Properties of oxides
oxides- these are complex chemicals, which are chemical compounds of simple elements with oxygen. They are salt-forming and not forming salts. In this case, salt-forming are of 3 types: main(from the word "foundation"), acidic and amphoteric.
An example of oxides that do not form salts can be: NO (nitric oxide) - is a colorless gas, odorless. It is formed during a thunderstorm in the atmosphere. CO (carbon monoxide) is an odorless gas produced by the combustion of coal. It is commonly referred to as carbon monoxide. There are other oxides that do not form salts. Now let's take a closer look at each type of salt-forming oxides.
Basic oxides
Basic oxides- These are complex chemical substances related to oxides that form salts by chemical reaction with acids or acid oxides and do not react with bases or basic oxides. For example, the main ones are:
K 2 O (potassium oxide), CaO (calcium oxide), FeO (2-valent iron oxide).
Consider chemical properties of oxides by examples
1. Interaction with water:
- interaction with water to form a base (or alkali)
CaO + H 2 O → Ca (OH) 2 (a well-known lime slaking reaction, while a large amount of heat is released!)
2. Interaction with acids:
- interaction with acid to form salt and water (solution of salt in water)
CaO + H 2 SO 4 → CaSO 4 + H 2 O (Crystals of this substance CaSO 4 are known to everyone under the name "gypsum").
3. Interaction with acid oxides: salt formation
CaO + CO 2 → CaCO 3 (This substance is known to everyone - ordinary chalk!)
Acid oxides
Acid oxides- these are complex chemicals related to oxides that form salts when chemically interacting with bases or basic oxides and do not interact with acidic oxides.
Examples of acidic oxides are:
CO 2 (well-known carbon dioxide), P 2 O 5 - phosphorus oxide (formed by combustion of white phosphorus in air), SO 3 - sulfur trioxide - this substance is used to produce sulfuric acid.
Chemical reaction with water
CO 2 +H 2 O→ H 2 CO 3 is a substance - carbonic acid - one of the weak acids, it is added to sparkling water for "bubbles" of gas. As the temperature rises, the solubility of the gas in water decreases, and its excess comes out in the form of bubbles.
Reaction with alkalis (bases):
CO 2 +2NaOH→ Na 2 CO 3 +H 2 O- the resulting substance (salt) is widely used in the economy. Its name - soda ash or washing soda - is an excellent detergent for burnt pans, grease, burns. I do not recommend working with bare hands!
Reaction with basic oxides:
CO 2 + MgO → MgCO 3 - received salt - magnesium carbonate - also called "bitter salt".
Amphoteric oxides
Amphoteric oxides- these are complex chemicals, also related to oxides, which form salts during chemical interaction with acids (or acid oxides) and bases (or basic oxides). The most common use of the word "amphoteric" in our case refers to metal oxides.
An example amphoteric oxides can be:
ZnO - zinc oxide (white powder, often used in medicine for the manufacture of masks and creams), Al 2 O 3 - aluminum oxide (also called "alumina").
The chemical properties of amphoteric oxides are unique in that they can enter into chemical reactions corresponding to both bases and acids. For example:
Reaction with acid oxide:
ZnO + H 2 CO 3 → ZnCO 3 + H 2 O - The resulting substance is a solution of "zinc carbonate" salt in water.
Reaction with bases:
ZnO + 2NaOH → Na 2 ZnO 2 + H 2 O - the resulting substance is a double salt of sodium and zinc.
Obtaining oxides
Obtaining oxides produced in various ways. This can happen in physical and chemical ways. The simplest way is the chemical interaction of simple elements with oxygen. For example, the result of a combustion process or one of the products of this chemical reaction are oxides. For example, if a red-hot iron rod, and not only iron (you can take zinc Zn, tin Sn, lead Pb, copper Cu, - in general, what is at hand) is placed in a flask with oxygen, then a chemical oxidation reaction of iron will occur, which accompanied by a bright flash and sparks. The reaction product will be black iron oxide FeO powder:
2Fe+O 2 → 2FeO
Completely similar chemical reactions with other metals and non-metals. Zinc burns in oxygen to form zinc oxide
2Zn+O 2 → 2ZnO
The combustion of coal is accompanied by the formation of two oxides at once: carbon monoxide and carbon dioxide.
2C+O 2 → 2CO - the formation of carbon monoxide.
C + O 2 → CO 2 - the formation of carbon dioxide. This gas is formed if there is more than enough oxygen, that is, in any case, the reaction proceeds first with the formation of carbon monoxide, and then the carbon monoxide is oxidized, turning into carbon dioxide.
Obtaining oxides can be done in another way - by a chemical reaction of decomposition. For example, to obtain iron oxide or aluminum oxide, it is necessary to ignite the corresponding bases of these metals on fire:
Fe(OH) 2 → FeO+H 2 O
Solid aluminum oxide - mineral corundum 
Iron(III) oxide. The surface of the planet Mars has a reddish-orange color due to the presence of iron (III) oxide in the soil. Solid aluminum oxide - corundum 
2Al(OH) 3 → Al 2 O 3 + 3H 2 O,
as well as in the decomposition of individual acids:
H 2 CO 3 → H 2 O + CO 2 - decomposition of carbonic acid
H 2 SO 3 → H 2 O + SO 2 - decomposition of sulfurous acid
Obtaining oxides can be made from metal salts with strong heating:
CaCO 3 → CaO + CO 2 - calcium oxide (or quicklime) and carbon dioxide are obtained by calcining chalk.
2Cu(NO 3) 2 → 2CuO + 4NO 2 + O 2 - in this decomposition reaction, two oxides are obtained at once: copper CuO (black) and nitrogen NO 2 (it is also called brown gas because of its really brown color).
Another way in which oxides can be obtained is through redox reactions.
Cu + 4HNO 3 (conc.) → Cu(NO 3) 2 + 2NO 2 + 2H 2 O
S + 2H 2 SO 4 (conc.) → 3SO 2 + 2H 2 O
Chlorine oxides
ClO 2 molecule 
Molecule Cl 2 O 7 
Nitrous oxide N 2 O 
Nitrous anhydride N 2 O 3 
Nitric anhydride N 2 O 5 
Brown gas NO 2 The following are known chlorine oxides: Cl 2 O, ClO 2 , Cl 2 O 6 , Cl 2 O 7 . All of them, with the exception of Cl 2 O 7 , are yellow or orange in color and are not stable, especially ClO 2 , Cl 2 O 6 . All chlorine oxides explosive and are very strong oxidizers.
Reacting with water, they form the corresponding oxygen-containing and chlorine-containing acids:
So, Cl 2 O - acid chlorine oxide hypochlorous acid.
Cl 2 O + H 2 O → 2HClO - Hypochlorous acid
ClO 2 - acid chlorine oxide hypochlorous and hypochlorous acids, since in a chemical reaction with water it forms two of these acids at once:
ClO 2 + H 2 O → HClO 2 + HClO 3
Cl 2 O 6 - too acid chlorine oxide chloric and perchloric acids:
Cl 2 O 6 + H 2 O → HClO 3 + HClO 4
And finally, Cl 2 O 7 - a colorless liquid - acid chlorine oxide perchloric acid:
Cl 2 O 7 + H 2 O → 2HClO 4
nitrogen oxides
Nitrogen is a gas that forms 5 different compounds with oxygen - 5 nitrogen oxides. Namely:
N 2 O - nitrogen hemioxide. Its other name is known in medicine under the name laughing gas or nitrous oxide- It is colorless sweetish and pleasant to the taste on the gas.
-NO- nitrogen monoxide A colorless, odorless, tasteless gas.
- N 2 O 3 - nitrous anhydride- colorless crystalline substance
- NO 2 - nitrogen dioxide. Its other name is brown gas- the gas really has a brown color
- N 2 O 5 - nitric anhydride- blue liquid boiling at a temperature of 3.5 0 C
Of all these listed nitrogen compounds, NO - nitrogen monoxide and NO 2 - nitrogen dioxide are of the greatest interest in industry. nitrogen monoxide(NO) and nitrous oxide N 2 O does not react with either water or alkalis. (N 2 O 3), when reacting with water, forms a weak and unstable nitrous acid HNO 2, which gradually turns into a more stable chemical substance nitric acid in air. Consider some chemical properties of nitrogen oxides:
Reaction with water:
2NO 2 + H 2 O → HNO 3 + HNO 2 - 2 acids are formed at once: nitric acid HNO 3 and nitrous acid.
Reaction with alkali:
2NO 2 + 2NaOH → NaNO 3 + NaNO 2 + H 2 O - two salts are formed: sodium nitrate NaNO 3 (or sodium nitrate) and sodium nitrite (salt of nitrous acid).
Reaction with salts:
2NO 2 + Na 2 CO 3 → NaNO 3 + NaNO 2 + CO 2 - two salts are formed: sodium nitrate and sodium nitrite, and carbon dioxide is released.
Nitrogen dioxide (NO 2) is obtained from nitrogen monoxide (NO) using a chemical reaction of the compound with oxygen:
2NO + O 2 → 2NO 2
iron oxides
Iron forms two oxide: FeO- iron oxide(2-valent) - black powder, which is obtained by reduction iron oxide(3-valent) carbon monoxide by the following chemical reaction:
Fe 2 O 3 + CO → 2FeO + CO 2
This basic oxide readily reacts with acids. It has reducing properties and is rapidly oxidized to iron oxide(3-valent).
4FeO +O 2 → 2Fe 2 O 3
iron oxide(3-valent) - red-brown powder (hematite), which has amphoteric properties (it can interact with both acids and alkalis). But the acidic properties of this oxide are so weakly expressed that it is most often used as basic oxide.
There are also so-called mixed iron oxide Fe 3 O 4 . It is formed during the combustion of iron, conducts electricity well and has magnetic properties (it is called magnetic iron ore or magnetite). If iron burns out, then as a result of the combustion reaction, scale is formed, consisting of two oxides at once: iron oxide(III) and (II) valence.
Sulfur oxide
Sulphur dioxide SO2 Sulfur oxide SO 2 - or sulphur dioxide refers to acid oxides, but does not form acid, although it dissolves perfectly in water - 40 liters of sulfur oxide in 1 liter of water (for the convenience of compiling chemical equations, such a solution is called sulfurous acid).
Under normal circumstances, it is a colorless gas with a pungent and suffocating smell of burnt sulfur. At a temperature of only -10 0 C, it can be transferred to a liquid state.
In the presence of a catalyst -vanadium oxide (V 2 O 5) sulfur oxide takes on oxygen and turns into sulfur trioxide
2SO 2 + O 2 → 2SO 3
dissolved in water sulphur dioxide- sulfur oxide SO 2 - oxidizes very slowly, as a result of which the solution itself turns into sulfuric acid
If a sulphur dioxide pass through an alkali solution, for example, sodium hydroxide, then sodium sulfite is formed (or hydrosulfite - depending on how much alkali and sulfur dioxide are taken)
NaOH + SO 2 → NaHSO 3 - sulphur dioxide taken in excess
2NaOH + SO 2 → Na 2 SO 3 + H 2 O
If sulfur dioxide does not react with water, then why does its aqueous solution give an acidic reaction?! Yes, it does not react, but it oxidizes itself in water, adding oxygen to itself. And it turns out that free hydrogen atoms accumulate in the water, which give an acidic reaction (you can check it with some indicator!)
To acid oxides relate:
- all oxides of non-metals, except for non-salt-forming ones (NO, SiO, CO, N 2 O);
- metal oxides in which the valency of the metal is quite high (V or higher).
Examples of acidic oxides are P 2 O 5 , SiO 2 , B 2 O 3 , TeO 3 , I 2 O 5 , V 2 O 5 , CrO 3 , Mn 2 O 7 . I would like to once again draw attention to the fact that metal oxides can also be acidic. A well-known school proverb "Metal oxides are basic, non-metals are acidic!" - This, sorry, is complete nonsense.
To basic oxides include metal oxides for which two conditions are simultaneously met:
- the valency of the metal in the compound is not very high (at least it does not exceed IV);
- the substance does not belong to amphoteric oxides.
Typical examples of basic oxides are Na 2 O, CaO, BaO and other oxides of alkali and alkaline earth metals, FeO, CrO, CuO, Ag 2 O, NiO, etc.
So, let's sum up. oxides non-metals can be:
- acidic (and those are the vast majority);
- non-salt-forming (the corresponding 4 formulas should simply be remembered).
- basic (if the degree of oxidation of the metal is not very high);
- acidic (if the oxidation state of the metal is +5 or higher);
- amphoteric (a few formulas should be remembered, but it should be understood that the list given in the first part is not exhaustive).
And now a little test to check how well you have mastered the topic "Classification of oxides". If the test result is below 3 points, I recommend that you carefully read the article again.
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 | red or yellow-orange solid | |
| 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 |
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 the metal or non-metal is in front of you, and then use the algorithm (you need to learn it!), Presented in the following table:
| non-metal oxide | metal oxide |
| 1) Non-metal oxidation state +1 or +2 Conclusion: non-salt-forming oxide Exception: Cl 2 O is not a non-salt-forming oxide |
1) Metal oxidation state +1 or +2 Conclusion: metal oxide is basic Exception: BeO, ZnO and PbO are not basic oxides |
| 2) The oxidation state is greater than or equal to +3 Conclusion: acidic oxide Exception: Cl 2 O is an acid oxide, despite the oxidation state of chlorine +1 |
2) Metal oxidation state +3 or +4 Conclusion: amphoteric oxide Exception: BeO, ZnO and PbO are amphoteric despite the +2 oxidation state of metals 3) Metal oxidation state +5, +6, +7 Conclusion: acidic oxide |
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 can take place. 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).
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 sulfur-containing acids studied in the school curriculum. 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 +6 oxidation state, as in oxide SO 3, contains only sulfuric acid H 2 SO 4. 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
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 between oxides belonging to different types is almost always possible, 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 of such an "acid residue" / anion in general form can be written as MeO 2 x - , where Me is a metal from an amphoteric oxide, and x = 2 in the case of amphoteric oxides with a general formula of the form 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 electrical neutrality of one of its structural units ("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" acidic 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?
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.) |
| 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 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 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
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 \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 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 suspensions 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
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 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 metal, alkaline earth metal, Mg, and also Al is impossible. In such cases, the formation of metal carbide and carbon monoxide occurs. 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
NO 2 + 2Cu = t o=> 2CuO + 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:
Oxides of any other chemical elements encountered in the real USE 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. FROM,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 |
| FROM | 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):
mixed Fe oxide +2,+3 3 O 4 can be further oxidized to Fe +3 2O3:
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 complex substances are called, the composition of the molecules of which includes oxygen atoms in the oxidation state - 2 and some other element.
can be obtained by direct interaction of oxygen with another element, or indirectly (for example, by the decomposition of salts, bases, acids). Under normal conditions, oxides are in a solid, liquid and gaseous state, this type of compounds is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.
They are salt-forming and 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 called oxides that do not form salts. An example is CO, N 2 O, NO.
Salt-forming oxides, in turn, are of 3 types: basic (from the word «
base »
), acidic and amphoteric.
Basic oxides such metal oxides are called, which 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. Interact 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 second element in the composition of the oxides is a non-metal or a metal exhibiting a higher valency (usually exhibits 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. This is, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acid oxides dissolve in water and alkalis, forming salt and water.
Chemical properties of acid oxides
1. Interact with water, forming acid:
SO 3 + H 2 O → H 2 SO 4.
But not all acidic oxides directly react with water (SiO 2 and others).
2. React with based oxides to form a salt:
CO 2 + CaO → CaCO 3
3. Interact with alkalis, forming salt and water:
CO 2 + Ba (OH) 2 → BaCO 3 + H 2 O.
Part amphoteric oxide includes an element that has amphoteric properties. Amphotericity is understood as the ability of compounds to exhibit acidic and basic properties depending on the conditions. For example, zinc oxide ZnO can be both a base and 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. Interact 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 - a characteristic that determines the number of nearest 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 is 4 or 6; For and Cr it is 6 or (very rarely) 4;
Amphoteric oxides usually do not dissolve in water and do not react with it.
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