Oxides. Oxides: classification and chemical properties Oxides are soluble or not

§ 1 Oxide and its signs

While studying the chemical properties of oxygen, we got acquainted with oxidation reactions and oxides. For example, oxides include substances having the following formulas: Na2O, CuO, Al2O3, SiO2, P2O5, SO3, Mn2O7.

So, all oxides are characterized by three common features in composition: any oxide is a complex substance, consists of atoms of two chemical elements, one of the elements is oxygen.

All these signs can be expressed by the general formula EhOy, in which E are the atoms of the chemical element that formed the oxide, O are the oxygen atoms; x, y - indices indicating the number of atoms of the elements that form the oxide.

There are many oxides. Almost all simple substances form oxides during oxidation. Atoms of many elements, exhibiting different valence values, participate in the formation of several oxides, for example, nitrogen corresponds to five oxides: nitrogen oxide (I) N2O, nitrogen oxide (II) NO, nitrogen oxide (III) N2O3, nitrogen oxide (IV) NO2, nitric oxide (V) N2O5.

§ 2 Properties of oxides and their classification

Let's get acquainted with the properties of some oxides.

Carbon monoxide (IV) is a colorless, odorless gas with a slightly sour taste, turning into a solid white snow-like substance, bypassing the liquid state at -780C, soluble in water.

Hydrogen oxide is water, under normal conditions it is a colorless liquid, the boiling point of which is 1000C.

Calcium oxide is a white solid with a melting point of 26270C, when mixed with water, it actively interacts with it.

Iron (III) oxide is a red-brown solid that melts at 15620C, does not dissolve in water.

Let us pass carbon monoxide (IV) through water and add a few drops of litmus to the resulting solution. Litmus will change color from blue to red, therefore, when carbon (IV) monoxide interacts with water, acid is formed. The reaction equation is as follows: СО2 + Н2О → Н2СО3. The reaction produced carbonic acid. Similarly, with the formation of acids, oxides of other non-metals interact with water. Therefore, oxides of non-metals are called acidic. Oxides of metals showing a valence of more than IV are also referred to acidic, for example, vanadium (V) oxide V2O5, chromium (VI) oxide CrO3, manganese (VII) oxide Mn2O7.

Put some white calcium oxide powder in a test tube with water and add a few drops of phenolphthalein to the resulting slightly turbid solution. Phenolphthalein changes color from colorless to crimson, which indicates the appearance of a base in the test tube. CaO + H2O → Ca (OH) 2. As a result of the reaction, a base was formed - calcium hydroxide. Metal oxides with a valency of no more than III are called basic.

Metals exhibiting valences III and IV, and sometimes II, form amphoteric oxides. These oxides differ from others in their chemical properties. We will get to know them in more detail later, but for now we will focus on acidic and basic oxides.

§ 3 Dissolution of oxides in water

Many acids and bases can be obtained by dissolving the corresponding oxides in water.

The dissolution of oxides in water is a chemical process accompanied by the formation of new chemical compounds - acids and bases.

For example, when sulfur (VI) oxide dissolves in water, sulfuric acid is formed: SO3 + H2O → H2SO4. And upon dissolution of phosphorus (V) oxide, phosphoric acid is formed: P2O5 + 3H2O → 2H3PO4. When sodium oxide dissolves, a base is formed - sodium hydroxide: Na2O + H2O → 2NaOH, when barium oxide dissolves - barium hydroxide: BaO + H2O → Ba (OH) 2.

The names of the oxide groups reflect their relationship with other classes of inorganic compounds: most of the acid oxides correspond to acids, and almost all basic oxides are bases.

However, not all oxides are soluble. So, most of the basic oxides are insoluble, and the only exceptions to them are oxides formed by elements of the main subgroups of the first and second groups of the periodic table of elements.

By contrast, most acidic oxides are water-soluble. An exception here is, for example, silicon oxide (IV) - SiO2. This substance is well known to all. Silicon oxide forms the basis of river sand and many minerals, including rare and very beautiful: rock crystal, amethyst, citrine, jasper. Many acidic oxides formed by metals are poorly soluble or insoluble.

If the oxides do not dissolve in water, then the corresponding acids and bases are obtained in other ways (indirectly), which we will get to know later.

List of used literature:

1. NOT. Kuznetsova. Chemistry. 8th grade. Textbook for educational institutions. - M. Ventana-Graf, 2012.

Today we begin our acquaintance with the most important classes of inorganic compounds. Inorganic substances are divided according to their composition, as you already know, into simple and complex ones.

Complex inorganic substances are divided into four classes: oxides, acids, bases, salts. We start with the oxide class.

OXIDES

Oxides are complex substances, consisting of two chemical elements, one of which is oxygen, with a valency equal to 2. Only one chemical element - fluorine, combining with oxygen, forms not an oxide, but oxygen fluoride OF 2.
They are called simply - "oxide + element name" (see table). If the valence of a chemical element is variable, then it is indicated by a Roman numeral, enclosed in parentheses, after the name of the chemical element.

Classification of oxides

All oxides can be divided into two groups: salt-forming (basic, acidic, amphoteric) and non-salt-forming or indifferent.

1). Basic oxidesAre the oxides to which the bases correspond. Basic oxides include oxides metals 1 and 2 groups, and metals side subgroups with valence I and II (except for ZnO - zinc oxide and BeO - beryllium oxide):

2). Acid oxides Are oxides to which acids correspond. Acidic oxides include nonmetal oxides (except for non-salt-forming - indifferent), as well as metal oxides side subgroups with a valence of V before Vii (For example, CrO 3 is chromium (VI) oxide, Mn 2 O 7 is manganese (VII) oxide):

3). Amphoteric oxides - these are oxides, which correspond to bases and acids. These include metal oxides major and minor subgroups with valence III sometimes IV as well as zinc and beryllium (For example,BeO, ZnO, Al 2 O 3, Cr 2 O 3).

4). Non-salt-forming oxides - these are oxides indifferent to acids and bases. These include nonmetal oxides with valence I and II (For example, N 2 O, NO, CO).

Conclusion: the nature of the properties of oxides primarily depends on the valence of the element.

For example, chromium oxides:

CrO (II - main);

Cr 2 O 3 (III- amphoteric);

CrO 3 (Vii - acidic).

Classification of oxides

(by solubility in water)

Complete tasks:

1. Write down separately the chemical formulas of salt-forming acidic and basic oxides.

NaOH, AlCl 3, K 2 O, H 2 SO 4, SO 3, P 2 O 5, HNO 3, CaO, CO.

2. Given substances : CaO, NaOH, CO 2, H 2 SO 3, CaCl 2, FeCl 3, Zn (OH) 2, N 2 O 5, Al 2 O 3, Ca (OH) 2, CO 2, N 2 O, FeO, SO 3, Na 2 SO 4, ZnO, CaCO 3, Mn 2 O 7, CuO, KOH, CO, Fe (OH) 3

Obtaining oxides

Simulator "Interaction of oxygen with simple substances"

Physical properties of oxides

At room temperature, most oxides are solids (CaO, Fe 2 O 3, etc.), some are liquids (H 2 O, Cl 2 O 7, etc.) and gases (NO, SO 2, etc.).

Chemical properties of oxides

Application of oxides

Some oxides do not dissolve in water, but many enter into a compound reaction with water:

SO 3 + H 2 O \u003d H 2 SO 4

CaO + H 2 O = Ca( OH) 2

The result is often highly desirable and useful compounds. For example, H 2 SO 4 is sulfuric acid, Ca (OH) 2 is slaked lime, etc.

If oxides are insoluble in water, then people skillfully use this property as well. For example, zinc oxide ZnO is a white substance, therefore it is used to prepare white oil paint (zinc white). Since ZnO is practically insoluble in water, zinc white can be used to paint any surfaces, including those that are exposed to atmospheric precipitation. Insolubility and non-toxicity make it possible to use this oxide in the manufacture of cosmetic creams and powders. Pharmacists make it an astringent and drying powder for external use.

Titanium (IV) oxide - TiO 2 has the same valuable properties. It also has a beautiful white color and is used to make titanium white. TiO 2 does not dissolve not only in water, but also in acids; therefore, coatings made of this oxide are especially resistant. This oxide is added to the plastic to give it a white color. It is part of enamels for metal and ceramic dishes.

Chromium (III) oxide - Cr 2 O 3 - very strong crystals of dark green color, insoluble in water. Cr 2 O 3 is used as a pigment (paint) in the manufacture of decorative green glass and ceramics. The GOI paste known to many (abbreviated from the name "State Optical Institute") is used for grinding and polishing optics, metal products, in jewelry.

Tasks for consolidation

1. Write down separately the chemical formulas of salt-forming acidic and basic oxides.

NaOH, AlCl 3, K 2 O, H 2 SO 4, SO 3, P 2 O 5, HNO 3, CaO, CO.

2. Given substances : CaO, NaOH, CO 2, H 2 SO 3, CaCl 2, FeCl 3, Zn (OH) 2, N 2 O 5, Al 2 O 3, Ca (OH) 2, CO 2, N 2 O, FeO, SO 3, Na 2 SO 4, ZnO, CaCO 3, Mn 2 O 7, CuO, KOH, CO, Fe (OH) 3

Choose from the list: basic oxides, acidic oxides, indifferent oxides, amphoteric oxides and give them names.

3. Finish CCM, indicate the type of reaction, name the reaction products

Na 2 O + H 2 O \u003d

N 2 O 5 + H 2 O \u003d

CaO + HNO 3 \u003d

NaOH + P 2 O 5 \u003d

K 2 O + CO 2 \u003d

Cu (OH) 2 \u003d? +?

4. Carry out the transformations according to the scheme:

1) K → K 2 O → KOH → K 2 SO 4

2) S → SO 2 → H 2 SO 3 → Na 2 SO 3

3) P → P 2 O 5 → H 3 PO 4 → K 3 PO 4

Modern chemical science represents many different branches, and each of them, in addition to the theoretical basis, is of great applied value, practical. Whatever you touch, everything around is chemical products. The main sections are inorganic and organic chemistry. Let us consider which main classes of substances are classified as inorganic and what properties they possess.

Main categories of inorganic compounds

These include the following:

1. Oxides.
2. Salt.
3. Foundations.
4. Acids.

Each of the classes is represented by a wide variety of compounds of inorganic nature and is important in almost any structure of economic and industrial human activity. All the main properties characteristic of these compounds, being in nature and receiving, are studied in the school chemistry course without fail, in grades 8-11.

There is a general table of oxides, salts, bases, acids, which presents examples of each of the substances and their state of aggregation, being in nature. It also shows interactions that describe chemical properties. However, we will consider each of the classes separately and in more detail.

Group of compounds - oxides

4. Reactions as a result of which the elements change CO

Me + n O + C \u003d Me 0 + CO

1. Reagent water: acid formation (SiO 2 exclusion)

KO + water \u003d acid

2. Reactions with bases:

CO 2 + 2CsOH \u003d Cs 2 CO 3 + H 2 O

3. Reactions with basic oxides: salt formation

P 2 O 5 + 3MnO \u003d Mn 3 (PO 3) 2

4. OVR reactions:

CO 2 + 2Ca \u003d C + 2CaO,

They show dual properties, interact according to the principle of the acid-base method (with acids, alkalis, basic oxides, acid oxides). They do not interact with water.

1.With acids: formation of salts and water

AO + acid \u003d salt + H 2 O

2.With bases (alkalis): the formation of hydroxo complexes

Al 2 O 3 + LiOH + water \u003d Li

3. Reactions with acid oxides: obtaining salts

FeO + SO 2 \u003d FeSO 3

4. Reactions with RO: formation of salts, fusion

MnO + Rb 2 O \u003d double salt Rb 2 MnO 2

5. Fusion reactions with alkalis and alkali metal carbonates: formation of salts

Al 2 O 3 + 2LiOH \u003d 2LiAlO 2 + H 2 O

Each higher oxide, formed by both metal and non-metal, dissolves in water, gives a strong acid or alkali.

Organic and inorganic acids

In the classical sound (based on the positions of ED - electrolytic dissociation - acids are compounds that dissociate in an aqueous medium into H + cations and anions of acid residues An -. However, today acids have also been thoroughly studied in anhydrous conditions, therefore there are many different theories for hydroxides.

The empirical formulas of oxides, bases, acids, salts are composed only of symbols, elements and indices indicating their amount in a substance. For example, inorganic acids are expressed by the formula H + acidic residue n-. Organic substances have a different theoretical display. In addition to the empirical one, a complete and abbreviated structural formula can be written for them, which will reflect not only the composition and quantity of the molecule, but also the order of arrangement of atoms, their relationship with each other and the main functional group for carboxylic acids --COOH.

In inorganic, all acids are divided into two groups:

• oxygen-free - HBr, HCN, HCL and others;
• oxygen-containing (oxo acids) - HClO 3 and everything where there is oxygen.

Also, inorganic acids are classified by stability (stable or stable - everything except carbonic and sulfurous, unstable or unstable - carbonic and sulfurous). In terms of strength, acids can be strong: sulfuric, hydrochloric, nitric, chloric and others, as well as weak: hydrogen sulfide, hypochlorous, and others.

Organic chemistry offers less variety. Acids that are organic in nature are carboxylic acids. Their common feature is the presence of the -COOH functional group. For example, HCOOH (formic), CH 3 COOH (acetic), C 17 H 35 COOH (stearic) and others.

There are a number of acids that are especially emphasized when considering this topic in a school chemistry course.

1. Salt.
2. Nitrogen.
3. Orthophosphoric.
4. Hydrobromic.
5. Coal.
6. Hydrogen iodide.
7. Sulfuric.
8. Acetic, or ethane.
9. Butane, or oil.
10. Benzoin.

These 10 acids in chemistry are the fundamental substances of the corresponding class both in the school course and in industry and synthesis in general.

Properties of inorganic acids

The main physical properties must be attributed primarily to a different state of aggregation. After all, there are a number of acids in the form of crystals or powders (boric, orthophosphoric) under normal conditions. The overwhelming majority of the known inorganic acids are different liquids. Boiling and melting points also vary.

Acids can cause severe burns, as they have a force that destroys organic tissue and skin. Indicators are used to detect acids:

• methyl orange (in a normal environment - orange, in acids - red),
• litmus (in neutral - violet, in acids - red) or some others.

The most important chemical properties include the ability to interact with both simple and complex substances.

When interacting with metals, not all acids react in the same way. Chemistry (grade 9) at school involves a very shallow study of such reactions, however, at this level, the specific properties of concentrated nitric and sulfuric acid are considered when interacting with metals.

Hydroxides: alkalis, amphoteric and insoluble bases

Oxides, salts, bases, acids - all these classes of substances have a common chemical nature, explained by the structure of the crystal lattice, as well as the mutual influence of atoms in the composition of molecules. However, while it was possible to give a very specific definition for oxides, it is more difficult to do it for acids and bases.

As well as acids, according to the theory of ED, bases are called substances that can decompose in an aqueous solution into metal cations Me n + and anions of hydroxo groups OH -.

• Soluble or alkalis (strong bases that change. Formed by metals of groups I, II. Example: KOH, NaOH, LiOH (that is, only the main subgroups are taken into account);
• Slightly soluble or insoluble (medium strength, do not change the color of indicators). Example: hydroxide of magnesium, iron (II), (III) and others.
• Molecular (weak bases, in an aqueous medium reversibly dissociate into ions-molecules). Example: N 2 H 4, amines, ammonia.
• Amphoteric hydroxides (show dual basic acidic properties). Example: beryllium, zinc, and so on.

Each group represented is studied in the school chemistry course in the "Foundations" section. Grade 8-9 chemistry involves a detailed study of alkalis and poorly soluble compounds.

The main characteristic properties of the bases

All alkalis and poorly soluble compounds are in nature in a solid crystalline state. At the same time, their melting points, as a rule, are low, and poorly soluble hydroxides decompose when heated. The color of the bases is different. If the alkali is white, then the crystals of poorly soluble and molecular bases can be of very different colors. The solubility of most compounds of this class can be seen in the table, which presents the formulas of oxides, bases, acids, salts, and shows their solubility.

Alkalis can change the color of indicators as follows: phenolphthalein - raspberry, methyl orange - yellow. This is ensured by the free presence of hydroxyl groups in the solution. That is why poorly soluble bases do not give such a reaction.

The chemical properties of each group of bases are different.

These are most of the chemical properties that bases exhibit. The chemistry of bases is quite simple and obeys the general laws of all inorganic compounds.

Class of inorganic salts. Classification, physical properties

Based on the position of ED, salts can be called inorganic compounds, in an aqueous solution dissociating into metal cations Ме + n and anions of acid residues An n-. So you can imagine salts. The definition of chemistry gives more than one, but it is the most accurate.

Moreover, by their chemical nature, all salts are subdivided into:

• Acidic (containing a hydrogen cation). Example: NaHSO 4.
• Basic (containing a hydroxyl group). Example: MgOHNO 3, FeOHCL 2.
• Medium (consist only of a metal cation and an acidic residue). Example: NaCL, CaSO 4.
• Double (includes two different metal cations). Example: NaAl (SO 4) 3.
• Complex (hydroxocomplexes, aquacomplexes and others). Example: K 2.

Salt formulas reflect their chemical nature, and also speak about the qualitative and quantitative composition of the molecule.

Oxides, salts, bases, acids have different solubility properties, which can be found in the corresponding table.

If we talk about the state of aggregation of salts, then we should notice their uniformity. They only exist in a solid, crystalline or powdery state. The color scheme is quite diverse. Complex salt solutions usually have bright, saturated colors.

Chemical interactions for the class of medium salts

They have similar chemical properties of base, acid, salt. Oxides, as we have already considered, differ somewhat from them in this factor.

In total, 4 main types of interactions can be distinguished for medium salts.

I. Interaction with acids (only strong in terms of ED) with the formation of another salt and a weak acid:

KCNS + HCL \u003d KCL + HCNS

II. Reactions with soluble hydroxides with the appearance of salts and insoluble bases:

CuSO 4 + 2LiOH \u003d 2LiSO 4 soluble salt + Cu (OH) 2 insoluble base

III. Interaction with other soluble salt to form insoluble salt and soluble:

PbCL 2 + Na 2 S \u003d PbS + 2NaCL

IV. Reactions with metals standing in the EHRNM to the left of the one that forms the salt. In this case, the metal that reacts should not interact with water under normal conditions:

Mg + 2AgCL \u003d MgCL 2 + 2Ag

These are the main types of interactions that are common for medium salts. The formulas of complex, basic, double and acidic salts speak for themselves about the specificity of the displayed chemical properties.

Formulas of oxides, bases, acids, salts reflect the chemical essence of all representatives of these classes of inorganic compounds, and in addition, give an idea of \u200b\u200bthe name of the substance and its physical properties. Therefore, you should pay special attention to their writing. A huge variety of compounds is offered to us as a whole by an amazing science - chemistry. Oxides, bases, acids, salts are just a part of the vast variety.

The invention relates to methods for dissolving uranium oxides and can be used in the technology of obtaining materials for the fuel cycle, in particular for obtaining enriched uranium. According to the method, the uranium oxide powder is placed under a layer of water with a ratio of the height of the water layer and the height of the uranium oxide layer not less than 1.3. Nitric acid is fed under the layer of uranium oxides at a rate of (0.30-0.36) t HNO 3 per 1 ton of uranium per hour. The invention makes it possible to reduce the volume of gases leaving the reactor-solvent and subject to cleaning before being discharged into the atmosphere, while reducing the content of nitrogen dioxide in them. 1 wp f-ly, 1 tab.

The invention relates to methods for dissolving uranium oxides and can be used in the technology of obtaining materials for the fuel cycle, in particular for obtaining enriched uranium. As a raw material for uranium enrichment, its oxides in the form of technical nitrous oxide - U 3 O 8 (2UO z + UO 2), obtained from natural raw materials, can be used. In this case, before the operation of fluorination, uranium must be further purified from the accompanying impurities present in the ore concentrate, including impurities that form volatile fluorides (molybdenum, silicon, iron, vanadium, etc.). In addition, it is necessary to clean up and from impurities that get into uranium during the processing of natural ores into nitrous oxide - uranium oxide (scale, under-calcining, graphite, coal, etc.). To purify uranium from impurities, one can use the extraction technology for purifying uranium nitric acid solutions using tributyl phosphate. Before extraction, uranium oxides must be dissolved. A known method of dissolving uranium oxides in a mixture of concentrated nitric and concentrated hydrochloric acids (Uranium and its compounds. Industry standard of the USSR OST 95175-90, p. 5). However, due to the high corrosion of equipment, this method is used only on a laboratory scale. A known method of dissolving uranium oxide-oxide in nitric acid (VM Vdovenko. Modern radiochemistry. - M., 1969, S. 257) (prototype). The method is carried out according to the following reaction: 2U 3 O 8 + 14HNO 3 \u003d 6UO 2 (NO) 3) 2 + 7H 2 O + NO + NO 2. As a result of the reaction, nitrogen oxide and dioxide are formed, which have a harmful effect on the environment and humans. In this regard, it becomes necessary to purify waste gases from nitrogen oxides. Nitrogen dioxide (NO 2) is a brown gas, nitrogen oxide (NO) is a colorless gas. Nitric oxide (NO) oxidizes to NO 2 on contact with atmospheric oxygen. Nitrogen dioxide is the main component in the gas effluent to be treated. If a feedstock containing more than 80% of uranium oxide is dissolved, the formation of nitrogen oxides per unit of raw material is increased compared to the dissolution of uranium oxide containing about 30% uranium oxide. The dissolution process of such raw materials is characterized by a significant release of nitrogen dioxide. In oxide raw materials, the content of uranium (IV) is 30%: In oxide raw materials, the content of uranium (IV) is 80%: With stirring of the reaction system, which is used to improve mass transfer in the system, the release of nitrogen oxides from the reaction mixture occurs especially rapidly. The objective of the invention is to reduce the volume of gases (nitrogen oxides) leaving the reactor-solvent and subject to purification before discharge into the atmosphere, while reducing the content of nitrogen dioxide in them. The problem is solved by the fact that in the method of dissolving uranium oxides, including their interaction with nitric acid, the uranium oxide powder is placed under a water layer with a ratio of the water layer height and uranium oxide layer height not less than 1.3, and nitric acid is fed under the uranium oxide layer at a rate (0.3-0.36) t HNO 3 per 1 ton of uranium per hour. The reaction mixture is sprayed with water in an amount equal to 10-20% of the aqueous layer. Example. Uranium oxide powder is placed under a layer of water. The acid solution is fed under the oxide layer. The acid solution is fed under the uranium oxide layer through a pipe lowered to the bottom of the solvent reactor. Four series of experiments are carried out. In the first series, the ratio of the water layer height to the uranium oxide layer height is changed. In the second series of experiments, the consumption of HNO 3 is changed per unit time. In the third series of experiments, the reaction mixture is stirred by supplying it with compressed air. In the fourth series of experiments, water is sprayed over the surface of the water layer to create a water mist in the solvent reactor. In experiment 6 of the first series, there is no water layer above the uranium oxide layer. Experiments are carried out without heating the reaction mixture. The results of the experiments are presented in the table. When nitric acid is fed under the layer of uranium oxides under water, the dissolution of uranium oxides proceeds uniformly throughout the entire volume. Nitrogen dioxide formed during the dissolution of uranium oxides, passing through a layer of water, interacts with the latter to form nitric acid, which, in turn, interacts with uranium oxides; the consumption of nitric acid (total for the experiment) supplied to the reactor-solvent decreases. As can be seen from the table, a decrease in the volume of gases leaving the solvent reactor, with a decrease in the content of nitrogen dioxide in them, occurs when the ratio of the height of the water layer to the height of the uranium oxide layer is not less than 1.3 and the consumption of nitric acid per unit time is 0.30. 0.36 t HNO 3 / t U per hour (experiments 3-5 of the first series, 1, 2 of the second series). Irrigation of the space above the water layer with water contributes to the additional capture of nitrogen dioxide and suppression of foam formation (experiments 1, 2 of the fourth series). The absence of an aqueous layer over uranium oxides during the dissolution process (experiment 6 of the first series) or its insufficient height (the ratio of the height of the water layer to the height of the uranium oxide layer is less than 1, 3, experiments 1, 2 of the first series) lead to an increase in gas evolution from the solvent reactor, the gas has a brown color inherent in nitrogen dioxide. An increase in the consumption of nitric acid per unit of time (more than 0.36 t HNO 3 / t U per hour) also leads to strong gas evolution, the gas contains a significant amount of brown nitrogen dioxide (experiments 3, 4 of the second series). Stirring the reaction mixture with air increases the total consumption of nitric acid and leads to strong gas evolution (experiments 1, 2 of the third series). The ratio of the height of the water layer to the height of the powder layer, equal to 1.30-1.36, is optimal from the point of view of obtaining a solution suitable in concentration for the subsequent operation in the technology of materials of the fuel cycle - extraction.

Claim

1. A method for dissolving uranium oxides, including their interaction with nitric acid, characterized in that the uranium oxide powder is placed under a layer of water with a ratio of the height of the water layer and the height of the uranium oxide layer not less than 1.3 and nitric acid is fed under the layer of uranium oxides at a rate (0,300,36) t НNО 3 per 1 ton of uranium per hour. 2. The method according to claim 1, characterized in that the reaction mixture is sprayed with water in an amount equal to 10-20% of the aqueous layer.

Oxidescomplex substances are called, the molecules of which include oxygen atoms in the oxidation state - 2 and some other element.

can be obtained by direct interaction of oxygen with another element, and indirectly (for example, by decomposition of salts, bases, acids). Under normal conditions, oxides are in a solid, liquid and gaseous state; this type of compound is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.

They are salt-forming and non-salt-forming.

Salt-forming oxides- these are oxides that form salts as a result of chemical reactions. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, they form the corresponding acidic and normal salts. For instance, copper oxide (CuO) is a salt-forming oxide, because, for example, when it interacts with hydrochloric acid (HCl), a salt is formed:

CuO + 2HCl → CuCl 2 + H 2 O.

As a result of chemical reactions, other salts can be obtained:

CuO + SO 3 → CuSO 4.

Non-salt-forming oxides such oxides are called which do not form salts. An example is CO, N 2 O, NO.

Salt-forming oxides, in turn, are of 3 types: basic (from the word « base » ), acidic and amphoteric.

Basic oxidessuch metal oxides are called, which correspond to hydroxides belonging to the class of bases. Basic oxides include, for example, Na 2 O, K 2 O, MgO, CaO, etc.

Chemical properties of basic oxides

1. Water-soluble basic oxides react with water to form bases:

Na 2 O + H 2 O → 2NaOH.

2. React with acidic oxides to form corresponding salts

Na 2 O + SO 3 → Na 2 SO 4.

3. React with acids to form salt and water:

CuO + H 2 SO 4 → CuSO 4 + H 2 O.

4. React with amphoteric oxides:

Li 2 O + Al 2 O 3 → 2LiAlO 2.

If in the composition of the oxides as the second element there is a non-metal or a metal exhibiting higher valence (usually from IV to VII), then such oxides will be acidic. Acid oxides (acid anhydrides) are those oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acidic oxides dissolve in water and alkalis to form salt and water.

Chemical properties of acid oxides

1. Interact with water, forming acid:

SO 3 + H 2 O → H 2 SO 4.

But not all acidic oxides react directly with water (SiO 2, etc.).

2. React with base oxides to form salt:

CO 2 + CaO → CaCO 3

3. Interact with alkalis, forming salt and water:

CO 2 + Ba (OH) 2 → BaCO 3 + H 2 O.

Part amphoteric oxideincludes an element that has amphoteric properties. Amphotericity is understood as the ability of compounds to exhibit acidic and basic properties, depending on the conditions.For example, zinc oxide ZnO can be both a base and an acid (Zn (OH) 2 and H 2 ZnO 2). Amphotericity is expressed in the fact that, depending on the conditions, amphoteric oxides exhibit either basic or acidic properties.

Chemical properties of amphoteric oxides

1. Interact with acids, forming salt and water:

ZnO + 2HCl → ZnCl 2 + H 2 O.

2. React with solid alkalis (when fusion), forming as a result of the reaction salt - sodium zincate and water:

ZnO + 2NaOH → Na 2 ZnO 2 + H 2 O.

When zinc oxide interacts with an alkali solution (the same NaOH), another reaction occurs:

ZnO + 2 NaOH + H 2 O \u003d\u003e Na 2.

The coordination number is a characteristic that determines the number of the nearest particles: atoms or inov in a molecule or crystal. Each amphoteric metal has its own coordination number. For Be and Zn it is 4; For and, Al is 4 or 6; For and, Cr is 6 or (very rarely) 4;

Amphoteric oxides usually do not dissolve in water and do not react with it.

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