oxides- This complex substances, consisting of atoms of two elements, one of which is oxygen with an oxidation state of -2. In this case, oxygen is associated only with a less electronegative element.

Depending on the second element, oxides exhibit different chemical properties. AT school course Oxides are traditionally divided into salt-forming and non-salt-forming. Some oxides are classified as salt-like (double).

Double oxides are some oxides, formed by the element with different degrees of oxidation.

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

Main Oxides are oxides that have characteristic basic properties. These include oxides formed by metal atoms with an oxidation state of +1 and +2.

Acidic oxides are oxides characterized by acidic properties. These include oxides formed by metal atoms with an oxidation state of +5, +6 and +7, as well as non-metal atoms.

Amphoteric oxides are oxides characterized by both basic and acidic properties. These are metal oxides with an oxidation state of +3 and +4, as well as four oxides with an oxidation state of +2: ZnO, PbO, SnO and BeO.

Non-salt-forming oxides do not show characteristic basic or acid properties, hydroxides do not correspond to them. The non-salt-forming oxides include four oxides: CO, NO, N 2 O and SiO.

Classification of oxides

Obtaining oxides

General methods for obtaining oxides:

1. Interaction of simple substances with oxygen :

1.1. Metal oxidation: most metals are oxidized by oxygen to oxides with stable oxidation states.

For example , aluminum reacts with oxygen to form an oxide:

4Al + 3O 2 → 2Al 2 O 3

Do not interact with oxygen gold, platinum, palladium.

Sodium when oxidized with atmospheric oxygen, it forms predominantly Na 2 O 2 peroxide,

2Na + O 2 → 2Na 2 O 2

Potassium, cesium, rubidium form predominantly peroxides of composition MeO 2:

K + O 2 → KO 2

Notes: metals with variable degree oxidations are oxidized by atmospheric oxygen, as a rule, to an intermediate oxidation state (+3):

4Fe + 3O 2 → 2Fe 2 O 3

4Cr + 3O 2 → 2Cr 2 O 3

Iron also burns with the formation of iron scale - iron oxide (II, III):

3Fe + 2O 2 → Fe 3 O 4

1.2. Oxidation of simple non-metal substances.

As a rule, during the oxidation of non-metals, a non-metal oxide with the highest oxidation state is formed, if oxygen is in excess, or a non-metal oxide with an intermediate oxidation state, if oxygen is in short supply.

for example, phosphorus is oxidized by an excess of oxygen to phosphorus (V) oxide, and under the action of a lack of oxygen to phosphorus (III) oxide:

4P + 5O 2(ex.) → 2P 2 O 5

4P + 3O 2(week) → 2P 2 O 3

But there are some exceptions .

for example, sulfur burns only to sulfur oxide (IV):

S + O 2 → SO 2

Sulfur oxide (VI) can only be obtained by oxidizing sulfur oxide (IV) under harsh conditions in the presence of a catalyst:

2SO2+ O2=2SO3

Nitrogen is oxidized by oxygen only at a very high temperature (about 2000 o C), or under the action of electrical discharge, and only up to nitric oxide (II):

N 2 + O 2 \u003d 2NO

Fluorine F 2 is not oxidized by oxygen (fluorine itself oxidizes oxygen). Other halogens (chlorine Cl 2 , bromine, etc.), inert gases (helium He, neon, argon, krypton) do not interact with oxygen.

2. Oxidation of complex substances(binary compounds): sulfides, hydrides, phosphides, etc.

When complex substances are oxidized with oxygen, which usually consist of two elements, a mixture of oxides of these elements is formed in stable oxidation states.

for example, when pyrite FeS 2 is burned, iron oxide (III) and sulfur oxide (IV) are formed:

4FeS 2 + 11O 2 → 2Fe 2 O 3 + 8SO 2

Hydrogen sulfide burns with the formation of sulfur oxide (IV) with an excess of oxygen and with the formation of sulfur with a lack of oxygen:

2H 2 S + 3O 2 (ex.) → 2H 2 O + 2SO 2

2H 2 S + O 2(week) → 2H 2 O + 2S

But ammonia burns with the formation a simple substance N 2, because nitrogen reacts with oxygen only under harsh conditions:

4NH 3 + 3O 2 → 2N 2 + 6H 2 O

But in the presence of a catalyst, ammonia is oxidized by oxygen to nitric oxide (II):

4NH 3 + 5O 2 → 4NO + 6H 2 O

3. Decomposition of hydroxides. Oxides can also be obtained from hydroxides - acids or bases. Some hydroxides are unstable, and spontaneously decompose into oxide and water; for the decomposition of some other (usually insoluble in water) hydroxides, it is necessary to heat (calcine) them.

hydroxide → oxide + water

Carbonic acid, sulfurous acid, ammonium hydroxide, silver (I), copper (I) hydroxides spontaneously decompose in an aqueous solution:

H 2 CO 3 → H 2 O + CO 2

H 2 SO 3 → H 2 O + SO 2

NH 4 OH → NH 3 + H2O

2AgOH → Ag 2 O + H 2 O

2CuOH → Cu 2 O + H 2 O

When heated, most of the insoluble hydroxides decompose into oxides - silicic acid, hydroxides heavy metals- iron hydroxide (III), etc.:

H 2 SiO 3 → H 2 O + SiO 2

2Fe(OH) 3 → Fe 2 O 3 + 3H 2 O

4. Another way to obtain oxides is decomposition of complex compounds - salts .

for example, insoluble carbonates and lithium carbonate, when heated, decompose into oxides:

Li 2 CO 3 → H 2 O + Li 2 O

CaCO 3 → CaO + CO 2

Salts formed by strong oxidizing acids (nitrates, sulfates, perchlorates, etc.), when heated, as a rule, decompose with a change in the oxidation state:

2Zn(NO 3) 2 → 2ZnO + 4NO 2 + O 2

You can read more about the decomposition of nitrates in the article.

Chemical properties of oxides

A significant part of the chemical properties of oxides is described by the scheme of the relationship between the main classes of inorganic substances.

Before we start talking about the chemical properties of oxides, we need to remember that all oxides are divided into 4 types, namely basic, acidic, amphoteric and non-salt-forming. In order to determine the type of any oxide, you first need to understand whether the oxide of a metal or non-metal is in front of you, and then use the algorithm (you need to learn it!), Presented in the following table:

In addition to the types of oxides indicated above, we also introduce two more subtypes of basic oxides, based on their chemical activity, namely active basic oxides and inactive basic oxides.

• To active basic oxides Let us refer oxides of alkali and alkaline earth metals (all elements of groups IA and IIA, except for hydrogen H, beryllium Be and magnesium Mg). For example, Na 2 O, CaO, Rb 2 O, SrO, etc.
• To inactive basic oxides we will assign all the main oxides that were not included in the list active basic oxides. For example, FeO, CuO, CrO, etc.

It is logical to assume that active basic oxides often enter into those reactions that do not enter into low-active ones.

It should be noted that despite the fact that water is actually an oxide of a non-metal (H 2 O), its properties are usually considered in isolation from the properties of other oxides. This is due to its specifically huge distribution in the world around us, and therefore, in most cases, water is not a reagent, but a medium in which countless chemical reactions. However, it often takes a direct part in various transformations, in particular, some groups of oxides react with it.

What oxides react with water?

Of all oxides with water react only:

1) all active basic oxides (oxides of alkaline metals and alkaline earth metals);

2) all acidic oxides, except for silicon dioxide (SiO 2);

those. From the foregoing, it follows that with water exactly do not react:

1) all low-active basic oxides;

2) all amphoteric oxides;

3) non-salt-forming oxides (NO, N 2 O, CO, SiO).

Note:

Magnesium oxide reacts slowly with water when boiled. Without strong heating, the reaction of MgO with H 2 O does not proceed.

The ability to determine which oxides can react with water, even without the ability to write the corresponding reaction equations, already allows you to get points for some questions of the test part of the exam.

Now let's see how, after all, certain oxides react with water, i.e. learn how to write the corresponding reaction equations.

Active basic oxides, reacting with water, form their corresponding hydroxides. Recall that the corresponding metal oxide is the hydroxide that contains the metal in the same oxidation state as the oxide. So, for example, when the active basic oxides K + 1 2 O and Ba + 2 O react with water, the corresponding hydroxides K + 1 OH and Ba + 2 (OH) 2 are formed:

K 2 O + H 2 O \u003d 2KOH– potassium hydroxide

BaO + H 2 O \u003d Ba (OH) 2– barium hydroxide

All hydroxides corresponding to active basic oxides (oxides of alkali metals and alkali earth metals) are alkalis. Alkalis are all water-soluble metal hydroxides, as well as poorly soluble calcium hydroxide Ca (OH) 2 (as an exception).

The interaction of acidic oxides with water, as well as the reaction of active basic oxides with water, leads to the formation of the corresponding hydroxides. Only in the case of acid oxides, they correspond not to basic, but to acidic hydroxides, more often called oxygenated acids. Recall that the corresponding acid oxide is an oxygen-containing acid that contains an acid-forming element in the same oxidation state as in the oxide.

Thus, if we, for example, want to write down the equation for the interaction of acidic oxide SO 3 with water, first of all we must recall the main ones studied within the framework of school curriculum, sulfur-containing acids. These are hydrogen sulfide H 2 S, sulfurous H 2 SO 3 and sulfuric H 2 SO 4 acids. Hydrosulfide acid H 2 S, as you can easily see, is not oxygen-containing, so its formation during the interaction of SO 3 with water can be immediately excluded. Of the acids H 2 SO 3 and H 2 SO 4, sulfur in the oxidation state +6, as in oxide SO 3, contains only sulfuric acid H2SO4. Therefore, it is she who will be formed in the reaction of SO 3 with water:

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

Similarly, oxide N 2 O 5 containing nitrogen in the oxidation state +5, reacting with water, forms nitric acid HNO 3, but in no case nitrous HNO 2, since in nitric acid the oxidation state of nitrogen, as in N 2 O 5 , equal to +5, and in nitrogenous - +3:

N +5 2 O 5 + H 2 O \u003d 2HN +5 O 3

Exception:

Nitric oxide (IV) (NO 2) is a non-metal oxide in the +4 oxidation state, i.e. in accordance with the algorithm described in the table at the very beginning of this chapter, it must be attributed to acidic oxides. However, there is no acid that contains nitrogen in the +4 oxidation state.

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

Interaction of oxides with each other

First of all, it is necessary to clearly understand the fact that among salt-forming oxides (acidic, basic, amphoteric), reactions between oxides of the same class almost never occur, i.e. In the vast majority of cases, interaction is impossible:

1) basic oxide + basic oxide ≠

2) acid oxide + acid oxide ≠

3) amphoteric oxide + amphoteric oxide ≠

While interaction is almost always possible between oxides belonging to different types, i.e. almost always flow reactions between:

1) basic oxide and acid oxide;

2) amphoteric oxide and acid oxide;

3) amphoteric oxide and basic oxide.

As a result of all such interactions, the product is always an average (normal) salt.

Let us consider all these pairs of interactions in more detail.

As a result of interaction:

Me x O y + acid oxide, where Me x O y - metal oxide (basic or amphoteric)

a salt is formed, consisting of the metal cation Me (from the original Me x O y) and the acid residue of the acid corresponding to the acid oxide.

For example, let's try to write down the interaction equations for the following pairs of reagents:

Na 2 O + P 2 O 5 and Al 2 O 3 + SO 3

In the first pair of reagents, we see a basic oxide (Na 2 O) and an acid oxide (P 2 O 5). In the second - amphoteric oxide (Al 2 O 3) and acid oxide (SO 3).

As already mentioned, as a result of the interaction of a basic/amphoteric oxide with an acidic one, a salt is formed, consisting of a metal cation (from the original basic/amphoteric oxide) and an acid residue of the acid corresponding to the original acidic oxide.

Thus, the interaction of Na 2 O and P 2 O 5 should form a salt consisting of Na + cations (from Na 2 O) and the acid residue PO 4 3-, since the oxide P +5 2 O 5 corresponds to acid H 3 P +5 O 4 . Those. As a result of this interaction, sodium phosphate is formed:

3Na 2 O + P 2 O 5 \u003d 2Na 3 PO 4- sodium phosphate

In turn, the interaction of Al 2 O 3 and SO 3 should form a salt consisting of Al 3+ cations (from Al 2 O 3) and the acid residue SO 4 2-, since the oxide S +6 O 3 corresponds to acid H 2 S +6 O 4 . Thus, as a result of this reaction, aluminum sulfate is obtained:

Al 2 O 3 + 3SO 3 \u003d Al 2 (SO 4) 3- aluminum sulfate

More specific is the interaction between amphoteric and basic oxides. These reactions are carried out at high temperatures, and their occurrence is possible due to the fact that the amphoteric oxide actually takes on the role of the acidic one. As a result of this interaction, a salt of a specific composition is formed, consisting of a metal cation that forms the initial basic oxide and an "acid residue" / anion, which includes the metal from the amphoteric oxide. The formula for such an "acid residue" / anion in general view can be written as MeO 2 x - where Me is the metal from the amphoteric oxide, and x = 2 in the case of amphoteric oxides with general formula type Me +2 O (ZnO, BeO, PbO) and x = 1 - for amphoteric oxides with the general formula of the form Me +3 2 O 3 (for example, Al 2 O 3, Cr 2 O 3 and Fe 2 O 3).

Let's try to write down as an example the interaction equations

ZnO + Na 2 O and Al 2 O 3 + BaO

In the first case, ZnO is an amphoteric oxide with the general formula Me +2 O, and Na 2 O is a typical basic oxide. According to the above, as a result of their interaction, a salt should be formed, consisting of a metal cation forming a basic oxide, i.e. in our case, Na + (from Na 2 O) and an "acid residue" / anion with the formula ZnO 2 2-, since the amphoteric oxide has a general formula of the form Me + 2 O. Thus, the formula of the resulting salt, subject to the condition of electroneutrality of one of its structural unit("molecules") will look like Na 2 ZnO 2:

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

In the case of an interacting pair of reagents Al 2 O 3 and BaO, the first substance is an amphoteric oxide with the general formula of the form Me +3 2 O 3 , and the second is a typical basic oxide. In this case, a salt containing a metal cation from the basic oxide is formed, i.e. Ba 2+ (from BaO) and "acid residue"/anion AlO 2 - . Those. the formula of the resulting salt, subject to the condition of electrical neutrality of one of its structural units (“molecules”), will have the form Ba(AlO 2) 2, and the interaction equation itself will be written as:

Al 2 O 3 + BaO = t o=> Ba (AlO 2) 2

As we wrote above, the reaction almost always proceeds:

Me x O y + acid oxide,

where Me x O y is either basic or amphoteric metal oxide.

However, two “finicky” acid oxides should be remembered - carbon dioxide(CO 2) and sulfur dioxide (SO 2). Their "fastidiousness" lies in the fact that, despite the obvious acidic properties, the activity of CO 2 and SO 2 is not enough for their interaction with low-active basic and amphoteric oxides. Of the metal oxides, they react only with active basic oxides(oxides of alkali metal and alkali earth metal). So, for example, Na 2 O and BaO, being active basic oxides, can react with them:

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

SO 2 + BaO = BaSO 3

While CuO and Al 2 O 3 oxides, which are not related to active basic oxides, do not react with CO 2 and SO 2:

CO 2 + CuO ≠

CO 2 + Al 2 O 3 ≠

SO 2 + CuO ≠

SO 2 + Al 2 O 3 ≠

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?

Deciding part of the exam with answer options, you should conditionally assume that acid oxides do not react with either acid oxides or acids, except in 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.)

3 P2O3	+	4HNO 3	+	7 H2O	=t o=>	4NO	+	6 H3PO4
		(razb.)

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 acidic acid residue corresponding to the acid oxide.

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

Acid oxides, which correspond to polybasic acids, 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, 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). In this case, 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

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 \u003d t o=> 2NaAlO 2 + H 2 O

Cr 2 O 3 + 2NaOH \u003d t o=> 2NaCrO 2 + H 2 O

Fe 2 O 3 + 2NaOH \u003d t 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 medium salts

Most often, medium 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 \u003d t o=> 2NaAlO 2 + CO 2

SiO 2 + K 2 SO 3 \u003d t o=> K 2 SiO 3 + SO 2

Also, the reactions of oxides with salts can conditionally include 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 carbonate suspension 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

Recovery of oxides of metals and non-metals

Just as metals can react with salt solutions of less active metals, displacing the latter in their free form, metal oxides can also react with more active metals when heated.

Recall that you can compare the activity of metals either using the activity series of metals, or, if one or two metals are not in the activity series at once, by their position relative to each other in the periodic table: the lower and to the left of the metal, the more active it is. It is also useful to remember that any metal from the SM and SHM family will always be more active than a metal that is not a representative of SHM or SHM.

In particular, the aluminothermy method used in industry to obtain such hard-to-recover metals as chromium and vanadium is based on the interaction of a metal with an oxide of a less active metal:

Cr 2 O 3 + 2Al = t o=> Al 2 O 3 + 2Cr

During the process of aluminothermy, an enormous amount of heat is generated, and the temperature of the reaction mixture can reach more than 2000 o C.

Also, oxides of almost all metals that are in the activity series to the right of aluminum can be reduced to free metals with hydrogen (H 2), carbon (C) and carbon monoxide (CO) when heated. For example:

Fe 2 O 3 + 3CO = t o=> 2Fe + 3CO 2

CuO+C= t o=> Cu + CO

FeO + H 2 \u003d t o=> Fe + H 2 O

It should be noted that if the metal can have several oxidation states, with a lack of the used reducing agent, incomplete reduction of oxides is also possible. For example:

Fe 2 O 3 + CO =to=> 2FeO + CO 2

4CuO+C= t o=> 2Cu 2 O + CO 2

Oxides of active metals (alkaline, alkaline earth, magnesium and aluminum) with hydrogen and carbon monoxide do not react.

However, oxides of active metals react with carbon, but in a different way than oxides of less active metals.

Within the framework of the USE program, in order not to be confused, it should be considered that as a result of the reaction of active metal oxides (up to Al inclusive) with carbon, the formation of free alkaline metals, alkaline earth metals, Mg, and also Al is impossible. In such cases, the formation of metal carbide and carbon monoxide. For example:

2Al 2 O 3 + 9C \u003d t o=> Al 4 C 3 + 6CO

CaO + 3C = t o=> CaC2 + CO

Non-metal oxides can often be reduced by metals to free non-metals. So, for example, oxides of carbon and silicon, when heated, react with alkali, alkaline earth metals and magnesium:

CO 2 + 2Mg = t o=> 2MgO + C

SiO2 + 2Mg = t o=> Si + 2MgO

With an excess of magnesium, the latter interaction can also lead to the formation magnesium silicide Mg2Si:

SiO 2 + 4Mg = t o=> Mg 2 Si + 2MgO

Nitrogen oxides can be reduced relatively easily even with less active metals, such as zinc or copper:

Zn + 2NO = t o=> ZnO + N 2

2NO2 + 4Cu = t o=> 4CuO + N 2

Interaction of oxides with oxygen

In order to be able to answer the question of whether any oxide reacts with oxygen (O 2) in the tasks of the real exam, you first need to remember that oxides that can react with oxygen (of those that you can come across on the exam itself) can form only chemical elements from the list:

carbon C, silicon Si, phosphorus P, sulfur S, copper Cu, manganese Mn, iron Fe, chromium Cr, nitrogen N

Found in real USE oxides of any other chemical elements react with oxygen will not (!).

For a more visual convenient memorization of the above list of elements, in my opinion, the following illustration is convenient:

All chemical elements capable of forming oxides that react with oxygen (from those encountered in the exam)

First of all, among the listed elements, nitrogen N should be considered, because. the ratio of its oxides to oxygen differs markedly from the oxides of the rest of the elements in the above list.

It should be clearly remembered that in total nitrogen is capable of forming five oxides, namely:

Of all nitrogen oxides, oxygen can react only NO. This reaction proceeds very easily when NO is mixed with both pure oxygen and air. In this case, a rapid change in the color of the gas from colorless (NO) to brown (NO 2) is observed:

2NO	+	O2	=	2NO 2
colorless				brown

In order to answer the question - does any oxide of any other of the above chemical elements react with oxygen (i.e. WITH,Si, P, S, Cu, Mn, Fe, Cr) — First of all, you need to remember them main oxidation state (CO). Here they are :

Next, you need to remember the fact that of the possible oxides of the above chemical elements, only those that contain the element in the minimum, among the above, oxidation states will react with oxygen. In this case, the oxidation state of the element rises to the nearest positive value possible:

element	The ratio of its oxidesto oxygen
With	The minimum among the main positive oxidation states of carbon is +2 , and the closest positive to it is +4 . Thus, only CO reacts with oxygen from the oxides C +2 O and C +4 O 2. In this case, the reaction proceeds: 2C +2 O + O 2 = t o=> 2C+4O2 CO 2 + O 2 ≠- the reaction is impossible in principle, because +4 is the highest oxidation state of carbon.
Si	The minimum among the main positive oxidation states of silicon is +2, and the closest positive to it is +4. Thus, only SiO reacts with oxygen from the oxides Si +2 O and Si +4 O 2 . Due to some features of the oxides SiO and SiO 2, only a part of the silicon atoms in the oxide Si + 2 O can be oxidized. as a result of its interaction with oxygen, a mixed oxide is formed containing both silicon in the +2 oxidation state and silicon in the +4 oxidation state, namely Si 2 O 3 (Si +2 O Si +4 O 2): 4Si +2 O + O 2 \u003d t o=> 2Si +2, +4 2 O 3 (Si +2 O Si +4 O 2) SiO 2 + O 2 ≠- the reaction is impossible in principle, because +4 is the highest oxidation state of silicon.
P	The minimum among the main positive oxidation states of phosphorus is +3, and the closest positive to it is +5. Thus, only P 2 O 3 reacts with oxygen from oxides P +3 2 O 3 and P +5 2 O 5 . In this case, the reaction of additional oxidation of phosphorus with oxygen proceeds from the oxidation state +3 to the oxidation state +5: P +3 2 O 3 + O 2 = t o=> P +5 2 O 5 P +5 2 O 5 + O 2 ≠- the reaction is impossible in principle, because +5 is the highest oxidation state of phosphorus.
S	The minimum among the main positive oxidation states of sulfur is +4, and the closest positive to it in value is +6. Thus, only SO 2 reacts with oxygen from oxides S +4 O 2 , S +6 O 3 . In this case, the reaction proceeds: 2S +4 O 2 + O 2 \u003d t o=> 2S +6 O 3 2S +6 O 3 + O 2 ≠- the reaction is impossible in principle, because +6 is the highest oxidation state of sulfur.
Cu	The minimum among the positive oxidation states of copper is +1, and the closest to it in value is the positive (and only) +2. Thus, only Cu 2 O reacts with oxygen from oxides Cu +1 2 O, Cu +2 O. In this case, the reaction proceeds: 2Cu +1 2 O + O 2 = t o=> 4Cu+2O CuO + O 2 ≠- the reaction is impossible in principle, because +2 is the highest oxidation state of copper.
Cr	The minimum among the main positive oxidation states of chromium is +2, and the closest positive to it in value is +3. Thus, only CrO reacts with oxygen from oxides Cr +2 O, Cr +3 2 O 3 and Cr +6 O 3, while being oxidized by oxygen to the next (out of possible) positive oxidation state, i.e. +3: 4Cr +2 O + O 2 \u003d t o=> 2Cr +3 2 O 3 Cr +3 2 O 3 + O 2 ≠- the reaction does not proceed, despite the fact that chromium oxide exists and in an oxidation state greater than +3 (Cr +6 O 3). The impossibility of this reaction occurring is due to the fact that the heating required for its hypothetical implementation greatly exceeds the decomposition temperature of CrO 3 oxide. Cr +6 O 3 + O 2 ≠ - this reaction cannot proceed in principle, because +6 is the highest oxidation state of chromium.
Mn	The minimum among the main positive oxidation states of manganese is +2, and the closest positive to it is +4. Thus, of the possible oxides Mn +2 O, Mn +4 O 2, Mn +6 O 3 and Mn +7 2 O 7, only MnO reacts with oxygen, while being oxidized by oxygen to the neighboring (out of possible) positive oxidation state, t .e. +4: 2Mn +2 O + O 2 = t o=> 2Mn +4 O 2 while: Mn +4 O 2 + O 2 ≠ and Mn +6 O 3 + O 2 ≠- reactions do not proceed, despite the fact that there is manganese oxide Mn 2 O 7 containing Mn in a higher oxidation state than +4 and +6. This is due to the fact that the required for further hypothetical oxidation of Mn oxides +4 O2 and Mn +6 O 3 heating significantly exceeds the decomposition temperature of the resulting oxides MnO 3 and Mn 2 O 7. Mn +7 2 O 7 + O 2 ≠- this reaction is impossible in principle, because +7 is the highest oxidation state of manganese.
Fe	The minimum among the main positive oxidation states of iron is +2 , and the closest to it among the possible - +3 . Despite the fact that for iron there is an oxidation state of +6, the acid oxide FeO 3, however, as well as the corresponding “iron” acid, does not exist. Thus, of the iron oxides, only those oxides that contain Fe in the +2 oxidation state can react with oxygen. It's either Fe oxide +2 O, or mixed iron oxide Fe +2 ,+3 3 O 4 (iron scale): 4Fe +2 O + O 2 \u003d t o=> 2Fe +3 2 O 3 or 6Fe +2 O + O 2 \u003d t o=> 2Fe +2,+3 3 O 4 mixed Fe oxide +2,+3 3 O 4 can be further oxidized to Fe +3 2O3: 4Fe +2 ,+3 3 O 4 + O 2 = t o=> 6Fe +3 2 O 3 Fe +3 2 O 3 + O 2 ≠ - the course of this reaction is impossible in principle, because oxides containing iron in an oxidation state higher than +3 do not exist.

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 are 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 compounds that, depending on the conditions, can exhibit either basic or acidic properties.

Rice. 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).

However, most of the basic oxides are solids of various colors.

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

Chemical properties of basic oxides

Basic oxides are oxides that correspond to bases. 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 valence in the lowest oxidation state (for example, CaO, FeO), react with acids and acid oxides, forming salts:

CaO (basic oxide) + CO 2 (acid oxide) \u003d CaCO 3 (salt)

FeO (basic oxide) + H 2 SO 4 (acid) \u003d FeSO 4 (salt) + 2H 2 O (water)

Basic oxides also interact 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) \u003d Ba (OH) 2 (alkaline earth metal base)

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

3CuO + 2NH 3 \u003d 3Cu + 3H 2 O + N 2

When heated, only oxides of mercury and precious 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 matter, insoluble in water
barium oxide	BaO	colorless crystals with a cubic lattice
Copper oxide II	CuO	black substance practically insoluble in water
	HgO	solid red or yellow-orange
potassium oxide	K2O	colorless or pale yellow substance
sodium oxide	Na2O	a substance consisting of colorless crystals
lithium oxide	Li2O	a substance consisting of colorless crystals that have a cubic lattice structure

In the main subgroups periodic system when moving from one element to another from top to bottom, an increase in the basic properties of oxides is observed

What have we learned?

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

Topic quiz

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Today we begin our acquaintance with the most important classes 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 the valency of a chemical element is variable, then it 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 Me	V-VII Me	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 valence 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 valency 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 valence 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 valence 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
	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 (r. compounds) 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. He also has a handsome White color and is used for the manufacture of 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.

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

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:

1) K → K 2 O → KOH → K 2 SO 4

2) S → SO 2 → H 2 SO 3 → Na 2 SO 3

3) P → P 2 O 5 → H 3 PO 4 → K 3 PO 4

About 2.

Oxides are divided:

Nomenclature of oxides.

Currently, international nomenclature is used, according to which any oxide is called an oxide, indicating the degree of oxidation of the element in Roman numerals: sulfur oxide (IV) - SO 2, iron(III) oxide - Fe 2 O 3 , carbon monoxide (II) CO etc.

However, there are still old names of oxides:

Obtaining salt-forming oxides.

Basic oxides- oxides of typical metals, their corresponding hydroxides, which have the properties of bases.

Acid oxides- oxides of non-metals or transition metals in high oxidation states.

Basic oxides	Acid oxides
1. Oxidation of metals when heated in an air atmosphere:	1. Oxidation of non-metals when heated in an air atmosphere:
2 mg + O 2 = 2 MgO This method is practically inapplicable for alkali metals, which usually form peroxides rather than oxides.	4 P + 5O 2 \u003d 2P 2 O 5,
2. Sulfide roasting:
2 CuS + 3 O 2 = 2 CuO + 2 SO 2 , This method is also not applicable to active metal sulfides that oxidize to sulfates.	2 ZnS + 3 O 2 \u003d 2ZnO + 2SO 2,
3. Decomposition of hydroxides at a temperature:
Cu (OH) 2 \u003d CuO + H 2 O, Alkali metal oxides cannot be obtained by this method either.
4. Decomposition of salts of oxygen-containing acids at a temperature:
BaCO 3 = BaO + CO 2 , This method is well applicable for nitrates and carbonates.

amphoteric oxides.

Amphoteric oxides have a dual nature: they can interact with acids and with bases (alkalis):

Al 2 O 3 + 6HCl \u003d 2AlCl 3 + 3 H 2 O,

Al 2 O 3 + 2NaOH + 3H 2 O \u003d 2Na.

Typical amphoteric oxides : H 2 O, BeO, Al 2 O 3, Cr 2 O 3, Fe 2 O 3 and etc.

Properties of oxides.

Basic oxides	Acid oxides
1. Decomposition when heated:
2HgO \u003d 2Hg + O 2 Only oxides of mercury and noble metals decompose, the rest do not decompose.
2. When heated, they react with acidic and amphoteric oxides:	Interact with basic oxides, amphoteric oxides, hydroxides:
BaO + SiO 2 \u003d BaSiO 3, MgO + Al 2 O 3 \u003d Mg (AlO 2) 2,	BaO + SiO 2 \u003d BaSiO 3, Ca (OH) 2 + CO 2 \u003d CaCO 3 + H 2 O,
React with water:
K 2 O + H 2 O \u003d 2KOH, CaO + H 2 O \u003d Ca (OH) 2,	SO 3 + H 2 O \u003d H 2 SO 4, CO 2 + H 2 O \u003d H 2 CO 3,
Fe 2 O 3 + 2Al \u003d Al 2 O 3 + 2Fe, 3CuO + 2NH 3 \u003d 3Cu + N 2 + 3H 2 O,	CO 2 + C \u003d 2CO, 2SO 2 + O 2 \u003d 2SO 3.