I.1 Oxides. Basic concepts and definitions. Oxides: classification and chemical properties All water-soluble oxides

Non-salt-forming (indifferent, indifferent) oxides CO, SiO, N 2 0, NO.

Salt-forming oxides:

Basic. Oxides whose hydrates are bases. Metal oxides with oxidation states +1 and +2 (rarely +3). Examples: Na 2 O - sodium oxide, CaO - calcium oxide, CuO - copper (II) oxide, CoO - cobalt (II) oxide, Bi 2 O 3 - bismuth (III) oxide, Mn 2 O 3 - manganese (III) oxide ).

Amphoteric. Oxides whose hydrates are amphoteric hydroxides. Metal oxides with oxidation states +3 and +4 (rarely +2). Examples: Al 2 O 3 - aluminum oxide, Cr 2 O 3 - chromium (III) oxide, SnO 2 - tin (IV) oxide, MnO 2 - manganese (IV) oxide, ZnO - zinc oxide, BeO - beryllium oxide.

Acid. Oxides whose hydrates are oxygen-containing acids. Oxides of non-metals. Examples: P 2 O 3 - phosphorus oxide (III), CO 2 - carbon monoxide (IV), N 2 O 5 - nitrogen oxide (V), SO 3 - sulfur oxide (VI), Cl 2 O 7 - chlorine oxide ( VII). Metal oxides with oxidation states +5, +6 and +7. Examples: Sb 2 O 5 - antimony (V) oxide. CrOz - chromium (VI) oxide, MnOz - manganese (VI) oxide, Mn 2 O 7 - manganese (VII) oxide.

Change in the nature of oxides with an increase in the degree of oxidation of the metal

Physical Properties

Oxides are solid, liquid and gaseous, of various colors. For example: copper (II) oxide CuO black, calcium oxide CaO white - solids. Sulfur oxide (VI) SO 3 is a colorless volatile liquid, and carbon monoxide (IV) CO 2 is a colorless gas under normal conditions.

State of aggregation

CaO, CuO, Li 2 O and other basic oxides; ZnO, Al 2 O 3 , Cr 2 O 3 and other amphoteric oxides; SiO 2, P 2 O 5, CrO 3 and other acid oxides.

SO 3, Cl 2 O 7, Mn 2 O 7 and others.

Gaseous:

CO 2 , SO 2 , N 2 O, NO, NO 2 and others.

Solubility in water

Soluble:

a) basic oxides of alkali and alkaline earth metals;

b) almost all acidic oxides (exception: SiO 2).

Insoluble:

a) all other basic oxides;

b) all amphoteric oxides

Chemical properties

1. Acid-base properties

Common properties of basic, acidic and amphoteric oxides are acid-base interactions, which are illustrated by the following scheme:

(only for oxides of alkali and alkaline earth metals) (except for SiO 2).

Amphoteric oxides, having the properties of both basic and acidic oxides, interact with strong acids and alkalis:

2. Redox properties

If an element has a variable oxidation state (s. o.), then its oxides with low s. O. can exhibit reducing properties, and oxides with high c. O. - oxidative.

Examples of reactions in which oxides act as reducing agents:

Oxidation of oxides with low s. O. to oxides with high s. O. elements.

2C +2 O + O 2 \u003d 2C +4 O 2

2S +4 O 2 + O 2 \u003d 2S +6 O 3

2N +2 O + O 2 \u003d 2N +4 O 2

Carbon monoxide (II) reduces metals from their oxides and hydrogen from water.

C +2 O + FeO \u003d Fe + 2C +4 O 2

C +2 O + H 2 O \u003d H 2 + 2C +4 O 2

Examples of reactions in which oxides act as oxidizing agents:

Recovery of oxides with high o.d. elements to oxides with low s. O. or down to simple substances.

C +4 O 2 + C \u003d 2C +2 O

2S +6 O 3 + H 2 S \u003d 4S +4 O 2 + H 2 O

C +4 O 2 + Mg \u003d C 0 + 2MgO

Cr +3 2 O 3 + 2Al \u003d 2Cr 0 + 2Al 2 O 3

Cu +2 O + H 2 \u003d Cu 0 + H 2 O

Use of oxides of low-active metals for the oxidation of organic substances.

Some oxides in which the element has an intermediate c. o., capable of disproportionation;

For example:

2NO 2 + 2NaOH \u003d NaNO 2 + NaNO 3 + H 2 O

How to get

1. Interaction of simple substances - metals and non-metals - with oxygen:

4Li + O 2 = 2Li 2 O;

2Cu + O 2 \u003d 2CuO;

4P + 5O 2 \u003d 2P 2 O 5

2. Dehydration of insoluble bases, amphoteric hydroxides and some acids:

Cu(OH) 2 \u003d CuO + H 2 O

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

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

H 2 SiO 3 \u003d SiO 2 + H 2 O

3. Decomposition of some salts:

2Cu(NO 3) 2 \u003d 2CuO + 4NO 2 + O 2

CaCO 3 \u003d CaO + CO 2

(CuOH) 2 CO 3 \u003d 2CuO + CO 2 + H 2 O

4. Oxidation of complex substances with oxygen:

CH 4 + 2O 2 \u003d CO 2 + H 2 O

4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2

4NH 3 + 5O 2 \u003d 4NO + 6H 2 O

5. Recovery of oxidizing acids by metals and non-metals:

Cu + H 2 SO 4 (conc) = CuSO 4 + SO 2 + 2H 2 O

10HNO 3 (conc) + 4Ca = 4Ca(NO 3) 2 + N 2 O + 5H 2 O

2HNO 3 (razb) + S \u003d H 2 SO 4 + 2NO

6. Interconversions of oxides during redox reactions (see redox properties of oxides).

The complication of the structure of a substance in the classification of inorganic compounds occurs in the following sequence: elements ® oxides (basic, acidic, amphoteric) ® hydroxides (bases and acids) ® salts (medium, acidic, basic).

Oxides Compounds are made up of two elements, one of which is oxygen.. By chemical nature, oxides are divided into three groups:

basic oxides, Na 2 O, MgO, CaO, FeO, NiO, Fe 2 O 3 , …;

acid oxides, SO 2, SO 3, CO 2, Mn 2 O 7, P 2 O 5, ...;

amphoteric oxides, Al 2 O 3 , ZnO, BeO, SnO, Cr 2 O 3 , PbO

solid oxides K 2 O, Al 2 O 3, P 2 O 5, ...

liquid: SO 3, N 2 O 4, ...

gaseous: CO 2 , NO 2 , SO 2 ...

According to their solubility in water, oxides are divided into:

on soluble(SO 2 , CO 2 , K 2 O, Na 2 O, Rb 2 O, CaO)

And insoluble :( CuO, FeO, NiO, SiO 2 , Al 2 O 3 , MoO 3 , amphoteric oxides)

1.1.1 Basic oxides

The maincalled oxides which react with acids to form salt and water. The main oxides include potassium oxide K 2 O, calcium oxide CaO, manganese (II) oxide MnO, copper (I) oxide Cu 2 O, etc.

Basic oxides react with acids to form

salt and water; MnO + 2HCl Þ MnCl 2 + H 2 O; Fe 2 O 3 + 3H 2 SO 4 \u003d Fe 2 (SO 4) 3 + 3H 2 O.

Basic oxides interact with acidic oxides with

salt formation: CaO + CO 2 = CaCO 3; 3Na 2 O + P 2 O 5 \u003d 2Na 3 PO 4.

2FeO + SiO 2 = Fe 2 SiO 4

Oxides of alkali and alkaline earth metals interact with water:

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

One can also define basic oxides as those oxides that correspond to bases. For example, manganese oxide MnO corresponds to hydroxide Mn(OH) 2 . The main oxides are the oxides s-, f- And d-elements in the lowest oxidation state and oxides of some p-elements.

Acid oxides

Acid oxides one can name the oxides to which the acids correspond. So, sulfur oxide (VI) SO 3 corresponds to sulfuric acid H 2 SO 4, higher manganese oxide (VII) Mn 2 O 7 - manganese acid HMnO 4.

(A). common property of all acid oxides is their ability to interact with bases to form salt and water:

CO 2 + 2NaOH \u003d Na 2 CO 3 + H 2 O to write the salt formula, you need to know

What acid corresponds to this oxide

N 2 O 5 + Ba(OH) 2 = Ba(NO 3) 2 + H 2 O; SO 3 + Ca (OH) 2 \u003d CaSO 4 + H 2 O

[ HNO3]

(b). Acid oxides interact with basic oxides to form salts: CaO + CO 2 = CaCO 3 ; 3Na 2 O + P 2 O 5 \u003d 2Na 3 PO 4.

(V). In relation to water, acid oxides can be well and poorly soluble. Soluble oxides include carbon monoxide (IV) CO 2 , sulfur oxides, etc. Poorly soluble acidic oxides include silicon oxide SiO 2 , molybdenum oxide MoO 3 , etc. When dissolved in water, acids are formed: CO 2 + H 2 O \u003d H 2 CO 3; SO 3 + H 2 O \u003d H 2 SO 4

increase

solubility of oxides and

hydroxides

Subgroup

Dissolving, ionic oxides enter into chemical interaction with water, forming the corresponding hydroxides:

Na 2 O + H 2 O → 2NaOH

CaO + H 2 O → Ca (OH) 2

very strong

basic oxide base

Hydroxides of alkali and alkaline earth metals are strong bases and completely dissociate in water into metal cations and hydroxide ions:

NaOH Na + + OH –

Since the concentration of OH - ions increases, the solutions of these substances have a strongly alkaline environment (pH>>7); they are called alkalis.

Second group highly soluble in water oxides and their corresponding hydroxy compounds - molecular oxides and acids with covalent type chemical bonds . These include compounds of typical non-metals in the highest degree oxidation and some d-metals in the oxidation state: +6, +7. Soluble molecular oxides (SO 3, N 2 O 5, Cl 2 O 7, Mn 2 O 7) interact with water to form the corresponding acids:

SO 3 + H 2 O H 2 SO 4

sulfur oxide (VI) sulfuric acid

strong acid strong acid

N 2 O 5 + H 2 O 2HNO 3

nitric oxide (V) nitric acid

Mn 2 O 7 + H 2 O 2HMnO 4

manganese(VII) oxide manganese acid

Strong acids (H 2 SO 4, HNO 3, HClO 4, HClO 3, HMnO 4) in solutions completely dissociate into H + cations and acid residues:

Stage 2: H 2 PO 4 – H + + HPO 4 2–

K 2 \u003d (= 6.2 ∙ 10 -8;

3rd stage: HPO 4 2– H + + PO 4 3–

K 3 \u003d () / \u003d 4.4 ∙ 10 -13,

where K 1 , K 2 , K 3 are the dissociation constants of orthophosphoric acid in the first, second and third stages, respectively.

The dissociation constant (Table 1 of the appendix) characterizes the strength of the acid, i.e. its ability to decompose (dissociate) into ions in the medium of a given solvent at a given temperature. The larger the dissociation constant, the more the equilibrium is shifted towards the formation of ions, the stronger the acid, i.e. in the first stage, the dissociation of phosphoric acid goes better than in the second, and, accordingly, in the third stage.

Moderately soluble oxides of sulfur (IV), carbon (IV), nitrogen (III), etc. form the corresponding weak acids in water, which partially dissociate.

CO 2 + H 2 O H 2 CO 3 H + + HCO 3 -

SO 2 + H 2 O H 2 SO 3 H + + HSO 3 -

N 2 O 3 + H 2 O 2HNO 2 H + + NO 2 -

weak-weak

acid acids

Neutralization reaction

The neutralization reaction can be expressed by the following scheme:

H 2 O

(base or (acid or acid-

basic oxide) ny oxide)

5.3.1. Basic Compound Properties exhibit oxides and hydroxides of s-metals (with the exception of Be), d-metals in the oxidation state (+1, +2) (with the exception of Zn), and some p-metals (see Fig. 3).

							VIIIA
I A	II A	IIIA	IVA	VA	VIA	VIIA
Li	Be	B	C	N	O	F

diagonal similarity Al Zn Ge Insoluble: usually basic Amphoteric oxides Weak acidic Oxides dissolve to form acids

Rice. 3. Acid-base properties of oxides and their corresponding hydroxy compounds

A characteristic property of basic compounds is their ability to interact with acids, acidic or amphoteric oxides to form salts, for example:

KOH + HCl KCl + H2O

Ba(OH) 2 + CO 2 BaCO 3 + H 2 O

2NaO + Al 2 O 3 2NaAlO 2 + H 2 O

Depending on the number of protons that can attach to the base, there are single acid bases (for example, LiOH, KOH, NH 4 OH), diacid bases, etc.

For polyacid bases, the neutralization reaction can proceed in stages with the formation of first basic and then intermediate salts.

Me(OH) 2 MeOHCl MeCl 2

hydroxide NaOH basic NaOH medium

metal salt salt

For example:

Stage 1: Co(OH) 2 + HCl CoOHCl + H 2 O

hydroxocobalt(II)

(basic salt)

Stage 2: Co(OH)Cl + HCl CoCl 2 + H 2 O

cobalt(II)

(medium salt)

5.3.2. Properties of acidic compounds exhibit oxides and acids of non-metals, as well as d-metals in the oxidation state (+5, +6, +7) (see Fig. 3).

A characteristic property is their ability to interact with bases, basic and amphoteric oxides to form salts, for example:

2HNO 3 + Cu(OH) 2 → Cu(NO 3) 2 + 2H 2 O

2HCl + CaO → CaCl 2 + H 2 O

H 2 SO 4 + ZnO → ZnSO 4 + H 2 O

CrO 3 + 2NaOH → Na 2 CrO 4 + H 2 O

According to the presence of oxygen in their composition, acids are divided into oxygen-containing(for example, H 2 SO 4, HNO 3) and anoxic(HBr, H2S). According to the number of hydrogen atoms contained in the acid molecule that can be replaced by metal atoms, monobasic acids are distinguished (for example, hydrogen chloride HCl, nitrous acid HNO 2), dibasic (sulphurous H 2 SO 3, coal H 2 CO 3), tribasic (orthophosphoric H 3 PO 4), etc.

Polybasic acids are neutralized stepwise with the formation of initially acidic, and then medium salts:

H 2 X NaHX Na 2 X

polybasic acid medium

acid salt salt

For example, orthophosphoric acid can form three types of salts, depending on the quantitative ratio of acid and alkali taken:

a) NaOH + H 3 PO 4 → NaH 2 PO 4 + H 2 O;

1:1 dihydrogen phosphate

b) 2NaOH + H 3 PO 4 → Na 2 HPO 4 + 2H 2 O;

2:1 hydrogen phosphate

c) 3NaOH + H 3 PO 4 → Na 3 PO 4 + 3H 2 O.

3:1 orthophosphate

5.3.3. Amphoteric oxides and hydroxides form Be, p-metals located near the “amphoteric diagonal” (Al, Ga, Sn, Pb), as well as d-metals in oxidation states (+3, +4) and Zn (+2) (see Fig. 3 ).

Slightly dissolving, amphoteric hydroxides dissociate in both basic and acidic types:

2H + + 2– Zn(OH) 2 Zn 2+ + 2OH –

Therefore, amphoteric oxides and hydroxides can interact with both acids and bases. When interacting with stronger acids, amphoteric compounds exhibit the properties of bases.

ZnO + SO 3 → ZnSO 4 + H 2 O

acid

Zn(OH) 2 + H 2 SO 4 → ZnSO 4 + H 2 O

basic acid

connections

When interacting with strong bases, amphoteric compounds exhibit the properties of acids, forming the corresponding salts. The composition of the salt depends on the reaction conditions. When fused, simple "dehydrated" salts are formed.

2NaOH + Zn(OH) 2 → Na 2 ZnO 2 + H 2 O

base acid sodium zincate

compound

2NaOH + ZnO → Na 2 ZnO 2 + H 2 O

In aqueous solutions of alkalis, complex salts are formed:

2NaOH + Zn(OH) 2 → Na 2

(aqueous tetrahydroxozincate

1 Moscow State Technical University them. N.E. Bauman

2 First Moscow State medical University them. THEM. Sechenov

3 Moscow State Pedagogical University

The issues of etching oxide deposits from the surface of steels containing cobalt and iron have always been of practical importance and have been relevant. Having studied a large amount of material on this issue, the authors state that some aspects of the problem have not yet been fully studied (these include the influence of the characteristics of electrolyte solutions, the identification of the mechanism of action of these factors). Cobalt and iron oxides are widely used as catalysts for various chemical processes(oxidation of methane and carbon monoxide, dehydrogenation of paraffins, etc.). Their properties depend on the features of the surface, which determines the kinetics of oxide dissolution. Conducted experimental studies on the effect of mineral acids (in particular, H2SO4) on the rate of a heterogeneous reaction (Co3O4 and Fe3O4 in an acidic medium) revealed the nature of the limiting stage, which consists in the formation of surface compounds of the form - and their subsequent transition into an electrolyte solution. Also designed system analysis oxide dissolution curves for calculating kinetic parameters: activation energy and reaction orders for hydrogen ions and sulfate ions.

cobalt oxide

iron oxide

kinetics

dissolution

modeling

Barton–Stransky model

Hougen–Watson method

1. Bokshtein B.S., Mendelev M.I., Pokhvisnev Yu.V. Physical chemistry: thermodynamics and kinetics. - M.: Publishing house "MISIS", 2012. - 258 p.

2. Butler J. Ionic equilibrium. - L.: Chemistry, 1973. - 448 p.

3. Delmon B. Kinetics of heterogeneous reactions. – M.: Mir, 1972. – 555 p.

4. Barre P. Kinetics of heterogeneous processes. – M.: Mir, 1976. – 400 p.

5. Kiselev M.Yu. Mechanism and kinetics of pyrite dissolution by electrochemical chlorination // Izvestiya Vysshikh educational institutions. Mining magazine. - 2010. - No. 4. - S. 101-104.

6. Kortsenshtein N.M., Samuilov E.V. Bulk condensation in heterogeneous reactions // Colloid journal. - 2013. - T. 75, No. 1. - 84 p.

7. Kolesnikov V.A., Kapustin V.A., Kapustin Yu.I., Isaev M.K., Kolesnikov A.V. Metal oxides – promising materials for electrochemical processes // Glass and ceramics. - 2016. - No. 12. - P. 23–28.

8. Yakusheva E.A., Gorichev I.G., Atanasyan T.K., Izotov A.D. Study of the dissolution kinetics of cobalt oxides (Co3O4, Co2O3) at various concentrations of H2SO4, HCl, EDTA, and pH // Volgograd: Abstracts XIX Mend. Congress on General and Applied Chemistry. - 2011. - T. 3 - S. 366.

9. Yakusheva E.A., Gorichev I.G., Atanasyan T.K., Liner Yu.A. Kinetics of dissolution of cobalt oxides in acid media // Metals. - 2010. - No. 2. - P. 21–27.

10. Yakusheva E.A., Gorichev I.G., Atanasyan T.K., Plakhotnaya O.N., Goryacheva V.N. Modeling of kinetic processes of dissolution of cobalt and copper oxides in sulfuric acid // Bulletin of MSTU im. N.E. Bauman. Ser. Natural Sciences. - 2017. - No. 3. - C. 124–134.

The experimental studies of the dissolution of oxide phases make it possible to describe in detail the processes of the behavior of a solid phase in an acidic medium, to explain the phenomena occurring on the surface of oxides, taking into account their acid-base characteristics and the mechanism of dissolution, and to simulate topochemical reactions.

Purpose of the study consists in studying and modeling the process of dissolution of Co3O4 and Fe3O4 in sulfuric acid.

Materials and methods of research

For research, samples were taken weighing 500 mg with d = 80÷100 µm. The identification of oxides was carried out by X-ray phase, IR and thermal analysis.

To elucidate the mechanism of dissolution of solid samples of metal oxides in acidic media, the experiment was carried out in a device (a thermostatically controlled reactor with a volume of 0.5 l) to study the kinetics of dissolution of solid samples, excluding the influence of any uncontrolled factors on the phenomenon under study. The temperature of the experiment was 363 K. The experiment was carried out at various pH values and mineral acid concentrations.

At certain intervals, the liquid phase was sampled from the reaction vessel with a Schott glass filter. The concentration of cobalt ions was determined spectrophotometrically (UV-3100 spectrophotometer) using ammonium thiocyanate, and iron - using o-phenanthroline.

The obtained experimental data on the effect of acid concentration on the dissolution rate of cobalt oxide Co3O4 and Fe3O4 are shown in Figs. 1 (points - experimental data, lines - simulation result). The solute fraction a was calculated using the equation: a = Dt/D∞.

Rice. 1. a) dependence of the proportion of dissolved oxide Co3O4 on time at various concentrations of sulfuric acid (mol / l): 1 - 10.0; 2 - 5.93; 3 - 2.97; 4 - 1.0; 5 - 0.57; 6 - 0.12; T = 363.2 K; b) dependence of the proportion of dissolved oxide Fe3O4 on time at various concentrations of sulfuric acid (mol/l): 1 - 10.3; 2 - 7.82; 3 - 3.86; 4 - 2.44; T = 293 K

Research results and discussion

Calculation of kinetic parameters. An analysis of the experimental kinetic data was carried out using the equations of heterogeneous kinetics, which made it possible to determine the orders of reactions for various ions (ni), the specific dissolution rate (Wi), its dependence on the concentration of the solution, and the activation energy of the reactions (Ea).

The kinetics of heterogeneous reactions is based on the obligatory consideration of changes in the surface of particles in the process of dissolution over time, in addition, as a rule, heterogeneous reactions are characterized by a constant rate over time (1) .

In this case, the dissolution rate of the oxide can be represented by the equation:

where Wi is the specific dissolution rate; f(α) is a function that takes into account how the oxide surface changes over time.

To elucidate the mechanism of dissolution and simulate this phenomenon, we took the Barton - Stranski model (2):

, (2)

where A is a constant. Its value is directly proportional to the number of active centers on the surface of one oxide particle.

To find the values of the variables W and A, the methods of nonlinear regression analysis and computer program MathCad.

Table 1

Specific dissolution rate of Co3O4 and Fe3O4 oxides depending on H2SO4 concentration

From the data of the table and fig. 2 (dots - experimental data, lines - the result of modeling by equation (3)) it follows that cobalt oxide Co3O4 dissolves faster in sulfuric acid than iron oxide Fe3O4. The reaction order in terms of hydrogen ions for the two oxides is approximately 0.5. (all results are obtained on the basis of the Barton - Stranski model).

Rice. 2. a) dependence of the logarithm of the rate (log W) on the logarithm of the concentration (log C(H2SO4)) in dissolving Co3O4 in sulfuric acid; b) dependence of the logarithm of the rate (log W) on the logarithm of the concentration (log C(H2SO4)) in the dissolution of Fe3O4 in sulfuric acid

The data obtained make it possible to describe the relationship between the specific dissolution rate of Co3O4 and Fe3O4 oxides and the concentration of H2SO4 by the generalized equation

, (3)

where ≡, W0 - dissolution rate constant, K1, K2 - constants.

Modeling of the mechanism of dissolution of cobalt and iron oxides in inorganic acid. Dissolution of oxides in acids occurs on surface defects crystal lattice, the so-called active centers of dissolution of oxides that adsorb H+ ions and H+…A- ion pairs.

The Hougen - Watson method makes it possible to simulate the influence of pH and acid concentration on the rate of dissolution of oxides .

In this case, the dissolution rate of cobalt and iron oxides will be expressed by the equation:

Presumably, particles of metal hydroxocomplexes of the same composition as those in solution are formed on the surface of oxides. To calculate the concentration of hydroxocomplexes, we used the material balance equations in hydrolysis reactions with respect to hydrogen, cobalt, and iron ions; hydrolysis equations for all steps to calculate the hydrolysis constants. The Hougen-Watson method assumes that the dependence of the concentration of ions on the surface of oxides and in solution obeys the Langmuir isotherm, which makes it possible to relate the surface and volume concentrations of ions (equation (5)).

The dependence of the specific dissolution rate of cobalt oxides Co3O4 and Fe3O4 in dilute sulfuric acid is expressed by equations (5-7).

The concentration of ions and can be expressed in terms of the total concentration of Co3+ and Fe3+ ions, if their content in the solution is established. In this case and . Then the speed is

If we simulate the oxide dissolution process and assume that the ions and act as surface-active particles, then the dependence of the process rate on the concentration of ions will look like this (a1 is the number of ions in the solution).

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.

OXIDE

ACID

BASE

SALT

E x O y

HnA

A - acid residue

Me(OH)b

OH - hydroxyl group

Me n A b

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 valence chemical element variable is indicated by a Roman numeral enclosed in parentheses after the name of the chemical element.

Formula	Name	Formula	Name
	carbon monoxide (II)	Fe2O3	iron(III) oxide
	nitric oxide (II)	CrO3	chromium(VI) oxide
Al2O3	aluminium oxide		zinc oxide
N 2 O 5	nitric oxide (V)	Mn2O7	manganese(VII) oxide

Classification of oxides

All oxides can be divided into two groups: salt-forming (basic, acidic, amphoteric) and non-salt-forming or indifferent.

metal oxides Me x O y

Non-metal oxides neMe x O y

Main

Acidic

Amphoteric

Acidic

Indifferent

I, II

V-VII

ZnO, BeO, Al 2 O 3,

Fe 2 O 3 , Cr 2 O 3

> II

neMe

I, II

neMe

CO, NO, N 2 O

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)

Acid oxides

Basic oxides

Amphoteric oxides

Soluble in water.

Exception - SiO 2

(not soluble in water)

Only oxides of alkali and alkaline earth metals dissolve in water.

(these are metals

I "A" and II "A" groups,

exception Be , Mg )

They do not interact with water.

Insoluble in water

Complete the tasks:

1. Write separately chemical formulas 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

Write down the oxides and classify them.

Obtaining oxides

Simulator "Interaction of oxygen with simple substances"

1. Combustion of substances (Oxidation by oxygen)	a) simple substances Training apparatus	2Mg + O 2 \u003d 2MgO
1. Combustion of substances (Oxidation by oxygen)	b) complex substances	2H 2 S + 3O 2 \u003d 2H 2 O + 2SO 2
2. Decomposition of complex substances (use table of acids, see appendices)	a) salt SALTt= BASIC OXIDE + ACID OXIDE	CaCO 3 \u003d CaO + CO 2
	b) Insoluble bases Me(OH)bt= Me x O y+ H 2 O	Cu (OH) 2 t \u003d CuO + H 2 O
	c) oxygen-containing acids HnA=ACID OXIDE + H 2 O	H 2 SO 3 \u003d H 2 O + SO 2

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

CHEMICAL PROPERTIES OF BASIC OXIDES

1. Basic oxide + Acid oxide \u003d Salt (p. Compound)

CaO + SO 2 \u003d CaSO 3

2. Basic oxide + Acid \u003d Salt + H 2 O (r. exchange)

3 K 2 O + 2 H 3 PO 4 = 2 K 3 PO 4 + 3 H 2 O

3. Basic oxide + Water \u003d Alkali (r. compounds)

Na 2 O + H 2 O \u003d 2 NaOH

CHEMICAL PROPERTIES OF ACID OXIDES

1. Acid oxide + Water \u003d Acid (p. Compounds)

With O 2 + H 2 O \u003d H 2 CO 3, SiO 2 - does not react

2. Acid oxide + Base \u003d Salt + H 2 O (r. exchange)

P 2 O 5 + 6 KOH \u003d 2 K 3 PO 4 + 3 H 2 O

3. Basic oxide + Acid oxide \u003d Salt (p. Compound)

CaO + SO 2 \u003d CaSO 3

4. Less volatiles displace more volatiles from their salts

CaCO 3 + SiO 2 \u003d CaSiO 3 + CO 2

CHEMICAL PROPERTIES OF AMPHOTERIC OXIDES

They interact with both acids and alkalis.

ZnO + 2 HCl = ZnCl 2 + H 2 O

ZnO + 2 NaOH + H 2 O \u003d Na 2 [Zn (OH) 4] (in solution)

ZnO + 2 NaOH = Na 2 ZnO 2 + H 2 O (when fused)

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.

Due to the insolubility and strength of chromium (III) oxide, it is also used in printing inks (for example, for coloring banknotes). In general, oxides of many metals are used as pigments for a wide variety of paints, although this is by no means their only application.

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.

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: