Co oxide acidic or basic. Amphoteric oxides

Oxides are a very common type of compound found in earth's crust and in the universe in general.

Classification of oxides

Salt-forming oxides - these are oxides, which as a result chemical reaction form salts. 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.

- basic oxides (for example, sodium oxide Na2O, copper (II) oxide CuO): metal oxides, the oxidation state of which is I-II;
- acidic oxides (for example, sulfur(VI) oxide SO3, nitric oxide(IV) NO2): metal oxides with oxidation state V-VII and non-metal oxides;
- amphoteric oxides (for example, zinc oxide ZnO, aluminum oxide Al2O3): metal oxides with oxidation states III-IV and exceptions (ZnO, BeO, SnO, PbO).

Non-salt-forming oxides:

carbon monoxide(II) CO, nitric oxide(I) N2O, nitric oxide(II) NO, silicon oxide(II) SiO.

Basic properties of chemical oxides

1.Water-soluble basic oxides react with water to form bases:

Na2O + H2O → 2NaOH.

2.React with acidic oxides to form the corresponding salts

Na2O + SO3 → Na2SO4.

3.React with acids to form salt and water:

CuO + H2SO4 → CuSO4 + H2O.

4.React with amphoteric oxides:

Li2O + Al2O3 → 2LiAlO2.

Chemical properties of acid oxides

If the second element in the composition of oxides is a non-metal or a metal exhibiting a higher valence (usually 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. These are, for example, CO2, SO3, P2O5, N2O3, Cl2O5, Mn2O7, etc. They dissolve in water and alkalis, forming salt and water.

1.React with water to form acid:

SO3 + H2O → H2SO4.

But not all acidic oxides directly react with water (SiO2, etc.).

2.React with based oxides to form a salt:

CO2 + CaO → CaCO3

3.They react with alkalis to form salt and water:

CO2 + Ba(OH)2 → BaCO3 + H2O.

Chemical properties of amphoteric oxides

In this composition of the amphoteric oxide, there is an element that has amphoteric properties. Amphotericity is understood as the ability of compounds to exhibit acidic and basic properties depending on the conditions.

1.React with acids to form salt and water:

ZnO + 2HCl → ZnCl2 + H2O.

2.They react with solid alkalis (during fusion), forming as a result of the reaction a salt - sodium zincate and water:

ZnO + 2NaOH → Na2 ZnO2 + H2O.

Physical Properties

Liquid (SO3, Mn2O7); Solid (K2O, Al2O3, P2O5); Gaseous (CO2, NO2, SO2).

You can get oxides with ...

The interaction of simple substances (with the exception of inert gases, gold and platinum) with oxygen:

2H2 + O2 → 2H2O

2Cu + O2 → 2CuO

When alkali metals (except lithium), as well as strontium and barium, are burned in oxygen, peroxides and superoxides are formed:

2Na + O2 → Na2O2

Roasting or combustion of binary compounds in oxygen:

4FeS2 + 11O2 → 2Fe2O3 + 8SO2

CS2 + 3O2 → CO2 + 2SO2

2PH3 + 4O2 → P2O5 + 3H2O

Thermal decomposition of salts:

CaCO3 → CaO + CO2

2FeSO4 → Fe2O3 + SO2 + SO3

Thermal decomposition of bases or acids:

2Al(OH)3 → Al2O3 + 3H2O

4HNO3 → 4NO2 + O2 + 2H2O

Oxidation of lower oxides to higher ones and reduction of higher ones to lower ones:

4FeO + O2 → 2Fe2O3

Fe2O3 + CO → 2FeO + CO2

The interaction of some metals with water at high temperature:

Zn + H2O → ZnO + H2

The interaction of salts with acid oxides during the combustion of coke with the release of a volatile oxide:

Ca3(PO4)2 + 3SiO2 + 5C(coke) → 3CaSiO3 + 2P+5CO

The interaction of metals with oxidizing acids:

Zn + 4HNO3(conc.) → Zn(NO3)2 + 2NO2 + 2H2O

Under the action of water-removing substances on acids and salts:

2KClO4 + H2SO4(conc) → K2SO4 + Cl2O7 + H2O

The interaction of salts of weak unstable acids with stronger acids:

NaHCO3 + HCl → NaCl + H2O + CO2

Nomenclature of oxides

The word "oxide" followed by the name chemical element in the genitive. When several oxides are formed, their names indicate its oxidation state with a Roman numeral in brackets immediately after the name. Other names of oxides are often used according to the number of oxygen atoms: if the oxide contains only one oxygen atom, then it is called monoxide, monoxide or nitrous if two - dioxide or dioxide, if three - then trioxide or trioxide etc.

oxides- these are complex inorganic compounds consisting of two elements, one of which is oxygen (in the oxidation state -2).

For example, Na 2 O, B 2 O 3, Cl 2 O 7 are oxides. All listed substances contain oxygen and another element. Substances Na 2 O 2 , H 2 SO 4 , HCl do not belong to oxides: in the first, the oxidation state of oxygen is -1, in the second there are not two, but three elements, and the third does not contain oxygen at all.

If you do not understand the meaning of the term "oxidation state", it's okay. First, you can refer to the relevant article on this site. Secondly, even without understanding this term, you can continue reading. You can temporarily forget about the mention of the degree of oxidation.

Oxides of almost all currently known elements have been obtained, except for some noble gases and "exotic" transuranium elements. Moreover, many elements form several oxides (for nitrogen, for example, six are known).

Nomenclature of oxides

We must learn to name oxides. It's very simple.

Example 1. Name the following compounds: Li 2 O, Al 2 O 3, N 2 O 5, N 2 O 3.

Li 2 O - lithium oxide,
Al 2 O 3 - aluminum oxide,
N 2 O 5 - nitric oxide (V),
N 2 O 3 - nitric oxide (III).

Pay attention to an important point: if the valence of an element is constant, we DO NOT mention it in the name of the oxide. If the valency changes, be sure to indicate it in brackets! Lithium and aluminum have a constant valence, while nitrogen has a variable valence; it is for this reason that the names of nitrogen oxides are supplemented with Roman numerals, symbolizing valency.

Exercise 1. Name the oxides: Na 2 O, P 2 O 3, BaO, V 2 O 5, Fe 2 O 3, GeO 2, Rb 2 O. Do not forget that there are elements with both constant and variable valence.

Another important point: it is more correct to call the substance F 2 O not "fluorine oxide", but "oxygen fluoride"!

Physical properties of oxides

The physical properties are very diverse. This is due, in particular, to the fact that oxides can exhibit different types chemical bond. Melting and boiling points vary widely. At normal conditions oxides can be in the solid state (CaO, Fe 2 O 3, SiO 2, B 2 O 3), liquid state (N 2 O 3, H 2 O), in the form of gases (N 2 O, SO 2, NO, CO ).

The color is varied: MgO and Na 2 O are white, CuO is black, N 2 O 3 is blue, CrO 3 is red, etc.

Oxide melts with an ionic type of bond conduct well electricity, covalent oxides tend to have low electrical conductivity.

Classification of oxides

All naturally occurring oxides can be divided into 4 classes: basic, acidic, amphoteric, and non-salt-forming. Sometimes the first three classes are combined into a group of salt-forming oxides, but for us this is not essential now. Chemical properties oxides from different classes differ very much, so the issue of classification is very important for further study of this topic!

Let's start with non-salt-forming oxides. They need to be remembered: NO, SiO, CO, N 2 O. Just learn these four formulas!

For further advancement, we must remember that in nature there are two types of simple substances - metals and non-metals (sometimes a group of semi-metals or metalloids is also distinguished). If you clearly understand which elements are metals, continue reading this article. If there is the slightest doubt, refer to the material "Metals and non-metals" on that website.

So, I inform you that all amphoteric oxides are metal oxides, but not all metal oxides are amphoteric. I will list the most important of them: BeO, ZnO, Al 2 O 3 , Cr 2 O 3 , SnO. The list is not complete, but the listed formulas should be remembered! In most amphoteric oxides, the metal exhibits an oxidation state of +2 or +3 (but there are exceptions).

In the next part of the article, we will continue to talk about classification; Let's discuss acidic and basic oxides.

Acid oxides

Acid oxides (anhydrides)- oxides showing acid properties and forming the corresponding oxygenated acids. Formed by typical non-metals and some transition elements. Elements in acidic oxides typically exhibit oxidation states from IV to VII. They can interact with some basic and amphoteric oxides, for example: calcium oxide CaO, sodium oxide Na 2 O, zinc oxide ZnO, or aluminum oxide Al 2 O 3 (amphoteric oxide).

characteristic reactions

Acid oxides can react With:

SO 3 + H 2 O → H 2 SO 4

2NaOH + CO 2 => Na 2 CO 3 + H 2 O

Fe 2 O 3 + 3CO 2 => Fe 2 (CO 3) 3

Acid oxides can be obtained from the corresponding acid:

H 2 SiO 3 → SiO 2 + H 2 O

Examples

Manganese(VII) oxide Mn 2 O 7;
Nitric oxide NO 2 ;
Chlorine oxide Cl 2 O 5 , Cl 2 O 3

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. about. can exhibit reducing properties, and oxides with high c. about. - oxidative.

Examples of reactions in which oxides act as reducing agents:

Oxidation of oxides with low s. about. to oxides with high s. about. 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. about. 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).

Interaction of oxides with acids

Basic and amphoteric oxides react with acids. This forms salts and water:

FeO + H 2 SO 4 \u003d FeSO 4 + H 2 O

Non-salting oxides do not react with acids at all, and acidic oxides do not react with acids in most cases.

When does acid oxide react with acid?

When solving the part of the exam with answer options, you should conditionally assume that acid oxides do not react with either acid oxides or acids, except for the following cases:

1) silicon dioxide, being an acidic oxide, reacts with hydrofluoric acid, dissolving in it. In particular, thanks to this reaction, glass can be dissolved in hydrofluoric acid. In the case of an excess of HF, the reaction equation has the form:

SiO 2 + 6HF \u003d H 2 + 2H 2 O,

and in case of lack of HF:

SiO 2 + 4HF \u003d SiF 4 + 2H 2 O

2) SO 2, being an acid oxide, easily reacts with hydrosulfide acid H 2 S according to the type co-proportionation:

S +4 O 2 + 2H 2 S -2 \u003d 3S 0 + 2H 2 O

3) Phosphorus (III) oxide P 2 O 3 can react with oxidizing acids, which include concentrated sulfuric acid and nitric acid of any concentration. In this case, the oxidation state of phosphorus increases from +3 to +5:

P2O3

2H2SO4

H2O

=t o=>

2SO2

2H3PO4

(conc.)

3P2O3

4HNO 3

7H2O

=t o=>

4NO

6H3PO4

(razb.)

P2O3	+	4HNO 3	+	H2O	=t o=>	2H3PO4	+	4NO2
		(conc.)

4) Sulfur oxide (IV) SO 2 can be oxidized nitric acid taken at any concentration. In this case, the oxidation state of sulfur increases from +4 to +6.

2HNO 3	+	SO2	=t o=>	H2SO4	+	2NO 2
(conc.)
2HNO 3	+	3SO2	+	2H2O	=t o=>	3H2SO4	+	2NO
(razb.)

Interaction of oxides with metal hydroxides

Acid oxides react with metal hydroxides, both basic and amphoteric. In this case, a salt is formed, consisting of a metal cation (from the initial metal hydroxide) and an acid residue of the acid corresponding to the acid oxide.

SO 3 + 2NaOH \u003d Na 2 SO 4 + H 2 O

Acid oxides, which correspond to weak acids or acids of medium strength, can form both normal and acidic salts with alkalis:

CO 2 + 2NaOH \u003d Na 2 CO 3 + H 2 O

CO 2 + NaOH = NaHCO 3

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

P 2 O 5 + 4KOH \u003d 2K 2 HPO 4 + H 2 O

P 2 O 5 + 2KOH + H 2 O \u003d 2KH 2 PO 4

The "finicky" oxides CO 2 and SO 2, whose activity, as already mentioned, is not enough for their reaction with low-activity basic and amphoteric oxides, nevertheless, react with most of the metal hydroxides corresponding to them. More precisely, carbon dioxide and sulfur dioxide interact with insoluble hydroxides in the form of their suspension in water. In this case, only basic about obvious salts, called hydroxocarbonates and hydroxosulfites, and the formation of medium (normal) salts is impossible:

2Zn(OH) 2 + CO 2 = (ZnOH) 2 CO 3 + H 2 O(in solution)

2Cu(OH) 2 + CO 2 = (CuOH) 2 CO 3 + H 2 O(in solution)

However, with metal hydroxides in the +3 oxidation state, for example, such as Al (OH) 3, Cr (OH) 3, Fe (OH) 3, etc., carbon dioxide and sulfur dioxide do not react at all.

It should also be noted the special inertness of silicon dioxide (SiO 2), which is most often found in nature in the form of ordinary sand. This oxide is acidic, however, among metal hydroxides, it is able to react only with concentrated (50-60%) solutions of alkalis, as well as with pure (solid) alkalis during fusion. In this case, silicates are formed:

2NaOH + SiO 2 =t o => Na 2 SiO 3 + H 2 O

Amphoteric oxides from metal hydroxides react only with alkalis (hydroxides of alkali and alkaline earth metals). Wherein when carrying out the reaction in aqueous solutions, soluble complex salts are formed:

ZnO + 2NaOH + H 2 O \u003d Na 2- sodium tetrahydroxozincate

BeO + 2NaOH + H 2 O \u003d Na 2- sodium tetrahydroxoberyllate

Al 2 O 3 + 2NaOH + 3H 2 O \u003d 2Na- sodium tetrahydroxoaluminate

Cr 2 O 3 + 6NaOH + 3H 2 O \u003d 2Na 3- sodium hexahydroxochromate (III)

And when these same amphoteric oxides are fused with alkalis, salts are obtained, consisting of an alkali or alkaline earth metal cation and an anion of the MeO 2 x- type, where x= 2 in the case of amphoteric oxide type Me +2 O and x= 1 for an amphoteric oxide of the form Me 2 +2 O 3:

ZnO + 2NaOH =t o => Na 2 ZnO 2 + H 2 O

BeO + 2NaOH =t o => Na 2 BeO 2 + H 2 O

Al 2 O 3 + 2NaOH \u003dt o => 2NaAlO 2 + H 2 O

Cr 2 O 3 + 2NaOH \u003dt o => 2NaCrO 2 + H 2 O

Fe 2 O 3 + 2NaOH \u003dt o => 2NaFeO 2 + H 2 O

It should be noted that salts obtained by fusing amphoteric oxides with solid alkalis can be easily obtained from solutions of the corresponding complex salts by their evaporation and subsequent calcination:

Na 2 =t o => Na 2 ZnO 2 + 2H 2 O

Na =t o => NaAlO 2 + 2H 2 O

Interaction of oxides with salts

Most often, salts do not react with oxides.

However, you should learn the following exceptions to this rule, which are often found on the exam.

One of these exceptions is that amphoteric oxides, as well as silicon dioxide (SiO 2), when fused with sulfites and carbonates, displace sulfurous (SO 2) and carbon dioxide (CO 2) gases from the latter, respectively. For example:

Al 2 O 3 + Na 2 CO 3 \u003dt o => 2NaAlO 2 + CO 2

SiO 2 + K 2 SO 3 \u003dt o => K 2 SiO 3 + SO 2

Also, the reactions of oxides with salts can be conditionally attributed to the interaction of sulfur dioxide and carbon dioxide with aqueous solutions or suspensions of the corresponding salts - sulfites and carbonates, leading to the formation of acid salts:

Na 2 CO 3 + CO 2 + H 2 O \u003d 2NaHCO 3

CaCO 3 + CO 2 + H 2 O \u003d Ca (HCO 3) 2

Also, sulfur dioxide, when passed through aqueous solutions or suspension of carbonates displaces carbon dioxide from them due to the fact that sulfurous acid is a stronger and more stable acid than carbonic acid:

K 2 CO 3 + SO 2 \u003d K 2 SO 3 + CO 2

OVR involving oxides

Co oxide acidic or basic. Amphoteric oxides

Basic properties of chemical oxides

Chemical properties of acid oxides

Chemical properties of amphoteric oxides

Physical Properties

You can get oxides with ...

Nomenclature of oxides

Nomenclature of oxides

Physical properties of oxides

Classification of oxides

characteristic reactions

Examples

see also

See what "Acid oxides" are in other dictionaries:

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

Physical Properties

State of aggregation

Solubility in water

Chemical properties

How to get