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Chemical properties of hydroxides. Metal oxides and hydroxides Chemical properties of hydroxides

Hydroxides can be thought of as the product of the addition (real or mental) of water to the corresponding oxides. Hydroxides are divided into bases, acids, and amphoteric hydroxides. Bases have the general composition M(OH)x, acids have the general composition HxCo. In molecules of oxygen-containing acids, the replaced hydrogen atoms are connected to the central element through oxygen atoms. In molecules of oxygen-free acids, hydrogen atoms are attached directly to a non-metal atom. Amphoteric hydroxides include primarily hydroxides of aluminum, beryllium and zinc, as well as hydroxides of many transition metals in intermediate oxidation states.
Based on solubility in water, soluble bases are distinguished - alkalis (formed by alkali and alkaline earth metals). The bases formed by other metals do not dissolve in water. Most inorganic acids are soluble in water. Only silicic acid H2SiO3 is a water-insoluble inorganic acid. Amphoteric hydroxides do not dissolve in water.

Chemical properties of bases.

All bases, both soluble and insoluble, have a common characteristic property - to form salts.
Let's consider the chemical properties of soluble bases (alkalis):
1. When dissolved in water, they dissociate to form a metal cation and a hydroxide anion. Change the color of the indicators: violet litmus - to blue, phenolphthalein - to crimson, methyl orange - to yellow, universal indicator paper - to blue.
2. Interaction with acid oxides:
alkali + acid oxide = salt.
3. Interaction with acids:
alkali + acid = salt + water.
The reaction between an acid and alkali is called a neutralization reaction.
4. Interaction with amphoteric hydroxides:
alkali + amphoteric hydroxide = salt (+ water)
5. Interaction with salts (subject to the solubility of the original salt and the formation of a precipitate or gas as a result of the reaction.
Let's consider the chemical properties of insoluble bases:
1. Interaction with acids:
base + acid = salt + water.
Polyacid bases are capable of forming not only intermediate, but also basic salts.
2. Heat decomposition:
base = metal oxide + water.

Chemical properties of acids.

All acids have a common characteristic property - the formation of salts when replacing hydrogen cations with metal/ammonium cations.
Let's consider the chemical properties of water-soluble acids:
1. When dissolved in water, they dissociate to form hydrogen cations and an acid residue anion. Change the color of the indicators to red (pink), with the exception of phenolphthalein (does not react to acids, remains colorless).
2. Interaction with metals in the activity series to the left of hydrogen (subject to the formation of a soluble salt):
acid + metal = salt + hydrogen.
When interacting with metals, the exceptions are oxidizing acids - nitric and concentrated sulfuric acids. Firstly, they also react with some metals that are to the right of hydrogen in the activity series. Secondly, the reaction with metals never releases hydrogen, but produces a salt of the corresponding acid, water and the reduction products of nitrogen or sulfur, respectively.
3. Interaction with bases/amphoteric hydroxides:
acid + base = salt + water.
4. Interaction with ammonia:
acid + ammonia = ammonium salt
5. Interaction with salts (subject to the formation of gas or sediment):
acid + salt = salt + acid.
Polybasic acids are capable of forming not only intermediate, but also acidic salts.
Insoluble silicic acid does not change the color of indicators (a very weak acid), but is capable of reacting with alkali solutions with slight heating:
1. Interaction of silicic acid with alkali solution:
silicic acid + alkali = salt + water.
2. Decomposition (during long-term storage or heating)
silicic acid = silicon(IV) oxide + water.

Chemical properties of amphoteric hydroxides.

Amphoteric hydroxides are capable of forming two series of salts, since when reacting with alkalis they exhibit the properties of an acid, and when reacting with acids they exhibit the properties of a base.
Let's consider the chemical properties of amphoteric hydroxides:
1. Interaction with alkalis:
amphoteric hydroxide + alkali = salt (+ water).
2. Interaction with acids:
amphoteric hydroxide + acid = salt + water.

Oxides are called complex substances whose molecules include oxygen atoms in oxidation state - 2 and some other element.

can be obtained through the direct interaction of oxygen with another element, or indirectly (for example, during the decomposition of salts, bases, acids). Under normal conditions, oxides come in solid, liquid and gaseous states; this type of compound is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.

They are either salt-forming or 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 These are oxides that do not form salts. Examples include CO, N 2 O, NO.

Salt-forming oxides, in turn, are of 3 types: basic (from the word « base » ), acidic and amphoteric.

Basic oxides These metal oxides are called those that 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. React 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 composition of the oxides contains a non-metal or a metal exhibiting the highest valence (usually from IV to VII) as the second element, then such oxides will be acidic. Acidic oxides (acid anhydrides) are those oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acidic oxides dissolve in water and alkalis, forming salt and water.

Chemical properties of acid oxides

1. React with water to form 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 to form a salt:

CO 2 + CaO → CaCO 3

3. React 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 refers to the ability of compounds to exhibit acidic and basic properties depending on conditions. For example, zinc oxide ZnO can be either a base or 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. React 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 is a characteristic that determines the number of nearby 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 it is 4 or 6; For and Cr it is 6 or (very rarely) 4;

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

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Oxides are binary compounds that contain oxygen.
Metal oxides are solids.
Hydroxides are complex substances corresponding to oxides if one or more hydroxide groups are attached to them.

1.Metal + oxygen = oxide or peroxide.
2.Metal + water = hydrogen + alkali (if the base is soluble in water)

or = hydrogen + base (if the base is not soluble in water)

The reaction occurs only if

the metal is in the activity series up to hydrogen.

Base - a complex substance in which each metal atom is associated with one or more hydroxo groups.

Metal oxides and hydroxides

in oxidation states +1 And +2 show basic properties ,

in oxidation states +3, +4, +5 show amphoteric ,
in oxidation states +6, +7 show acidic .

Fill out the table:

metals of the main subgroups I - III groups

Comparison Questions

I group

General formula of the oxide.

II group

2. Physical properties.

III group

Character of oxides

Interaction:

a) with water

b) with acids

c) with acid oxides

d) with amphoteric oxides

d) with alkalis

5. Hydroxide formula.

6. Physical properties

Nature of hydroxides

Interaction:

a) action on indicators

b) with acids

c) with acid oxides

d) with salt solutions

e) with non-metals

e) with alkalis

h) attitude to heating

The properties of oxides and hydroxides in the period change from basic through amphoteric to acidic, because the positive oxidation state of elements increases.

Na 2 O , Mg +2 O , Al 2 O 3

basic amphoteric

Na +1 O N , Mg +2 (O N ) 2 , Al +3 (O N ) 3

alkali Weak Amphoteric

base hydroxide

In the main subgroups, the basic properties of oxides and hydroxides increase from top to bottom .

Metal compounds I A groups

Alkali metal oxides

General formula Meh 2 ABOUT

Physical properties: Solid, crystalline substances, highly soluble in water.

Li 2 O, Na 2 O - colorless, K 2 O, Rb 2 O - yellow, Cs 2 O - orange.

Methods of obtaining:

Oxidation of the metal produces only lithium oxide

4 Li + O 2 → 2 Li 2 O

(in other cases, peroxides or superoxides are obtained).

All oxides (except Li 2 O) are obtained by heating a mixture of peroxide (or superoxide) with an excess of metal:

Na 2 O 2 + 2Na → 2Na 2 O

KO 2 + 3K → 2K 2 O

Chemical properties

Typical basic oxides:

React with water, forming alkalis: Na 2 O + H 2 O →

2. React with acids, forming salt and water: Na 2 O + H Cl →

3. Interact with acid oxides, forming salts: Na 2 O + SO 3 →

4. Interact with amphoteric oxides, forming salts: Na 2 O + ZnO → Na 2 ZnO 2

Alkali metal hydroxides

General formula – MeOH

Physical properties: White crystalline substances, hygroscopic, highly soluble in water (with the release of heat). The solutions are soapy to the touch and very caustic.

NaOH – sodium hydroxide

KOH – caustic potassium

Strong bases - Alkalis. The main properties are enhanced in the following order:

LiOH → NaOH → KOH → RbOH → CsOH

Methods of obtaining:

1. Electrolysis of chloride solutions:

2NaCl + 2H2O → 2NaOH + H 2 + Cl 2

2. Exchange reactions between salt and base:

K 2 CO 3 + Ca(OH) 2 → CaCO 3  + 2KOH

3. Interaction of metals or their basic oxides (or peroxides and superoxides) with water:

2 Li + 2 H 2 O → 2 LiOH + H2

Li 2 O + H 2 O → 2 LiOH

Na 2 O 2 + 2 H 2 O → 2 NaOH + H 2 O 2

Chemical properties

1. Change the color of the indicators:

Litmus - blue

Phenolphthalein – to raspberry

Methyl orange - to yellow

2. Interact with all acids.

NaOH + HCl → NaCl + H2O

3. Interact with acid oxides.

2NaOH + SO 3 → Na 2 SO 4 + H 2 O

4. Interact with salt solutions if gas or sediment is formed.

2 NaOH + CuSO 4 → Cu(OH) 2 ↓ + Na 2 SO 4

5. Interact with some non-metals (sulfur, silicon, phosphorus)

2 NaOH + Si + H 2 O → Na 2 SiO 3 + 2H 2

6. Interact with amphoteric oxides and hydroxides

2 NaOH + Zn O + H 2 O → Na 2 [Zn (OH) 4 ]

2 NaOH + Zn (OH) 2 → Na 2 [Zn (OH) 4 ]

7. When heated, they do not decompose, except for LiOH.

II groups

Metal oxides II A groups

General formula MeO

Physical properties: Solid, crystalline substances of white color, slightly soluble in water.

Methods of obtaining:

Oxidation of metals (except Ba, which forms peroxide)

2Ca + O 2 → 2CaO

2) Thermal decomposition of nitrates or carbonates

CaCO 3 → CaO + CO 2

2Mg(NO 3) 2 → 2MgO + 4NO 2 + O 2

Chemical properties

BeO – amphoteric oxide

Oxides of Mg, Ca, Sr, Ba – basic oxides

They interact with water (except BeO), forming alkalis (Mg (OH) 2 - weak base):

CaO + H 2 O →

2. React with acids, forming salt and water: CaO + H Cl →

3. Interact with acid oxides, forming salts: CaO + SO 3 →

4. BeO interacts with alkalis: BeO + 2 NaOH + H 2 O → Na 2 [Be (OH) 4 ]

Metal hydroxides II A groups

General formula – Me(OH) 2

Physical properties: White crystalline substances are less soluble in water than alkali metal hydroxides. Be(OH) 2 – insoluble in water.

The main properties are enhanced in the following order:

Be(OH) 2 → Mg (HE) 2 → Ca (HE) 2 → Sr (HE) 2 → B a (HE) 2

Methods of obtaining:

Reactions of alkaline earth metals or their oxides with water:

Ba + 2 H 2 O → Ba (OH) 2 + H 2

CaO (quicklime) + H 2 O → Ca (OH) 2 (slaked lime)

Chemical properties

Be(OH) 2 – amphoteric hydroxide

Mg (OH) 2 – weak base

Ca(OH) 2, Sr (OH) 2, Ba(OH) 2 - strong bases - alkalis.

Change the color of the indicators:

Litmus - blue

Phenolphthalein – to raspberry

Methyl orange - to yellow

2. React with acids, forming salt and water:

Be(OH) 2 + H 2 SO 4 →

3. Interact with acid oxides:

Ca(OH) 2 + SO 3 →

4. Interact with salt solutions if gas or sediment is formed:

Ba(OH) 2 + K 2 SO 4 →

Beryllium hydroxide reacts with alkalis:

Be(OH) 2 + 2 NaOH → Na 2 [Be(OH) 4 ]

When heated, they decompose: Ca(OH) 2 →

Compounds of metals of the main subgroup III groups

Aluminum connections

Aluminium oxide

Al 2 O 3

O = Al – O – Al = O

Physical properties: Alumina, corundum, colored – ruby (red), sapphire (blue).

Solid refractory (t° pl. = 2050 ° C) substance; exists in several crystal modifications.

Methods of obtaining:

Combustion of aluminum powder: 4 Al + 3 O 2 → 2 Al 2 O 3

Decomposition of aluminum hydroxide: 2 Al (OH) 3 → Al 2 O 3 + 3 H 2 O

Chemical properties

Al 2 O 3 - amphoteric oxide with predominant basic properties; does not react with water.

As a basic oxide: Al 2 O 3 + 6 HCl → 2 AlCl 3 + 3 H 2 O

As an acidic oxide: Al 2 O 3 + 2 NaOH + 3 H 2 O → 2 Na [Al (OH) 4 ]

2) Alloyed with alkalis or alkali metal carbonates:

Al 2 O 3 + Na 2 CO 3 → 2 NaAlO 2 (sodium aluminate) + CO 2

Al 2 O 3 + 2 NaOH → 2 NaAlO 2 + H 2 O

Aluminum hydroxide Al ( OH ) 3

Physical properties: white crystalline substance,

insoluble in water.

Methods of obtaining:

1) Precipitation from salt solutions with alkalis or ammonium hydroxide:

AlCl 3 + 3NaOH → Al(OH) 3 + 3NaCl

Al 2 (SO 4) 3 + 6NH 4 OH → 2Al(OH) 3 + 3(NH 4) 2 SO 4

Al 3+ + 3 OH ¯ → Al (OH) 3 (white gelatinous)

2) Weak acidification of aluminate solutions:

Na + CO 2 → Al(OH) 3 + NaHCO 3

Chemical properties

Al ( OH ) 3 - A mphoteric hydroxide :

1) Reacts with acids and alkali solutions:

As a base Al (OH) 3 + 3 HCl → AlCl 3 + 3 H 2 O

As acid Al (OH) 3 + NaOH → Na [Al (OH) 4 ]

(sodium tetrahydroxyaluminate)

When heated, it decomposes: 2 Al (OH) 3 → Al 2 O 3 + 3 H 2 O

Fill out the table: Comparative characteristics of oxides and hydroxides

metals of the main subgroups I - III groups

Comparison Questions

I group

General formula of the oxide.

II group

Oxidation state of Me in the oxide.

2. Physical properties.

III group

3. Chemical properties (compare).

4. Methods for producing oxides.

Character of oxides

Interaction:

a) with water

b) with acids

c) with acid oxides

d) with amphoteric oxides

d) with alkalis

5. Hydroxide formula.

Oxidation state of Me in hydroxide.

6. Physical properties

7. Chemical properties (compare).

Nature of hydroxides

8. Methods for producing hydroxides.

Interaction:

a) action on indicators

b) with acids

c) with acid oxides

d) with salt solutions

e) with non-metals

e) with alkalis

g) with amphoteric oxides and hydroxides

h) attitude to heating

THINGS

_________________________________

simple complex

____/______ ______________/___________

metals nonmetals oxides hydroxides salts

K, Ba S, P P 2 O 5 H 2 SO 4 Cu(NO 3) 2

Na 2 O Ba(OH) 2 Na 2 CO 3

Let's consider the classification, chemical properties and methods of obtaining complex substances.

OXIDES

OXIDE is a complex substance consisting of two elements, one of which is oxygen, which is in the -2 oxidation state.

The exceptions are:

1) compounds of oxygen and fluorine - fluorides: for example, oxygen fluoride OF 2 (oxidation state of oxygen in this compound +2)

2) peroxides (compounds of some elements with oxygen in which there is a bond between oxygen atoms), for example:

hydrogen peroxide H 2 O 2 potassium peroxide K 2 O 2

Examples of oxides: calcium oxide - CaO, barium oxide - BaO. If an element forms several oxides, then the valence of the element is indicated in their names in parentheses, for example: sulfur oxide (IV) - SO 2, sulfur oxide (VI) - SO 3.

All oxides can be divided into two large groups: salt-forming (salt-forming) and non-salt-forming.

Salt-forming substances are divided into three groups: basic, amphoteric and acidic.

O OXIDES

_________________/__________________

salt-forming non-salt-forming

CO, N2O, NO

↓ ↓ ↓

basic amphoteric acid

(they (they correspond to

correspond, acids)

grounds)

CaO, Li 2 O ZnO, BeO, PbO P 2 O 5, Mn 2 O 7

Cr 2 O 3, Al 2 O 3

Non-metals form acidic oxides, for example: nitrogen oxide (V) - N 2 O 5, carbon monoxide (IV) - CO 2. Metals with a valence of less than three, as a rule, form basic oxides, for example: sodium oxide - Na 2 O, magnesium oxide - MgO; and with a valence of more than four - acidic oxides, for example, manganese (VII) oxide - Mn 2 O 7, tungsten (VI) oxide - WO 3.

Let's consider the chemical properties of acidic and basic oxides.

CHEMICAL PROPERTIES OF OXIDES

BASIC ACID

Interaction with water

The product of the reaction is:

base acid

(if, in the composition of the oxide P 2 O 5 + 3H 2 O à 2H 3 PO 4

includes active metal, SiO 2 +H 2 O ≠

Li, Na, K, Rb, Cs, Fr, Ba, Ca)

CaO + H 2 O à Ca(OH) 2

2. Interaction with each other, forming salts CuO + SO 3 à CuSO 4

3. Interaction with hydroxides:

With soluble acids, with soluble bases

As a result of the reaction, salt and water are formed

CuO + H 2 SO 4 àCuSO 4 + H 2 O CO 2 +Ca(OH) 2 àCaCO 3 + H 2 O

Less volatile oxides

Replaces more volatile ones

from their salts:

K 2 CO 3 + SiO 2 à K 2 SiO 3 + CO 2

Amphoteric oxides include: metal oxides with a valence of three, for example: aluminum oxide - Al 2 O 3, chromium (III) oxide - Cr 2 O 3, iron (III) oxide - Fe 2 O 3, as well as a few exceptions , in which the metal is divalent, for example: beryllium oxide BeO, zinc oxide ZnO, lead (II) oxide - PbO. .

Amphoteric oxides have a dual nature: they are simultaneously capable of reactions in which they enter as basic and as acidic oxides

Let us prove the amphoteric nature of aluminum oxide. Let us present the equations for the reactions of interaction with hydrochloric acid and alkali (in an aqueous solution and when heated). When aluminum oxide and hydrochloric acid interact, a salt is formed - aluminum chloride. In this case, aluminum oxide acts as the main oxide.

Al 2 O 3 + 6HCl à2AlCl 3 + 3H 2 O

as main

In an aqueous solution, a complex salt is formed -

sodium tetrahydroxyaluminate:

Al 2 O 3 + 2NaOH + 3H 2 Oà 2Na sodium tetrahydroxoaluminate

like acidic

When fused with alkalis, meta-aluminates are formed.

Let us imagine the molecule of aluminum hydroxide Al(OH) 3 in the form of an acid, i.e. In the first place we write all the hydrogen atoms, in the second the acid residue:

H 3 AlO 3 - aluminum acid

For trivalent metals, subtract 1 H 2 O from the acid formula, obtaining meta-aluminum acid:

- H 2 O

HAlO 2 - meta-aluminum acid

fusion

Al 2 O 3 +2 NaOHà 2NaAlO 2 + H 2 O sodium metaaluminate

like acidic

METHODS FOR OBTAINING OXIDES:

1. Interaction of simple substances with oxygen:

4Al + 3O 2 à 2Al 2 O 3

2. Combustion or roasting of complex substances:

CH 4 + 2O 2 à CO 2 + 2H 2 O

2ZnS + 3O 2 à 2SO 2 + 2ZnO

3. Decomposition when heating insoluble hydroxides:

Cu(OH) 2 à CuO + H 2 O H 2 SiO 3 à SiO 2 + H 2 O

4. Decomposition when heating medium and acidic salts:

CaCO 3 à CaO + CO 2

2КHCO 3 àK 2 CO 3 + CO 2 +H 2 O

4AgNO 3 à4Ag + 4NO 2 + O 2

HYDROXIDES

Hydroxides are divided into three groups: bases, acids and amphoteric hydroxides (showing properties of both bases and acids).

BASE is a complex substance consisting of metal atoms and one or more hydroxyl groups

(- HE).

For example: sodium hydroxide - NaOH, barium hydroxide Ba(OH) 2. The number of hydroxyl groups in the base molecule is equal to the valence of the metal.

ACID is a complex substance that consists of hydrogen atoms that can be replaced by metal atoms and an acidic residue.

For example: sulfuric acid - H 2 SO 4, phosphoric acid - H 3 PO 4.

The valency of the acid residue is determined by the number of hydrogen atoms. In chemical compounds, the valency of the acid residue is retained (see Table 1).

TABLE 1 FORMULAS OF SOME ACIDS AND

ACID RESIDUE

Acid name	Formula	Acid residue	Valency of acid residue	Name of the salt formed by this acid
Fluorescent	HF	F	I	fluoride
Solyanaya	HCl	Cl	I	chloride
Hydrobromic	HBr	Br	I	bromide
Hydroiodic	HI	I	I	iodide
Nitrogen	HNO3	NO 3	I	nitrate
Nitrogenous	HNO2	NO 2	I	nitrite
Vinegar	CH 3 COOH	CH 3 COO	I	acetate
Sulfuric	H2SO4	SO 4	II	sulfate
Sulphurous	H2SO3	SO 3	II	sulfite
Hydrogen sulfide	H2S	S	II	sulfide
Coal	H2CO3	CO3	II	carbonate
Flint	H2SiO3	SiO3	II	silicate
Phosphorus	H3PO4	PO 4	III	phosphate

Based on their solubility in water, hydroxides are divided into two groups: soluble (for example, KOH, H 2 SO 4) and insoluble (H 2 SiO 3, Cu(OH) 2). Bases that dissolve in water are called alkalis.

Oxides - these are complex substances consisting of some element and oxygen with an oxidation state -2.

For example: K2O, CaO, Fe2O3, CO2, P2O5, SO3, Cl2O7, OsO4. Oxides are formed by all chemical elements except He, Ne, Ar. The chemical bond between oxygen and another element can be ionic or covalent. Based on their chemical properties, oxides are divided into salt-forming and non-salt-forming. The latter include, for example, N2O, NO, NO 2, SiO, SO.

Salt-forming oxides are divided into basic, acidic and amphoteric.

Basic oxides. Oxides whose hydrates are bases are called basic oxides. For example, Na2O, CuO are basic oxides, since the bases NaOH, Cu(OH)2 correspond to them. As a rule, the main oxides can be metal oxides with an oxidation state of +1, +2. The chemical bond here is ionic.

Oxides of alkali (Li, Na, K, Rb, Cs, Fr) and alkaline earth metals (Ca, Sr, Ba, Ra), interacting with water, give bases. For example:

K2O + H2O = 2KOH

BaO + H2O = Ba(OH)2

The remaining basic oxides practically do not interact with water. Basic oxides react with acids to produce salt and water:

Fe 2 O 3 + 3H 2 SO 4 = Fe 2 (SO 4) 3 + 3H 2 O

Fe 2 O 3 + 6H + = 2Fe 3 + + 3H 2 O

Basic oxides react with acidic oxides to give salts:

FeO + SiO 2 = FeSiO 3 (t)

ACID OXIDES. Oxides whose hydrates are acids are called acidic. Acid oxides include oxides of non-metals and metals with an oxidation state of +4, +5, +6, +7. For example, N 2 O 3, P 2 O 5 , СrО 3 , Mn 2 O 7, CO 2, V 2 O 5, SO 3, Cl 2 O 7 - acidic oxides, since the acids HNO 2, H 3 PO 4, H 2 CrO 4, HMnO 4, etc. correspond to the acids (the chemical bond here is covalent and ionic). Most acidic oxides react with water and form acids. For example:

SO 3 + H2O = H2SO4

Мn2O7+ H2O = 2HMnO4

SiO2 + H2O ≠

Acidic oxides react with bases (alkalis) and give salt and water:

N 2 O 5 + Ca(OH) 2 = Ca(NO 3) 2 + H 2 O

N 2 O 5 + 2OH‾ = 2NO 3 ‾ + H 2 O

Amphoteric oxides. Metal oxides with an oxidation state of +3, +4 and sometimes +2, which, depending on the environment, exhibit basic or acidic properties, i.e., react with acids and bases, are called amphoteric. They correspond to hydrates, acids and bases. For example:

Zn(OH)2 ← ZnO → H2ZnO2

H2O Al(OH) 3 ← Al 2 O 3 → H 3 AlO 3 → HalO 2

Amphoteric oxides react with acids and bases:

Al2Oz + 3H2SO4 = Al2 (SO4)z + 3H2O

Al2Oz + 6H + = 2Al 3+ + 3H2O

Al2Oz + 2NaOH + 3H2O = 2Na

Al2Oz + 2OH‾ + 3H2O = 2[Al(OH)4]‾

When Al2O3 is fused with alkalis, metaaluminates are formed:

fusion of Al2Oz + 2NaOH → 2NaAlO2 + H2O

sodium metaaluminate

Аl2Оз + 2ОН‾ = 2Аl O2‾ + H2O

Amphoteric oxides do not directly combine with water.