Weak basic oxide properties. Basic oxides

Modern chemical science is a wide variety of branches, and each of them, in addition to the theoretical base, is of great applied and practical importance. 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 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

They do not form acids or alkalis. They exhibit highly specific properties.

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 substances have a different theoretical mapping. 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 tissues and skin. 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.

Chemical properties of inorganic acids

What do they interact with?	Reaction Example
1. With simple substances-metals. Mandatory condition: the metal must stand in the ECHRNM before hydrogen, since the metals standing after hydrogen are not able to displace it from the composition of acids. As a result of the reaction, hydrogen is always formed in the form of a gas and a salt.
2. With bases. The result of the reaction is salt and water. Such reactions of strong acids with alkalis are called neutralization reactions.	Any acid (strong) + soluble base = salt and water
3. With amphoteric hydroxides. Bottom line: salt and water.	2HNO 2 + beryllium hydroxide \u003d Be (NO 2) 2 (medium salt) + 2H 2 O
4. With basic oxides. Outcome: water, salt.	2HCL + FeO = iron (II) chloride + H 2 O
5. With amphoteric oxides. Final effect: salt and water.	2HI + ZnO = ZnI 2 + H 2 O
6. With salts formed by weaker acids. Final effect: salt and weak acid.	2HBr + MgCO 3 = magnesium bromide + H 2 O + CO 2

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, according to the ED theory, bases are substances that can decompose in an aqueous solution 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.

Chemical properties
alkalis	sparingly soluble bases	Amphoteric hydroxides
I. Interact with KO (total - salt and water): 2LiOH + SO 3 \u003d Li 2 SO 4 + water II. Interact with acids (salt and water): conventional neutralization reactions (see acids) III. Interact with AO to form a hydroxocomplex of salt and water: 2NaOH + Me + n O \u003d Na 2 Me + n O 2 + H 2 O, or Na 2 IV. Interact with amphoteric hydroxides to form hydroxo complex salts: The same as with AO, only without water V. Interact with soluble salts to form insoluble hydroxides and salts: 3CsOH + iron (III) chloride = Fe(OH) 3 + 3CsCl VI. Interact with zinc and aluminum in an aqueous solution to form salts and hydrogen: 2RbOH + 2Al + water = complex with hydroxide ion 2Rb + 3H 2	I. When heated, they can decompose: insoluble hydroxide = oxide + water II. Reactions with acids (total: salt and water): Fe(OH) 2 + 2HBr = FeBr 2 + water III. Interact with KO: Me + n (OH) n + KO \u003d salt + H 2 O	I. React with acids to form salt and water: (II) + 2HBr = CuBr 2 + water II. React with alkalis: result - salt and water (condition: fusion) Zn(OH) 2 + 2CsOH \u003d salt + 2H 2 O III. They react with strong hydroxides: the result is salts, if the reaction takes place in an aqueous solution: Cr(OH) 3 + 3RbOH = Rb 3

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 essence 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.

Oxides are complex substances consisting of two elements, one of which is oxygen. In the names of oxides, the word oxide is first indicated, then the name of the second element by which it is formed. What features do acid oxides have, and how do they differ from other types of oxides?

Classification of oxides

Oxides are divided into salt-forming and non-salt-forming. Already by name it is clear that non-salt-forming do not form salts. There are few such oxides: it is water H 2 O, oxygen fluoride OF 2 (if it is conventionally considered an oxide), carbon monoxide, or carbon monoxide (II), carbon monoxide CO; nitrogen oxides (I) and (II): N 2 O (diatrogen oxide, laughing gas) and NO (nitrogen monoxide).

Salt-forming oxides form salts when interacting with acids or alkalis. As hydroxides, they correspond to bases, amphoteric bases and oxygen-containing acids. Accordingly, they are called basic oxides (eg CaO), amphoteric oxides (Al 2 O 3) and acid oxides or acid anhydrides (CO 2).

Rice. 1. Types of oxides.

Often, students are faced with the question of how to distinguish a basic oxide from an acid one. First of all, you need to pay attention to the second element next to oxygen. Acid oxides - contain a non-metal or transition metal (CO 2, SO 3, P 2 O 5) basic oxides - contain a metal (Na 2 O, FeO, CuO).

Basic properties of acid oxides

Acid oxides (anhydrides) are substances that exhibit acidic properties and form oxygen-containing acids. Therefore, acids correspond to acid oxides. For example, acid oxides SO 2, SO 3 correspond to acids H 2 SO 3 and H 2 SO 4.

Rice. 2. Acid oxides with corresponding acids.

Acid oxides formed by non-metals and metals with variable valence in the highest oxidation state (for example, SO 3, Mn 2 O 7) react with basic oxides and alkalis, forming salts:

SO 3 (acidic oxide)+CaO (basic oxide)=CaSO 4 (salt);

Typical reactions are the interaction of acidic oxides with bases, resulting in the formation of salt and water:

Mn 2 O 7 (acid oxide) + 2KOH (alkali) \u003d 2KMnO 4 (salt) + H 2 O (water)

All acid oxides, except for silicon dioxide SiO 2 (silicic anhydride, silica), react with water to form acids:

SO 3 (acid oxide) + H 2 O (water) \u003d H 2 SO 4 (acid)

Acid oxides are formed when simple and complex substances interact with oxygen (S + O 2 \u003d SO 2), or during decomposition as a result of heating of complex substances containing oxygen - acids, insoluble bases, salts (H 2 SiO 3 \u003d SiO 2 + H 2 O).

List of acid oxides:

Name of acid oxide	Acid Oxide Formula	Acid oxide properties
Sulfur(IV) oxide	SO2	colorless toxic gas with a pungent odor
Sulfur(VI) oxide	SO 3	highly volatile colorless toxic liquid
Carbon monoxide (IV)	CO2	colorless, odorless gas
Silicon(IV) oxide	SiO2	colorless crystals with strength
Phosphorus(V) oxide	P2O5	white flammable powder with an unpleasant odor
Nitric oxide (V)	N 2 O 5	a substance consisting of colorless volatile crystals
Chlorine(VII) oxide	Cl2O7	colorless oily toxic liquid
Manganese(VII) oxide	Mn2O7	liquid with a metallic luster, which is a strong oxidizing agent.

Oxides are inorganic compounds consisting of two chemical elements, one of which is oxygen in the -2 oxidation state. the only the non-oxidizing element is fluorine, which combines with oxygen to form oxygen fluoride. This is because fluorine is a more electronegative element than oxygen.

This class of compounds is very common. Every day a person encounters a variety of oxides in everyday life. Water, sand, the carbon dioxide we exhale, car exhaust, rust are all examples of oxides.

Classification of oxides

All oxides, according to their ability to form salts, can be divided into two groups:

1. Salt-forming oxides (CO 2, N 2 O 5, Na 2 O, SO 3, etc.)
2. Non-salt-forming oxides (CO, N 2 O, SiO, NO, etc.)

In turn, salt-forming oxides are divided into 3 groups:

• Basic oxides- (Metal oxides - Na 2 O, CaO, CuO, etc.)
• Acid oxides- (Non-metal oxides, as well as metal oxides in the oxidation state V-VII - Mn 2 O 7, CO 2, N 2 O 5, SO 2, SO 3, etc.)
• (Metal oxides with oxidation state III-IV as well as ZnO, BeO, SnO, PbO)

This classification is based on the manifestation of certain chemical properties by oxides. So, basic oxides correspond to bases, and acidic oxides correspond to acids. Acid oxides react with basic oxides to form the corresponding salt, as if the base and acid corresponding to these oxides had reacted: Likewise, amphoteric oxides correspond to amphoteric bases, which can exhibit both acidic and basic properties: Chemical elements exhibiting different oxidation states can form various oxides. In order to somehow distinguish between the oxides of such elements, after the name of the oxides, valency is indicated in brackets.

CO 2 - carbon monoxide (IV)

N 2 O 3 - nitric oxide (III)

Physical properties of oxides

Oxides are very diverse in their physical properties. They can be both liquids (H 2 O), and gases (CO 2, SO 3) or solids (Al 2 O 3, Fe 2 O 3). At the same time, basic oxides are, as a rule, solid substances. Oxides also have the most diverse color - from colorless (H 2 O, CO) and white (ZnO, TiO 2) to green (Cr 2 O 3) and even black (CuO).

• Basic oxides

Some oxides react with water to form the corresponding hydroxides (bases): Basic oxides react with acidic oxides to form salts: They react similarly with acids, but with the release of water: Oxides of metals less active than aluminum can be reduced to metals:

• Acid oxides

Acid oxides react with water to form acids: Some oxides (for example, silicon oxide SiO2) do not react with water, so acids are produced in other ways.

Acid oxides react with basic oxides to form salts: In the same way, with the formation of salts, acid oxides react with bases: If a given oxide corresponds to a polybasic acid, then an acid salt can also form: Non-volatile acid oxides can replace volatile oxides in salts:

As mentioned earlier, amphoteric oxides, depending on the conditions, can exhibit both acidic and basic properties. So they act as basic oxides in reactions with acids or acid oxides, with the formation of salts: And in reactions with bases or basic oxides, they exhibit acidic properties:

Obtaining oxides

Oxides can be obtained in a variety of ways, we will give the main ones.

Most oxides can be obtained by direct interaction of oxygen with a chemical element: When firing or burning various binary compounds: Thermal decomposition of salts, acids and bases: Interaction of some metals with water:

Application of oxides

Oxides are extremely common throughout the globe and are used both in everyday life and in industry. The most important oxide, hydrogen oxide, water, made life possible on Earth. Sulfur oxide SO 3 is used to produce sulfuric acid, as well as for food processing - this increases the shelf life, for example, of fruits.

Iron oxides are used to produce paints, the production of electrodes, although most iron oxides are reduced to metallic iron in metallurgy.

Calcium oxide, also known as quicklime, is used in construction. Oxides of zinc and titanium are white and insoluble in water, therefore they have become a good material for the production of paints - white.

Silicon oxide SiO 2 is the main component of glass. Chromium oxide Cr 2 O 3 is used for the production of colored green glasses and ceramics, and due to its high strength properties, for polishing products (in the form of GOI paste).

Carbon monoxide CO 2 , which all living organisms emit during respiration, is used for fire extinguishing, and also, in the form of dry ice, for cooling something.

Oxides, their classification and properties are the basis of such an important science as chemistry. They begin to study in the first year of study of chemistry. In such exact sciences as mathematics, physics and chemistry, all the material is interconnected, which is why the failure to assimilate the material entails a misunderstanding of new topics. Therefore, it is very important to understand the topic of oxides and fully navigate it. We will try to talk about this in more detail today.

What are oxides?

Oxides, their classification and properties - this is what needs to be understood paramount. So what are oxides? Do you remember this from the school curriculum?

Oxides (or oxides) are binary compounds, which include atoms of an electronegative element (less electronegative than oxygen) and oxygen with an oxidation state of -2.

Oxides are incredibly common substances on our planet. Examples of an oxide compound are water, rust, some dyes, sand, and even carbon dioxide.

Oxide formation

Oxides can be obtained in a variety of ways. The formation of oxides is also studied by such a science as chemistry. Oxides, their classification and properties - that's what scientists need to know in order to understand how this or that oxide was formed. For example, they can be obtained by direct connection of an oxygen atom (or atoms) with a chemical element - this is the interaction of chemical elements. However, there is also an indirect formation of oxides, this is when oxides are formed by the decomposition of acids, salts or bases.

Classification of oxides

Oxides and their classification depend on how they were formed. According to their classification, oxides are divided into only two groups, the first of which is salt-forming, and the second is non-salt-forming. So let's take a closer look at both groups.

Salt-forming oxides are a fairly large group, which is divided into amphoteric, acidic and basic oxides. As a result of any chemical reaction, salt-forming oxides form salts. As a rule, the composition of salt-forming oxides includes elements of metals and non-metals, which, as a result of a chemical reaction with water, form acids, but when interacting with bases, they form the corresponding acids and salts.

Non-salt-forming oxides are oxides that do not form salts as a result of a chemical reaction. Examples of such oxides are carbon.

Amphoteric oxides

Oxides, their classification and properties are very important concepts in chemistry. Salt-forming compounds include amphoteric oxides.

Amphoteric oxides are oxides that can exhibit basic or acidic properties, depending on the conditions of chemical reactions (show amphotericity). Such oxides are formed by transition metals (copper, silver, gold, iron, ruthenium, tungsten, rutherfordium, titanium, yttrium, and many others). Amphoteric oxides react with strong acids, and as a result of a chemical reaction they form salts of these acids.

Acid oxides

Or anhydrides are such oxides that, in chemical reactions, exhibit and also form oxygen-containing acids. Anhydrides are always formed by typical non-metals, as well as some transitional chemical elements.

Oxides, their classification and chemical properties are important concepts. For example, acidic oxides have completely different chemical properties from amphoteric ones. For example, when an anhydride interacts with water, the corresponding acid is formed (the exception is SiO2 - Anhydrides interact with alkalis, and as a result of such reactions, water and soda are released. When interacting with, a salt is formed.

Basic oxides

Basic (from the word "base") oxides are oxides of the chemical elements of metals with oxidation states of +1 or +2. These include alkali, alkaline earth metals, as well as the chemical element magnesium. Basic oxides differ from others in that they are able to react with acids.

Basic oxides interact with acids, in contrast to acid oxides, as well as with alkalis, water, and other oxides. As a result of these reactions, as a rule, salts are formed.

Properties of oxides

If you carefully study the reactions of various oxides, you can independently draw conclusions about what chemical properties the oxides are endowed with. The common chemical property of absolutely all oxides is the redox process.

Nevertheless, all oxides are different from each other. The classification and properties of oxides are two related topics.

Non-salt-forming oxides and their chemical properties

Non-salt-forming oxides are a group of oxides that exhibit neither acidic, nor basic, nor amphoteric properties. As a result of chemical reactions with non-salt-forming oxides, no salts are formed. Previously, such oxides were called not non-salt-forming, but indifferent and indifferent, but such names do not correspond to the properties of non-salt-forming oxides. According to their properties, these oxides are quite capable of chemical reactions. But there are very few non-salt-forming oxides; they are formed by monovalent and divalent non-metals.

From non-salt-forming oxides, salt-forming oxides can be obtained as a result of a chemical reaction.

Nomenclature

Almost all oxides are usually called like this: the word "oxide", followed by the name of the chemical element in the genitive case. For example, Al2O3 is aluminum oxide. In chemical language, this oxide is read like this: aluminum 2 o 3. Some chemical elements, such as copper, can have several degrees of oxidation, respectively, the oxides will also be different. Then CuO oxide is copper (two) oxide, that is, with an oxidation degree of 2, and Cu2O oxide is copper (three) oxide, which has an oxidation degree of 3.

But there are other names of oxides, which are distinguished by the number of oxygen atoms in the compound. A monoxide or monoxide is an oxide that contains only one oxygen atom. Dioxides are those oxides that contain two oxygen atoms, as indicated by the prefix "di". Trioxides are those oxides that already contain three oxygen atoms. Names such as monoxide, dioxide, and trioxide are already obsolete, but are often found in textbooks, books, and other manuals.

There are also so-called trivial names of oxides, that is, those that have developed historically. For example, CO is the oxide or monoxide of carbon, but even chemists most often refer to this substance as carbon monoxide.

So, an oxide is a combination of oxygen with a chemical element. The main science that studies their formation and interactions is chemistry. Oxides, their classification and properties are several important topics in the science of chemistry, without understanding which it is impossible to understand everything else. Oxides are gases, minerals, and powders. Some oxides should be known in detail not only by scientists, but also by ordinary people, because they can even be dangerous for life on this earth. Oxides are a very interesting and fairly easy topic. Oxide compounds are very common in everyday life.

Na 2 O + H 2 O \u003d 2NaOH;

CaO + H 2 O \u003d Ca (OH) 2;

with acidic compounds (acid oxides, acids) to form salts and water:

CaO + CO 2 \u003d CaCO 3;

CaO + 2HCl \u003d CaCl 2 + H 2 O;

3) with amphoteric compounds:

Li 2 O + Al 2 O 3 \u003d 2Li AlO 2;

3NaOH + Al(OH) 3 = Na 3 AlO 3 + 3H 2 O;

Acid oxides react:

1) with water to form acids:

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

2) with basic compounds (basic oxides and bases) with the formation of salts and water:

SO 2 + Na 2 O \u003d Na 2 SO 3;

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

with amphoteric compounds

CO 2 + ZnO \u003d ZnCO 3;

CO 2 + Zn(OH) 2 = ZnCO 3 + H 2 O;

Amphoteric oxides exhibit properties of both basic and acidic oxides. They are answered by amphoteric hydroxides:

acidic medium alkaline medium Be (OH) 2 BeO H 2 BeO 2

Zn(OH) 2 ZnO H 2 ZnO 2

Al (OH) 3 Al 2 O 3 H 3 AlO 3, HAlO 2

Cr(OH) 3 Cr 2 O 3 HCrO 2

Pb (OH) 2 PbO H 2 PbO 2

Sn(OH) 2 SnO H 2 SnO 2

Amphoteric oxides interact with acidic and basic compounds:

ZnO + SiO 2 \u003d ZnSiO 3; ZnO + H 2 SiO 3 \u003d ZnSiO 3 + H 2 O;

Al 2 O 3 + 3Na 2 O \u003d 2Na 3 AlO 3; Al 2 O 3 + 2NaOH \u003d 2NaAlO 2 + H 2 O.

Variable valence metals can form oxides of all three types. For example:

CrO basic Cr(OH) 2 ;

Cr 2 O 3 amphoteric Cr(OH) 3 ;

Cr 2 O 7 acidic H 2 Cr 2 O 7 ;

MnO, Mn 2 O 3 basic;

MnO 2 amphoteric;

Mn 2 O 7 acidic HMnO 4 .

Foundations

Bases are complex substances, which include metal atoms and one or more hydroxide groups (OH ‾). The general formula of bases is Me (OH) y, where y is the number of hydroxide groups equal to the valency of the metal.

Nomenclature

The name of the base consists of the word "hydroxide" + the name of the metal.

If the metal has a variable valency, then it is indicated at the end in brackets. For example: CuOH - copper (I) hydroxide, Cu (OH) 2 - copper (II) hydroxide, NaOH - sodium hydroxide.

Bases (hydroxides) are electrolytes. Electrolytes are substances that, in melts or solutions of polar liquids, decompose into ions: positively charged cations and negatively charged anions. The breakdown of a substance into ions is called electrolytic dissociation.

All electrolytes can be divided into two groups: strong and weak. Strong electrolytes in aqueous solutions are almost completely dissociated. Weak electrolytes dissociate only partially and in solutions a dynamic equilibrium is established between undissociated molecules and ions: NH 4 OH NH 4 + + OH - .

2.2. Classification

a) by the number of hydroxide groups in the molecule. The number of hydroxide groups in the base molecule depends on the valency of the metal and determines the acidity of the base.

The bases are divided into:

Single acid, the molecules of which contain one hydroxide group: NaOH, KOH, LiOH, etc.;

Biacid, the molecules of which contain two hydroxide groups: Ca (OH) 2, Fe (OH) 2, etc.;

Triacid, the molecules of which contain three hydroxide groups: Ni (OH) 3, Bi (OH) 3, etc.

Two- and three-acid bases are called polyacid.

b) according to the strength of the base are divided into:

Strong (alkalis): LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Sr(OH) 2 , Ba(OH) 2 ;

Weak: Cu (OH) 2, Fe (OH) 2, Fe (OH) 3, etc.

Strong bases are soluble in water, while weak bases are insoluble.

Base dissociation

Strong bases dissociate almost completely:

Ca (OH) 2 \u003d Ca 2+ + 2OH -.

Weak bases dissociate in steps. With the successive elimination of the hydroxide ion from polyacid bases, basic hydroxocation residues are formed, for example:

Fe(OH) 3 OH - + Fe(OH) 2 + iron dihydroxocations;

Fe(OH) 2 + OH - + FeOH 2+ iron hydroxocations;

Fe (OH) 2+ OH - + Fe 3+ iron cations.

The number of basic residues is equal to the acidity of the base.