Heating is easily decomposed oxides. Lessons on inorganic chemistry for preparation for the exam

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

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

They are shaking and uncoupled.

Saline-forming oxides- These are such oxides, which as a result of chemical reactions form salts. These are oxides of metals and non-metals, which, when interacting with water, form appropriate acids, and when interacting with bases, corresponding acidic and normal salts. For example, Copper oxide (CUO) is salt-forming oxide, because, for example, when interacting with hydrochloric acid (HCl), 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-self-forming oxides They are called such oxides that do not form salts. An example is CO, N 2 O, NO.

Shaft-forming oxides in turn are 3 types: the main (from the word « base » ), acid and amphoteric.

The main oxidesthese oxides of metals are called, which correspond to hydroxides belonging to the base class. The main oxides include, for example, Na 2 O, K 2 O, MGO, CaO, etc.

Chemical properties of major oxides

1. Water soluble main oxides react with water, forming bases:

Na 2 O + H 2 O → 2naoh.

2. interact with acid oxides, forming appropriate salts

Na 2 O + SO 3 → Na 2 SO 4.

3. React with acids, forming 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 composition of oxides as the second element will be non-metall or metal, manifesting the highest valence (usually exhibit from IV to VII), then such oxides will be acidic. Acid oxides (acid anhydrides) are such oxides, which correspond to hydroxides relating to the class of acids. This, 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 an acid:

SO 3 + H 2 O → H 2 SO 4.

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

2. React with based oxides with salt formation:

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 oxideit includes an element that has amphoteric properties. Under amphoteriness understand the ability of compounds to exercise depending on the conditions of acid and basic properties.For example, ZNO zinc oxide can be both base and acid (Zn (OH) 2 and H 2 ZnO 2). Amphoterity is expressed in that, depending on the conditions of amphoteric oxides, either basic or acidic properties are shown.

Chemical properties of amphoteric oxides

1. Interact with acids, forming salt and water:

Zno + 2HCl → ZnCl 2 + H 2 O.

2. react with solid alkalis (when fusing), forming a sodium cinat and water as a result of the reaction.

Zno + 2NaOH → Na 2 ZnO 2 + H 2 O.

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

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

The coordination number is a characteristic that determines the number of nearest particles: atoms or yn in a molecule or crystal. For each amphoteric metal, its coordination number is characteristic. For BE and ZN - this is 4; For and Al are 4 or 6; For and CR is 6 or (very rare) 4;

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

Have questions? Want to know more about oxides?
To get a tutor help - register.
The first lesson is free!

the site, with full or partial copying of the material reference to the original source is required.

2. Classification, obtaining and properties of oxides

Oxides are most famous from binary compounds. Oxides are called compounds consisting of two elements, one of which is oxygen having a degree of oxidation -2. According to functional signs, oxides are divided into sale-forming and non-forming (indifferent). Solving oxides, in turn, are divided into basic, acid and amphoteric.

The names of the oxides are formed using the word "oxide" and the Russian name of the element in the parental case, indicating the roman numbers of the valence of the element, 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. Main oxides

The mains are called oxides, interacting with acids (or with acidic oxides) to form salts.

The main oxides include oxides of typical metals, they correspond to hydroxides with base properties (main hydroxides), and the degree of oxidation of the element does not change during the transition from the oxide to hydroxide, for example,

Getting the main 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 for alkali metals, which, when oxidation, is usually given peroxides and superoxides, and only lithium, burning, forms oxideLi 2 O.

2. Sulfide firing:

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 for the sulphides of active metals, oxidizing to sulfates.

3. Decomposition of hydroxides (at high temperature):

C U (OH) 2 \u003d Cuo + H 2 O.

This method cannot be obtained alkali metal oxides.

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

Vaso 3 \u003d Vao + 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 particularly easily carried out for nitrates and carbonates, including for basic salts:

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

Properties of main oxides

Most of the main oxides are ionic solid crystalline substances, metal ions are located in the nodes of the crystal lattice, which are quite strongly associated with oxide ions O -2, so the oxides of typical metals have high melting and boiling points.

1. Most of the main oxides are not disintegrated by heating, the exclusion is oxides of mercury and noble metals:

2hgo \u003d 2HG + O 2,

2AG 2 O \u003d 4AG + O 2.

2. Basic oxides when heated can be 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. Attaching (directly or indirectly) water, the main oxides form bases (main hydroxides). Alkaline and alkaline earth metal oxides react directly with water:

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

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

The exception is magnesium oxideMGO. . It is impossible to get magnesium hydroxideMG (Oh. ) 2 When interacting with water.

4. Like all other types of oxides, main oxides can enter into oxidative reaction 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. AndrewOv, L.N. BOPODY

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

Salt-forming oxides are divided into main, acid and amphoteric oxides. If base oxides correspond to the base, then acidic acids, and amphoteric formations correspond to the amphoteric oxides. Amphoteric oxides are connected, which, depending on the conditions, can be either the main or acidic properties.

Fig. 1. Classification of oxides.

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

At the same time, most of the main oxides are solid substances of different colors.

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

Chemical properties of major oxides

The main oxides are the oxides that correspond to the base. For example, the main oxides K 2 O, Cao correspond to the base Koh, Ca (OH) 2.

Fig. 2. The main oxides and the corresponding bases.

Main oxides are formed by typical metals, as well as valence variable metals in a lower oxidation (for example, Cao, FEO), react with acids and acidic oxides, forming salts:

Cao (main oxide) + CO 2 (acid oxide) \u003d CaO 3 (salt)

Feo (main oxide) + H 2 SO 4 (acid) \u003d FESO 4 (salt) + 2H 2 O (water)

Main oxides also interact with amphoteric oxides, resulting in salt formation, for example:

With water, only alkaline and alkaline earth metal oxides react:

Bao (main oxide) + H 2 O (water) \u003d Ba (OH) 2 (base alkhank. Metal)

Many major oxides are characteristic to substances consisting of atoms of one chemical element:

3Cuo + 2NH 3 \u003d 3CU + 3H 2 O + N 2

When heated, only mercury and noble metal oxides are decomposed:

Fig. 3. Mercury oxide.

List of main oxides:

Oxide name	Chemical formula	Properties
Calcium oxide	Cao.	Negashned lime, white crystalline
Magnesium oxide	MGO.	white substance, poorly soluble in water
Barium oxide	Bao.	Colorless crystals with cubic grille
Copper II oxide	Cuo.	black substance is practically insoluble in water
	HGO.	Red or yellow-orange solid
Potassium oxide	K 2 O.	Colorless or pale yellow substance
Sodium oxide	Na 2 O.	Consisting of colorless crystals
Lithium oxide	Li 2 O.	A substance consisting of colorless crystals that have a structure of a cubic lattice

In the main subgroups of the periodic system during the transition from one element to another from top to bottom, there is an amplification of the main properties of oxides.

What did we know?

In the formation of basic oxides, one of the mandatory elements is oxygen. The base oxides have a number of physical and chemical properties, such as interaction with water, acids and other oxides.

Test on the topic

Report assessment

Average rating: 4.6. Total ratings received: 734.

Definition

Oxides. - The class of inorganic compounds are compounds of the chemical element with oxygen in which oxygen shows the degree of oxidation "-2".

The exclusion of oxygen diffluoride (of 2), since the fluorine electronegability is higher than at oxygen and fluorine always shows the degree of oxidation "-1".

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

Chemical properties of non-forming oxides

Non-forming oxides do not exhibit acidic, nor basic, no amphoteric properties, do not form salts. Nitrogen oxides (I) and (II) (N 2 O, NO), carbon monoxide (II) (CO), silicon (II) oxide SiO and others include nitrogenous oxides.

Despite the fact that the non-forming oxides are not capable of forming salts in the interaction of carbon oxide (II) with sodium hydroxide forms an organic salt - sodium formate (agriculture salt):

CO + NaOH \u003d hcoona.

In the interaction of non-forming oxyades with oxygen, higher oxides of the elements are obtained:

2Co + O 2 \u003d 2CO 2;

2no + O 2 \u003d 2NO 2.

Chemical properties of salt-forming oxides

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

Main oxides react with water to form grounds:

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

Li 2 O + H 2 O \u003d 2LIOH.

In the interaction of the main oxides with acidic or amphoteric oxides, salts are obtained:

Cao + SiO 2 \u003d Casio 3;

Cao + Mn 2 O 7 \u003d Ca (MNO 4) 2;

Cao + Al 2 O 3 \u003d Ca (ALO 2) 2.

Main oxides react with acids with salts and water formation:

Cao + H 2 SO 4 \u003d Caso 4 + H 2 O;

Cuo + H 2 SO 4 \u003d Cuso 4 + H 2 O.

In the interaction of the main oxides formed by metals facing a series of activity after aluminum, with hydrogen, there is a restoration of metals included in oxide:

Cuo + H 2 \u003d Cu + H 2 O.

Acid oxides react with water to form acids:

P 2 O 5 + H 2 O \u003d HPO 3 (metaphosphoric acid);

HPO 3 + H 2 O \u003d H 3 PO 4 (orthophosphoric acid);

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

Some acidic oxides, for example, silicon oxide (IV) (SiO 2), do not enter into the reaction of water interaction, therefore, corresponding to these acid oxides are obtained indirectly.

In the interaction of acidic oxides with basic or amphoteric oxides, salts are obtained:

P 2 O 5 + 3CaO \u003d Ca 3 (PO 4) 2;

CO 2 + CaO \u003d Caco 3;

P 2 O 5 + Al 2 O 3 \u003d 2AlPO 4.

Acid oxides react with bases to form salts and water:

P 2 O 5 + 6NAOH \u003d 3NA 3 PO 4 + 3H 2 O;

Ca (OH) 2 + CO 2 \u003d Caco 3 ↓ + H 2 O.

Amphoteric oxides We interact with acid and main oxides (see above), as well as with acids and bases:

Al 2 O 3 + 6HCl \u003d 2ALCl 3 + 3H 2 O;

Al 2 O 3 + NaOH + 3H 2 O \u003d 2NA;

Zno + 2HCl \u003d ZnCl 2 + H 2 O;

Zno + 2KOH + H 2 O \u003d k 2 4

Zno + 2KOH \u003d K 2 ZnO 2.

Physical properties of oxides

Most oxides are solids at room temperature (Cuo - black powder, Cao - white crystalline substance, CR 2 O 3 - green powder, etc.). Some oxides are liquids (water - hydrogen oxide - a colorless liquid, CL 2 O 7 is a colorless liquid) or gases (CO 2 - gas without color, 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 reacting the interaction of a particular element with oxygen, for example:

2CU + O 2 \u003d 2CUO.

The formation of oxides also leads thermal decomposition of salts, bases and acids:

Caco 3 \u003d Cao + CO 2;

2AL (OH) 3 \u003d Al 2 O 3 + 3H 2 O;

4HNO 3 \u003d 4NO 2 + O 2 + 2H 2 O.

Among other methods of obtaining oxides, binary compounds are isolated, for example, sulphides, the oxidation of higher oxides to the lower, the reduction of lower oxides to the highest, the interaction of metals with water at high temperatures, etc.

Examples of solving problems

Example 1.

The task

With electrolysis, 40 mol of water was distinguished 620 g of oxygen. Determine the oxygen yield.

Decision

The yield of the reaction product is determined by the formula: η \u003d M PR / M Theor × 100%. The practical mass of oxygen is the mass specified in the condition of the problem - 620. The theoretical mass of the reaction product is the mass calculated by the reaction equation. We write the equation for the reaction of water decomposition under the action of an electric current: 2H 2 O \u003d 2H 2 + O 2. According to the reaction equation N (H 2 O): N (O 2) \u003d 2: 1, therefore N (O 2) \u003d 1/2 × n (H 2 O) \u003d 20 mol. Then, the theoretical mass of oxygen will be equal to: