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

§ 1 Oxide and its signs

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

So, all oxides in composition are characterized by three common features: 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 ExOy, in which E are atoms chemical element, which formed the oxide, O - oxygen atoms; x, y are indices indicating the number of atoms of the elements forming the oxide.

Lots of oxides. Almost all simple substances form oxides when oxidized. Atoms of many elements, showing different meanings valencies, are involved in the formation of several oxides, for example, five oxides correspond to nitrogen: nitric oxide (I) N2O, nitric oxide (II) NO, nitric oxide (III) N2O3, nitric 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 - water, under normal conditions - 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 and is insoluble in water.

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 monoxide (IV) reacts with water, an acid is formed. The reaction equation is as follows: CO2 + H2O → H2CO3. As a result of the reaction, carbonic acid was formed. Similarly, with the formation of acids, oxides of other non-metals interact with water. Therefore, non-metal oxides are called acidic. Acid also includes oxides of metals exhibiting a valence of more than IV, for example, vanadium oxide (V) V2O5, chromium oxide (VI) CrO3, manganese oxide (VII) Mn2O7.

Let's put a little white powder of calcium oxide into a test tube with water and add a few drops of phenolphthalein to the resulting slightly cloudy 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 whose valency is not more than III are called basic.

Metals exhibiting valency III and IV, and sometimes II, form amphoteric oxides. These oxides differ from other oxides 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 oxide (VI) is dissolved in water, sulfuric acid is formed: SO3 + H2O → H2SO4. And when phosphorus (V) oxide is dissolved, phosphoric acid is formed: Р2O5 + 3H2O → 2H3РO4. When sodium oxide is dissolved, a base is formed - sodium hydroxide: Na2O + H2O → 2NaOH, when barium oxide is dissolved, barium hydroxide is formed: BaO + H2O → Ba(OH)2.

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

However, not all oxides are soluble. Thus, 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. periodic system elements.

Most acidic oxides, on the other hand, are soluble in water. Here the exception is, for example, silicon oxide (IV) - SiO2. This substance is well known to everyone. Silicon oxide forms the basis of river sand and many minerals, including rare and very beautiful ones: rock crystal, amethyst, citrine, jasper. Many acid oxides formed by metals are sparingly soluble or insoluble.

If the oxides do not dissolve in water, then the acids and bases corresponding to them 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 by composition, as you already know, into simple and complex.

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

OXIDES

oxides - this is 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 valency 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 oxides are oxides that correspond to bases. The main oxides are oxides metals 1 and 2 groups, as well as metals side subgroups with valency I and II (except ZnO - zinc oxide and BeO – beryllium oxide):

2). Acid oxides are oxides to which acids correspond. Acid oxides are non-metal oxides (except for non-salt-forming - indifferent), as well as metal oxides side subgroups with valency from V before VII (For example, CrO 3 is chromium (VI) oxide, Mn 2 O 7 is manganese (VII) oxide):

3). Amphoteric oxides are oxides, which correspond to bases and acids. These include metal oxides main and secondary subgroups with valency 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 are oxides that are indifferent to acids and bases. These include non-metal oxides with valency I and II (For example, N 2 O, NO, CO).

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

For example, chromium oxides:

CrO(II- main);

Cr 2 O 3 (III- amphoteric);

CrO 3 (VII- acid).

Classification of oxides

(by solubility in water)

Complete the 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. Substances are given : 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 react with water to combine:

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

CaO + H 2 O = Ca( Oh) 2

The result is often very 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, any surface can be painted with zinc white, 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 oxide (IV) - TiO 2 has the same valuable properties. It also has a beautiful white color and is used to make titanium white. TiO 2 is insoluble not only in water, but also in acids; therefore, coatings made of this oxide are particularly stable. This oxide is added to plastic to give it a white color. It is part of the enamels for metal and ceramic utensils.

Chromium oxide (III) - 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 well-known GOI paste (short for the name “State Optical Institute”) is used for grinding and polishing optics, metal products in jewelry.

Tasks for fixing

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. Substances are given : 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

Select from the list: basic oxides, acidic oxides, indifferent oxides, amphoteric oxides and name them.

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

Na 2 O + H 2 O =

N 2 O 5 + H 2 O =

CaO + HNO 3 =

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 is a wide variety of branches, and each of them, in addition to the theoretical base, has a large applied value, practical. Whatever you touch, everything around is the products of chemical production. The main sections are inorganic and organic chemistry. Consider what main classes of substances are classified as inorganic and what properties they have.

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 inorganic compounds and is important in almost any structure of human economic and industrial activity. All the main properties characteristic of these compounds, being in nature and obtaining 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 the 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 elements change CO

Me + n O + C = Me 0 + CO

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

KO + water = 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): formation of hydroxo complexes

Al 2 O 3 + LiOH + water \u003d Li

3. Reactions with acid oxides: preparation of salts

FeO + SO 2 \u003d FeSO 3

4. Reactions with RO: formation of salts, fusion

MnO + Rb 2 O = 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 both by a metal and a non-metal, when dissolved in water, gives a strong acid or alkali.

Acids organic and inorganic

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

Empirical formulas of oxides, bases, acids, salts are made up only of symbols, elements and indices indicating their amount in a substance. For example, inorganic acids are expressed by the formula H + acid residue n-. organic matter have a different theoretical representation. In addition to the empirical one, it is possible to write down a full and abbreviated structural formula for them, which will reflect not only the composition and amount of the molecule, but also the arrangement of atoms, their relationship to each other and the main functional group for carboxylic acids -COOH.

In the inorganic, all acids are divided into two groups:

• anoxic - 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 sulphurous, unstable or unstable - carbonic and sulphurous). By strength, acids can be strong: sulfuric, hydrochloric, nitric, perchloric and others, as well as weak: hydrogen sulfide, hypochlorous and others.

Organic chemistry does not offer such diversity at all. Acids that are organic in nature are carboxylic acids. Their common feature is the presence of a functional group -COOH. For example, HCOOH (antic), CH 3 COOH (acetic), C 17 H 35 COOH (stearic) and others.

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

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

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

Properties of inorganic acids

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

Acids can cause severe burns, as they have the power to destroy organic tissue and skin covering. Indicators are used to detect acids:

• methyl orange (in 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, even 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, which is explained by the structure of the crystal lattice, as well as the mutual influence of atoms in the composition of molecules. However, if for oxides it was possible to give a very specific definition, then for acids and bases it is more difficult to do so.

Just like acids, bases, according to the ED theory, are substances capable of aqueous solution decompose into metal cations Me n + and anions of hydroxo groups OH - .

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

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

The main characteristic properties of the bases

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

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

The chemical properties of each group of bases are different.

These are the most 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 provisions of the ED, salts can be called inorganic compounds that dissociate in an aqueous solution into metal cations Me + n and anions of acid residues An n- . So you can imagine salt. Chemistry gives more than one definition, but this is the most accurate.

At the same time, according to their chemical nature, all salts are divided into:

• Acidic (containing a hydrogen cation). Example: NaHSO4.
• Basic (having a hydroxo group). Example: MgOHNO 3 , FeOHCL 2.
• Medium (consist only of a metal cation and an acid residue). Example: NaCL, CaSO 4.
• Double (include two different metal cations). Example: NaAl(SO 4) 3.
• Complex (hydroxocomplexes, aquacomplexes and others). Example: K 2 .

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

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

If we talk about the state of aggregation of salts, then you need to notice their uniformity. They exist only in a solid, crystalline or powdered state. The color scheme is quite varied. Solutions of complex salts, as a rule, have bright saturated colors.

Chemical interactions for the class of medium salts

They have similar chemical properties of bases, acids, salts. 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 = KCL + HCNS

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

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

III. Interaction with another soluble salt to form an insoluble salt and a soluble one:

PbCL 2 + Na 2 S = PbS + 2NaCL

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

Mg + 2AgCL = MgCL 2 + 2Ag

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

The formulas of oxides, bases, acids, salts reflect the chemical nature of all representatives of these classes of inorganic compounds, and in addition, give an idea of ​​the name of the substance and its physical properties. Therefore, special attention should be paid to their writing. A huge variety of compounds offers us a generally amazing science - chemistry. Oxides, bases, acids, salts - this is only part of the vast variety.

The invention relates to methods for dissolving uranium oxides and can be used in the technology for obtaining fuel cycle materials, in particular for obtaining enriched uranium. According to the method, uranium oxide powder is placed under a layer of water at a ratio of the height of the water layer and the height of the uranium oxide layer of at least 1.3. Under the layer of uranium oxides nitric acid with a consumption of (0.30-0.36) t HNO 3 per 1 ton of uranium per hour. EFFECT: invention makes it possible to reduce the volume of gases leaving the reactor-solvent and to be cleaned before being discharged into the atmosphere, while reducing the content of nitrogen dioxide in them. 1 z.p. f-ly, 1 tab.

The invention relates to methods for dissolving uranium oxides and can be used in the technology for obtaining fuel cycle materials, in particular for obtaining enriched uranium. As a feedstock for uranium enrichment, its oxides in the form of technical nitrous oxide - oxide U 3 O 8 (2UO s +UO 2), obtained from natural raw materials, can be used. At the same time, before the fluorination operation, uranium must be further purified from accompanying impurities present in the ore concentrate, including impurities that form volatile fluorides (molybdenum, silicon, iron, vanadium, etc.). In addition, it is also necessary to remove impurities that get into uranium in the process of processing natural ores into nitrous oxide - uranium oxide (scale, undershot marks, graphite, coal, etc.). To purify uranium from impurities, one can use the extraction technology for the purification of uranium nitric acid solutions using tributyl phosphate. Uranium oxides must be dissolved before extraction. 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 large corrosion of the equipment, this method is used only on a laboratory scale. A known method of dissolving uranium oxide in nitric acid (VM Vdovenko. Modern radiochemistry. - M., 1969, p. 257) (prototype). The method is carried out according to the following reaction: 2U 3 O 8 +14HNO 3 =6UO 2 (NO) 3)2+7H 2 O+NO+NO 2 . As a result of the reaction, oxide and nitrogen dioxide are formed, which have a harmful effect on environment and a person. In this regard, there is a need to clean waste gases from nitrogen oxides. Nitrogen dioxide (NO 2) is a brown gas, nitric oxide (NO) is a colorless gas. Nitric oxide (NO) oxidizes to NO 2 in contact with atmospheric oxygen. Nitrogen dioxide is the main component in gas discharges to be treated. If a feed containing more than 80% uranium oxide is dissolved, then the formation of nitrogen oxides per unit of feed is increased compared to the dissolution of uranium oxide containing about 30% uranium oxide. The process of dissolution 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%: When stirring the reaction system, which is used to improve the mass transfer in the system, the release of nitrogen oxides from the reaction mixture occurs particularly rapidly. The objective of the invention is to reduce the volume of gases (nitrogen oxides) leaving the solvent reactor and to be cleaned before being discharged 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 powder of uranium oxides 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 of at least 1.3, and nitric acid is fed under the layer of uranium oxides with a flow rate of (0.3-0.36) t HNO 3 per 1 ton of uranium per hour. The reaction mixture is irrigated 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 layer of oxides. The supply of the acid solution under the layer of uranium oxides is carried out through a pipe lowered to the bottom of the solvent reactor. Conduct four series of experiments. In the first series, the ratio of the height of the water layer to the height of the uranium oxide layer is changed. In the second series of experiments, the flow rate of HNO 3 is changed per unit time. In the third series of experiments, the reaction mixture is stirred by supplying compressed air into it. 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. The experiments are carried out without heating the reaction mixture. The results of the experiments are presented in the table. When nitric acid is supplied under a layer of uranium oxides under water, the dissolution of uranium oxides proceeds evenly throughout the 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 experience) supplied to the solvent reactor is reduced. 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 flow rate 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 additional trapping of nitrogen dioxide and suppression of foaming (experiments 1, 2 of the fourth series). The absence of an aqueous layer above the 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 release from the solvent reactor, in this case, the gas has a brown color inherent in nitrogen dioxide. An increase in the consumption of nitric acid per unit 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 fuel cycle materials - extraction.

Claim

1. A method for dissolving uranium oxides, including their interaction with nitric acid, characterized in that the powder of uranium oxides 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 of at least 1.3 and nitric acid is fed under the layer of uranium oxides with a flow rate of (0.300.36) t HNO 3 per 1 ton of uranium per hour. 2. The method according to p. 1, characterized in that the reaction mixture is irrigated with water in an amount equal to 10-20% of the aqueous layer.

Oxides complex substances are called, the composition of the molecules of which includes oxygen atoms in the oxidation state - 2 and some other element.

can be obtained by direct interaction of oxygen with another element, or indirectly (for example, by the decomposition of salts, bases, acids). Under normal conditions, oxides are in a solid, liquid and gaseous state, this type of compounds 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 are oxides that, as a result, chemical reactions form salts. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, the corresponding acidic and normal salts. For example, copper oxide (CuO) is a salt-forming oxide, because, for example, when it reacts 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 called oxides that 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 oxides such 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. Interact with acid oxides, forming the 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 the second element in the composition of oxides is a non-metal or a metal exhibiting a higher valency (usually exhibits from IV to VII), then such oxides will be acidic. Acid oxides (acid anhydrides) are oxides that correspond to hydroxides belonging to the class of acids. This is, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acid oxides dissolve in water and alkalis, forming 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 directly react with water (SiO 2 and others).

2. React with based oxides to form a 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 oxide includes 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 to form salt and water:

ZnO + 2HCl → ZnCl 2 + H 2 O.

2. React with solid alkalis (during 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 => Na 2.

Coordination number - a characteristic that determines the number of nearest particles: atoms or ions 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 it is 6 or (very rarely) 4;

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

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