Metals nonmetals oxides bases acids salts. Lesson topic: “Oxides of metals and non-metals - composition and names. Chemical properties of oxides and hydroxides of non-metals
In the Unified State Examination tasks there are questions where you need to determine the type of oxide. First of all, there are four types of oxides to remember:
1) non-salt-forming
2) basic
3) acidic
4) amphoteric
Basic, acidic and amphoteric oxides are also often grouped together salt-forming oxides.
Without going into theoretical details, I will outline a step-by-step algorithm for determining the type of oxide.
First- determine: the metal oxide in front of you or the non-metal oxide.
Second- having established which metal or non-metal oxide is in front of you, determine the oxidation state of the element in it and use the table below. Naturally, the rules for assigning oxides in this table need to be learned. At first, you can solve tasks by looking at it, but your goal is to remember it, since there are no sources of information in the exam except the D.I. table. You will not have a periodic table, solubility tables or activity series for metals.
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Non-metal oxide |
Metal oxide |
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1) Oxidation state of non-metal +1 or +2 Conclusion: non-salt-forming oxide Exception: Cl 2 O is not a non-salt-forming oxide |
1) The oxidation state of the metal is +1, +2 Conclusion: metal oxide is basic Exception:BeO,ZnO, SnO and PbO are not includedto basic oxides!! |
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2) The oxidation state is greater than or equal to +3 Conclusion: acid oxide Exception: Cl 2 O is an acidic oxide, despite the oxidation state of chlorine +1 |
2) Metal oxidation state +3, +4, Conclusion: the oxide is amphoteric. Exception: BeO, ZnO, SnO and PbOamphoteric, despite the +2 oxidation state of metals |
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3) Metal oxidation state +5,+6,+7 Conclusion: acidic oxide. |
Examples:
Exercise: determine the type of MgO oxide.
Solution: MgO is a metal oxide, and the oxidation state of the metal in it is +2. All metal oxides in the +1 and +2 oxidation states are basic, except beryllium or zinc oxide.
Answer: MgO is the main oxide.
Exercise: determine the type of oxide Mn 2 O 7
Solution: Mn 2 O 7 is a metal oxide, and the oxidation state of the metal in this oxide is +7. Metal oxides in high oxidation states (+5, +6, +7) are classified as acidic.
Answer: Mn 2 O 7 – acidic oxide
Exercise: determine the type of oxide Cr 2 O 3.
Solution: Cr 2 O 3 is a metal oxide, and the oxidation state of the metal in this oxide is +3. Metal oxides in oxidation states +3 and +4 are classified as amphoteric.
Answer: Cr 2 O 3 is an amphoteric oxide.
Exercise: determine the type of N 2 O oxide.
Solution: N 2 O is a non-metal oxide, and the oxidation state of the non-metal in this oxide is +1. Non-metal oxides in oxidation states +1 and +2 are non-salt-forming.
Answer: N 2 O is a non-salt-forming oxide.
Exercise: determine the type of BeO oxide.
Solution: Beryllium oxide as well as zinc oxide are exceptions. Despite the oxidation state of the metals in them being +2, they are amphoteric.
Answer: BeO is an amphoteric oxide.
You can familiarize yourself with the chemical properties of oxides
Binary compounds of oxygen with non-metallic elements are a large group of substances that are included in the class of oxides. Many non-metal oxides are well known to everyone. These are, for example, carbon dioxide, water, nitrogen dioxide. In our article we will look at their properties, find out the areas of application of binary compounds and their impact on the environment.
General characteristics
Almost all non-metallic elements, with the exception of fluorine, argon, neon and helium, can form oxides. Most elements have multiple oxides. For example, sulfur forms two compounds: sulfur dioxide and sulfuric anhydride. These are substances in which the valence of sulfur is four and six, respectively. Hydrogen and boron have only one oxide each, and the largest number of binary substances with oxygen is characteristic of nitrogen. Higher oxides are those in which the oxidation state of the nonmetal atom is equal to the number of the group where the element is located in the periodic table. Thus, CO 2 and SO 3 are higher oxides of carbon and sulfur. Some compounds may undergo further oxidation. For example, carbon monoxide in this case turns into carbon dioxide.
Structure and physical properties
Almost all known non-metal oxides consist of molecules whose atoms form covalent bonds. The particles of the substance themselves can be either polar (for example, sulfur dioxide) or non-polar (carbon dioxide molecules). Silicon dioxide, a natural form of sand, has an atomic structure. The physical state of a number of acid oxides may be different. Thus, carbon oxides, such as carbon monoxide and carbon dioxide, are gaseous, and binary oxygen compounds of hydrogen (H 2 O) or sulfur in the highest oxidation state (SO 3) are liquids. The peculiarity of water is that the oxide is non-salt-forming. They are also called indifferent.
Sulfur trioxide or sulfuric anhydride is a crystalline white substance. It quickly absorbs moisture from the air, so sulfur dioxide is stored in sealed glass flasks. The substance is used as an air dehumidifier and in the production of sulfate acid. Oxides of phosphorus or silicon are crystalline solids. Mutual transformation of the state of aggregation is characteristic of nitrogen oxides. Thus, the NO 2 compound is a brown gas, and the compound with the formula N 2 O 4 appears as a colorless liquid or white solid. When heated, a liquid turns into a gas, and cooling it leads to the formation of a liquid phase.
Interaction with water
Reactions of acid oxides with water are known. The reaction products will be the corresponding acids:
SO 3 + H 2 O = H 2 SO 4 - sulfate acid
These include the interaction of phosphorus pentoxide, as well as sulfur, nitrogen, and carbon dioxides with H 2 O molecules. However, silicon oxide does not react directly with water. To obtain silicic acid, an indirect method is used. First, SiO 2 is fused with an alkali, for example, sodium hydroxide. The resulting middle salt, sodium silicate, is treated with a strong acid, such as chloride.
As a result, a white gelatinous precipitate of silicic acid precipitates. When heated, silicon dioxide can react with salts to form volatile acidic oxides. Acid oxides include several compounds of nitrogen, sulfur and phosphorus, which occupy a leading position in air pollution. They interact with atmospheric moisture, which leads to the formation of sulfuric, nitrate and nitrous acid. Their molecules, along with rain or snow, fall on plants and soil. Acid precipitation not only harms crops, reducing their productivity, but also negatively affects human health. They destroy buildings made of limestone or marble and cause corrosion of metal structures.
Indifferent oxides
Acidic oxides include a group of compounds that cannot react with either acids or alkalis and do not form salts. All of the above compounds do not correspond to either an acid or a base, that is, they are non-salt-forming. There are few such connections. For example, these include carbon monoxide, nitrous oxide and its monoxide - NO. It, along with nitrogen dioxide and sulfur dioxide, is involved in the formation of smog over large industrial enterprises and cities. The formation of toxic oxides can be prevented by lowering the combustion temperature of the fuel.
Interaction with alkalis
The ability to react with alkalis is an important feature of acid oxides. For example, when sodium hydroxide and sulfur trioxide react, salt (sodium sulfate) and water are formed:
SO 3 + 2NaOH → Na 2 SO 4 + H 2 O
Acidic oxides include nitrogen dioxide. Its interesting feature is its reaction with alkali; two types of salts are found in products: nitrates and nitrites. This is explained by the ability of nitric oxide (IV) when interacting with water to form two acids - nitric and nitrous. Sulfur dioxide also reacts with alkalis, resulting in the formation of medium salts - sulfites, as well as water. The compound, when released into the air, greatly pollutes it, therefore, at enterprises using fuel with an admixture of SO 2, waste industrial gases are purified by spraying quicklime or chalk into them. You can also pass sulfur dioxide through lime water or sodium sulfite solution.
The role of binary oxygen compounds of non-metallic elements
Many acid oxides are of great practical importance. For example, carbon dioxide is used in fire extinguishers because it does not support combustion. Silicon oxide sand is widely used in the construction industry. Carbon monoxide is the starting material for the production of methyl alcohol. Phosphorus pentoxide is an acidic oxide. This substance is used in the production of orthophosphoric acid.
Binary oxygen compounds of nonmetals affect the human body. Most of them are toxic. We talked about the harmful effects of carbon monoxide earlier. Nitrogen oxides, especially nitrogen dioxide, have also been shown to have negative effects on the respiratory and cardiovascular systems. Acidic oxides include carbon dioxide, which is not considered a toxic substance. But if its volume fraction in the air exceeds 0.25%, a person experiences symptoms of suffocation, which can be fatal due to respiratory arrest.
In our article, we studied the properties of acid oxides and gave examples of their practical importance in human life.
13. Main classes of inorganic compounds. Oxides of metals and non-metals. Nomenclature of these compounds. Chemical properties of basic, acidic and amphoteric oxides.
Oxides– compounds of an element with oxygen.
Oxides that do not form acids, bases or salts under normal conditions are called non-salt-forming.
Salt-forming oxides are divided into acidic, basic and amphoteric (having dual properties). Nonmetals form only acidic oxides, metals form all others and some are acidic.
Basic oxides- These are complex chemical substances related to oxides that form salts upon chemical reaction with acids or acidic oxides and do not react with bases or basic oxides.
Properties:
1. Interaction with water:
Reaction with water to form a base (or alkali)
CaO+H2O = Ca(OH)2 (a well-known lime slaking reaction, which releases a large amount of heat!)
2. Interaction with acids:
Reaction with acid to form salt and water (salt solution in water)
CaO+H2SO4 = CaSO4+ H2O (Crystals of this substance CaSO4 are known to everyone under the name “gypsum”).
3. Interaction with acid oxides: salt formation
CaO+CO2=CaCO3 (Everyone knows this substance - ordinary chalk!)
Acidic oxides- these are complex chemical substances related to oxides that form salts upon chemical interaction with bases or basic oxides and do not interact with acidic oxides.
Properties:
Chemical reaction with water CO 2 +H 2 O=H 2 CO 3 - this substance is carbonic acid - one of the weak acids, it is added to carbonated water to create gas “bubbles”.
Reaction with alkalis (bases): CO 2 +2NaOH=Na 2 CO 3 +H 2 O- soda ash or washing soda.
Reaction with basic oxides: CO 2 +MgO=MgCO 3 - the resulting salt is magnesium carbonate - also called “bitter salt”.
Amphoteric oxides- these are complex chemical substances, also related to oxides, which form salts during chemical interaction with acids (or acidic oxides) and bases (or basic oxides). The most common use of the word "amphoteric" in our case refers to metal oxides.
Properties:
The chemical properties of amphoteric oxides are unique in that they can enter into chemical reactions with both bases and acids. For example:
Reaction with acid oxide:
ZnO+H2CO3 = ZnCO3 + H2O - The resulting substance is a solution of the salt “zinc carbonate” in water.
Reaction with bases:
ZnO+2NaOH=Na2ZnO2+H2O - the resulting substance is a double salt of sodium and zinc.
14. Grounds. Nomenclature of bases. Chemical properties of bases. Amphoteric bases, their reactions with acids and alkalis.
Bases are substances in which metal atoms are bonded to hydroxy groups.
If a substance contains hydroxy groups (OH) that can be broken off (like a single "atom") in reactions with other substances, then the substance is a base.
Properties:
Interaction with non-metals:
under normal conditions, hydroxides do not interact with most non-metals, with the exception of the interaction of alkalis with chlorine
Interaction with acid oxides to form salts: 2NaOH + SO 2 = Na 2 SO 3 + H 2 O
Interaction with acids - neutralization reaction:
with the formation of medium salts: 3NaOH + H3PO4 = Na3PO4 + 3H2O
the condition for the formation of medium salt is an excess of alkali;
with the formation of acid salts: NaOH + H3PO4 = NaH2PO4 + H2O
the condition for the formation of an acidic salt is an excess of acid;
with the formation of basic salts: Cu(OH)2 + HCl = Cu(OH)Cl + H2O
the condition for the formation of a basic salt is an excess of base.
Bases react with salts when a precipitate forms as a result of the reaction, the release of gas, or the formation of a poorly dissociating substance.
Amphoteric are called hydroxides that exhibit both basic and acidic properties depending on conditions, i.e. dissolve in acids and alkalis.
To all properties of bases, interactions with bases are added:
Al(OH)3 + NaOH = Na
Oxides of non-metals In oxides of non-metals, the bond between atoms is covalent polar. Among the oxides of molecular structure there are gaseous ones - CO2, CO, N2O, NO, NO2, Cl2O, CIO2, etc.; liquid (volatile) SO3, N2O3, Cl2O6, Cl2O7; solid (volatile) - P2O5, N2O5, SeO2; solid, very refractory non-volatile oxide SiO2 - a substance with an atomic crystal lattice. Non-metal oxides, as you know, are divided into two subclasses: non-salt-forming and salt-forming. Non-salt-forming oxides include SiO, IM20, NO, CO. All other non-metal oxides are salt-forming and acidic. Sulfur oxides. Sulfur forms two oxides - SO2 and SO3. Both oxides are acidic, i.e. interact with alkalis, basic oxides and water. (Write the equations for the corresponding reactions.) When sulfur is burned, hydrogen sulfide is completely burned, and sulfides are burned, sulfur oxide (IV) is formed, which is often called sulfur dioxide. (Write the equations for the corresponding reactions.) It dissolves well in water, forming weak sulfurous acid. It is unstable and decomposes into its original substances: H2O + SO2 ⇄ H2SO3 When interacting with alkalis, sulfur dioxide forms two series of salts - medium, or sulfites, and acidic - hydrosulfites. (Why!) Sodium hydrosulfite NaHSO3 and sodium sulfite Na2SO3, like sulfur dioxide itself, are used to bleach wool, silk, paper and straw, and also as preservatives to preserve fresh fruits and vegetables. Nitrogen oxides. Nitrogen forms many oxides, of which the best known are oxides with the entire spectrum of nitrogen oxidation states from +1 to +5: N2O, NO, N2O3, NO2 (or N2O4) and N2O5. Nitrogen oxides (I), (II) N2O and NO are non-salt-forming oxides; the rest are salt-forming acid oxides. Nitrogen(II) oxide NO is toxic. It is a colorless gas, odorless, almost insoluble in water. Nitric oxide (II) is easily oxidized by atmospheric oxygen into nitrogen oxide (IV): 2NO + O2 = 2NO2 Nitric oxide (IV) NO2 is a very toxic brown gas. If NO2 is dissolved in water in the presence of oxygen, then nitric acid is formed: 4NO2 + O2 + 2H2O = 4HNO3 Similarly, NO2 oxide reacts with alkali solutions: 4NO2 + 2Ca(OH)2 = Ca(NO3)2 + Ca(NO2)2 + 2H2O Nitrogen oxide (V) N2O5 - colorless crystals at temperatures below 33.3 °C. This is a typical acidic oxide, which corresponds to nitric acid. Interacts with water, alkalis, metal oxides. (Write the equations for the corresponding reactions.) Phosphorus(V) oxide. Phosphorus(V) oxide, or phosphorus anhydride, is formed when phosphorus burns in the form of thick white smoke consisting of small white crystals: 4P + 5O2 = 2P2O5 This is a typical acidic oxide that reacts with water, forming phosphoric acid, as well as with basic oxides and alkalis with the formation of various salts: medium, or phosphates, and acidic - hydrophosphates and dihydrogen phosphates: P2O5 + 6NaOH = 2Na3PO4 + 3H2O P2O5 + 4NaOH = 2Na2HPO4 + H2O P2O5 + 2NaOH + H2O = 2NaH2PO4 Carbon oxides. Carbon forms two oxides: carbon oxide (II) CO and carbon monoxide (IV) CO2. Carbon(II) monoxide has a number of synonyms: carbon monoxide, carbon monoxide, carbon monoxide. It is a colorless, odorless and tasteless gas; poorly soluble in water. As its trivial name suggests, carbon monoxide is very poisonous because it combines with hemoglobin in the blood and deprives it of its ability to carry oxygen. First aid for fumes is fresh air. Carbon monoxide (II) is a strong reducing agent, so it burns: 2CO + O2 = 2CO2 It also reduces metals from their oxides and is therefore used in pyrometallurgy. The basis of the blast furnace process are reactions, the overall equation of which is: Fe2O3 + 3CO = 2Fe + 3CO2 Carbon monoxide (IV) has many synonymous names: carbon dioxide, carbonic anhydride, carbon dioxide, and even the chemically incorrect name “carbon dioxide”. In industry, CO2 is produced by burning limestone, burning coke or hydrocarbons. In the laboratory, carbon dioxide is obtained by the action of hydrochloric acid on marble (Fig. 7.5): CaCO3 + 2HCl = CaCl2 + H2O + CO2 Fig. 7.5. Obtaining carbon dioxide in laboratory conditions The carbon dioxide molecule is formed by two double polar covalent bonds: O=C=O Due to the linear structure, despite the polarity of the bonds, the molecule is generally non-polar, therefore carbon dioxide is slightly soluble in water (0.88 volumes of CO2 in 1 volume water at a temperature of 20 ° C). When cooled under pressure, carbon dioxide turns into dry ice - a solid snow-like mass, which is pressed in industry and used to cool products, primarily ice cream. Under normal conditions, carbon dioxide is colorless, odorless and approximately 1.5 times heavier than air. In terms of properties, this is a typical acidic oxide, therefore it interacts with alkalis, basic oxides and water: CO2 + BaO = BaCO3 CO2 + Ca(OH)2 = CaCO3 + H2O The last reaction is a qualitative reaction to carbon dioxide, as it is accompanied by turbidity of lime water (color . inset, Fig. 27), which, however, disappears with further passage of carbon dioxide due to the transformation of insoluble calcium carbonate into soluble bicarbonate: CaCO3 + CO2 + H20 = Ca(HCO,)2 Fig. 27. Qualitative reaction to carbon dioxide: a – before transmission; b – after passing CO2 Carbon dioxide is used in the production of sugar (to purify beet juice), soda, urea, for the preparation of carbonated drinks, when extinguishing fires (Fig. 7.6), in gas lasers. Solid CO is a refrigerant. Rice. 7.6. To extinguish fires, the carbon dioxide fire extinguisher Silicon(IV) oxide is used. Many minerals are formed by silicon(IV) oxide SiO2. These include rock crystal, quartz, and silica. Silicon(IV) oxide forms the basis of such semiprecious stones as agate, amethyst, and jasper (color plate, Fig. 28). Fig.28. Quartz crystals (a) and cross section of agate (b) Silicon dioxide is a solid crystalline substance with a polymer structure, in which each silicon atom is bonded to four oxygen atoms by strong bonds: This is a typical acidic oxide that is insoluble in water. Its hydroxides - silicic acids - are obtained by indirect methods. SiO2 dioxide reacts with alkalis, forming silicates: SiO2 + 2KOH = K2 SiO 3 + H2O Silicon dioxide is fused to form silicates: with basic oxides also with SiO 2 + CaO = Ca SiO3 Silicon dioxide does not interact with acids (except for hydrofluoric acid). Silicon dioxide single crystals are used in ultrasound generators, sound-reproducing equipment, etc. Such crystals are grown under hydrothermal conditions from SiO 2 melts. Natural SiO 2 is a raw material in the production of silicon, quartz glass, a component of ceramics, ordinary glass and cement. Various quartz chemical vessels are made from molten quartz, which can withstand high temperatures and do not crack during sudden cooling. Questions 1. What types of oxides do nonmetals form? What state of aggregation is typical for them? 2. What types of crystal lattices are characteristic of solid non-metal oxides? Which oxides have a polymer structure? 3. Write the formulas of sulfur oxides, as well as reaction equations characterizing their properties. 4. Write the formulas of nitrogen oxides, as well as reaction equations characterizing their properties. 5. Write the formulas of carbon oxides, as well as reaction equations characterizing their properties. 6. Write the reaction equations with which you can carry out the following transformations: a) FeS2 ⟶ SO, ⟶ Na2SO3 ⟶ SO2 ⟶ SO3 ⟶ H2SO4 ⟶ Na2SO4 ⟶ BaSO4 b) N2 ⟶ NH3 ⟶ NO ⟶ NO2 ⟶ НNO3 ⟶ Cu(NO3)3 ⟶ NO2 c) CaCO3 ⟶ CO2 ⟶ CaCO3 ⟶ Ca(HCO3)2 ⟶ CaCO3 ⟶ CO2 d) SiO2 ⟶ Si ⟶ Mg2Si ⟶ SiH4 ⟶ SiO2 ⟶ Mg2SiO3 Consider the processes in the light of the theory of electrolytic dissociation and oxidation-reduction. 7. Compare the structure and properties of carbon(IV) and silicon(IV) oxides.
Oxides are called complex substances whose molecules include oxygen atoms in oxidation state - 2 and some other element.
can be obtained through the direct interaction of oxygen with another element, or indirectly (for example, during the decomposition of salts, bases, acids). Under normal conditions, oxides come in solid, liquid and gaseous states; this type of compound is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.
They are either salt-forming or non-salt-forming.
Salt-forming oxides- These are oxides that form salts as a result of chemical reactions. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, the corresponding acidic and normal salts. For example, Copper oxide (CuO) is a salt-forming oxide, because, for example, when it reacts with hydrochloric acid (HCl), a salt is formed:
CuO + 2HCl → CuCl 2 + H 2 O.
As a result of chemical reactions, other salts can be obtained:
CuO + SO 3 → CuSO 4.
Non-salt-forming oxides These are oxides that do not form salts. Examples include CO, N 2 O, NO.
Salt-forming oxides, in turn, are of 3 types: basic (from the word «
base »
), acidic and amphoteric.
Basic oxides These are the metal oxides that correspond to hydroxides belonging to the class of bases. Basic oxides include, for example, Na 2 O, K 2 O, MgO, CaO, etc.
Chemical properties of basic oxides
1. Water-soluble basic oxides react with water to form bases:
Na 2 O + H 2 O → 2NaOH.
2. React with acid oxides, forming the corresponding salts
Na 2 O + SO 3 → Na 2 SO 4.
3. React with acids to form salt and water:
CuO + H 2 SO 4 → CuSO 4 + H 2 O.
4. React with amphoteric oxides:
Li 2 O + Al 2 O 3 → 2LiAlO 2.
If the composition of the oxides contains a non-metal or a metal exhibiting the highest valence (usually from IV to VII) as the second element, then such oxides will be acidic. Acidic oxides (acid anhydrides) are those oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO 2, SO 3, P 2 O 5, N 2 O 3, Cl 2 O 5, Mn 2 O 7, etc. Acidic oxides dissolve in water and alkalis, forming salt and water.
Chemical properties of acid oxides
1. React with water to form an acid:
SO 3 + H 2 O → H 2 SO 4.
But not all acidic oxides react directly with water (SiO 2, etc.).
2. React with based oxides to form a salt:
CO 2 + CaO → CaCO 3
3. React with alkalis, forming salt and water:
CO 2 + Ba(OH) 2 → BaCO 3 + H 2 O.
Included amphoteric oxide includes an element that has amphoteric properties. Amphotericity refers to the ability of compounds to exhibit acidic and basic properties depending on conditions. For example, zinc oxide ZnO can be either a base or an acid (Zn(OH) 2 and H 2 ZnO 2). Amphotericity is expressed in the fact that, depending on the conditions, amphoteric oxides exhibit either basic or acidic properties.
Chemical properties of amphoteric oxides
1. React with acids to form salt and water:
ZnO + 2HCl → ZnCl 2 + H 2 O.
2. React with solid alkalis (during fusion), forming as a result of the reaction salt - sodium zincate and water:
ZnO + 2NaOH → Na 2 ZnO 2 + H 2 O.
When zinc oxide interacts with an alkali solution (the same NaOH), another reaction occurs:
ZnO + 2 NaOH + H 2 O => Na 2.
Coordination number is a characteristic that determines the number of nearby particles: atoms or ions in a molecule or crystal. Each amphoteric metal has its own coordination number. For Be and Zn it is 4; For and Al it is 4 or 6; For and Cr it is 6 or (very rarely) 4;
Amphoteric oxides are usually insoluble in water and do not react with it.
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