases and place them inside cavities between the molecules of the internal structure. Such compounds are usually called clathrates.
With many metals, hydrogen oxide forms crystalline hydrates, in which it is included unchanged. For example, copper sulfate (CuSO 4 * 5H 2 O), as well as ordinary hydrates (NaOH * H 2 O and others).
Water is characterized by compound reactions in which new classes of substances (acids, alkalis, bases) are formed. They are not redox.
Electrolysis. Under the influence of an electric current, the molecule decomposes into its component gases - hydrogen and oxygen. One of the ways to obtain them is in the laboratory and industry.

From the point of view of Lewis theory, water is weak acid and a weak base at the same time (ampholyte). That is, we can talk about a certain amphotericity in chemical properties.

Water and its beneficial properties for living beings

It is difficult to overestimate the importance that hydrogen oxide has for all living things. After all, water is the very source of life. It is known that without it a person could not live even a week. Water, its properties and importance are simply colossal.

It is universal, that is, capable of dissolving both organic and inorganic compounds, a solvent active in living systems. That is why water is the source and medium for all catalytic biochemical transformations to occur, with the formation of complex vital complex compounds.
The ability to form hydrogen bonds makes this substance universal in withstanding temperatures without changing its state of aggregation. If this were not so, then with the slightest decrease in degrees it would turn into ice inside living beings, causing cell death.
For humans, water is the source of all basic household goods and needs: cooking, washing, cleaning, taking a bath, bathing and swimming, etc.
Industrial plants (chemical, textile, engineering, food, oil refining and others) would not be able to carry out their work without the participation of hydrogen oxide.
Since ancient times it was believed that water is a source of health. It was and is used today as a medicinal substance.
Plants use it as their main source of nutrition, due to which they produce oxygen, the gas that allows life to exist on our planet.

We can name dozens more reasons why water is the most widespread, important and necessary substance for all living and artificially created objects. We have cited only the most obvious, main ones.

Hydrological cycle of water

In other words, this is its cycle in nature. A very important process that allows us to constantly replenish dwindling water supplies. How does it happen?

There are three main participants: underground (or groundwater) water, surface water and the World Ocean. The atmosphere, which condenses and produces precipitation, is also important. Also active participants in the process are plants (mainly trees), capable of absorbing huge amounts of water per day.

So, the process goes as follows. Groundwater fills underground capillaries and flows to the surface and the World Ocean. Surface water is then absorbed by plants and transpired into environment. Evaporation also occurs from vast areas of oceans, seas, rivers, lakes and other bodies of water. Once in the atmosphere, what does water do? It condenses and flows back in the form of precipitation (rain, snow, hail).

If these processes had not occurred, then water supplies, especially fresh water, would have run out long ago. That is why people pay great attention to the protection and normal hydrological cycle.

Concept of heavy water

In nature, hydrogen oxide exists as a mixture of isotopologues. This is due to the fact that hydrogen forms three types of isotope: protium 1 H, deuterium 2 H, tritium 3 H. Oxygen, in turn, also does not lag behind and forms three stable forms: 16 O, 17 O, 18 O. It is thanks to Therefore, there is not just ordinary protium water of the composition H 2 O (1 H and 16 O), but also deuterium and tritium.

At the same time, it is deuterium (2 H) that is stable in structure and form, which is included in the composition of almost all natural waters, but in small quantities. This is what they call heavy. It is somewhat different from normal or light in all respects.

Heavy water and its properties are characterized by several points.

Crystallizes at a temperature of 3.82 0 C.
Boiling is observed at 101.42 0 C.
The density is 1.1059 g/cm3.
As a solvent it is several times worse than light water.
Has chemical formula D2O.

When conducting experiments showing the influence of such water on living systems, it was found that only some types of bacteria are capable of living in it. It took time for the colonies to adapt and acclimatize. But, having adapted, they completely restored all vital functions (reproduction, nutrition). In addition, steel is very resistant to radiation. Experiments on frogs and fish did not give a positive result.

Modern areas of application of deuterium and the heavy water formed by it - nuclear and nuclear power. Such water can be obtained in laboratory conditions using ordinary electrolysis - it is formed as a by-product. Deuterium itself is formed during repeated distillations of hydrogen in special devices. Its use is based on its ability to slow down neutron fusions and proton reactions. It is heavy water and hydrogen isotopes that are the basis for creating nuclear and hydrogen bombs.

Experiments on the use of deuterium water by people in small quantities have shown that it does not linger for long - complete withdrawal is observed after two weeks. It cannot be used as a source of moisture for life, but its technical significance is simply enormous.

Melt water and its use

Since ancient times, the properties of such water have been identified by people as healing. It has long been noticed that when the snow melts, animals try to drink water from the resulting puddles. Later, its structure and biological effects on the human body were carefully studied.

Melt water, its characteristics and properties are in the middle between ordinary light water and ice. From the inside, it is formed not just by molecules, but by a set of clusters formed by crystals and gas. That is, inside the voids between the structural parts of the crystal there are hydrogen and oxygen. By general appearance The structure of melt water is similar to the structure of ice - its structure is preserved. The physical properties of such hydrogen oxide change slightly compared to conventional ones. However, the biological effect on the body is excellent.

When water is frozen, the first fraction turns into ice, the heavier part is deuterium isotopes, salts and impurities. Therefore, this core should be removed. But the rest of the part is clean, structured and healthy water. What is the effect on the body? Scientists from the Donetsk Research Institute named the following types of improvements:

Acceleration of recovery processes.
Strengthening the immune system.
In children, after inhalation of such water, colds are restored and cured, coughs, runny noses, etc. go away.
Breathing, condition of the larynx and mucous membranes improves.
The general well-being of a person and activity increase.

Today there are a number of supporters of treatment with melt water who write their positive reviews. However, there are scientists, including doctors, who do not support these views. They believe that there will be no harm from such water, but there is little benefit either.

Energy

Why can the properties of water change and be restored when transitioning to different states of aggregation? The answer to this question is: of this connection has its own information memory, which records all changes and leads to the restoration of structure and properties in right time. The bioenergy field through which part of the water passes (that which comes from space) carries a powerful charge of energy. This pattern is often used in treatment. However, from a medical point of view, not every water can have a beneficial effect, including informational.

Structured water - what is it?

This is water that has a slightly different structure of molecules, location crystal lattices(the same as seen in ice), but it is still a liquid (melt is also of this type). In this case, the composition of water and its properties with scientific point vision do not differ from those characteristic of ordinary hydrogen oxide. Therefore, structured water cannot have such a broad healing effect that esotericists and supporters of alternative medicine attribute to it.

Hydrogen oxide (H 2 O), much better known to all of us under the name “water,” without exaggeration, is the main liquid in the life of organisms on Earth, since all chemical and biological reactions take place either with the participation of water or in solutions.

Water is the second most important substance for the human body, after air. A person can live without water for no more than 7-8 days.

Pure water in nature can exist in three states of aggregation: solid - in the form of ice, liquid - water itself, in gaseous - in the form of steam. Such variety states of aggregation There is no other substance in nature that can boast of this.

Physical properties of water

at no. - it is a colorless, odorless and tasteless liquid;
water has high heat capacity and low electrical conductivity;
melting point 0°C;
boiling point 100°C;
the maximum density of water at 4°C is 1 g/cm 3 ;
water is a good solvent.

Structure of a water molecule

A water molecule consists of one oxygen atom, which is connected to two hydrogen atoms, while O-H connections form an angle of 104.5°, while the common electron pairs are shifted towards the oxygen atom, which is more electronegative compared to hydrogen atoms, therefore, a partial negative charge is formed on the oxygen atom, respectively, a positive charge is formed on the hydrogen atoms. Thus, a water molecule can be considered as a dipole.

Water molecules can form hydrogen bonds with each other, being attracted by oppositely charged parts (hydrogen bonds are shown with dotted lines in the figure):

Formation hydrogen bonds explains the high density of water, its boiling and melting points.

The number of hydrogen bonds depends on temperature - the higher the temperature, the fewer bonds are formed: in water vapor there are only individual molecules; in the liquid state - associates (H 2 O) n are formed, in crystalline state Each water molecule is connected to neighboring molecules by four hydrogen bonds.

Chemical properties of water

Water “willingly” reacts with other substances:

Water reacts with alkali and alkaline earth metals at zero conditions: 2Na+2H 2 O = 2NaOH+H 2
Water reacts with less active metals and non-metals only when high temperature: 3Fe+4H 2 O=FeO → Fe 2 O 3 +4H 2 C+2H 2 O → CO 2 +2H 2
with basic oxides at no. water reacts to form bases: CaO+H 2 O = Ca(OH) 2
with acid oxides at no. water reacts to form acids: CO 2 + H 2 O = H 2 CO 3
water is the main participant in hydrolysis reactions (for more details, see Hydrolysis of Salts);
water participates in hydration reactions by joining organic matter with double and triple bonds.

Solubility of substances in water

highly soluble substances - more than 1 g of substance dissolves in 100 g of water at standard conditions;
poorly soluble substances - 0.01-1 g of substance dissolves in 100 g of water;
practically insoluble substances - less than 0.01 g of substance dissolves in 100 g of water.

Absolutely insoluble substances does not exist in nature.

Grounds – complex substances that consist of a metal cation Me + (or a metal-like cation, for example, ammonium ion NH 4 +) and a hydroxide anion OH -.

Based on their solubility in water, bases are divided into soluble (alkalis) And insoluble bases . There is also unstable foundations, which spontaneously decompose.

Getting grounds

1. Interaction of basic oxides with water. In this case, only those oxides that correspond to a soluble base (alkali). Those. in this way you can only get alkalis:

basic oxide + water = base

For example , sodium oxide forms in water sodium hydroxide(sodium hydroxide):

Na 2 O + H 2 O → 2NaOH

At the same time about copper(II) oxide With water doesn't respond:

CuO + H 2 O ≠

2. Interaction of metals with water. At the same time react with waterunder normal conditionsonly alkali metals(lithium, sodium, potassium, rubidium, cesium), calcium, strontium and barium.In this case, a redox reaction occurs, hydrogen is the oxidizing agent, and the metal is the reducing agent.

metal + water = alkali + hydrogen

For example, potassium reacts with water very stormy:

2K 0 + 2H 2 + O → 2K + OH + H 2 0

3. Electrolysis of solutions of some alkali metal salts. As a rule, to obtain alkalis, electrolysis is carried out solutions of salts formed by alkali or alkaline earth metals and oxygen-free acids (except for hydrofluoric acid) - chlorides, bromides, sulfides, etc. This issue is discussed in more detail in the article .

For example , electrolysis of sodium chloride:

2NaCl + 2H 2 O → 2NaOH + H 2 + Cl 2

4. Bases are formed by the interaction of other alkalis with salts. In this case, only soluble substances interact, and no soluble salt, or an insoluble base:

alkali + salt 1 = salt 2 ↓ + alkali

For example: Potassium carbonate reacts in solution with calcium hydroxide:

K 2 CO 3 + Ca(OH) 2 → CaCO 3 ↓ + 2KOH

For example: Copper(II) chloride reacts in solution with sodium hydroxide. In this case it falls out blue copper(II) hydroxide precipitate:

CuCl 2 + 2NaOH → Cu(OH) 2 ↓ + 2NaCl

Chemical properties of insoluble bases

1. Insoluble bases react with strong acids and their oxides (and some medium acids). In this case, salt and water.

insoluble base + acid = salt + water

insoluble base + acid oxide= salt + water

For example ,copper(II) hydroxide reacts with strong hydrochloric acid:

Cu(OH) 2 + 2HCl = CuCl 2 + 2H 2 O

In this case, copper (II) hydroxide does not interact with the acid oxide weak carbonic acid - carbon dioxide:

Cu(OH) 2 + CO 2 ≠

2. Insoluble bases decompose when heated into oxide and water.

For example, Iron(III) hydroxide decomposes into iron(III) oxide and water when heated:

2Fe(OH) 3 = Fe 2 O 3 + 3H 2 O

3. Insoluble bases do not reactwith amphoteric oxides and hydroxides.

insoluble base + amphoteric oxide ≠

insoluble base + amphoteric hydroxide ≠

4. Some insoluble bases can act asreducing agents. Reducing agents are bases formed by metals with minimum or intermediate oxidation state, which can increase their oxidation state (iron (II) hydroxide, chromium (II) hydroxide, etc.).

For example , Iron (II) hydroxide can be oxidized with atmospheric oxygen in the presence of water to iron (III) hydroxide:

4Fe +2 (OH) 2 + O 2 0 + 2H 2 O → 4Fe +3 (O -2 H) 3

Chemical properties of alkalis

1. Alkalis react with any acids - both strong and weak . In this case, medium salt and water are formed. These reactions are called neutralization reactions. Education is also possible sour salt, if the acid is polybasic, at a certain ratio of reagents, or in excess acid. IN excess alkali medium salt and water are formed:

alkali (excess) + acid = medium salt + water

alkali + polybasic acid (excess) = acid salt + water

For example , Sodium hydroxide, when interacting with tribasic phosphoric acid, can form 3 types of salts: dihydrogen phosphates, phosphates or hydrophosphates.

In this case, dihydrogen phosphates are formed in an excess of acid, or when the molar ratio (ratio of the amounts of substances) of the reagents is 1:1.

NaOH + H 3 PO 4 → NaH 2 PO 4 + H 2 O

When the molar ratio of alkali and acid is 2:1, hydrophosphates are formed:

2NaOH + H3PO4 → Na2HPO4 + 2H2O

In an excess of alkali, or with a molar ratio of alkali to acid of 3:1, alkali metal phosphate is formed.

3NaOH + H3PO4 → Na3PO4 + 3H2O

2. Alkalis react withamphoteric oxides and hydroxides. At the same time ordinary salts are formed in the melt , A in solution - complex salts .

alkali (melt) + amphoteric oxide = medium salt + water

alkali (melt) + amphoteric hydroxide = medium salt + water

alkali (solution) + amphoteric oxide = complex salt

alkali (solution) + amphoteric hydroxide = complex salt

For example , when aluminum hydroxide reacts with sodium hydroxide in the melt sodium aluminate is formed. A more acidic hydroxide forms an acid residue:

NaOH + Al(OH) 3 = NaAlO 2 + 2H 2 O

A in solution a complex salt is formed:

NaOH + Al(OH) 3 = Na

Please note how the complex salt formula is composed:first we select the central atom (toas a rule, it is an amphoteric hydroxide metal).Then we add to it ligands- in our case these are hydroxide ions. The number of ligands is usually 2 times greater than the oxidation state of the central atom. But the aluminum complex is an exception; its number of ligands is most often 4. We enclose the resulting fragment in square brackets - this is a complex ion. We determine its charge and add the required number of cations or anions on the outside.

3. Alkalis interact with acidic oxides. At the same time, education is possible sour or medium salt, depending on the molar ratio of alkali and acid oxide. In an excess of alkali, a medium salt is formed, and in an excess of an acidic oxide, an acid salt is formed:

alkali (excess) + acid oxide = medium salt + water

or:

alkali + acid oxide (excess) = acid salt

For example , when interacting excess sodium hydroxide With carbon dioxide, sodium carbonate and water are formed:

2NaOH + CO 2 = Na 2 CO 3 + H 2 O

And when interacting excess carbon dioxide with sodium hydroxide only sodium bicarbonate is formed:

2NaOH + CO 2 = NaHCO 3

4. Alkalis interact with salts. Alkalis react only with soluble salts in solution, provided that Gas or sediment forms in the food . Such reactions proceed according to the mechanism ion exchange.

alkali + soluble salt = salt + corresponding hydroxide

Alkalies interact with solutions of metal salts, which correspond to insoluble or unstable hydroxides.

For example, sodium hydroxide reacts with copper sulfate in solution:

Cu 2+ SO 4 2- + 2Na + OH - = Cu 2+ (OH) 2 - ↓ + Na 2 + SO 4 2-

Also alkalis react with solutions of ammonium salts.

For example , Potassium hydroxide reacts with ammonium nitrate solution:

NH 4 + NO 3 - + K + OH - = K + NO 3 - + NH 3 + H 2 O

! When salts interact amphoteric metals with excess alkali a complex salt is formed!

Let's look at this issue in more detail. If the salt formed by the metal to which it corresponds amphoteric hydroxide , interacts with a small amount of alkali, then the usual exchange reaction occurs, and a precipitate occurshydroxide of this metal .

For example , excess zinc sulfate reacts in solution with potassium hydroxide:

ZnSO 4 + 2KOH = Zn(OH) 2 ↓ + K 2 SO 4

However, in this reaction it is not a base that is formed, but mphoteric hydroxide. And, as we already indicated above, amphoteric hydroxides dissolve in excess alkalis to form complex salts . T Thus, when zinc sulfate reacts with excess alkali solution a complex salt is formed, no precipitate forms:

ZnSO 4 + 4KOH = K 2 + K 2 SO 4

Thus, we obtain 2 schemes for the interaction of metal salts, which correspond to amphoteric hydroxides, with alkalis:

amphoteric metal salt (excess) + alkali = amphoteric hydroxide↓ + salt

amph.metal salt + alkali (excess) = complex salt + salt

5. Alkalis interact with acidic salts.In this case, medium salts or less acidic salts are formed.

sour salt + alkali = medium salt + water

For example , Potassium hydrosulfite reacts with potassium hydroxide to form potassium sulfite and water:

KHSO 3 + KOH = K 2 SO 3 + H 2 O

It is very convenient to determine the properties of acidic salts by mentally dividing the acidic salt into 2 substances - acid and salt. For example, we break sodium bicarbonate NaHCO 3 into uolic acid H 2 CO 3 and sodium carbonate Na 2 CO 3. The properties of bicarbonate are largely determined by the properties of carbonic acid and the properties of sodium carbonate.

6. Alkalis interact with metals in solution and melt. In this case, an oxidation-reduction reaction occurs, forming in the solution complex salt And hydrogen, in the melt - medium salt And hydrogen.

Pay attention! Only those metals whose oxide with the minimum positive oxidation state of the metal is amphoteric react with alkalis in solution!

For example , iron does not react with alkali solution, iron (II) oxide is basic. A aluminum dissolves in aqueous solution alkalis, aluminum oxide - amphoteric:

2Al + 2NaOH + 6H 2 + O = 2Na + 3H 2 0

7. Alkalies interact with non-metals. In this case, redox reactions occur. As a rule, nonmetals are disproportionate in alkalis. They don't react with alkalis oxygen, hydrogen, nitrogen, carbon and inert gases (helium, neon, argon, etc.):

NaOH +O 2 ≠

NaOH +N 2 ≠

NaOH +C ≠

Sulfur, chlorine, bromine, iodine, phosphorus and other non-metals disproportionate in alkalis (i.e. they self-oxidize and self-recover).

For example, chlorinewhen interacting with cold lye goes into oxidation states -1 and +1:

2NaOH +Cl 2 0 = NaCl - + NaOCl + + H 2 O

Chlorine when interacting with hot lye goes into oxidation states -1 and +5:

6NaOH +Cl 2 0 = 5NaCl - + NaCl +5 O 3 + 3H 2 O

Silicon oxidized by alkalis to oxidation state +4.

For example, in solution:

2NaOH + Si 0 + H 2 + O= NaCl - + Na 2 Si +4 O 3 + 2H 2 0

Fluorine oxidizes alkalis: