Oxides, their types and properties. Acidic oxides

Oxides - complex substances consisting of two elements, one of which is an oxygen atom in oxidation state -2.
Based on their ability to form salts, oxides are divided into salt-forming And non-salt-forming(CO, SiO, NO, N 2 O). Salt-forming oxides, in turn, are classified into basic, acidic and amphoteric.
Basic are the oxides that correspond to bases, and acidic are the oxides that correspond to acids. Amphoteric oxides include oxides that exhibit the chemical properties of both basic and acidic oxides.
Basic oxides are formed only by metal elements: alkali (Li 2 O, Na 2 O, K 2 O, Cs 2 O, Rb 2 O), alkaline earth (CaO, SrO, BaO, RaO) and magnesium (MgO), as well as metals d-family in oxidation state +1, +2, less often +3 (Cu 2 O, CuO, Ag 2 O, CrO, FeO, MnO, CoO, NiO).

Acidic oxides form both non-metal elements (CO 2, SO 2, NO 2, P 2 O 5, Cl 2 O 7) and metal elements, the oxidation state of the metal atom must be +5 and higher (V 2 O 5, СrO 3, Mn 2 O 7, MnO 3). Amphoteric oxides are formed only by metal elements (ZnO, AI 2 O 3, Fe 2 O 3, BeO, Cr 2 O 3, PbO, SnO, MnO 2).

Under normal conditions, oxides can be in three states of aggregation: all basic and amphoteric oxides are solids, acidic oxides can be liquid (SO 3, Cl 2 O7, Mn 2 O7), gaseous (CO 2, SO 2, NO 2) and solid (P 2 O 5, SiO 2). Some have an odor (NO 2, SO 2), but most oxides are odorless. Some oxides are colored: brown gas NO 2, cherry red CrO 3, black CuO and Ag 2 O, red Cu 2 O and HgO, brown Fe 2 O 3, white SiO 2, Al 2 O 3 and ZnO, others are colorless ( H 2 O, CO 2, SO 2).

Most oxides are stable when heated; Mercury and silver oxides easily decompose when heated. Basic and amphoteric oxides have a crystal lattice of the ionic type. Most acidic oxides of the substance (one of the few exceptions is silicon (IV) oxide, which has an atomic crystal lattice).

Al 2 O 3 +6KOH+3H 2 O=2K 3 - potassium hexahydroxoaluminate;
ZnO+2NaOH+H 2 O=Na 2 - sodium tetrahydroxozincate;

August 6, 2018

Every schoolchild came across the concept of “oxide” in chemistry lessons. From this one word the object began to seem something indescribably terrible. But there's nothing wrong with that. Higher oxides are substances that contain compounds of simple substances with oxygen (in oxidation state -2). It is worth noting that they react with:

O 2 (oxygen), if the element is not in higher CO. For example, SO 2 reacts with oxygen (since CO is +4), but SO 3 does not (since its highest oxidation state is +6).
H 2 (hydrogen) and C (carbon). Only some oxides react.
Water if a soluble alkali or acid is obtained.

All oxides react with salts and non-metals (except for the substances listed above).

It is worth noting that some substances (for example, nitric oxide, iron oxide and chlorine oxide) have their own characteristics, that is, their chemical characteristics may differ from other substances.

Oxides classification

They are divided into two branches: those who can form salt, and those who cannot form it.

Examples of formulas of higher oxides that do not form salts: NO (divalent nitrogen oxide; a colorless gas formed during thunderstorms), CO (carbon monoxide), N 2 O (monovalent nitrogen oxide), SiO (silicon oxide), S 2 O (sulfur oxide), water.

These compounds can react with bases, acids and salt-forming oxides. But when these substances react, salts are never formed. For example:

CO (carbon monoxide) + NaOH (sodium hydroxide) = HCOONa (sodium formate)

Salt-forming oxides are divided into three types: acidic, base and amphoteric oxides.

Acidic oxides

An acidic higher oxide is a salt-forming oxide that corresponds to an acid. For example, hexavalent sulfur oxide (SO 3) has a corresponding chemical compound - H 2 SO 4. These elements react with basic and amphoteric oxides, bases and water. A salt or acid is formed.

With alkaline oxides: CO 2 (carbon dioxide) + MgO (magnesium oxide) = MgCO 3 (bitter salt).
With amphoteric oxides: P 2 O 5 (phosphorus oxide) + Al 2 O 3 (aluminum oxide) = 2AlPO 4 (aluminum phosphate or orthophosphate).
With bases (alkalis): CO 2 (carbon dioxide) + 2NaOH (caustic soda) = Na 2 CO 3 (sodium carbonate or soda ash) + H 2 O (water).
With water: CO 2 (carbon dioxide) + H 2 O = H 2 CO 3 (carbonic acid, after the reaction instantly breaks down into carbon dioxide and water).

Acid oxides do not react with each other.

Basic oxides

A basic higher oxide is a salt-forming oxide of the metal to which the base corresponds. Calcium oxide (CaO) corresponds to calcium hydroxide (Ca(OH) 2). These substances interact with acidic and amphoteric oxides, acids (with the exception of H 2 SiO 3, since silicic acid is insoluble) and water.

With acidic oxides: CaO (calcium oxide) + CO 2 (carbon dioxide) = CaCO 3 (calcium carbonate or regular chalk).
With amphoteric oxide: CaO (calcium oxide) + Al 2 O 3 (aluminum oxide) = Ca(AlO 2) 2 (calcium aluminate).
With acids: CaO (calcium oxide) + H 2 SO 4 (sulfuric acid) = CaSO 4 (calcium sulfate or gypsum) + H 2 O.
With water: CaO (calcium oxide) + H 2 O = Ca (OH) 2 (calcium hydroxide or lime slaking reaction).

They don't interact with each other.

Amphoteric oxides

Amphoteric higher oxide is the oxide of an amphoteric metal. Depending on conditions, it may exhibit basic or acidic properties. For example, the formulas of higher oxides that exhibit amphoteric properties: ZnO (zinc oxide), Al 2 O 3 (alumina). Amphoteric oxides react with alkalis, acids (also with the exception of silicic acid), basic and acidic oxides.

With bases: ZnO (zinc oxide) + 2NaOH (sodium base) = Na 2 ZnO 2 (double salt of zinc and sodium) + H 2 O.
With acids: Al 2 O 3 (aluminum oxide) + 6HCl (hydrochloric acid) = 2AlCl 3 (aluminum chloride or aluminum chloride) + 3H 2 O.
With acidic oxides: Al 2 O 3 (aluminum oxide) + 3SO 3 (hexavalent sulfur oxide) = Al 2 (SO 4) 3 (aluminum alum).
With basic oxides: Al 2 O 3 (aluminum oxide) + Na 2 O (sodium oxide) = 2NaAlO 2 (sodium aluminate).

Elements of higher oxides of an amphoteric nature do not interact with each other or with water.

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Oxides are complex substances consisting of two elements, one of which is oxygen. Oxides can be salt-forming and non-salt-forming: one type of salt-forming oxides is basic oxides. How do they differ from other species, and what are their chemical properties?

Salt-forming oxides are divided into basic, acidic and amphoteric oxides. If basic oxides correspond to bases, then acidic oxides correspond to acids, and amphoteric oxides correspond to amphoteric formations. Amphoteric oxides are those compounds that, depending on conditions, can exhibit either basic or acidic properties.

Rice. 1. Classification of oxides.

The physical properties of oxides are very diverse. They can be either gases (CO 2), solids (Fe 2 O 3) or liquid substances (H 2 O).

However, most basic oxides are solids of various colors.

oxides in which elements exhibit their highest activity are called higher oxides. The order of increase in the acidic properties of higher oxides of the corresponding elements in periods from left to right is explained by a gradual increase in the positive charge of the ions of these elements.

Chemical properties of basic oxides

Basic oxides are the oxides to which bases correspond. For example, the basic oxides K 2 O, CaO correspond to the bases KOH, Ca(OH) 2.

Rice. 2. Basic oxides and their corresponding bases.

Basic oxides are formed by typical metals, as well as metals of variable valency in the lowest oxidation state (for example, CaO, FeO), react with acids and acid oxides, forming salts:

CaO (basic oxide) + CO 2 (acid oxide) = CaCO 3 (salt)

FeO (basic oxide)+H 2 SO 4 (acid)=FeSO 4 (salt)+2H 2 O (water)

Basic oxides also react with amphoteric oxides, resulting in the formation of a salt, for example:

Only oxides of alkali and alkaline earth metals react with water:

BaO (basic oxide)+H 2 O (water)=Ba(OH) 2 (alkali earth metal base)

Many basic oxides tend to be reduced to substances consisting of atoms of one chemical element:

3CuO+2NH 3 =3Cu+3H 2 O+N 2

When heated, only oxides of mercury and noble metals decompose:

Rice. 3. Mercury oxide.

List of main oxides:

Oxide name	Chemical formula	Properties
Calcium oxide	CaO	quicklime, white crystalline substance
Magnesium oxide	MgO	white substance, slightly soluble in water
Barium oxide	BaO	colorless crystals with a cubic lattice
Copper oxide II	CuO	black substance practically insoluble in water
	HgO	red or yellow-orange solid
Potassium oxide	K2O	colorless or pale yellow substance
Sodium oxide	Na2O	substance consisting of colorless crystals
Lithium oxide	Li2O	a substance consisting of colorless crystals that have a cubic lattice structure

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

What are oxides?

Oxides, their classification and properties are what needs to be understood first. So, what are oxides? Do you remember this from school?

Oxides (or oxides) are binary compounds that contain 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 oxide compounds include water, rust, some dyes, sand, and even carbon dioxide.

Formation of oxides

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 - this is what scientists need to know in order to understand how this or that oxide was formed. For example, they can be obtained by directly combining an oxygen atom (or atoms) with a chemical element - this is the interaction of chemical elements. However, there is also indirect formation of oxides, this is when oxides are formed by the decomposition of acids, salts or bases.

Oxides classification

Oxides and their classification depend on how they are 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 form acids as a result of a chemical reaction with water, but when interacting with bases they form the corresponding acids and salts.

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

Amphoteric oxides

Oxides, their classification and properties are very important concepts in chemistry. The composition of salt-forming compounds includes amphoteric oxides.

Amphoteric oxides are oxides that can exhibit basic or acidic properties, depending on the conditions of chemical reactions (they exhibit amphotericity). Such oxides are formed (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.

Acidic oxides

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

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

Basic oxides

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

Basic oxides interact with acids, unlike acidic oxides, as well as with alkalis, water, and other oxides. As a result of these reactions, salts are usually 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.

But nevertheless, all oxides are different from each other. The classification and properties of oxides are two interrelated topics.

Non-salt-forming oxides and their chemical properties

Non-salt-forming oxides are a group of oxides that exhibit neither acidic, basic, nor amphoteric properties. As a result of chemical reactions with non-salt-forming oxides, no salts are formed. Previously, such oxides were not called 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 nonmetals.

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 this way: 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 reads like this: aluminum 2 o 3. Some chemical elements, such as copper, can have several degrees of oxidation; accordingly, 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 for oxides, which are distinguished by the number of oxygen atoms in the compound. Monoxides or monoxides are those oxides that contain only one oxygen atom. Dioxides are those oxides that contain two oxygen atoms, which are indicated by the prefix “di”. Trioxides are those oxides that already contain three oxygen atoms. Names such as monoxide, dioxide and trioxide are already outdated, but are often found in textbooks, books and other aids.

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

So, an oxide is a compound 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 one cannot understand everything else. Oxides are gases, minerals, and powders. Some oxides are worth knowing in detail not only for scientists, but also for ordinary people, because they can even be dangerous to life on this earth. Oxides are a very interesting and quite easy topic. Oxide compounds are very common in everyday life.

DEFINITION

Oxides– a class of inorganic compounds, they are compounds of a chemical element with oxygen, in which oxygen exhibits an oxidation state of “-2”.

The exception is oxygen difluoride (OF 2), since the electronegativity of fluorine is higher than that of oxygen and fluorine always exhibits an oxidation state of "-1".

Oxides, depending on the chemical properties they exhibit, are divided into two classes - salt-forming and non-salt-forming oxides. Salt-forming oxides have an internal classification. Among them, acidic, basic and amphoteric oxides are distinguished.

Chemical properties of non-salt-forming oxides

Non-salt-forming oxides exhibit neither acidic, basic, nor amphoteric properties and do not form salts. Non-salt-forming oxides include oxides of nitrogen (I) and (II) (N 2 O, NO), carbon monoxide (II) (CO), silicon oxide (II) SiO, etc.

Despite the fact that non-salt-forming oxides are not capable of forming salts, when carbon monoxide (II) reacts with sodium hydroxide, an organic salt is formed - sodium formate (formic acid salt):

CO + NaOH = HCOONa.

When non-salt-forming oxides interact with oxygen, higher oxides of elements are obtained:

2CO + O 2 = 2CO 2 ;

2NO + O 2 = 2NO 2.

Chemical properties of salt-forming oxides

Among salt-forming oxides, basic, acidic and amphoteric oxides are distinguished, the first of which, when interacting with water, form bases (hydroxides), the second - acids, and the third - exhibit the properties of both acidic and basic oxides.

Basic oxides react with water to form bases:

CaO + 2H 2 O = Ca(OH) 2 + H 2 ;

Li 2 O + H 2 O = 2LiOH.

When basic oxides react with acidic or amphoteric oxides, salts are obtained:

CaO + SiO 2 = CaSiO 3;

CaO + Mn 2 O 7 = Ca(MnO 4) 2;

CaO + Al 2 O 3 = Ca(AlO 2) 2.

Basic oxides react with acids to form salts and water:

CaO + H 2 SO 4 = CaSO 4 + H 2 O;

CuO + H 2 SO 4 = CuSO 4 + H 2 O.

When basic oxides formed by metals in the activity series after aluminum interact with hydrogen, the metals included in the oxide are reduced:

CuO + H 2 = Cu + H 2 O.

Acidic oxides react with water to form acids:

P 2 O 5 + H 2 O = HPO 3 (metaphosphoric acid);

HPO 3 + H 2 O = H 3 PO 4 (orthophosphoric acid);

SO 3 + H 2 O = H 2 SO 4.

Some acidic oxides, for example, silicon (IV) oxide (SiO 2), do not react with water, therefore, the acids corresponding to these oxides are obtained indirectly.

When acidic oxides react with basic or amphoteric oxides, salts are obtained:

P 2 O 5 + 3CaO = Ca 3 (PO 4) 2;

CO 2 + CaO = CaCO 3 ;

P 2 O 5 +Al 2 O 3 = 2AlPO 4.

Acidic oxides react with bases to form salts and water:

P 2 O 5 + 6NaOH = 3Na 3 PO 4 + 3H 2 O;

Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 O.

Amphoteric oxides interact with acidic and basic oxides (see above), as well as with acids and bases:

Al 2 O 3 + 6HCl = 2AlCl 3 + 3H 2 O;

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

ZnO + 2HCl = ZnCl 2 + H 2 O;

ZnO + 2KOH + H 2 O = K 2 4

ZnO + 2KOH = K 2 ZnO 2 .

Physical properties of oxides

Most oxides are solids at room temperature (CuO is a black powder, CaO is a white crystalline substance, Cr 2 O 3 is a green powder, etc.). Some oxides are liquids (water - hydrogen oxide - colorless liquid, Cl 2 O 7 - colorless liquid) or gases (CO 2 - colorless gas, NO 2 - brown gas). The structure of oxides is also different, most often molecular or ionic.

Obtaining oxides

Almost all oxides can be obtained by the reaction of a specific element with oxygen, for example:

2Cu + O 2 = 2CuO.

The formation of oxides also results from the thermal decomposition of salts, bases and acids:

CaCO 3 = CaO + CO 2;

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

4HNO 3 = 4NO 2 + O 2 + 2H 2 O.

Other methods for producing oxides include roasting binary compounds, for example, sulfides, oxidation of higher oxides to lower ones, reduction of lower oxides to higher ones, interaction of metals with water at high temperatures, etc.

Examples of problem solving

EXAMPLE 1

Exercise

During the electrolysis of 40 mol of water, 620 g of oxygen were released. Determine the oxygen yield.

Solution

The yield of the reaction product is determined by the formula:

η = m pr / m theor × 100%.

The practical mass of oxygen is the mass indicated in the problem statement – 620 g. The theoretical mass of the reaction product is the mass calculated from the reaction equation. Let us write down the equation for the reaction of water decomposition under the influence of electric current:

2H 2 O = 2H 2 + O 2.

According to the reaction equation n(H 2 O):n(O 2) = 2:1, therefore n(O 2) = 1/2×n(H 2 O) = 20 mol. Then, the theoretical mass of oxygen will be equal to: