Chemical properties and methods for obtaining amphoteric oxides. Obtaining oxides and their properties

Properties of oxides

oxides- these are complex chemicals, which are chemical compounds of simple elements with oxygen. They are salt-forming and not forming salts. In this case, salt-forming are of 3 types: main(from the word "foundation"), acidic and amphoteric.
An example of oxides that do not form salts can be: NO (nitric oxide) - is a colorless gas, odorless. It is formed during a thunderstorm in the atmosphere. CO (carbon monoxide) is an odorless gas produced by the combustion of coal. It is commonly referred to as carbon monoxide. There are other oxides that do not form salts. Now let's take a closer look at each type of salt-forming oxides.

Basic oxides

Basic oxides- These are complex chemical substances related to oxides that form salts by chemical reaction with acids or acid oxides and do not react with bases or basic oxides. For example, the main ones are:
K 2 O (potassium oxide), CaO (calcium oxide), FeO (2-valent iron oxide).

Consider chemical properties of oxides by examples

1. Interaction with water:
- interaction with water to form a base (or alkali)

CaO + H 2 O → Ca (OH) 2 (a well-known lime slaking reaction, while a large amount of heat is released!)

2. Interaction with acids:
- interaction with acid to form salt and water (solution of salt in water)

CaO + H 2 SO 4 → CaSO 4 + H 2 O (Crystals of this substance CaSO 4 are known to everyone under the name "gypsum").

3. Interaction with acid oxides: salt formation

CaO + CO 2 → CaCO 3 (This substance is known to everyone - ordinary chalk!)

Acid oxides

Acid oxides- these are complex chemicals related to oxides that form salts when chemically interacting with bases or basic oxides and do not interact with acidic oxides.

Examples of acidic oxides are:

CO 2 (well-known carbon dioxide), P 2 O 5 - phosphorus oxide (formed by combustion of white phosphorus in air), SO 3 - sulfur trioxide - this substance is used to produce sulfuric acid.

Chemical reaction with water

CO 2 +H 2 O→ H 2 CO 3 is a substance - carbonic acid - one of the weak acids, it is added to sparkling water for "bubbles" of gas. As the temperature rises, the solubility of the gas in water decreases, and its excess comes out in the form of bubbles.

Reaction with alkalis (bases):

CO 2 +2NaOH→ Na 2 CO 3 +H 2 O- the resulting substance (salt) is widely used in the economy. Its name - soda ash or washing soda - is an excellent detergent for burnt pans, grease, burns. I do not recommend working with bare hands!

Reaction with basic oxides:

CO 2 + MgO → MgCO 3 - received salt - magnesium carbonate - also called "bitter salt".

Amphoteric oxides

Amphoteric oxides- these are complex chemicals, also related to oxides, which form salts during chemical interaction with acids (or acid oxides) and bases (or basic oxides). The most common use of the word "amphoteric" in our case refers to metal oxides.

An example amphoteric oxides can be:

ZnO - zinc oxide (white powder, often used in medicine for the manufacture of masks and creams), Al 2 O 3 - aluminum oxide (also called "alumina").

The chemical properties of amphoteric oxides are unique in that they can enter into chemical reactions corresponding to both bases and acids. For example:

Reaction with acid oxide:

ZnO + H 2 CO 3 → ZnCO 3 + H 2 O - The resulting substance is a solution of "zinc carbonate" salt in water.

Reaction with bases:

ZnO + 2NaOH → Na 2 ZnO 2 + H 2 O - the resulting substance is a double salt of sodium and zinc.

Obtaining oxides

Obtaining oxides produced in various ways. This can happen in physical and chemical ways. The simplest way is the chemical interaction of simple elements with oxygen. For example, the result of a combustion process or one of the products of this chemical reaction are oxides. For example, if a red-hot iron rod, and not only iron (you can take zinc Zn, tin Sn, lead Pb, copper Cu, - in general, what is at hand) is placed in a flask with oxygen, then a chemical oxidation reaction of iron will occur, which accompanied by a bright flash and sparks. The reaction product will be black iron oxide FeO powder:

2Fe+O 2 → 2FeO

Completely similar chemical reactions with other metals and non-metals. Zinc burns in oxygen to form zinc oxide

2Zn+O 2 → 2ZnO

The combustion of coal is accompanied by the formation of two oxides at once: carbon monoxide and carbon dioxide.

2C+O 2 → 2CO - the formation of carbon monoxide.

C + O 2 → CO 2 - the formation of carbon dioxide. This gas is formed if there is more than enough oxygen, that is, in any case, the reaction proceeds first with the formation of carbon monoxide, and then the carbon monoxide is oxidized, turning into carbon dioxide.

Obtaining oxides can be done in another way - by a chemical reaction of decomposition. For example, to obtain iron oxide or aluminum oxide, it is necessary to ignite the corresponding bases of these metals on fire:

Fe(OH) 2 → FeO+H 2 O

Solid aluminum oxide - mineral corundum Iron(III) oxide. The surface of the planet Mars has a reddish-orange color due to the presence of iron (III) oxide in the soil. Solid aluminum oxide - corundum

2Al(OH) 3 → Al 2 O 3 + 3H 2 O,
as well as in the decomposition of individual acids:

H 2 CO 3 → H 2 O + CO 2 - decomposition of carbonic acid

H 2 SO 3 → H 2 O + SO 2 - decomposition of sulfurous acid

Obtaining oxides can be made from metal salts with strong heating:

CaCO 3 → CaO + CO 2 - calcium oxide (or quicklime) and carbon dioxide are obtained by calcining chalk.

2Cu(NO 3) 2 → 2CuO + 4NO 2 + O 2 - in this decomposition reaction, two oxides are obtained at once: copper CuO (black) and nitrogen NO 2 (it is also called brown gas because of its really brown color).

Another way in which oxides can be obtained is through redox reactions.

Cu + 4HNO 3 (conc.) → Cu(NO 3) 2 + 2NO 2 + 2H 2 O

S + 2H 2 SO 4 (conc.) → 3SO 2 + 2H 2 O

Chlorine oxides

The following are known chlorine oxides: Cl 2 O, ClO 2 , Cl 2 O 6 , Cl 2 O 7 . All of them, with the exception of Cl 2 O 7 , are yellow or orange in color and are not stable, especially ClO 2 , Cl 2 O 6 . All chlorine oxides explosive and are very strong oxidizers.

Reacting with water, they form the corresponding oxygen-containing and chlorine-containing acids:

So, Cl 2 O - acid chlorine oxide hypochlorous acid.

Cl 2 O + H 2 O → 2HClO - Hypochlorous acid

ClO 2 - acid chlorine oxide hypochlorous and hypochlorous acids, since in a chemical reaction with water it forms two of these acids at once:

ClO 2 + H 2 O → HClO 2 + HClO 3

Cl 2 O 6 - too acid chlorine oxide chloric and perchloric acids:

Cl 2 O 6 + H 2 O → HClO 3 + HClO 4

And finally, Cl 2 O 7 - a colorless liquid - acid chlorine oxide perchloric acid:

Cl 2 O 7 + H 2 O → 2HClO 4

nitrogen oxides

Nitrogen is a gas that forms 5 different compounds with oxygen - 5 nitrogen oxides. Namely:

N 2 O - nitrogen hemioxide. Its other name is known in medicine under the name laughing gas or nitrous oxide- It is colorless sweetish and pleasant to the taste on the gas.
-NO- nitrogen monoxide A colorless, odorless, tasteless gas.
- N 2 O 3 - nitrous anhydride- colorless crystalline substance
- NO 2 - nitrogen dioxide. Its other name is brown gas- the gas really has a brown color
- N 2 O 5 - nitric anhydride- blue liquid boiling at a temperature of 3.5 0 C

Of all these listed nitrogen compounds, NO - nitrogen monoxide and NO 2 - nitrogen dioxide are of the greatest interest in industry. nitrogen monoxide(NO) and nitrous oxide N 2 O does not react with either water or alkalis. (N 2 O 3), when reacting with water, forms a weak and unstable nitrous acid HNO 2, which gradually turns into a more stable chemical substance nitric acid in air. Consider some chemical properties of nitrogen oxides:

Reaction with water:

2NO 2 + H 2 O → HNO 3 + HNO 2 - 2 acids are formed at once: nitric acid HNO 3 and nitrous acid.

Reaction with alkali:

2NO 2 + 2NaOH → NaNO 3 + NaNO 2 + H 2 O - two salts are formed: sodium nitrate NaNO 3 (or sodium nitrate) and sodium nitrite (salt of nitrous acid).

Reaction with salts:

2NO 2 + Na 2 CO 3 → NaNO 3 + NaNO 2 + CO 2 - two salts are formed: sodium nitrate and sodium nitrite, and carbon dioxide is released.

Nitrogen dioxide (NO 2) is obtained from nitrogen monoxide (NO) using a chemical reaction of the compound with oxygen:

2NO + O 2 → 2NO 2

iron oxides

Iron forms two oxide: FeO- iron oxide(2-valent) - black powder, which is obtained by reduction iron oxide(3-valent) carbon monoxide by the following chemical reaction:

Fe 2 O 3 + CO → 2FeO + CO 2

This basic oxide readily reacts with acids. It has reducing properties and is rapidly oxidized to iron oxide(3-valent).

4FeO +O 2 → 2Fe 2 O 3

iron oxide(3-valent) - red-brown powder (hematite), which has amphoteric properties (it can interact with both acids and alkalis). But the acidic properties of this oxide are so weakly expressed that it is most often used as basic oxide.

There are also so-called mixed iron oxide Fe 3 O 4 . It is formed during the combustion of iron, conducts electricity well and has magnetic properties (it is called magnetic iron ore or magnetite). If iron burns out, then as a result of the combustion reaction, scale is formed, consisting of two oxides at once: iron oxide(III) and (II) valence.

Sulfur oxide

Sulfur oxide SO 2 - or sulphur dioxide refers to acid oxides, but does not form acid, although it dissolves perfectly in water - 40 liters of sulfur oxide in 1 liter of water (for the convenience of compiling chemical equations, such a solution is called sulfurous acid).

Under normal circumstances, it is a colorless gas with a pungent and suffocating smell of burnt sulfur. At a temperature of only -10 0 C, it can be transferred to a liquid state.

In the presence of a catalyst -vanadium oxide (V 2 O 5) sulfur oxide takes on oxygen and turns into sulfur trioxide

2SO 2 + O 2 → 2SO 3

dissolved in water sulphur dioxide- sulfur oxide SO 2 - oxidizes very slowly, as a result of which the solution itself turns into sulfuric acid

If a sulphur dioxide pass through an alkali solution, for example, sodium hydroxide, then sodium sulfite is formed (or hydrosulfite - depending on how much alkali and sulfur dioxide are taken)

NaOH + SO 2 → NaHSO 3 - sulphur dioxide taken in excess

2NaOH + SO 2 → Na 2 SO 3 + H 2 O

If sulfur dioxide does not react with water, then why does its aqueous solution give an acidic reaction?! Yes, it does not react, but it oxidizes itself in water, adding oxygen to itself. And it turns out that free hydrogen atoms accumulate in water, which give an acidic reaction (you can check it with some indicator!)

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 - these are complex substances consisting of two chemical elements, one of which is oxygen, with a valence 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 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 valence 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

2. Classification, preparation and properties of oxides

Of the binary compounds, oxides are the best known. Oxides are compounds consisting of two elements, one of which is oxygen, which has an oxidation state of -2. According to functional characteristics, oxides are subdivided into salt-forming and non-salt-forming (indifferent). Salt-forming oxides, in turn, are divided into basic, acidic and amphoteric.

The names of oxides are formed using the word "oxide" and the Russian name of the element in the genitive case, indicating the valency of the element in Roman numerals, for example: SO 2 - sulfur oxide (IV), SO 3 - sulfur oxide (VI), CrO - chromium oxide (II), Cr 2 O 3 - chromium oxide (III).

2.1. Basic oxides

Basic oxides are those that react with acids (or acid oxides) to form salts.

Basic oxides include oxides of typical metals, they correspond to hydroxides with the properties of bases (basic hydroxides), and the oxidation state of the element does not change when moving from oxide to hydroxide, for example,

Obtaining basic oxides

1. Oxidation of metals when heated in an oxygen atmosphere:

2Mg + O 2 \u003d 2MgO,

2Cu + O 2 \u003d 2CuO.

This method is not applicable to alkali metals, which, when oxidized, usually give peroxides and superoxides, and only lithium, when burned, forms an oxide. Li2O.

2. Sulfide roasting:

2 CuS + 3 O 2 \u003d 2 CuO + 2 SO 2,

4 FeS 2 + 11 O 2 \u003d 2 Fe 2 O 3 + 8 SO 2.

The method is not applicable to active metal sulfides oxidizing to sulfates.

3. Decomposition of hydroxides (at high temperature):

C u (OH) 2 \u003d CuO + H 2 O.

Alkali metal oxides cannot be obtained by this method.

4. Decomposition of salts of oxygen-containing acids (at high temperature):

VaCO 3 \u003d BaO + CO 2,

2Pb (NO 3) 2 \u003d 2PbO + 4NO 2 + O 2,

4 FeSO 4 \u003d 2 Fe 2 O 3 + 4 SO 2 + O 2.

This method of obtaining oxides is especially easy for nitrates and carbonates, including basic salts:

(ZnOH) 2 CO 3 \u003d 2ZnO + CO 2 + H 2 O.

Properties of basic oxides

Most of the basic oxides are solid crystalline substances of an ionic nature, at the nodes of the crystal lattice there are metal ions that are quite strongly associated with oxide ions O - 2, therefore, oxides of typical metals have high melting and boiling points.

1. Most basic oxides do not decompose when heated, with the exception of oxides of mercury and noble metals:

2HgO \u003d 2Hg + O 2,

2Ag 2 O \u003d 4Ag + O 2.

2. When heated, basic oxides can react with acidic and amphoteric oxides, with acids:

BaO + SiO 2 \u003d BaSiO 3,

MgO + Al 2 O 3 \u003d Mg (AlO 2) 2,

ZnO + H 2 SO 4 \u003d ZnSO 4 + H 2 O.

3. By adding (directly or indirectly) water, basic oxides form bases (basic hydroxides). Oxides of alkali and alkaline earth metals directly react with water:

Li 2 O + H 2 O \u003d 2 LiOH,

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

The exception is magnesium oxide. MgO . Magnesium hydroxide cannot be obtained from it. Mg(OH ) 2 upon interaction with water.

4. Like all other types of oxides, basic oxides can enter into redox reactions:

Fe 2 O 3 + 2Al \u003d Al 2 O 3 + 2Fe,

3CuO + 2NH 3 \u003d 3Cu + N 2 + 3H 2 O,

4 FeO + O 2 \u003d 2 Fe 2 O 3.

M.V. Andryukhova, L.N. Borodin

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 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- 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, 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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