In chemistry, all the diversity inorganic substances: it is customary to divide into two groups - simple and complex. Simple substances are classified into metals and non-metals. And complex ones are derivatives of simple ones, formed by their interaction with oxygen, water and among themselves. This classification of inorganic substances in the form of a diagram is depicted as follows:
Rice. 2.1. Classification of inorganic compounds.
Classification of reactions in inorganic chemistry. In inorganic chemistry, reactions are distinguished: 1) compounds, 2) decomposition (both of which may or may not be redox reactions), 3) exchange, 4) substitutions, which are always redox. Reaction schemes and examples are given in table 2.1.
Table 2.1
Classification of reactions
Consider the preparation and properties of the most important classes of inorganic compounds.
OXIDES(oxides) - complex substances, consisting of two elements, one of which is oxygen in the oxidation state equal to -2. The general formula for any oxide is E x O y -2. Distinguish salt-forming (the main: Li 2 O, CaO, MgO, FeO; amphoteric: ZnO, Al 2 O 3, SnO 2, Cr 2 O 3, Fe 2 O 3; acidic: B 2 O 3, SO 3, CO 2, P 2 O 5 Mn 2 O 7) and non-salt-forming: N 2 O, NO, CO oxides. Elements with a variable oxidation state form several oxides (MnO, MnO 2, Mn 2 O 7, NO, N 2 O 3, NO 2, N 2 O 5). In the higher oxide, as a rule, the element is in the oxidation state equal to the group number.
According to the modern international nomenclature, the names of oxides are as follows: the word "oxide", then the Russian name of the element in the genitive case, the oxidation state of the element (if it is variable). For example: FeO - iron (II) oxide, P 2 O 5 - phosphorus (V) oxide.
Basic oxides these are those which correspond to hydroxides - bases. The main oxides are those that interact with acids to form salt and water. Basic oxides are formed only by metals in the oxidation state +1, + 2 (sometimes +3), for example: BaO, SrO, FeO, MnO, CrO, Li 2 O, Bi 2 O 3, Ag 2 O.
Obtaining basic oxides:
1) Oxidation of metals when heated in an oxygen atmosphere:
This method is practically inapplicable for alkali metals, which usually give peroxides upon oxidation; therefore, the oxides Na 2 O, K 2 O are extremely difficult to obtain.
2) Roasting of sulfides:
2CuS + 3O 2 = 2CuO + 2SO 2;
4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2.
3) Decomposition of hydroxides:
Cu (OH) 2 = CuO + H 2 O.
This method cannot be used to obtain alkali metal oxides.
4) Decomposition of salts of some oxygen-containing acids:
BaCO 3 = BaO + CO 2,
2Pb (NO 3) 2 = 2PbO + 4NO 2 + O 2
Basic oxide properties. Most basic oxides are ionic solid crystalline substances; metal ions are located at the nodes of the crystal lattice, which are sufficiently tightly bound to O 2- ions; therefore, the oxides of typical metals have high melting and boiling points.
Let us note one feature characteristic of oxides. The closeness of the ionic radii of many metal ions leads to the fact that in the crystal lattice of oxides, part of the ions of one metal can be replaced by ions of another metal. This leads to the fact that the law of constancy of composition is often not fulfilled for oxides, and mixed oxides of variable composition can exist.
1) Attitude to water.
The process of attaching water is called hydration, and the resulting substance is called hydroxide. Of the basic oxides, only oxides of alkali (Li, Na, K, Rb, Cs, Fr) and alkaline earth metals (Ca, Sr, Ba, Ra) interact with water.
Li 2 O + H 2 O = 2LiOH;
BaO + H 2 O = Ba (OH) 2.
Most of the basic oxides do not dissolve in water and do not interact with it. Their corresponding hydroxides are obtained indirectly - by the action of alkalis on salts (see below).
2) Attitude towards acids.
CaO + H 2 SO 4 = CaSO 4 + H 2 O;
FeO + 2HCl = FeCl 2 + H 2 O.
3) Relation to acidic and amphoteric oxides.
Basic oxides of alkali and alkaline earth metals during alloying interact with solid acidic and amphoteric oxides, as well as with gaseous acidic oxides when normal conditions.
CaO + CO 2 = CaCO 3;
3BaO + P 2 O 5 = Ba 3 (PO 4) 2;
fusion
Li 2 O + Al 2 O 3 = 2LiAlO 2.
fusion
Basic oxides of less active metals interact only with solid acidic oxides during fusion.
Acidic oxides- oxides, which, when interacting with bases, form salt and water. Acidic oxides correspond to hydroxides - acids. Acid oxides are oxides of non-metals in various oxidation states, or metal oxides in a high oxidation state (+4 and higher). Examples: SO 2, SO 3, Cl 2 O 7, Mn 2 O 7, CrO 3.
The chemical bond in acidic oxides is covalent polar. Under normal conditions, acidic oxides of non-metals can be gaseous (CO 2, SO 2), liquid (N 2 O 3, Cl 2 O 7), solid (P 2 O 5, SiO 2).
Getting acidic oxides.
1) Oxidation of non-metals:
2) Oxidation of sulfides:
2ZnS + 3O 2 = 2ZnO + 2SO 2
3) Displacement of fragile weak acids from their salts:
CaCO 3 + 2HCl = CaCl 2 + CO 2 + H 2 O.
Properties of acidic oxides.
1) Attitude to water.
Most acidic oxides dissolve in water, chemically interacting with it and forming acids:
SO 3 + H 2 O = H 2 SO 4,
CO 2 + H 2 O = H 2 CO 3.
2) Relation to the grounds.
Acidic oxides interact with soluble bases - alkalis, forming salt and water.
SO 2 + 2NaOH = Na 2 SO 3 + H 2 O;
P 2 O 5 + 6NaOH = 2Na 3 PO 4 + 3H 2 O
fusion
3) Relation to basic and amphoteric oxides.
Solid acidic oxides react with basic and amphoteric oxides upon fusion. Liquid and gaseous oxides interact with oxides of alkali and alkaline earth metals under normal conditions.
P 2 O 5 + 3CuO = Cu 3 (PO 4) 2;
fusion
3SiO 2 + Al 2 O 3 = Al 2 (SiO 3) 3
fusion
Amphoteric oxides interact with acids and alkalis, exhibiting the properties of acidic and basic oxides. They correspond to amphoteric hydroxides. They are all solids, insoluble in water. Examples of amphoteric oxides: ZnO, BeO, SnO, PbO, Al 2 O 3, Cr 2 O 3, Sb 2 O 3, MnO 2.
Properties of amphoteric oxides.
Amphoteric oxides react with acids as basic:
Al 2 O 3 + 6HCl = 2AlCl 3 + 3H 2 O,
and with alkalis - as acidic. The composition of the reaction products depends on the conditions. When fusing:
ZnO + 2NaOH = Na 2 ZnO 2 + H 2 O;
Sodium zincate
In an alkali solution, a soluble complex salt is formed containing a hydroxocomplex ion:
ZnO + 2NaOH + H 2 O = Na 2
Sodium tetrahydroxozincate
Non-salt-forming oxides - these are oxides of non-metals, which do not correspond to hydroxides and salts. Examples: CO, N 2 O, NO, SiO.
Oxides are widespread in nature. So water, the most common oxide, covers 71% of the planet's surface. Silicon oxide (IV) in the form of 400 varieties of quartz makes up 12% of the mass of the earth's crust. Carbon monoxide (IV) (carbon dioxide) is contained in the atmosphere - 0.03% by volume, as well as in natural waters. The most important ores: hematite, magnetite, brown iron ore are composed of various iron oxides. Bauxites contain aluminum oxide, etc.
Foundations- complex substances in which there is one or more OH - hydroxo groups per metal atom. The oxidation state of metal atoms is usually +1, +2 (rarely +3). The general formula of the bases is Me (OH) x, where x is the number of hydroxo groups - the acidity of the base. (MeOH - one-acid base, Me (OH) 2 - two-acid base, Me (OH) 3 - tri-acid base).
The names of the bases are given as follows: "hydroxide", then the Russian name of the metal in the genitive case, and in parentheses in Roman numerals - the oxidation state, if it is variable. For example: KOH - potassium hydroxide, Ni (OH) 2 - nickel (II) hydroxide.
Under normal conditions, bases are solids, except for ammonium hydroxide - an aqueous solution of ammonia NH 4 OH (NH 4 + is an ammonium ion, which is part of ammonium salts).
Classification of bases. Depending on the attitude to water, the bases are divided into soluble (alkalis) and insoluble. Soluble bases - alkalis include only hydroxides of alkali and alkaline earth metals (LiOH, NaOH, KOH, CsOH, RbOH, FrOH, Ca (OH) 2, Sr (OH) 2, Ba (OH) 2, Ra (OH) 2) a also aqueous ammonia solution. All other bases are practically insoluble in water.
From the point of view of the theory of electrolytic dissociation, bases are electrolytes that dissociate in an aqueous solution to form only hydroxide ions as anions:
Ме (ОН) x Ме х + + хОН -.
The presence of hydroxide ions in the solution is determined using indicators: litmus (blue), phenolphthalein (raspberry), methyl orange (yellow). Insoluble bases do not change the color of the indicators.
And their derivatives. All other substances are inorganic.
Classification of inorganic substances
Inorganic substances are divided into simple and complex in composition.
Simple substances consist of atoms of one chemical element and are subdivided into metals, non-metals, noble gases. Complex substances are made up of atoms of different elements chemically bonded to each other.
Complex inorganic substances in composition and properties are divided into the following most important classes: oxides, bases, acids, amphoteric hydroxides, salts.
Lesson content lesson outline support frame lesson presentation accelerative methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photos, pictures, charts, tables, schemes humor, jokes, jokes, comics parables, sayings, crosswords, quotes Supplements abstracts articles chips for the curious cheat sheets textbooks basic and additional vocabulary of terms others Improving textbooks and lessonsbug fixes in the tutorial updating a fragment in the textbook elements of innovation in the lesson replacing obsolete knowledge with new ones For teachers only perfect lessons calendar plan for a year guidelines discussion agenda Integrated lessonsSimple substances and chemical compounds. Oxides: basic, acidic and amphoteric. Nomenclature of oxides. Dependence of the acid-base character of oxides on the position in the periodic system and the oxidation state of the element. Chemical interaction between oxides with the formation of salts. Basic and amphoteric hydroxides, acids. Their nomenclature and receipt. Salts: normal, acidic and basic. Salt nomenclature. Obtaining and properties of salts.
Nomenclature and properties of complex compounds.
Inorganic compounds are distinguished by their composition (binary and multielement) and functional characteristics. TO binary connections include compounds of elements with oxygen ( oxides), halogens ( halides- fluorides, chlorides, bromides, iodides), chalcogenes ( chalcogenides- sulfides, selenides, tellurides), nitrogen (nitrides), phosphorus (phosphides), carbon (carbides), silicon ( silicides), as well as compounds of metals with each other ( intermetallic compounds) and hydrogen ( hydrides). Among multi-element compounds emit hydroxides(substances containing hydroxide groups - OH), derivatives of hydroxides - salt, and complex compounds, hydrates and crystal hydrates.
In accordance with the IUPAC rules, the name of any substance must unambiguously indicate its composition. Therefore, the basis of systematic. The name of any substance must unambiguously indicate its composition, therefore, the system of compounds, these ratios of the names of inorganic substances, are based on the names of the elements that make up their composition.
The name of a binary compound is formed from the Latin root of the name of a more electronegative element with the ending -id and the Russian name of a less electronegative element in the genitive case. When writing a formula for a substance, the less electronegative element is to the left. For example, Al 2 O 3 is aluminum oxide, AgI is silver iodide, OF 2 is oxygen fluoride. For some elements, the roots of their Russian names coincide with the roots of Latin, with the exception of the elements presented in table 1 below:
Table 1
Chemical element names
| Character notation | Russian name | Latin name |
| Ag | Silver | Argent |
| As | Arsenic | Ars-, arsen- |
| Au | Gold | Aur- |
| C | Carbon | Carb-, carbon- |
| Cu | Copper | Cupr- |
| Fe | Iron | Ferr- |
| H | Hydrogen | Hydr-, hydrogen- |
| N | Nitrogen | Nitre- |
| Ni | Nickel | Nikkol- |
| O | Oxygen | Ox-, oxygen- |
| Pb | Lead | Plumb |
| S | Sulfur | Sulf-, thio- |
| Sb | Antimony | Stib- |
| Si | Silicon | Sil-, silits-, silic- |
| Hg | Mercury | Merkur- |
| Mn | Manganese | Mangan- |
| Sn | Tin | Stann |
To designate the quantitative composition, Greek numerals are used as a prefix, for example, Hg 2 Cl 2 - dichloride dirtuti, CO - carbon monoxide, CO 2 - carbon dioxide.
Numeral prefixes have the following names:
1 - Mono- 5 - Penta 9 -Nona-
2 - Di- 6 - Hexa- 10 -Deca
3 - Three- 7- Hepta- 11 -Undeca-
4 - Tetra- 8 - Octa- 12- Dodeca-.
The name of a multi-element compound reflects its functional characteristics, such as belonging to hydroxides or acids. Hydroxides are compounds of oxides with water. They are divided into main, exhibiting the properties of bases in chemical reactions, acidic- showing the properties of acids, amphoteric- capable of exhibiting both acidic and basic properties.
To the class grounds, according to the theory of electrolytic dissociation, include substances that can dissociate in an aqueous solution to form hydroxide ions OH -: The name of the main hydroxide (or base) is formed from the word "hydroxide" and the name of the element in the genitive case, after which, if necessary, indicate the oxidation state of the element. For example, NaOH is sodium hydroxide, Fe (OH) 2 is iron (II) hydroxide or iron dihydroxide. The general base formula can be written as M (OH) m, where M is a metal, m is the number of hydroxyl groups, or acidity of the base.
Substances that can dissociate in solution to form hydrogen ionsН +, in accordance with the theory of electrolytic dissociation belongs to the class acids.
Acids, depending on the presence of oxygen in their composition, are divided into oxygenated and on oxygen-free... In general, the acid formula can be written as H n A, where A is an acid residue, n is the number of hydrogen atoms in a molecule, or acid basicity.
The systematic name of an acid includes the name of two parts: electropositive (hydrogen atoms) and electronegative (acid residue, anion). In the name of the anion, first indicate the oxygen atoms (-oxo), then the acid-forming element with the addition of the suffix -at, then in parentheses the absolute value of the oxidation state of this element. For example, H 2 CO 3 is hydrogen trioxocarbonate (IY), H 2 SO 4 is hydrogen tetraoxosulfate (VI). If there are other atoms in the anion, the name of the anion is made up of the Latin roots of the names of the corresponding elements and the connecting vowel -o in the order of their placement in the formula from right to left. For example, H 2 SO 3 (O 2) is hydrogen peroxotrioxosulfate (VI), H 2 SO 3 S is hydrogen thiotrioxosulfate (VI). The systematic names of the most commonly used acids are presented in Table 3.
The traditional name consists of two words - an adjective derived from the root of the name of the acid-forming element, and the word "acid", for example, H 2 SO 4 - sulfuric acid, HNO 3 - nitric acid.
Amphoteric hydroxides able to dissociate in aqueous solutions both by the type of bases and by the type of acids, for example,
When interacting with acids, they exhibit the properties of bases, and when interacting with bases, the properties of acids. Their names are made up according to the scheme corresponding to the main hydroxides.
table 2
The names of the most important acids and their salts
| Acid formula | Names | |
| Acid | Salt | |
| HAlO 2 | Meta-aluminum | Metaaluminate |
| HAsO 3 | Metamarsenic | Metaarsenate |
| H 3 AsO 4 | Orthomarsenic | Orthoarsenate |
| HAsO 2 | Meta-arsenic | Metaarsenite |
| H 3 AsO 3 | Orthmysyak | Orthoarsenite |
| HBO 2 | Metabolic | Metaborate |
| H 3 BO 3 | Orthographic | Ortoborate |
| H 2 B 4 O 7 | Four-run | Tetraborate |
| HBr | Hydrogen bromide | Bromide |
| HOBr | Bromine | Hypobromite |
| HBrO 3 | Bromic | Bromate |
| HCOOH | Formic | Formate |
| CH 3 COOH | Acetic | Acetate |
| HCN | Hydrogen cyanide | Cyanide |
| H 2 CO 3 | Coal | Carbonate |
| H 2 C 2 O 4 | Sorrel | Oxalate |
| HCl | Hydrogen chloride | Chloride |
| HOCl | Hypochlorous | Hypochlorite |
| HClO 2 | Chloride | Chlorite |
| HClO 3 | Chloric | Chlorate |
| HClO 4 | Chlorine | Perchlorate |
| HCrO 2 | Metachromous | Metachromite |
| H 2 CrO 4 | Chrome | Chromate |
| H 2 Cr 2 O 7 | Two-chrome | Dichromat |
| HI | Hydrogen iodide | Iodide |
| HOI | Iodine | Hypoioditis |
| HIO 3 | Iodic | Iodate |
| HIO 4 | Iodine | Periodat |
| HMnO 4 | Manganese | Permanganate |
| H 2 MnO 4 | Manganese | Manganat |
| H 2 MoO 4 | Molybdenum | Molybdate |
| HN 3 | Hydrogen azide (hydrogen nitrogen) | Azide |
| HNO 2 | Nitrogenous | Nitrite |
| HNO 3 | Nitrogen | Nitrate |
| HPO 3 | Metaphosphoric | Metaphosphate |
| H 3 PO 4 | Orthophosphoric | Orthophosphate |
| H 4 P 2 O 7 | Biphosphoric (pyrophosphoric) | Diphosphate (pyrophosphate) |
| H 3 PO 3 | Phosphorous | Phosphite |
| H 3 PO 2 | Phosphorous | Hypophosphite |
| H 2 S | Hydrogen sulfide | Sulfide |
| HSCN | Rodan hydrogen | Rodanid |
| H 2 SO 3 | Sulphurous | Sulfite |
| H 2 SO 4 | Sulfur | Sulfate |
| H 2 S 2 O 3 | Thiosernaya | Thiosulfate |
| H 2 S 2 O 7 | Two-sided (pyroserine) | Disulfate (pyrosulfate) |
| H 2 S 2 O 8 | Peroxodvusernaya (supersulfuric) | Peroxidosulfate (persulfate) |
| H 2 Se | Hydrogen selenide | Selenide |
| H 2 SeO 3 | Selenium | Selenite |
| H 2 SeO 4 | Selenium | Selenate |
| H 2 SiO 3 | Silicon | Silicate |
| HVO 3 | Vanadium | Vanadat |
| H 2 WO 4 | Tungsten | Tungstate |
Salt are the products of replacement of hydrogen ions of an acid by a metal or hydroxyl groups of a base by an acid residue. Depending on the completeness of substitution of hydrogen atoms or hydroxyl groups, salts are subdivided into average(or normal), for example K 2 SO 4, sour(or hydrosalts) for example NaHCO 3, and the main(or hydroxosalts) for example FeOHCl. Distinguish also double salts formed by two metals and one acidic residue (КАl (SO 4) 2), and mixed salts formed with one metal and two acidic residues (CaClOCl). The names of the salts are due to the systematic names of the corresponding acids, for example, K 2 SO 4 - potassium tetraoxosulfate (VI), NaHCO 3 - hydrogen-sodium trioxocarbonate (IY), FeOHCl or, more precisely, FeClOH - iron (II) hydroxy chloride.
In the presence of numeric prefixes (1, 2,...) In the name of the substance, for a correct understanding of the formula, multiplication of the prefix is used (for example, КАl 3 (SO 4) 2 (OH) 6 - trialuminium-potassium hexahydroxide bis (sulfate)). The prefix names are as follows:
1 Monoxide 5 Pentakis- 9 Nonakis-
3 Tris- 7Heptakis- 11Undecasis-
Traditional names of salts also contain the names of anions in the nominative case and the names of cations in the genitive case (see Table 2), for example, K 2 SO 4 - potassium sulfate, NaHCO 3 - sodium bicarbonate, FeOHCl - iron (II) hydroxychloride.
Oxides depending on the characteristic functions performed in chemical reactions, they are divided into salt-forming(among them there are basic, acidic and amphoteric) and non-salt-forming.
Basic oxides form salts when interacting with acids or acidic oxides. They correspond to bases, since they form them when interacting with water, for example, CaO - Ca (OH) 2.
Acidic oxides form salts by reaction with bases or basic oxides. They can be obtained by separating water from the corresponding acid. Therefore, they are also called anhydrides acids, for example SO 3 - anhydride H 2 SO 4.
Amphoteric oxides form salts both when interacting with acids and when interacting with bases, for example, ZnO, Al 2 O 3.
Hydrates and crystal hydrates- compounds containing water, for example, NH 3 ∙ H 2 O ∙ Fe 2 O 3, n H 2 O, СuSO 4 ∙ 5Н 2 О. Both systematic and traditional names of such compounds begin with the word "hydrate" with the corresponding prefix: NH 3 ∙ Н 2 О - ammonia hydrate, Fe 2 O 3 ∙ n H 2 O - iron (III) oxide polyhydrate, CuSO 4 ∙ 5H 2 O - copper (II) tetraoxosulfate pentahydrate, or copper (II) sulfate pentahydrate.
Lecture 5. Chemical thermodynamics
Chemical thermodynamics. Thermodynamic systems. Thermodynamic parameters. Thermodynamic process. Internal energy, warmth, work. The first law of thermodynamics. Enthalpy. Hess's law and consequences from it. Entropy. The second law of thermodynamics. Gibbs free energy and Helgmoltz free energy.
Chemical thermodynamics.
Thermodynamics studies the mutual transformation of heat, work and different types energy. The word thermodynamics comes from the Greek words thermos (heat) and dynamos (strength, power). The term thermodynamics was introduced by Thomson in 1854, who used it as a synonym for heat and work.
Thermodynamics is based on three fundamental principles called the principles of thermodynamics. They are a generalization of numerous experimental facts.
The application of thermodynamic methods to chemical reactions and processes gave rise to the appearance of chemical thermodynamics. The subject of the study of chemical thermodynamics is the transformation of energy during chemical interactions that occur during the course of chemical processes.
Thermodynamic systems. Thermodynamic parameters. Thermodynamic process.
Thermodynamics uses a number of concepts and model concepts, such as thermodynamic system, state parameters, energy, heat, work. Let's move on to considering them.
The concept of a system means that part of the material world that we are exploring. For example, a beaker with water, a reactor at a chemical plant. The rest of the material world, outside the conventionally distinguished system, is called the environment.
Thermodynamic system- is called a set of bodies that can actually or mentally be isolated from the environment. The system is separated from the environment by a boundary through which material exchange takes place - mass transfer and / or heat transfer. Depending on the degree of isolation, open, closed, isolated systems are distinguished.
Open systems Are systems that exchange matter, mechanical work, heat and radiation with the external environment. For example, sodium carbonate (soda) is mixed in a test tube with a solution of hydrochloric acid. As a result, the reaction proceeds
Na 2 CO 3 + HCl = NaCl + CO 2 + H 2 O.
In the chemical process under consideration, the mass of the system decreases, since carbon dioxide evaporates, and heat is released, part of which goes to heating the surrounding air.
Closed systems- systems that do not exchange matter with the external environment, but interact with it through mechanical work, heat exchange and radiation. An example of a closed system is a test tube in which soda is mixed with hydrochloric acid, closed with a stopper.
Isolated systems- systems that do not interact with the external environment. There is no exchange of matter or energy between the isolated system and the environment. In practice, the concept of absolutely isolated systems does not exist; it is an abstract, mental construction. An example of a roughly isolated system is a thermos or Dewar flask.
The system can be in one state or another. State system is a set of physical and chemical properties that characterize the system.
The state of the thermodynamic system is characterized by status parameters: pressure, volume, temperature, concentration.
Pressure (P) characterizes the mobility of molecules and is determined by the force with which gaseous particles act on the walls of the vessel. Pressure is measured in Pa (Pascal), atm (atmosphere), mm Hg. Art. (millimeters of mercury): 1 atm = 760 mm Hg. Art. = 101325 Pa.
Volume (V) characterizes the part of the space occupied by the substance. Measure the volume in m 3 (cubic meter), cm 3 (cubic centimeter), l (liter), ml (milliliter): 1 m 3 = 1000 l; 1L = 1000 ml.
Temperature (T, t) characterizes the degree of heating of the system and is measured in K (Kelvin scale) and 0 C (Celsius scale). To convert temperatures expressed in different scales, use the expression
T = t + 273 (1).
Concentration substance (c) determines the quantitative composition of the solution, mixture, melt. For example, molar concentration is the number of moles of a substance in 1 liter of a solution or mixture, denoted by mol / l.
Thus, the set of parameters (p, V, T) is called the state of the system, since it is considered that it completely determines the state. Thermodynamic parameters are macroscopic quantities measured in an experiment. They are functions of the state, that is, their change is determined only by the initial and final states and does not depend on the path of the process that resulted in this change.
∆ T = T end - T start = T 2 - T 1 (2).
For infinitesimal changes, you can write
∆ Т = dT (3).
If the quantity is not a function of the state, but depends on the path of the process, then it is a function of the transition. In this case, the infinitesimal change in the value of A is written in the form
∆А = δА (4).
Thus, the sign ∆ - denotes a change in a quantity that is a function of the state, the sign δ - denotes a change in a quantity that is a function of the transition.
Thermodynamic parameters are not independent, but are related by the equation of state. An example of such an equation is the equation of state for an ideal gas, which is called the Mendeleev-Cliperon equation
where n is the number of moles of gas; R is the gas constant.
The state of a thermodynamic system can change over time. Usually, such a change is recorded when measuring one of the thermodynamic parameters. Therefore, in thermodynamics, the concept of a thermodynamic process is used.
Thermodynamic process is called any change in the system associated with a change in at least one parameter. Thus, a thermodynamic process is a change in the state of a system. The following processes are distinguished: isochoric (V = const), isobaric (p = const), isothermal (T = const), adiabatic (heat Q = 0).
Thermodynamic processes are:
-reversible when the transition from one state to another and back can occur along the same path, and after returning to the initial state, no macroscopic changes remain in the environment; an example of a reversible process is compression and extension of a spring;
- irreversible or non-equilibrium when the parameters change with a finite speed and the transition from one state to another and back cannot occur along the same path, as a result, macroscopic changes remain in the environment; an example of an irreversible process is plastic deformation of a metal wire.
Internal energy, warmth, work.
In addition to thermodynamic parameters, other thermodynamic quantities, such as work and heat, play an important role. They are a quantitative measure of thermodynamic processes and characterize the participation of the system in thermodynamic processes. Work and heat are energy characteristics. Therefore, consider the concept of energy.
Energy comes from the Greek word "action" - is a measure of the ability to do work. Energy is measured in J (Joule). Numerous observations and experimental facts indicate the following properties of energy.
Energy does not disappear and does not arise from nothing.
Energy can exist in a variety of forms.
In an isolated system, energy can change from one form to another, but its amount remains constant.
If the system is not isolated, then its energy can change, but with a simultaneous change in energy external environment by exactly the same amount.
Any system has a certain amount of energy, that is, energy is an integral property of the system.
For the consideration of chemical processes, the following forms of energy are important: solar, mechanical, chemical, nuclear, electrical.
There are the following types of energy: kinetic (energy of motion), potential (energy of position and interaction) and internal energy (energy of state).
Chemistry studies the transformation of chemicals, of which more than 20 million are known today. Therefore, it is important to classify chemical compounds, that is, to combine them into groups or classes with similar properties. This lesson will help you study the modern classification of inorganic substances and introduce you to the rules for compiling their names by chemical formulas.
Topic: The main classes of compounds, their properties and typical reactions
Lesson: Classification and nomenclature of inorganic substances
Inorganic substances are usually divided into two groups according to their composition: a small group of simple substances (there are about 400 of them) and a very numerous group of complex substances. Simple substances consist of one chemical element, and complex substances - of several.
All simple substances can be divided into metals and non-metals, since their properties are significantly different. Metals have a metallic luster, high thermal and electrical conductivity, are plastic, and exhibit reducing properties. Non-metals have very different physical and chemical properties, but, as a rule, they are brittle in the solid state, poorly conduct electric current and heat.
The border between metals and non-metals is arbitrary. There are substances that have the properties of both metals and non-metals. For example, gray arsenic has a metallic luster and electrical conductivity (Fig. 1), while another allotropic modification, yellow arsenic, has purely non-metallic properties.
Rice. 1. Gray arsenic
Complex substances are usually divided into classes: oxides, acids, bases, amphoteric hydroxides and salts (Fig. 2). This classification is imperfect, since there is no room for ammonia, metal compounds with phosphorus, nitrogen, carbon, etc.
Rice. 2. Classification of inorganic substances
Oxides can be salt-forming and non-salt-forming. Salt-forming oxides correspond to hydroxides and salts with an element in the same oxidation state as in the oxide. Non-salt-forming oxides have no corresponding hydroxides and salts. There are few such oxides: N 2 O, NO, SiO, CO.
Salt-forming oxides, depending on the acid-base nature, are divided into acidic, amphoteric and basic.
Basic oxides are formed by metals with small oxidation states +1, +2. Amphoteric oxides are formed by transition metals with oxidation states +3, +4, as well as Be, Zn, Sn, Pb. Acidic oxides are formed by non-metals, as well as metals with an oxidation state greater than +4. Rice. 3.
Rice. 3. Classification of oxides
Acids are complex substances consisting of hydrogen atoms that can be replaced by metals and acid residues. Acids can be divided into groups by oxygen content: oxygen-containing (for example, HNO 3, H 2 SO 4, H 3 PO 4) and anoxic (HI, H 2 S). Rice. 4.
Rice. 4. Classification of acids
Bases are complex substances consisting of metal cations and one or more hydroxide anions. The classification of grounds can be based on different signs. For example, their relationship to water. On this basis, the bases are divided into water-soluble (alkali) and water-insoluble. Rice. 5.
Rice. 5. Classification of grounds
Amphoteric hydroxides are complex substances that have the properties of both acids and bases, and therefore their formulas can be written in different forms:
Zn (OH) 2 = H 2 ZnO 2
base form acid form
There are several types of salts (Fig. 6).
Rice. 6. Types of salts
Medium salts are composed of metal (or ammonium) cations and acid anions. Acid salts, in addition to metal cations, contain hydrogen cations and an acid residue anion. Basic salts contain hydroxide anions.
If the salt is formed by two types of metal cations and one anion, then it is called double. For example, potassium aluminum sulfate KAl (SO 4) 2.
Salts with two different anions and one cation are called mixed. For example, Ca (OCl) Cl is calcium chloride-hypochlorite.
Complex salts contain a complex ion, which is usually enclosed in square brackets.
Bibliography
- Kuznetsova N.E., Litvinova T.N., Levkin A.N. Chemistry: Grade 11: a textbook for general students. institutions (profile level): in 2 hours. Part 2. - M .: Ventana-Graf, 2008. (§55)
- Radetskiy A.M. Chemistry. Didactic material. 10-11 grades. - M .: Education, 2011.
- Khomchenko I.D. Collection of tasks and exercises in chemistry for high school... - M .: RIA "New Wave": Publisher Umerenkov, 2008. (p. 27-30)
- Encyclopedia for children. Volume 17. Chemistry / Chap. ed. V.A. Volodin, led. scientific. ed. I. Leenson. - M .: Avanta +, 2003. (p. 156-159)