The nature of the properties of the higher oxide. How to determine the nature of the oxide

Oxides (oxides) are chemical compounds consisting of two elements, one of which is .

Non-salt-forming are so called because during chemical reactions with other substances they do not form salts. These include H 2 O, carbon monoxide CO, nitrogen oxide NO. Among the salt-forming oxides, basic, acidic and amphoteric oxides are distinguished (Table 2).
Main are called, which correspond to those belonging to the class of bases. Basic ones react with acids to form salt and water.
Basic oxides are metal oxides. They are characterized by the ionic type chemical bond. For metals that make up basic oxides, the value is no higher than 3. Typical examples of basic oxides are calcium oxide CaO, barium oxide BaO, copper oxide CuO, iron oxide Fe 2 O 8, etc.

The names of the main oxides are relatively simple. If a metal that is part of a basic oxide has a constant , its oxide is called oxide, for example, sodium oxide Na 2 O, potassium oxide K 2 O, magnesium oxide MgO, etc. If the metal has a variable, the oxide in which it exhibits the highest valency is called an oxide, and the oxide in which it exhibits the lowest valency is called an oxide. called nitrous oxide, for example Fe 2 O 3 - iron oxide, FeO - ferrous oxide, CuO - copper oxide, Cu 2 O - copper oxide.

Write down the definition of oxides in your notebook.

Oxides are called acidic; they correspond to acids and react with bases to form salt and water.

Acidic oxides- These are mainly oxides of non-metals. Their molecules are built according to covalent type communications. The valency of nonmetals in oxides is usually equal to 3 or higher. Typical examples of acidic oxides are sulfur dioxide SO 2, carbon dioxide CO 2, sulfuric anhydride SO 3.
The name of an acidic oxide is often based on the number of oxygen atoms in its molecule, for example CO 2 - carbon dioxide, SO 3 - sulfur trioxide, etc. The name “anhydride” (devoid of water) is no less often used in relation to acidic oxides, for example CO 2 - carbonic anhydride, SO 3 - sulfuric anhydride, P 2 O 5 - phosphoric anhydride, etc. You will find an explanation for these names when studying the properties of oxides.

By modern system names, all oxides are called the single word “oxide”, and if an element can have different meanings valency, they are indicated by a Roman numeral next to each other in parentheses. For example, Fe 2 O 3 is iron (III) oxide, SO 3 is (VI).
Using the periodic table, it is convenient to determine the nature of the higher oxide of an element. It is safe to say, for example, that the higher oxides of the elements of the main subgroups of groups I and II are typical basic oxides, since these elements are typical. Higher oxides of elements of the main subgroups V, VI, VII groups- typical acid oxides, since the elements that form them are non-metals:
It often happens that those located in group IV-VII form higher oxides of an acidic nature, for example, they form higher oxides Mn 2 O 7 and CrO 3, which are acidic and are respectively called manganese and chromic anhydride.

■ 46. Indicate among the substances listed below those that are oxides: CaO; FeCO3; NaNO3; SiO2; CO 2; Ba(OH) 2; R 2 O 5; H2CO3; PbO; HNO3; FeO; SO 3; MgCO 3 ; MnO; CuO; Na 2 O; V 2 O 6; Ti02. Which group of oxides do they belong to? Name the given oxides according to the modern system. ()

Chemical properties of oxides

Despite the fact that the molecules of many oxides are built according to the ionic type, they are not electrolytes, since they do not dissolve in water in the sense in which we understand dissolution. Some of them can only interact with water, forming soluble products. But then it is not the oxides that dissociate, but the products of their interaction with water. Thus, electrolytic dissociation oxides are not affected. But when melting, they can undergo thermal dissociation - decomposition into ions in the melt.
It is most convenient to first consider the properties of basic and acidic oxides.
All basic oxides are solid, odorless, and may have different colors: magnesium oxide - white, iron oxide - rusty-brown, copper oxide - black.

By physical properties among acidic oxides there are solid (silicon dioxide SiO 2, phosphoric anhydride P 2 O 5, sulfuric anhydride SO 3), gaseous (sulfur dioxide SO 2, carbon dioxide CO 2). Sometimes anhydrides have color and odor.
The chemical properties of basic and acidic oxides are very different from each other. Considering them, we will always draw a parallel between basic and acidic oxides.

Basic oxides	Acidic oxides
1. Basic and acidic oxides can react with water
CaO + H 2 O = Ca(OH) 2 CaO + H 2 O = Ca 2+ + 2OH - In this case, basic oxides form alkalis (bases). This property explains the formulation of the definition that bases correspond to basic oxides. Not all basic oxides react directly when a compound reacts with water, but only the most active metals(sodium, potassium, calcium, barium, etc.).	SO 3 + H 2 O = H 2 SO 4 SO 3 + H2O = 2H + + SO 2 4 - Acidic oxides react with water to form acids. This property explains the name “anhydride” (acid devoid of water). In addition, this property explains the formulation of the definition that acids correspond to acidic oxides. But not all acidic oxides can react directly with water. Silicon dioxide SiO 2 and some others do not react with water.
2. Basic oxides interact with acids, forming salt and water: CuO + H2SO 4 = CuSO 4 + H 2 O CuO + 2H + SO 2 4 - =Cu 2+ + SO 2 4 - + H 2 O Abbreviated CuO +2H + = Cu 2+ + H 2 O
3. Basic and acidic oxides can: CaO + SiO 2 = CaSiO 3 during fusion
Obtaining oxides
	1. Oxidation of non-metals with oxygen S + O2 = SO 2
2. Decomposition of bases: Cu(OH) 2 = CuO + H 2 O	2. Decomposition of acids: H 2 CO 3 = H 2 O + CO 2
3. Decomposition of some salts (in this case one basic oxide is formed and the other is acidic): CaCO 3 = CaO + CO 2

Amphoteric oxides are those oxides that have dual properties and behave as basic under some conditions and as acidic under others. Amphoteric oxides include oxides Al 2 O 3 , ZnO and many others.

Let us consider the properties of amphoteric oxides using the example of the oxide zinc ZnO. Amphoteric oxides usually correspond to weak ones, which practically do not dissociate, therefore amphoteric oxides do not interact with water. However, due to their dual nature, they can react with both acids and alkalis:
ZnO + H 2 SO 4 = ZnSO 4 + H 2 O

ZnO + 2H + + SO 2 4 - = Zn 2+ + SO 2 4 - + H2O
ZnO + 2H + = Zn 2+ + H 2 O
In this reaction, zinc oxide behaves as a basic
oxide.
If zinc oxide gets into alkaline environment, then she behaves like acid oxide, which corresponds to the acid H 2 ZnO 2 (the formula is easy to find if you mentally add water H 2 O to the formula of zinc oxide). Therefore, the equation for the reaction of zinc oxide with alkali is written as follows:
ZnO + 2NaOH = Na 2 ZnO 2 + H 2 O
sodium zincate (soluble salt)
ZnO + 2Na + + 2OH - = 2Na + + ZnO 2 2 - + H 2 O
Abbreviated:
ZnO + 2OH - = ZnO 2 2 - + H 2 O

■ 47. What amount of carbon dioxide will be produced when 6 g of coal is burned? If you have forgotten how to solve chemical equation problems, refer to Appendix 1 and then solve this problem. ()
48. How many gram molecules of copper oxide are required to react with 49 g of sulfuric acid? (You can find out what a gram molecule is and how to use this concept in calculations by reading Appendix 1 on page 374).
49. How much sulfuric acid can be obtained by reacting 4 gram molecules of sulfuric anhydride with water?
50. What volume of oxygen is consumed to burn 8 g of sulfur? (The problem is solved using the concept of “volume of a gram-molecule of a gas.”).
51. How to make transformations:

Write the reaction equations in molecular and total ionic form.

52. What oxides are obtained from the decomposition of the following hydroxides: CuONH. Fe(OH)3, H2SiO3, Al(OH)3, H2SO3? Explain with reaction equations.
53. With which of them listed substances barium oxide will react: a) , b) , c) potassium oxide; d) copper oxide, e) calcium hydroxide; f) phosphoric acid; g) sulfur dioxide? Write the formulas of all the listed substances. Where possible, write the reaction equations in molecular, full ionic, and reduced ionic form.
54. Suggest a method for producing copper oxide CuO based on copper sulfate, water and sodium metal. ()

Determination of the nature of the properties of higher oxides using the periodic table

elements of D. I. Mendeleev
Knowing that the most typical metals are located at the beginning of the period, we can predict that the higher oxides of elements of the main subgroups of groups I and II should have basic properties. Some exception is represented by , the oxide of which is amphoteric in nature. At the end of the period there are nonmetals, the higher oxides of which must have acidic properties. Depending on the position of the elements in the periodic table, the corresponding elements can also be basic, acidic or amphoteric in nature. Based on this, we can make well-founded assumptions about the composition and properties of the oxides and hydroxides of certain elements.

■ 55. Write the formulas of higher oxides of strontium and indium. Can they react with sulfuric acid, with caustic soda? Write the reaction equations. ()
56. Write the formulas of rubidium, barium, lanthanum hydroxides.
57. How do reactions occur between rubidium hydroxide and nitric acid, between barium hydroxide and hydrochloric acid? Write the reaction equations.
58. Knowing that the formula of the highest selenium oxide is SeO 3, write the equations for the reactions of selenium anhydride with calcium hydroxide and sodium oxide.
59. Write the equations for the reactions of selenic acid with rubidium hydroxide, potassium oxide, barium hydroxide, calcium oxide.
60. Using the periodic table of elements, find the formulas of telluric acid (No. 52), perchloric acid (No. 17), germanic acid (No. 32), chromic acid (No. 24).
61. Write the equation for the reaction between rubidium hydroxide and antimony acid (No. 37, No. 51). ()

In addition to oxides and hydroxides, many elements can form compounds with hydrogen under common name hydrides. The specific properties of hydrides depend on the relative electronegativity of hydrogen and the element with which it combines.
Hydrogen compounds with typical metals, such as (NaH), (KH), (CaH 2), etc., are formed according to the type of ionic bond, and this is negative ion, and the metal is positive. Metal hydrides are solid, resemble salts, and have an ionic crystal lattice.
Hydrogen compounds with non-metals have more or less polar molecules, for example HCl, H 2 O, NH 3, etc., and are gaseous substances.
During education covalent bonds elements with hydrogen, the number of electron pairs is equal to the number of electrons missing to complete the outer electron layer of these elements (octet). This number does not exceed 4, therefore, volatile hydrogen compounds can only be formed by elements of the main subgroups of groups IV-VII, which have a pronounced electronegativity compared to hydrogen. The valence of an element in a volatile hydrogen compound can be calculated by subtracting from the number 8 the number of the group in which the element is located.
Elements of secondary subgroups IV-VII groups do not form volatile hydrides, since these are elements belonging to d-family having 1 - 2 electrons on the outer layer, which indicates weak electronegativity.

■ 62. Determine the valence in volatile hydrogen compounds of the elements silicon, phosphorus, oxygen, sulfur, bromine, arsenic, chlorine. ()
63. Write the formulas of volatile hydrogen compounds of arsenic (No. 33), bromine (No. 35), carbon (No. 6), selenium (No. 34).
64. Will the following elements form volatile compounds with hydrogen: a) (No. 41); b) (No. 83); c) iodine (No. 53); d) (No. 56); e) (No. 81); f) (No. 32); g) (No. 8); (No. 43); i) (No. 21); j) (No. N); l) (No. 51)? ()

If so, write the corresponding formulas.
The same principle underlies the compilation of formulas for binary compounds, i.e., compounds consisting of two elements, using the periodic system of elements. In this case, the element with the least metallic properties, i.e., more electronegative, will exhibit the same valence as in volatile hydrogen compounds, and the element with less electronegativity will exhibit the same valence as in the higher oxide. When writing the formula for a binary compound, the symbol of the less electronegative element is placed first, and the symbol of the more negative element is placed second. So, when writing, for example, the formula of lithium sulfide, we determine that as a metal exhibits lower electronegativity, its valence is the same as in the oxide, i.e. 1, equal to the group number. exhibits greater electronegativity and, therefore, its valence is 8-6 = 2 (the group number is subtracted from 8). Hence the formula Li 2 S.

■ 65. Based on the position of the elements in the periodic table, write the formulas for the following compounds:
a) tin chloride (No. 50, No. 17);
b) indium bromide (No. 49, No. 35);
c) cadmium iodine (No. 48, iodine No. 53);
d) nitrogen or lithium nitride (No. 3, No. 7);
e) strontium fluoride (No. 38, No. 9);
f) sulphide, or cadmium sulfide (No. 48, No. 16).
g) aluminum bromide (No. 13, No. 35). ()

Using the periodic table of elements, you can write formulas for salts oxygen acids and compose chemical equations. For example, to write the formula of barium chromate, you need to find the formula of the higher chromium oxide CrO 3, then find chromic acid H 2 CrO 4, then find the valency of barium (it is equal to 2 - according to the group number) and compose the formula BaCrO 4.

■ 66. Write the formulas for calcium permanganate and rubidium arsenic acid.
67. Write the following reaction equations:
a) cesium hydroxide + perchloric acid;
b) thallium hydroxide + phosphoric acid;
c) strontium hydroxide + ;
d) rubidium oxide + sulfuric anhydride;
e) barium oxide + carbonic anhydride;
e) strontium oxide + sulfuric anhydride;
g) cesium oxide + silicon anhydride;
h) lithium oxide + phosphoric acid;
i) beryllium oxide + arsenic acid;
j) rubidium oxide + chromic acid;
l) sodium oxide + periodic acid;
l) strontium hydroxide + aluminum sulfate;
m) rubidium hydroxide + gallium chloride;
o) strontium hydroxide + arsenic anhydride;
n) barium hydroxide + selenium anhydride. ()

The meaning of the periodic law and the periodic system of elements of D. I. Mendeleev in the development of chemistry

The periodic table is a system of elements, and all living and inanimate nature. Therefore, this is not only the main chemical law, but also a fundamental law of nature that has philosophical significance.
The discovery of the periodic law had a huge impact on the development of chemistry and has not lost its significance to this day. Using the periodic system of elements, D.I. Mendeleev was able to check and correct the atomic weights of a number of elements, for example, osmium, iridium, platinum, gold, etc. Based on the periodic system, D.I. Mendeleev, for the first time in the history of chemistry, successfully predicted the discovery of new elements.
In the 60s of the last century, some elements, such as (No. 21), (No. 31), (No. 32), etc., were not yet known. Nevertheless, D.I. Mendeleev left for them free places in the periodic table, because he was convinced that these elements would be discovered, and predicted their properties with exceptional accuracy. For example, the properties of the element, the existence of which D.I. Mendeleev predicted in 1871 and which he named eca-silicon, coincide with the properties of germanium, discovered in 1885 by Winkler.
Currently, knowing about the structure of atoms and molecules, we can characterize in more detail the properties of elements based on their position in the periodic table according to the following plan.
1. The position of the element in the table of D.I. Mendeleev. 2. Charge of the nucleus of an atom and total number electrons.
3. Number energy levels and the distribution of electrons on them.
4. Electronic configuration atom. 5. Nature of properties (metallic, non-metallic, etc.).
6. Higher valence in the oxide. The formula of the oxide, the nature of its properties, reaction equations confirming the assumed properties of the oxide.

7. Hydroxide. Properties of higher hydroxide. Reaction equations confirming the expected nature of the properties of the hydroxide.
8. Possibility of formation of volatile hydride. Hydride formula. Valency of the element in the hydride.
9. Possibility of chloride formation. Chloride formula. The type of chemical bond between the element and chlorine.
Mendeleev predicted 11 elements, and all of them were discovered: in 1875 by P. Lecoq de Boisbaudran, in 1879 by L. Nilsson and P. Kleve -, in 1898 by Marie Sklodowska-Curie and Pierre - (No. 84 ) and (No. 88), in 1899 by A. Debiern - (No. 89, predicted ecalantane). In 1917 O. Hahn and L. Meitner (Germany) discovered (No. 91), in 1925 V. Noddack, I. Noddack and O. Berg - (No. 75), in 1937 C. Perrier and E Segre (Italy) -technetium (No. 43), in 1939 M. Perey (France) - (No. 87), and in 1940 D. Corson, K. McKenzie and E. Segre (USA) - (No. 85).

Some of these elements were discovered during the lifetime of D.I. Mendeleev. At the same time, using the periodic system, D.I. Mendeleev checked the atomic weights of many already known elements and made corrections to them. Experimental verification These amendments confirmed the correctness of D.I. Mendeleev. Logically completed periodic table discovery in 1894 by Ramsay inert gases, which until this year were not in the periodic table.
The discovery of the periodic law directed scientists to search for the causes of periodicity. It contributed to revealing the essence serial numbers groups and periods, i.e. the study internal structure an atom considered indivisible. explained a lot, but at the same time presented scientists with a number of problems, the solution of which led to the study internal structure atom, explaining differences in the behavior of elements in chemical reactions. The discovery of the periodic law created the prerequisites for the artificial production of elements.
The periodic table, whose centenary we celebrated in 1969, is still a subject of study.
The ideas of D.I. Mendeleev marked the beginning of a new period in the development of chemistry.

Biography of D. I. Mendeleev

D.I. Mendeleev was born on February 8, 1834 in Tobolsk, where his father was the director of the gymnasium. At the Tobolsk gymnasium, where he entered in 1841, D. I. Mendeleev showed great interest in natural sciences. In 1849 he entered the Faculty of Science and Mathematics of St. Petersburg pedagogical institute. After the death of his parents and sister, D.I. Mendeleev was left alone. Nevertheless, he continued his education with great persistence. At the institute, professor of chemistry A. A. Voskresensky had a huge influence on him. Along with chemistry, D.I. Mendeleev was interested in mechanics, mineralogy, and botany.
In 1855, D.I. Mendeleev graduated from the institute with a gold medal and was sent as a natural science teacher to Simferopol, since intensive studies at the institute undermined his health and doctors recommended that he go south. Then he moved to Odessa. Here, as a teacher at the first Odessa gymnasium, he worked on the “hydrate” theory of solutions and on his master’s thesis “On specific volumes.” In 1856, D.I. Mendeleev brilliantly passed his master's exams and defended his dissertation. The originality and courage of thought in this work aroused admiring responses in the press and great interest in the scientific world.
Soon, 23-year-old D.I. Mendeleev became an associate professor and received the right to

read lectures in St. Petersburg University. In an extremely poorly equipped university laboratory, he continued his research, but work in such conditions could not satisfy the scientist, and in order to continue it more successfully, he was forced to leave for Germany. Having purchased the necessary reagents, glassware and instruments, he created a laboratory at his own expense and began to study the nature of gases and the issues of converting them into liquid state and intermolecular adhesion of liquids. D. I. Mendeleev was the first to talk about critical temperatures for gases and experimentally determined many of them, thereby proving that when certain temperature All gases can be converted into liquids.
In Germany, D.I. Mendeleev became close to many remarkable Russian scientists, who were also forced to work abroad. Among them were N. N. Beketov, A. P. Borodin, I. M. Sechenov and others. In 1860, D. I. Mendeleev took part in the I international congress chemists in Karlsruhe.

In 1861 he returned to St. Petersburg and began teaching the course organic chemistry in the University. Here for the first time he created a textbook of organic chemistry, reflecting latest achievements this science. In this textbook, D.I. Mendeleev considered all processes from a purely materialistic point of view, criticizing the “vitalists”, adherents of the so-called vitality, thanks to which, as they believed, life exists and is formed organic matter.
DI. Mendeleev first drew attention to isomerism - a phenomenon in which organic substances, having the same composition, have different properties. Soon this phenomenon was explained by A.M. Butlerov.
After defending his doctoral dissertation in 1864 on the topic “On the combination of alcohol with water,” D. I. Mendeleev in 1865 became a professor at St. Petersburg Institute of Technology and university.

In 1867, he received an invitation to France to organize the Russian pavilion at the World industrial exhibition. He outlined his impressions of the trip in his work “About modern development some chemical production as applied to Russia regarding the World Exhibition of 1867.”
In this work, the author expressed many valuable thoughts, in particular, he touched upon the issue of poor use in Russia natural resources, mainly oil, and the need to build chemical plants that produce locally the raw materials that Russia imports from abroad.

With his research in the field of hydration theory of solutions, D. I. Mendeleev, following Lomonosov, laid the foundation new area science - physical chemistry.
In 1867 D.I. Mendeleev was elected head of the department inorganic chemistry at St. Petersburg University, which he directed for 28 years. His lectures were extremely popular among students of all faculties and all courses. At the same time, D.I. Mendeleev led a great community work aimed at strengthening and developing Russian science. On his initiative, the Russian Physicochemical Society was founded in 1868, where D.I. Mendeleev first sent his report “Experience of a system of elements based on their atomic weight and chemical similarity." This was the famous one, on the basis of which D.I. Mendeleev wrote his famous work"Fundamentals of Chemistry".

The periodic law and the periodic system of elements allowed D.I. Mendeleev to predict the discovery of new elements and describe their properties with great accuracy. These elements were discovered during the life of D.I. Mendeleev and brought great fame to the periodic law and its discoverer.
But in reactionary circles St. Petersburg Academy science, glory to D.I. Mendeleev, his progressive ideas made a completely different impression. Despite his enormous services to science, D.I. Mendeleev was not elected to the Academy. This attitude towards the great scientist caused a storm of protest throughout the country. The Russian Physics and Chemical Society elected D.I. Mendeleev as an honorary member. In 1890, D.I. Mendeleev had to leave his job at the university. Nevertheless, his scientific and Practical activities didn't crumble. He was constantly busy with questions economic development country, participated in the preparation of customs tariffs, worked in the Chamber of Weights and Measures. But in all his endeavors, he invariably encountered opposition from the tsarist government. D. I. Mendeleev died in 1907. In his person, the world lost a brilliant, versatile scientist who put forward a number of ideas that were destined to be realized only in our time.

D.I. Mendeleev was an ardent champion of the development of domestic industry. Especially great attention he devoted to development oil industry. Even then he spoke about the construction of oil pipelines and chemical oil refining. But oil owners preferred to exploit oil fields predatorily.
For the first time, D.I. Mendeleev put forward the idea of ​​underground gasification, which was developed only in our time coal, which was highly appreciated back in 1913. V. I. Lenin, Necessities of creation chemical industry in Russia, D.I. Mendeleev devoted a number of his works, but its development became possible only in Soviet times: D.I. Mendeleev developed new methods for exploring iron ores, methods for extracting coal from deep-lying seams, put forward a project for the development of the North, was interested in problems of aeronautics and the study upper layers atmosphere. D.I. Mendeleev proposed a method for producing smokeless gunpowder, which the tsarist government ignored, but which was used by the American military department.

Checking the completion of tasks and answers to questions for Ch. I 1. 16; 61; 14; 42. 2. Difference in atomic weight...

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Chemical compounds consisting of oxygen and any other element of the periodic table are called oxides. Depending on their properties, they are classified into basic, amphoteric and acidic. The nature of the oxides can be determined theoretically and in a practical way.

You will need

• - periodic system;
• - glassware;
• - chemical reagents.

Instructions

You need to have a good understanding of how properties change chemical elements depending on their location in the D.I. table. Mendeleev. So repeat periodic law, electronic structure atoms (the oxidation state of elements depends on it) and so on.

Without any hands-on work, you can establish the nature of the oxide using only the periodic system. After all, it is known that in periods, in the direction from left to right alkaline properties oxides are replaced by amphoteric ones, and then by acidic ones. For example, in III period sodium oxide (Na2O) exhibits basic properties, the compound of aluminum with oxygen (Al2O3) is amphoteric in nature, and chlorine oxide (ClO2) is acidic.

Keep in mind that in the main subgroups the alkaline properties of the oxides increase from top to bottom, and the acidity, on the contrary, weakens. Thus, in group I, cesium oxide (CsO) has a stronger basicity than lithium oxide (LiO). In group V, nitrogen oxide (III) is acidic, and bismuth oxide (Bi2O5) is already basic.

Another way to determine the nature of the oxides. Let's say the task is given to experimentally prove the basic, amphoteric and acidic properties of calcium oxide (CaO), 5-valent phosphorus oxide (P2O5(V)) and zinc oxide (ZnO).

First, take two clean test tubes. From the bottles, using a chemical spatula, pour a little CaO into one and P2O5 into the other. Then pour 5-10 ml of distilled water into both reagents. Stir with a glass rod until the powder is completely dissolved. Dip pieces of litmus paper into both test tubes. Where calcium oxide is located, the indicator will become of blue color, which is evidence of the basic nature of the compound under study. In a test tube with phosphorus (V) oxide, the paper will turn red, therefore P2O5 is an acidic oxide.

Since zinc oxide is insoluble in water, react with an acid and a hydroxide to prove that it is amphoteric. In both cases, ZnO crystals will enter chemical reaction. For example:
ZnO + 2KOH = K2ZnO2 + H2O
3ZnO + 2H3PO4 Zn3(PO4)2 + 3H2O

note

Remember, the nature of the properties of the oxide directly depends on the valency of the element included in its composition.

Helpful advice

Do not forget that there are also so-called indifferent (non-salt-forming) oxides that do not react in normal conditions neither with hydroxides nor with acids. These include non-metal oxides with valence I and II, for example: SiO, CO, NO, N2O, etc., but there are also “metallic” ones: MnO2 and some others.

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Chemical compounds consisting of oxygen and any other element of the periodic table are called oxides. Depending on their properties, they are classified into basic, amphoteric and acidic. The nature of the oxides can be determined theoretically and practically.

You will need

• - periodic system;
• - glassware;
• - chemical reagents.

Instructions

• You need to have a good understanding of how the properties of chemical elements change depending on their location in the D.I. table. Mendeleev. Therefore, repeat the periodic law, the electronic structure of atoms (the oxidation state of elements depends on it), etc.
• Without any hands-on work, you can establish the nature of the oxide using only the periodic system. After all, it is known that in periods, in the direction from left to right, the alkaline properties of oxides change to amphoteric, and then to acidic. For example, in the III period, sodium oxide (Na2O) exhibits basic properties, the compound of aluminum with oxygen (Al2O3) is amphoteric in nature, and chlorine oxide (ClO2) is acidic.
• Keep in mind that in the main subgroups the alkaline properties of the oxides increase from top to bottom, and the acidity, on the contrary, weakens. Thus, in group I, cesium oxide (CsO) has a stronger basicity than lithium oxide (LiO). In group V, nitrogen oxide (III) is acidic, and bismuth oxide (Bi2O5) is already basic.
• Another way to determine the nature of the oxides. Let's say the task is given to experimentally prove the basic, amphoteric and acidic properties of calcium oxide (CaO), 5-valent phosphorus oxide (P2O5(V)) and zinc oxide (ZnO).
• First, take two clean test tubes. From the bottles, using a chemical spatula, pour a little CaO into one and P2O5 into the other. Then pour 5-10 ml of distilled water into both reagents. Stir with a glass rod until the powder is completely dissolved. Dip pieces of litmus paper into both test tubes. Where calcium oxide is located, the indicator will turn blue, which is proof of the basic nature of the compound being tested. In a test tube with phosphorus (V) oxide, the paper will turn red, therefore P2O5 is an acidic oxide.
• Since zinc oxide is insoluble in water, react with an acid and a hydroxide to prove that it is amphoteric. In both cases, ZnO crystals will enter into a chemical reaction. For example:
  ZnO + 2KOH = K2ZnO2 + H2O
  3ZnO + 2H3PO4→ Zn3(PO4)2↓ + 3H2O

Let's talk about how to determine the nature of the oxide. Let's start with the fact that all substances are usually divided into two groups: simple and complex. Simple substances are divided into metals and non-metals. Complex connections They are divided into four classes: bases, oxides, salts, acids.

Definition

Since the nature of the oxides depends on their composition, let us first give a definition this class inorganic substances. Oxides are those that consist of two elements. Their peculiarity is that oxygen is always located in the formula as the second (last) element.

The most common option is the interaction of simple substances (metals, non-metals) with oxygen. For example, when magnesium reacts with oxygen, it forms a compound that exhibits basic properties.

Nomenclature

The nature of the oxides depends on their composition. Exist certain rules by which such substances are named.

If the oxide is formed by metals of the main subgroups, the valence is not indicated. For example, calcium oxide CaO. If the first metal in the compound is a metal of a similar subgroup, which has a variable valency, then it must be indicated by a Roman numeral. Placed after the name of the compound in parentheses. For example, there are iron oxides (2) and (3). When composing formulas for oxides, you need to remember that the sum of the oxidation states in it must be equal to zero.

Classification

Let's consider how the nature of the oxides depends on the degree of oxidation. Metals with oxidation states +1 and +2 form with oxygen basic oxides. A specific feature of such compounds is basic character oxides Such connections enter into chemical reaction with salt-forming oxides of non-metals, forming salts with them. In addition, they react with acids. The reaction product depends on the quantity of the starting substances taken.

Nonmetals, as well as metals with oxidation states from +4 to +7, form acidic oxides with oxygen. The nature of the oxides suggests interaction with bases (alkalis). The result of the interaction depends on the quantity of the original alkali taken. When it is deficient, it forms as a product of interaction acid salt. For example, the reaction of carbon monoxide (4) with sodium hydroxide produces sodium bicarbonate (acid salt).

In the case of interaction of an acidic oxide with an excess amount of alkali, the reaction product will be a medium salt (sodium carbonate). Character acid oxides depends on the degree of oxidation.

They are divided into salt-forming oxides (in which the oxidation state of the element is equal to the group number), as well as indifferent oxides, which are not capable of forming salts.

Amphoteric oxides

There is also an amphoteric nature of the properties of oxides. Its essence lies in the interaction of these compounds with both acids and alkalis. Which oxides exhibit dual (amphoteric) properties? These include binary metal compounds with an oxidation state of +3, as well as beryllium and zinc oxides.

Methods of obtaining

Exist various ways The most common option is interaction with oxygen simple substances(metals, non-metals). For example, when magnesium reacts with oxygen, it forms a compound that exhibits basic properties.

In addition, oxides can also be obtained by reacting complex substances with molecular oxygen. For example, when burning pyrite (iron sulfide 2), two oxides can be obtained at once: sulfur and iron.

Another option for producing oxides is the decomposition reaction of salts oxygen-containing acids. For example, the decomposition of calcium carbonate can produce carbon dioxide and calcium oxide

Basic and amphoteric oxides are also formed during decomposition insoluble bases. For example, when iron (3) hydroxide is calcined, iron (3) oxide is formed, as well as water vapor.

Conclusion

Oxides are a class of inorganic substances with a wide range of industrial application. They are used in the construction industry, pharmaceutical industry, and medicine.

In addition, amphoteric oxides are often used in organic synthesis as catalysts (accelerators of chemical processes).