BASIC CONCEPTS AND LAWS OF CHEMISTRY 

LAW OF MASS CONVERSATION(M.V. Lomonosov, 1748, A. Lavoisier 1789)

 The mass of the substances entering into a reaction equal the mass of the substances formed as a result of the reaction.Atomic-molecular concept explains this law by following manner: as a result of chemical reactions atoms do not appear and do not disappear, but occurs their rearrangement (i.e. chemical conversion-process of bond breakup between atoms with another bond formation, as a result of such conversation the molecules of source substances transform into the molecules of products of reaction). As far as a number of atoms before and after reaction stays unchangeable their general mass also must not change. At term «mass» has understood a value-characterizing amount of matter.At the beginning of 20 century a formulation of mass conversation law was revising in connection with the appearance of relativity theory (A. Einstein, 1905), according to which the mass of substance depends on its velocities, and consequently characterizes not only matter amount, as well as its motion. An Energy E, obtained by substance, is connected with increasing its mass m by the correlation E = m * c2, where c is a light velocity. This correlation is not used in chemical reactions, since 1kJ of energy is corresponding ~ 10-11g mass changing and practically cannot be measured.In nucleus reactions, where E greater in 106 times than in chemical reactions, m should take into account.Originating from the mass conservation law equations of chemical reactions is possible to form with the following calculations. It is a basis of quantitative chemical analysis. 

Arranging of chemical equations Include three stages:1.      Record formulas of substances: entered in the reaction (on the left) and products of reaction

(on the right), having connected them on the sense by signs «+», «»: 

HgO Hg + O2

 2.      Selection the coefficients for each substance so that amount of atoms of each element in left

and right part of equation will be equally: 

2HgO 2Hg + O2

 3.      Checking a number of atoms of each element in left and right parts of equation. 

Calculations on chemical equations Calculations on chemical equations (stoichiometric calculations) are based on the mass conservation law of substances. In real chemical processes because of incomplete running chemical reactions and losses a products mass usually less theoretically calculated.Yield of reaction ( ) is a ratio of real product mass (mr) to theoretically possible (mt), expressed in shares of units or percent.If in conditions of problems a yield of reactions products does not specified, its take in calculations as 100% (quantitative output). 

= mr  

––– * 100%mt  

 example 1Calculated the mass of copper formed when reduction 8 g copper oxide by hydrogen. The yield of reaction – 82% from theoretical. solution

CuO + H2 Cu + H2O 1.      Calculate a theoretical yield of copper on the equation of reaction: 80 g (1 g-mol) CuO when

reducing can form 64 g (1 g-mol) Cu. 8 g CuO – X g Cu. 

X =8 * 64––––

80= 6.4 g

 2.      Define how much grams of copper will be formed at 82% yield of product

 6.4 g –– 100% 100% yield (theoretical)

X g –– 82%   

X =6.4 * 82––––––

100= 5.25 g

 example 2Calculate the yield of reaction of tungsten preparation by aluminizing, if from 33.14 g of ore concentrate, containing WO3 and non-reduce admixtures (mass share of admixtures 0.3), were obtained 12.72 g of metal. solution1.      Define the WO3 mass (g) in 33.14 g of ore concentrate. (WO3) = 1.0 – 0.3 = 0.7m(WO3) = (WO3) * more = 0.7 * 33.14 = 23.2 g 2.      Define the theoretical yield of tungsten as a result of reduction 23.2 g by aluminum powder. 

WO3 + 2Al Al2 + O3 + W When reducing 232 g (1g-mol) WO3 form 187 g (1g-mol) W, but at 23.2 g WO3 – X g W 

X =23.2 * 187

—————232

= 18.7 g W

 3.      Calculate the practical yield of tungsten 

18.7 g W –– 100%12.72 g W –– Y%

 

Y =12.72 * 100–––––––––

18.7= 68 %

 

example 3How much grams of barium sulphate will be formed at pouring together the solutions containing 20.8 g of barium chloride and 18.0 g of sodium sulphate? solution

BaCl2 + Na2SO4 BaSO4 + 2NaCl Calculation of product amount carries on the source substance, which is taken in the deficit.a)     Beforehand define which substance stand in the deficit.

Mark the amount of Na2SO4 – X208 g (1 g-mol) BaCl2 react with 132 g (1 g-mol) Na2SO4

20.8 g with X g 

X =20.8 * 132

—————208

= 13.2 g Na2SO4

 We found, that on the reaction with 20.8 g BaCl2 will be spend 13.2 g Na2SO4, but we have 18.0 g. Thus, sodium sulphate in the reaction is taken in the excess and further calculation is necessary to carry on the BaCl2, which is taken in deficit.

b)     Define quantity of BaSO4 precipitate. 208 g (1 g-mol) BaCl2 form 233 g BaSO4.20.8 g –– Y g.

     233 * 20.8    Y = ————— = 23.3 g    208    

 Law of constant composition

For the first time has formulated by G. Prust (1808) "All individual chemical substances have constant quality and quantity composition and definite chemical structure and does not depend on how this substance was prepared."From the law of constant composition follows that at complex substance formation the elements combine with each other in definite mass proportions. exampleCuS- copper sulphide. m (Cu) : m (S) = Ar (Cu) : Ar (S) = 64 : 32 = 2 : 1To get copper sulphide (CuS) it is necessary to mix up the powders of copper and sulphur in mass relations 2:1.If taken amounts of source substances do not correspond their correlation in the chemical formula of compound one of them stay in the excess.For instance, if take 3 g. copper and 1 g. sulphur than after the reaction 1 g. copper, which did not enter in the chemical reaction will stay.Substances with non-molecular structure do not possess strictly constant composition. Their composition depends on conditions of preparation.The mass share of element (e) shows what part forms the mass of given element from the whole mass of substance: where n – a number of atoms; Ar(e) – relative atomic mass of element; Mr – relative molecular mass of substance. 

    n * Ar(e)

(e) = ———    Mr

 Knowing the quantitative element composition of substance its simplest molecular formula is possible to determine:1.      Mark formula of compounds Ax By Cz.

2.      Calculate an attitude X: Y: Z through the mass shares of elements: 

    х * Ar(А)     y * Ar(B)     z * Ar(C)

(A) = ————— (B) = ————— (C) = —————    Mr(AxByCz)     Mr(AxByCz)     Mr(AxByCz)

 

X =(A) * Mr

—————Ar(А)

Y =(B)  * Mr

—————Ar(B)

Z =(C)  * Mr

—————Ar(C)

 

x : y : z =(A)

——Ar(А)

:(B)

——Ar(B)

:(C)

——Ar(C)

 3.      Obtained numerals divide on the least for getting total numbers.4.      Write a formula of compound. 

Law of multiple proportions(D. Dalton, 1803)

 If two elements form several chemical compounds with each other, then the masses of one of the elements corresponding to the same mass of the other element in these compounds are in a simple integral proportion. 

N2O                 N2O3               NO2(N2O4)                  N2O5

 A number of oxygen atoms in molecules of such compounds corresponding to the two nitrogen atoms are in a proportion 1:3:4:5. 

Law of combining volumes(Gay-Lussac, 1808)

 "When gases react, the volumes consumed and produced, measured at the same temperature and pressure, are in ratios of small whole numbers".Consequence. Stoichiometric coefficients in equations of chemical reactions for molecules of gaseous substances shows in which volume combinations gaseous substances are got or react. examples

a)      2CO + O2 2CO2

 In the time of oxidizing of two volumes of carbon (II) oxide by one volume of oxygen forms 2 volume of carbon (IV) oxide, i.e. the volume of source reaction mixture decrease on 1 volume.

b)     In the time of synthesis of ammonia from elements: 

N2 + 3H2 2NH3

 One volume of nitrogen is reacting with three volumes of hydrogen: 2 volumes of ammonia are forming – the volume of source reaction mixture will be decreased in 2 times.

 Avogadro law

(1811) 

Equal volumes of all gases at the same conditions (temperature, pressure) contain the same number of molecules.This law truth for gaseous substances only.Consequences:1.      On mole of any substance in the gaseous state occupies the same volume at the same

temperature and pressure.2.      One mole of any gas in standard conditions (0°C = 273K, 1 atm = 101.3 kPa) occupies a

volume of 22.4 litres. example 1What volume of hydrogen at s.t.p. would be evolved at dissolution 4.8 g magnesium in excess of hydrochloric acid? solution

Mg + 2HCl MgCl2 + H2

 At dissolution of 24 g (1 g-mol) magnesium in HCl –– 22.4 l (1 g-mol) of hydrogen is evaluated; at dissolution of 4.8 g of magnesium –– X l of hydrogen. 

X =4.8 * 22.4————

24= 4.48 l of hydrogen

 example 23.17 g of chlorine is borrowing volume, which equal 1 l (at s.t.p.). Calculate the molecular mass of chlorine. solutionFind mass of 22.4 l chlorine.

1 l –– 3.17 g of hydrogen22.4 l –– X g of hydrogen

 X = 3.17 * 22.4 = 71 g

 General gas law

 General gas law is association of three independent private gas laws: Gay-Lussac’s, Charle’s, Boyl’s- Mariott’s, equation which possible write like this: 

P1V1   P2V2

—— = ——T1   T2

 Conversely, from general gas law under P= const. (P1=P2), possible to get: 

V1   V2

— = —T1   T2

(Gay-Lussac’s law) On the T=const. (T1=T2):       P1V1= P2V2 (Boyl’s-Mariott’s law).On the V=const.

P1   P2

— = —T1   T2

(Charle’s law). 

Clapeyron’s - Mendeleyev’s equation If write general gas law for any mass of any gas than would be Clapeyron’s - Mendeleyev’sequation:

    m  PV = — RT    M  

 where, m - gas mass; M - molecular mass; p - pressure; V - volume; T - absolute temperature (K); R - molar gas constant (8.314 J/(mol * K) or 0.082 l atm/(mol * K)).For given mass of concrete gas the ratio m/M is a constant, therefore general gas law is obtained from Clapeyron’s - Mendeleyev’s equation. exampleWhat volume would be reserved by carbon (II) oxide with mass 84 g at temperature 17°C and pressure 250 kPa? solutionQuantity g-mol of CO is: 

    m(CO)   84    (CO) = —— = — = 3 g-mol

    M(CO)   28     CO volume at s.t.p is 3 * 22.4 l = 67.2 lFrom general gas law of Boyl’s-Mariott’s and Gay-Lussac’s: 

P * V   P0 * V0

—— = ——T   T2

follows:    P0 * T * V0   101.3 * (273 + 17) * 67.2    

V(CO) = ————— = ——————————— = 28.93 l    P * T0   250 * 273    

 Relative density of gases shows in how many times 1 mol of one gas more heavy (or easier) than 1 mol of another.

    (B)   M(B)

DA(B) = —— = ——    (A)   M(A)

 The average molecular mass of gases mixture is peer to a common mass of mixture bisected on a total number of moles: 

    m1 +.... + mn   M1 * V1 + .... Mn * Vn

Mav = —————— = —————————    1 +.... + n   1 +.... + n

 example 1The density of certain gaseous substance on hydrogen is 17. Calculate its density on air (Mav=29). solution

DH2   Msub   Мsub

= —— = ——  MH2   2

 Мsub = 2DH2 = 34

 

Dair =Msub

=34

= 1.17——— ——Mair av. 29

 example 2Define the density of nitrogen, argon, and carbon (II) oxide mixture on air, if the mass parts of components are 15, 50 and 35% respectively. solution

Dmix (on air)

  Mmix   Мmix

= —— = ——  Mair   29

     15 * 28 + 50 * 40 + 35 * 44   420 + 2000 + 1540    

Mmix = ——————————— = ———————— = 39.6    100   100    

 

Dmix (on air)

  Mmix   39.6    = —— = —— = 1.37  29   29    

 Planetary model of atom structure

(E. Rutherford, 1911) 1.      Atoms of chemical elements have a complex internal structure.2.      In the center of atom locate positive charged nucleus, occupying insignificant part of spaces

inside atom.3.      The whole positive charge and almost the whole mass of atom concentrated in atom nucleus

(the mass of electron is 1/1823 a.e.m.)4.      Electrons are moved around the nucleus on the closed orbital. Their number is a charge of a

nucleus. Therefore, atom as a whole is electrically neutral. 

Nucleus of atom Atomic nuclei consist of protons and neutrons (general title - nucleons). The number of protons (Z) in atomic nuclei is strictly defined and equal to the serial number of element in the Periodic system. The number of neutrons in the atomic nuclei of one and the same element can be different - A-Z (where A - relative atomic mass of element; Z- serial number).The number of protons defines nucleus charge of atom.Nucleus mass is defined by the sum of protons and neutrons. 

Isotopes Isotopes- variety of atoms of certain chemical elements, having an identical atomic number, but different mass numbers. Isotopes have nucleuses with an identical number of protons and different number of neutrons.Isotopes have an identical structure of electronic shell and occupy one and the same place in the Periodic table of chemical elements. exampleNative thallium (atomic number 81, atomic mass 204.383) consist of two isotopes:

 Thallium-203203

Tl (81 p1 ;  122

n1) - 29,5%81 1 0

 Thallium-205205

Tl (81 p1 ;  124

n1) - 70,5%81 1 0

 Average atomic mass of thallium is: 

    0.295 * 203 + 0.705 * 205    Aav.(Tl) = ———————————— = 204.383    2    

 Hydrogen isotopes have special symbols and names: 

1H- protium;

2D - deuterium;

3T- tritium.

1 1 1 Chemical properties of isotopes of one element are equal. Isotopes having an identical mass numbers, but different nucleus charge are called isobars. 

(40

Ar,40

K and  40

Ca;112

Cd and 112

Sn).18 19 20 48 50

THE PERIODIC LAW(D. I. MENDELEEV)

 "The properties of elements, as well as its compounds (complex and simple) are periodic function of the their atomic weight."Modern formulation:“The properties of chemical elements, as well as the forms and properties of the compounds of the elements are periodic function of the nuclear charge of atoms of the chemical elements”. 

Physical meaning of the chemical periodicity Periodic changes of chemical properties of elements are stipulated by the correct repetition of electronic configuration of external energy level (valence electrons) their atoms with increasing a charge of nuclear.Graphic inventing of a Periodic law is a Periodic Table. It is kept 7 periods and 8 groups.Period - horizontal rows of elements in the Periodic Table with the alike maximum value of the main quantum number of electrons. Period number marks a number of energy levels in the atom of element.Periods can consist of 2 (first), 8 (second and third), 18 (fourth and fifth) or 32 (sixth) electrons, depending on the amounts of electrons on the external energy level. Seventh period is not completed.All periods (except first) begin an alkaline metal (s-element), but finish by a noble gas (ns2 np6).Metallic properties are considered as an ability of atoms of elements easy to return electrons, but nonmetallic - to accept electrons because of the longing of atoms to gain a firm configuration with fill sublevels. Filling an external s-sublevel is pointed out to metallic properties of atom, but shaping an external p-sublevel (from 1 till 5) is intensified nonmetallic properties of atom. Atoms with completely formed, energy firm configuration of the external electronic layer (ns2 np6) are chemical inert.At greater periods a conversation of the properties from the active metal to the noble gas occurs more smoothly, than at small periods, since occurs a shaping an internal (n-1) d-sublevel at the conservation of external ns2-layer. Greater periods consist of even and odd rows. At even row of elements on the external layer ns2-electrons, so metallic properties are dominated and their weakening with the growing of nuclear

charge is not great; in odd rows the np-sublevel is formed, that explains a significant weakening of metallic properties.Groups - vertical rows of elements with the alike valence number electrons, which equal group number. Main and secondary sub-groups are distinguished.Main sub-groups consist of elements of small and greater periods; valence electrons are situated on the external ns- and np-sublevels.Secondary groups consist from elements of greater periods only. Their valence electrons are situated on the external ns-sublevel and internal (n-1) d-sublevel (or (n-2) f-sub-level).Depending on the sub-level, which is filled by valences electrons, the periodic system of elements is subdivided into: s-elements (elements of main sub-group of I and II groups), p-elements (elements of main sub-groups of III-VII groups), d-elements (elements of secondary sub-groups), f-elements (lanthanoid, actinoid).In main subgroups from top to bottom the metallic properties are intensified, but nonmetallic weaken.The number of the group shows a highest valence of element (except N, O, F, elements of cooper sub-group and eighth group).Formulas of highest oxides are general for elements of main and secondary sub-groups (and their hydrates). At highest oxides and their hydrates - elements of I-III groups (except boron) the basic properties are dominated, but from IV till VII - acid. 

Group I II III IV V VI VII VIII(except inert gases)

Highest oxide E2О EО E2О3 EО2 E2О5 EО3 E2О7 EО4

Hydrate of highest oxide EОН E(ОН)2 E(ОН)3 Н2EО3 Н3EО4 Н2EО4 НEО4 Н4EО4

 For elements of main sub-groups formulas of hydrogen compounds are general. Elements of main sub-groups of I-III groups form hard substances - hydrides (hydrogen has oxidation number -1), but IV-VII - gaseous. Hydrogen compounds of main sub-group of IV group (EН4) are neutral, V group (EН3) - bases, VI and VII groups (Н2E and НE) - acids.The properties of atom depend on the position of elements in the Periodic system which connected with its electronic configuration: atomic radius - on a period decreases from left to right, but in the sub-group from top to bottom increases; ionization energy - on a period increases, but in the sub-group decreases; electro negativity - on a period increases, but in the sub-group decreases.On the position of element in the Periodic system possible to forecast its basic properties, as average of all its neighbors: 

CHEMICAL BOND  

Covalent bond Covalent bond is formed by an electron pair shared by both atoms. Two mechanisms of covalent bond formation are recognized: exchange mechanism and donor-acceptor mechanism.1.      Exchange mechanism. Each atom donates one unpaired electron to their common electron pair: 

 

 2.      Donor-acceptor mechanism. One atom (donor) donates the electron pair, and another one (acceptor)

donates a free orbital for this pair: 

 Two atoms may share several electron pares. Bonds of this kind are called multiple bonds:

  (или N N) - тройная связь

 If electron density is distributed symmetrically between atoms, the covalent bond is called non-polar. If the electron density is shifted in the direction of one of the atoms, the bond is called polar. The larger is the difference in electro negativity of the bonded atoms, the higher is polarity of the bond.Electro negativity is the ability of an atom to draw electron density from other atoms to itself. The most electronegative element is fluorine; the most electro positive one is francium.   

Ionic bond Ions are charged particles formed as a result of atoms losing or acquiring electrons: 

(sodium fluoride consists of sodium ions Na+ and fluoride ions F-).

 If the difference in electro negativity of atoms is high, the bonding electron pair completely shifts to one of the atoms, and both atoms become ions.Chemical bond between ions formed by means of electrostatic attraction is called ionic bond. 

Hydrogen bond Hydrogen bond is a bond formed by a positively charged hydrogen atom belonging to one molecule and a negatively charged atom of another molecule. Hydrogen bond is by its nature partly electrostatic and partly coordinate (donor-acceptor). 

 (Hydrogenbondsareshownbydots)

 Presence of H-bonds explains high boiling points of water, alcohols, and carbonic acids.  

 

Metal bond Valence electrons in metals are sufficiently loosely held by their nuclei and may easily part with them. Hence a metal is composed of a number of positive ions arranged into a crystal lattice and a large number of electrons, freely moving through the whole crystal. Electrons in metal hold all the atoms together. 

Hybridization of orbitals Hybridization of orbitals is a transformation of some orbitals during formation of covalent bonds enabling more effective overlapping of orbitals. 1.      sp3-Hybridization. One s-orbital and three p-orbitals combine to form four equivalent "hybrid"

orbitals. Axes of these orbitals form angles of 109°28'. 

 Molecules formed by sp3-hybridized atoms have tetrahedral symmetry (CH4, NH3).

2.      sp2-Hybridization. One s-orbital and one p-orbital combine to form two equivalent "hybrid" orbitals, whose axes form an angle of 120 degrees.

 

 If the chemical bond is formed by overlap of orbitals along the line connecting nuclei, it is called -bond. If the orbitals overlap outside the line connecting nuclei, -bond is formed. Three sp2-orbitals can form three sigma bonds (BF3, AlCl3). Yet another bond (-bond) may form if an orbital not taking part in hybridization has an electron (ethylene C2H4).Molecules formed by an sp2-hybridized atom have a flat structure.

3.      sp-Hybridization. One s-orbital and one p-orbital combine to form two equivalent "hybride" orbitals, whose axes form an angle of 180 degrees.

 

 These two sp-orbitals can form two -bonds (BeH2, ZnCl2). Two additional -bonds may form if another two -orbitals not taking part in hybridization have electrons (acetylene C2H2).Molecules formed by sp-hybridized atoms are linear.

 

KINETIC OF THE CHEMICAL REACTION  

Rate of a chemical reaction The rate of a reaction is the rate at which products are formed or the rate at which reactants are used up in the reaction. The rate of a reaction is defined by change of molar concentrations of one of the reacting substances: 

  С2 - С1   СV =

––––– =

–––

  t2 - t1   t where C1 and C2 - are molar concentrations of substance at moments of the time t1 and t2 respectively. Symbol (+) if the rate is defined on the product of reactions, symbol (-) if the rate is defined on the initial substance.Reaction occurs at the colliding of molecules of reacting substances. Its rate is determined by quantity of collisions and by probability that this process bring about the conversion. The number of collisions is determined by concentrations of reacting substances, but probability of reactions is determined by energy of colliding molecules. 

Numbers of factors influencing on the rate of any particular reaction  The most important of these are:the nature of reactants;concentration of reactants;temperature;presence of catalysts.Below, the influence of each factor on the rate of chemical reactions is described.1.      Dependence of reaction rate on the nature of reactants. The character of chemical bonds and structure

of reactant molecules has a great importance. Reactions run toward destroying of less strong bonds and stronger substances are formed. Thus, for a bonds breakup in molecules H2 and N2 high energies are required; such molecules have small reaction ability. For a bonds breakup in strong polarized molecules (HCl, H2O) less energy is required and the rate of reactions well above. Reactions between ions in solutions of electrolytes run practically instantly.examples1)     Fluorine react with hydrogen with explosion at the room temperature, bromine slowly interact with

hydrogen under the heating.2)     Calcium oxide energetically reacts with water with extracting of heat; cooper oxide - does not

react.2.      Dependence of reaction rate on the reactant concentrations. The rate of a reaction is proportional to the

number of collisions experienced by the molecules of the reactant. The number of collision grows with the concentration of each of the reactant (the number of particles in the unit of volume are growing), thus the rate of a reaction is increasing.

 Low of mass action

(C. Guldberg and P. Waage in 1867)  At a constant temperature, the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants. 

aA + bB + . . . . . . 

V = k * [A]a * [B]b * . . . The value of the rate constant k depends on the nature of the reactant, on the temperature, and on the presence of catalysts, but does not depend on the concentration of the substances.

The physical meaning of the rate constant is: its equal to the rate of a reaction at the singles concentrations of the reactants.

For heterogeneous reactions the concentration of solid phase does not include in the expression of the rate of a reaction.

3.      Dependence of reaction rate on the temperature. When the temperature of the system increases by each 10°C the rate of a reaction increases in 2-4 times (Vant-Hoff rule). In the time of a temperature increases from till the change of reaction rate is possible to calculate:

 Vt2  (t2 - t1)/10–– =

 

Vt1    

(Vt2 and Vt1 - is a reactions rate at temperatures t2 and t1 correspondingly, - is a temperature coefficient of reaction).Vant-Hoff rule is applicable in the narrow interval of temperatures only. More exact is Arrhenius equation: 

k = A * e -Ea/RT

 A - is a constant for the reaction depends on the nature of reactant;R - is the gas constant {8.314 J/mol * K)=0.082 liters * atm/(mol * K);Ea - is the activation energy, i.e. the excess energy that molecules must have for their collision been effective. 

Energy diagram of chemical reaction 

Reaction coordinate Reaction coordinateEndothermic reaction Exothermic reaction

 A - reagents, B- activated complex (transition state), C - products.Than energy of activation Ea higher that more strong increases of the rate of a reaction when increasing a temperature is observed.

4.      Dependence of reaction rate on the surface of reactants. For heterogeneous systems (when reactants stand in the different aggregation condition) the greater contact surface the reaction runs faster. The surface of solid substances can be increase by means of shallower, but for soluble substances by means of dissolution.

5.      Catalysis. Substances that are not consumed in a reaction, but affect its rate, are called catalysts. The phenomenon of the change in the rate of a reaction under the action of such substances is known as catalysis. Reactions proceeding under the action of catalysts are called catalytic. The action of a catalyst in the majority of cases is explained by the fact that it lowers the activation energy of a

reaction. In homogeneous catalysis, the catalyst and the reactant form a single phase (stand in one the same aggregation condition), in heterogeneous catalysis, the catalyst forms an independent phase (stand in the different aggregation condition). In number of events sharply slow down the undesirable chemical reactions by means of adding in the reactionary ambience inhibitors is possible (phenomena of «negative catalysis»).

 

CHEMICAL EQUILIBRIUM Reversible reactions - chemical reactions, simultaneously running in two opposite directions. 

 Chemical equilibrium - is a system condition, in which the rate of direct reaction (V1) is equal to the rate of inverse reactions (V2). At chemical equilibrium concentrations of substances stay unchangeable. Chemical equilibrium is called dynamic equilibrium. This stresses the fact that both the forward and reverse reactions proceed in equilibrium, but their rates are the same, and as a result no changes are noticeable in the system.Chemical equilibrium is characterized quantitatively by a quantity known as the chemical equilibrium constant. Equilibrium constant is a relation of constants of forward (K1) and reverse (K2) reactions.For reaction mA + nB pC + dD equilibrium constant is 

  K1   [C]p * [D]d

K = –– = –––––––  K2   [A]m * [B]n

 The magnitude of the equilibrium constant depends on the nature of the reacting substances and on the temperature. It does not depend on the presence of catalyst. Since a catalyst changes the activation energy of both the forward and reverse reactions by the same amount, it does not affect the ratio of their rate constant. 

Displacement of chemical equilibrium Le Chatelier’s principle. Any system in stable chemical equilibrium, when subjected to the influence of an external cause which tends to change either temperature or condensation (pressure, concentration, number of molecules in unit volume), throughout or in only some of its part, can undergo only such internal modifications which, if they occurred on their own, would bring about a change of temperature or of condensation of a sign contrary to that resulting from the external cause. 

  V1  A + Б В

  V2   1.      Pressure. When the pressure is increased by compressing a system, equilibrium shifts in the direction

of a reduction in the number of molecules of the gases (i.e. in the direction of lowering pressure). 

  V1    A + Б В ; increasing P brings about V1 > V2

V2  2   1  

 2.      Temperature. Upon elevation of the temperature, equilibrium shifts in the direction of the endothermic

reaction (i.e. aside reaction, running with absorbing a heat). 

  V1  A + Б В + Q, increasing t°C brings about V2 > V1

  V2   

  V1  A + Б В - Q, increasing t°C brings about V1 > V2

  V2   3.      Increasing a concentration of source substances and removing the products from the reaction sphere

shift equilibrium in the direction of forward reaction. Increasing the concentrations of source substances [A] or [Б] or [A] and [Б]: V1 > V2

4.      Catalyst has no influence on the position of equilibrium.

THE MAIN CLASSES OF INORGANIC COMPOUNDS  

CLASSIFICATION OF INORGANIC SUBSTANCES Simple substances. Molecules consist of one-type atoms (atoms of one element). In chemical reactions cannot be decomposed with forming other substances.Complex substances (or chemical compounds). Molecules consist of different type atoms (atoms of different chemical elements). In chemical reactions are decomposed with formation several other substances. 

Inorganic substancesSimple Metals

Non-metalsComplex Oxides

BasesAcidsSalts

 Sharp border between metals and non-metals does not exist, since be simple substances showing dual properties. 

BASES Bases - complex substances, in which atoms of metals bonded with one or several hydroxyls groups (according to electrolytic dissociation theory bases - complex substances, which under the dissociating in water solution are formed metal cations (or NH4

+) and hydroxide anions OH-). 

Classification Soluble in water (alkalis) and insoluble. Amphoteric bases show also properties of weak acids. 

Preparation 1.      Reactions of active metals (alkaline and alkaline earth metals) with water 

2Na + 2H2O 2NaOH + H2

Ca + 2H2O Ca(OH)2 + H2

 2.      Interaction oxides of active metals with water 

BaO + H2O Ba(OH)2

 3.      Electrolysis water solutions of salts 

2NaCl + 2H2O 2NaOH + H2 + Cl2

Chemical properties 

Alkalis Insoluble bases

1.      Action to indicators

litmus - bluemethylorange - yellowphenolphthalein - crimson

––

2.      Interaction with acid oxides

2KOH + CO2 K2CO3 + H2OKOH + CO2 KHCO3

––

3.      Interaction with acids (reaction of neutralization)

NaOH + HNO3 NaNO3 + H2O Cu(OH)2 + 2HCl CuCl2 + 2H2O

4.      Reaction of exchange with salts

Ba(OH)2 + K2SO4 2KOH + BaSO43KOH + Fe(NO3)3 Fe(OH)3 + 3KNO3

––

5.      Thermal decomposition

––                tCu(OH)2 CuO + H2O

 

OXIDES 

Classification Oxides - complex substances, consisting from two elements, one of which oxygen. 

Oxides

Non-salts forming

(CO,N2O,NO)

 

Salts formingBasic-it is a metal oxides in which metals displaylow oxidation number +1, +2

Na2O; MgO; CuO

Amphoteric(for metals with oxidation number +3, +4).As a hydrates it corresponding amphoteric hydroxideZnO; Al2O3; Cr2O3; SnO2

Acid-it is oxide of nonmetals and metals with oxidationnumber from +5 to +7.SO2; SO3; P2O5; Mn2O7; CrO3

 Basic, amphoteric- corresponding bases; amphoteric, acid- corresponding acids 

Preparation 1.      Interaction of simple and complex substances with oxygen: 

2Mg + O2 2MgO4P + 5O2 2P2O5

S + O2 SO2

2CO + O2 2CO2

2CuS + 3O2 2CuO + 2SO2

CH4 + 2O2 CO2 + 2H2O 

  cat.  4NH3  + 5O2 4NO + 6H2O

 2.      Decomposition some substances containing oxygen (bases, acids, salts) under the heating: 

  t  Cu(OH)2 CuO + H2O

   t  

(CuOH)2CO3 2CuO + CO2 + H2O 

  t  2Pb(NO3)2 2PbO + 4NO2 + O2

   H2SO4 (conc.)  

2HMnO4 Mn2O7 + H2O  t  

 

Chemical properties 

Basic oxides Acid oxides

1.      Interaction with waterBase formed:Na2O + H2O 2NaOHCaO + H2O Ca(OH)2

Acid formed:SO3 + H2O H2SO4

P2O5 + 3H2O 2H3PO4

2.      InteractionwithacidorbaseOn reactions with acid salt and water are formed                          tMgO + H2SO4 MgSO4 + H2O

On reactions with base salt and water are formed CO2 + Ba(OH)2 BaCO3 + H2O

                       tCuO + 2HCl CuCl2 + H2O

SO2 + 2NaOH Na2SO3 + H2O 

Amphoteric oxides interact with acids as basic:ZnO + H2SO4 ZnSO4 + H2O

with bases as acid:ZnO + 2NaOH Na2ZnO2 + H2O(ZnO + 2NaOH + H2O Na2[Zn(OH)4])

3.      Interaction of basic and acid oxide with each other leads to salt formationNa2O + CO2 Na2CO3

4.      Reduction up to simple substances:

3CuO + 2NH3 3Cu + N2 + 3H2OP2O5 + 5C 2P + 5CO

 

ACIDS Acids - complex substances, consisting from hydrogen atoms and acid radical (according to electrolytic dissociation theory: acids - electrolytes, which under the dissociating form only H+ in the capacity of cations). 

Classification 1.      On composition: oxygenless and oxoacids.2.      On hydrogen atoms number, which capable to substituted on metal: mono-, di-, tribasic. 

Oxygenless:   Saltsname:HCl - hydrogen chloride (hydrochloric)

monobasic chloride

HBr - hydrogen bromide monobasic bromideHI - hydrogeniodide monobasic IodideHF - hydrogen fluorine (hydrofluoric) monobasic fluorideH2S - hydrogensulphide bibasic sulphide     Containing oxygen:    HNO3 – nitric monobasic nitrateH2SO3 – sulphurous bibasic sulphiteH2SO4 – sulphuric bibasic sulphateH2CO3 – carbonic bibasic carbonateH2SiO3 – silicon bibasic silicateH3PO4 – ortophosphoric tribasic ortophosphate

 

Preparation 1.      Interaction of acid oxides with water (for oxoacids): 

SO3 + H2O H2SO4

P2O5 + 3H2O 2H3PO4

 2.      Interaction of hydrogen with non-metals and following dissolution product in water (for oxygenless

acids). 

H2 + Cl2 2HClH2 + S H2S

 3.      Reactions of exchange between salt and acid 

Ba(NO3)2 + H2SO4 BaSO4 + 2HNO3

 including displacement weak, flying or slightly soluble acid from its salts by means of more strong acids. 

Na2SiO3 + 2HCl H2SiO3Ү + 2NaCl 

  t  2NaCl (hard) + H2SO4 (conc.) Na2SO4 +

2HCl 

Chemical properties 1.      Action to indicators.

 litmus - redmethylorange – pink 

2.      Interaction with bases (reaction of neutralisation) 

H2SO4 + 2KOH K2SO4 + 2H2O2HNO3 + Ca(OH)2 Ca(NO3)2 + 2H2O

 3.      Interaction with basic oxides. 

  t  CuO + 2HNO3 Cu(NO3)2 + H2O

 4.      Interaction with metals. 

Zn + 2HCl ZnCl2 + H2

2Al + 6HCl 2AlCl3 + 3H2

(metals standing in the electrochemical series before hydrogen, acid-oxidizers). 5.      Interaction with salts (reactions of exchange) at which stands out gas or formed residual. 

H2SO4 + BaCl2 BaSO4 +2HCl2HCl + K2CO3 2KCl + H2O + CO2

 

SALTS Salts - complex substances, which consist from atoms of metal and acid residuals. This the most multiple class of inorganic compounds. 

Classification 

SaltsMediumAcidBasicDouble

MixedComplex

 Medium salts. In the time of dissociation give only metal cations (or NH4

+) and anions of acid radical. Products of full substitution hydrogen atoms of acids to atoms of metals: 

Na2SO4 2Na+ +SO42-

CaCl2 Ca2+ + 2Cl-

 Acid salts. In the time of dissociation give only metal cations (or NH4

+), hydrogen anions and anions of acid radical. Products of full substitution hydrogen atoms of multibasic acid to atoms of metal: 

NaHCO3 Na+ + HCO3- Na+ + H+ + CO3

2-

 Basic salts. In the time of dissociation give only metal cations, hydroxyl anions and anions of acid radical. Products of incomplete substitution OH groups, corresponding bases to acid radicals: 

Zn(OH)Cl [Zn(OH)]+ + Cl- Zn2+ + OH- + Cl-

 Double salts. In the time of dissociation gives two cations and one anion: 

KAl(SO4)2 K+ + Al3+ + 2SO42-

 Mixed salts. Formed by means of one cation and two anions: 

CaOCl2 Ca2+ + Cl- + OCl-

 Complex salts. Contain complex cations and anions: 

[Ag(NH3)2]Br [Ag(NH3)2]+ + Br -

Na[Ag(CN)2] Na+ + [Ag(CN)2]-

  

Medium salts 

Preparation Most of ways of getting the salts is based on the interaction of substances with opposite properties:1)     Metal with non-metal: 

2Na + Cl2 2NaCl 2)     Metal with acid: 

Zn + 2HCl ZnCl2 + H2

 3)     Metal with solution of salt of less active metal: 

Fe + CuSO4 FeSO4 + Cu 4)     Basic oxide with the acid oxide: 

MgO + CO2 MgCO3

 

5)     Basic oxide with acid: 

  t  CuO + H2SO4 CuSO4 + H2O

 6)     Bases with acid oxide: 

Ba(OH)2 + CO2 BaCO3 + H2O 7)     Bases with acid: 

Ca(OH)2 + 2HCl CaCl2 + 2H2O 8)     Salts with the acid: 

MgCO3 + 2HCl MgCl2 + H2O + CO2

BaCl2 + H2SO4 BaSO4Ү + 2HCl 9)     Bases solution with salt solution: 

Ba(OH)2 + Na2SO4 2NaOH + BaSO4Ү 10) Solutions of two salts: 

3CaCl2 + 2Na3PO4 Ca3(PO4)2Ү + 6NaCl 

Chemical properties 1.      Thermal decomposition 

CaCO3 CaO + CO2

2Cu(NO3)2 2CuO + 4NO2 + O2

NH4Cl NH3 + HCl 2.      Hydrolysis 

Al2S3 + 6H2O 2Al(OH)3 + 3H2SFeCl3 + H2O Fe(OH)Cl2 + HCl

Na2S + H2O NaHS +NaOH 3.      Exchange reactions with acids, bases and other salts 

AgNO3 + HCl AgCl + HNO3

Fe(NO3)3 + 3NaOH Fe(OH)3 + 3NaNO3

CaCl2 + Na2SiO3 CaSiO3 + 2NaCl 4.      Oxidation-reduction reactions, stipulated by properties of cation or anion 

2KMnO4 + 16HCl 2MnCl2 + 2KCl + 5Cl2 + 8H2O 

 Acid salts

 

Preparation 1.      Interaction of acid with the deficit of basis. 

KOH + H2SO4 KHSO4 + H2O 2.      Interaction of bases with plenty acid oxides. 

Ca(OH)2 + 2CO2 Ca(HCO3)2

 3.      Interaction of medium salts with acid. 

Ca3(PO4)2 + 4H3PO4 3Ca(H2PO4)2

 

Chemical properties 1.      Thermal decomposition with medium salts formation. 

Ca(HCO3)2 CaCO3 + CO2 + H2O 2.      Interaction with the alkali. Reception of medium salts. 

Ba(HCO3)2 + Ba(OH)2 2BaCO3 + 2H2O 

 Basic salts

 

Preparation 1.      Hydrolysis of salts, formed by weak base and strong acid. 

ZnCl2 + H2O [Zn(OH)]Cl + HCl 2.      Addition (by drops) a small quantities of alkalis to solutions of medium salts of metals. 

AlCl3 + 2NaOH [Al(OH)2]Cl + 2NaCl 3.      Interaction of weak acids salts with medium salts. 

2MgCl2 + 2Na2CO3 + H2O [Mg(OH)]2CO3 + CO2 + 4NaCl  

Chemical properties 1.      Thermal decomposition. 

[Cu(OH)]2CO3 2CuO + CO2 + H2Omalachite  

 2.      Interaction with the acid: formation of medium salts. 

Sn(OH)Cl + HCl SnCl2 + H2O

  Complex salts

 

Structure K4[Fe(CN)6]

K4[Fe(CN)6] – External spherK4[Fe(CN)6] – Internal sphereK4[Fe(CN)6] – Central atomK4[Fe(CN)6] – Coordinate relationK4[Fe(CN)6] – Ligand Central, complex forming, atoms is usually serves ions of metals of greater periods (Co, Ni, Pt, Hg, Ag, Cu). Typical ligands are OH-, CN-, NH3, CO, H2O; they connected with the central atom by donor-acceptor bound. 

Preparation Reactions of salts with ligands 

AgCl + 2NH3 [Ag(NH3)2]ClFeCl3 + 6KCN K3[Fe(CN)6] + 3KCl

 

Chemical properties 1.      Destruction of complexes at the expense of forming the slightly-soluble compounds 

2[Cu(NH3)2]Cl + K2S CuS + 2KCl + 4NH3

 2.      The exchange of ligands between external and internal spheres 

K2[CoCl4] + 6H2O [Co(H2O)6]Cl2 + 2KCl 

Genetically relationship of classes 

Genetic relationship between different classes of compounds 

1.      metal; non-metal – salt2.      basic oxide; acid oxide – salt3.      basic; acid – salt 4.      metal – basic oxide5.      non-metal – acid oxide6.      basic oxide – bases7.      acid oxide – acid examples:1.       

Hg + S HgS   2Al + 3I2 2AlI3

metal   non-metal

  salt    

 

2.       Li2O + CO2 Li2CO3   CaO + SiO2 CaSiO3

basicoxide

  acidoxide

  salt    

 3.       

Cu(OH)2+2HClCuCl2+ 2H2O FeCl3+ 3HNO3 Fe(NO3)3 + 3HClbases   acid   salt     salt   acid   salt   acid

 4.       

2Ca + O2 2CaO   4Li + O2 2Li2Ometal

   basic

oxide   

 5.       

S + O2 SO2   4As + 5O2 2As2O5

non-metal

  acidoxide

   

 6.       

BaO + H2O Ba(OH)2   Li2O + H2O 2LiOHbasicoxide

  bases    

 7.       

P2O5 + 3H2O 2H3PO4   SO3 + H2O H2SO4

acidoxide

  acid