The MINISTRY OF EDUCATION And SCIENCES УКРАИНЫ
ВОСТОЧНОУКРАИНСКИЙ NATIONAL UNIVERSITY
Name ВЛАДИМИРА ДАЛЯ
THE BRIEF ABSTRACT OF LECTURES IN CHEMISTRY
For students of the correspondence form of training.
Lugansk ВНУ 2003
4
The MINISTRY OF EDUCATION And SCIENCES УКРАИНЫ
ВОСТОЧНОУКРАИНСКИЙ NATIONAL UNIVERSITY
Name ВЛАДИМИРА ДАЛЯ
THE BRIEF ABSTRACT OF LECTURES IN CHEMISTRY
For students of the correspondence form of training of all engineering specialities
УТВЕЖДЕНО
On faculty meeting of chemistry
The report ____ from..
Lugansk ВНУ 2003
УДК54
THE BRIEF ABSTRACT OF LECTURES IN CHEMISTRY
For students of the correspondence form of training of all engineering specialities.
/ Сост: S.P.Bugrim, I.A.Horuzhaja.-Lugansk: Publishing house Vostochnoukr. нац. ф Ў-that, 2003.–104с.
The brief abstract of lectures in chemistry includes 12 lectures with examples of the decision of typical problems and
the instruction of references on the basic themes: « Стехиометрические laws of chemistry », « Квантовомеханическое
representation about a structure of atom », « Rules and the order of filling nuclear орбиталей », « D.I.Mendeleeva's
Periodic law. Laws of periodic system », « Chemical thermodynamics », « the Second beginning of chemical
thermodynamics », « Chemical кинетика », « Solutions of electrolits, weak electrolits », « Complex connections », «
Oxidation-reduction reactions », « Bases of electrochemistry », « Chemical sources of a current », « Corrosion of metals
and protection of metals against corrosion », «Электролиз». The brief abstract of lectures meets the requirements of the
program of a rate of chemistry for technical specialities. It is recommended for students of the correspondence form of
training of all engineering specialities.
.
Composers: S.P.Bugrim, item преп., I.A.Horuzhaja, доц.кафедры
Chemistry ВНУ it. V.Dalja
Отв. For release: V.L.Abramenko, доц.
Reviewers: A.A.Grigoriev, доц.
5
STOICHIOMETRY LAWS.
Obgectives After studying this chapter, students should
be able to:
1. The law of preservation of a matter.
2. The law of Proust.
3. The Law of Аvоgadro. Consequences from law Аvоgadro.
4. The law of equivalent attitudes.
STEHIOMETRI is the part of a chemistry in which we studie quantitative attitudes
between compounds in chemical processes. Stehiometri is the base of the chemical
analysis and is the base in development of theoretical chemistry.
The basic stehiometric laws are
1. The law of safety of a matter.
The weight of the substances entering chemical reaction is equal to weight of the
substances formed as a result of it.
The law was found in 1748 and proved in 1756 year by Russian scientist
M.Lomonosov.
From the point of view of the atomic-molecular doctrine the sense of the law of
preservation of weight of substances consists that nuclears have constant weight, and
their number does not change during reaction, therefore the weight of substances before
the reaction and after it remains a constant. For example:
t 0C
2Mg + O2 2MgO t 0C
( NH4) 2 Cr2O7 N2 + Cr2O3 +4H2O
2∙24 + 16.2 t 0C
2(24+16)
28 + 152 + 72
80
t 0C
80 252 252
On the bases of the law of preservation of weight it is possible to make the chemical
equations and on them to make necessary calculations.
Problem.
How many will be allocated lead (Pb) if the weight of the immersing zinc plates in a
solution of the lead nitrate Pb (NO3) 2 is increased on 7, 1g?
For the decision of a problem it is necessary to write down the equation of reaction:
Pb (NO3) 2 + Zn Zn (NO3) 2 + Pb,
65 207
Where 65 – molar weight of zinc; 207 – molar weight of Pb. According to this equation
of reaction we can write down this proportion
Whan weight of a zinc plate is increased on 142 grams (207-65) it means thet will be
allocated 207g of lead Pb. So, Whan weight of a zinc plate is increased on 7, 1 g it
means thet will be allocated X g of lead Pb. Will weight of Pb be allocated?
6
7,1 207
X = (mPb) = 10,35 g .
142
2. The law of a constancy of structure.
Any pure chemical compound always has constant quantitative and qualitative
structure are not dependent from method of its obtaining. The law has been
formulated by French scientist Joseph Proust in 1808.
For example, the molecular of water quantitative (on two atoms of hydrogen it
is necessary one atom of oxygen) and has constant qualitative structure (Н; O) are not
dependent on way of reaction:
CuO + H2 H2O + Cu
CH4 + 2O2 2H2O + CO2
C2H5OH + 3O2 3H2O + 2CO2
H2SO4 + 2NaOH 2H2O + Na2SO4
Cleanliness of substances is defined on t0C fusion, t0Сboiling, density, to specters.
3. Law of the Аvоgadro.
In equal volumes of various gases under identical conditions
(t0С, P) the same number of molecules contains. The law is formulated by Italian
physicist Avogadro in 1811 and has consequences.
Consequence 1. One mol of any substance contains 6, 02 10 23 molecules.
number 6, 02 10 23 mol–1 can be called as number of the Аvоgadro (NA).
Consequence 2. The meaning of the volume’ one mol of any gas under normal
conditions (n.c). (00С (273 K), 1,03.105 Па) equals to 22,4 liter/mol.
1mol О2 (M (О2) =32 g/mol) – contains 6, 02.10 23 molecules of oxygen, it volume is
22,4 liter/mol.
1 mol Н2 (M (Н2) =2 g/mol) – contains 6, 02 .10 23 molecules of hydrogen, it is volume
22,4 liter/mol.
Problem. How many hydrogen will be allocated after the reaction 3,25 Zn g with a
hydrochloric acid?
For the decision of a problem we write down the equation of the reaction:
Zn + 2 HCl ZnCl2 + H2
65 g/mol 22,4 liter/mol
When molar weight of zinc equals to 65 g/mol; molar volume of hydrogen is
22,4 liter/mol. During etching of 65 g zinc allocates 22,4 л/mol hydrogen, and during
etching of the 32,5 г zinc allocates X л hydrogen.Let’s find the volume of the allocated
hydrogen at n.c.
3,25 22,4
V (H 2 ) = X = 1,12 л
65
As a result of works of German chemist Richter, English scientists Dalton and
Vollaston (1792 – 1800) “connecting weights” or equivalents of reacting substances
was established.
7
Chemical equivalent of substance is such substance quantity which can to
connect with one mol of hydrogen atoms or replaces the same quantity of hydrogen
in its compounds.
For example, in compounds such as НС1, H2О, NH3 equivalents of chlorine, oxygen,
nitrogen are accordingly equal to 1 mol, 1/2 mol, 1/3 mol. For unit of an equivalent
takes equivalent of hydrogen Э (H) =1 mol of atoms). An equivalent express in mol.
Notion ‘molar weight of an equivalent’ is used too except ‘equivalent’ notion.
The mоlar weight of an equivalent is a weight of one chemical equivalent of a
substance. МE (H) = 1 g/mol; МE (N) = 14∙1/3 = 4,67 g/mol; МE (Cl) = 35,45 g/mol; МЭ
(S) = 32∙1/2 = 16 g/mol.
Element’ mоlar weight of an equivalent - it is the ratio of mоlar weight of an
element (M) per its valency (V.) For example:
S+4O2, valency of sulfur equals to IV; ME (S+4) = M (S)/V = 32/4 = 8 g/mol;
S+6O3, valency of sulfur equals to VI; ME (S+6) = (S)/V = 32/6 = 5,3 g/mol.
The notion “Equivalent volume” is used for gaseous compounds.
The equivalent volume (Vэ) is the volume of one chemical equivalent of any gas
under normal conditions. The equivalent weight of hydrogen МЭ (H) = 1 g/mol equals
to 1/2 of its molar weight( M(H2) =2 g/mol). The molar volume of hydrogen equals to
22,4 liter (n.c.), then the equivalent volume of hydrogen equals to 11,2 л/mol. The
equivalent weight of oxygen equals to 5,6 liter/mol.
The molar volume of oxygen equals to 22,4 л/mol (n.c.), then the equivalent volume
of oxygen is equal 5,6 liter/mol.
Molar weights of equivalents of compounds can be fined
For оxide:
Ì ( Al2 O3 )
The first way: МE (Al2O3) = , where n – number of element’s atoms in a
n V
molecule; V – its valency. МE (Al2O3) = 102/2∙3 = 17 g/mol
The second way: МE (Al2O3) = МE (O-2) + МE (Al+3) =16/2 + 27/3 =17 g/mol
For the basis:
М (Са (ОН ) 2 ) 74
The first way: МE (Са (OH) 2) = 37 g/mol , where acidity (acidness) of
acidity 2
the basis-it is number (ОН-) in a molecule of the basis.
The second way: МE (Са (OH) 2) = МE (Са2 +) + МE (ОН-) = 40/2 + 17 = 37 g/mol
For the acid:
8
М ( Н 3 РО4 )
The first way: МE (H3PO4) = 98 / 3 32 ,6 g/mol , where basicity of the acid-it
basicity
is number cathions of the hydrogen Н + in a molecule of the acid.
The second way:
МE (Н3РО4) = МЭ (Н+) + МE (РО4)3- = 1 + 95/3 = 1 + 31,6 = 32,6 g/mol
.
For the salt:
М (Са3 ( РО4 ) 2 ) 310
The first way: МE (Са3 (РО4) 2) = 51,7 g/mol
n V 3 2
М ( NaHCO3 ) 84
МE (Nа HCO3) = 84 g/mol
n V 11
М ( А1(ОН )С12 ) 115
МE (A1 (OH) C12) = 57,5 g/mol ,
n V 1 2
Where V – valency of metal or a cathion charge of the basic salt.
n – number of atoms of metal in a molecule of salt.
The second way:
МE (Са3 (РО4) 2) = МE (Са2+) + МE (РО4)3- = 40/2 + 95/3 = 51,7 g/mol;
МE (NaHCO3) = МE (Na+) + МE (HCO)3- = 23 + 61 = 84 g/mol;
МE (А1ОНС12) = МE (А1ОН)2 + + МE (С1-) = 44/2 + 35,5 = 57,5 g/mol.
Finding molar weight of equivalent of compounds in the chemical reaction.
For acids.
Two ions of hydrogen was replaced in this reaction, so the basicity of phosphoric
acid in this case equals to two.
М ( Н 3 РО4 ) 98
H3PO4 + 2NaOH = Na2HPO4 + 2H2O; МE (Н3РО4) = 49 g/mol ;
2 2
Three ions of hydrogen was replaced in this reaction, so the basicity of an acid in this
case equals to three
М ( Н 3 РО4 ) 98
H3PO4 + 3NaOH = Na3PO4 + 3H2O; МE (Н3РО4) = 32,2 g/mol .
3 3
For the bases:
А1 (OH) 3 + НС1 А1 (OH) 2С1 + Н2О, acidity of this basis equals to 1;
МE (А1 (OH) 3) = М ( А1(ОН ) 3 ) 78 g/mol
1
А1 (OH) 3 + 2НС1 А1ОНС12 + 2Н2О, acidity of the basis equals to 2
МE (А1 (OH) 3) = 78/2 = 39 g/mol
.
9
Finding molar weights of equivalents of substances during of the oxidation-
reduction reactions:
2KMnO4 + 5SnCl2 + 16HCl = 5SnCl4 + 2MnCl2 + 2KCl + 8H2O
Reducer Sn+2 - 2 Sn+4 5 is oxidized
Oxidizer Mn+7 + 5 Mn+2 2 is restored
Oxidizer’ molar weight of an equivalent equals to the ratio of the oxidizer’ molar
weight (M (KMnO4)) per quantity of the accepted electrons.
М ( KMnO4 ) 158
МE (KMnO4) = 31,6 g/mol .
5 5
Reducer’s molar weight of an equivalent equals to the ratio of the reducer’ molar
weight (M (SnCl2)) to quantity of the efficienced electrons.
(M E (SnCl2)) = s.
4. The law of the ratio of equivalents.
The ratio of the weight of the compounds the m (A) and m (B) is such the ratio as
their molar weight of equivalents: МE (A) and МE (B).
Mathematical expressions of this law:
m( A) M E ( A) m( A) M E ( A) V ( A) V E ( A)
; ; .
m( B ) M E ( B ) V ( B) VE ( B) V ( B) VE ( B)
Let's consider examples of the problems.
The problem 1. The оxid contains 52 % of the metal. Calculate metal’s molar weight of
an equivalent in this оxid. Is this metal called, if its valensy equals to six? Write down
oxid‘s formula.
The decision: We can calculate quantity of oxygen in this оxid as
100 % – 52 % = 48 %. Using the law of the ratio of equivalent attitudes we can write
down the expression:
m(Me) M E (Me) 52 8
; M E (Me) 8,66 g/mol
m(O) M E (O) 48
m (Me) = ME (Ме) ∙Valensy = 8,66∙6 = 52 g/mol
Six-valent metal with nuclear weight 52 а.u.м. Chrome is. Its оxid is CrO3.
The problem 2. For restoration 7,09 g оxid of the metal it is required 2,24 liter
hydrogen (n.c.). Calculate моlar weight of an equivalent of metal and its оxid.
The decision.
Using the law of the ratio of equivalent attitudes we can write down the expression:
m( MexOy ) M E ( MexOy ) 7,09 11,02
; M E ( МеxОy ) 35,45 g/mol
V (H 2 ) VE ( H 2 ) 2,24
10
ME (Ме xОy) = ME (Ме) +ME (O); (МЭ (=8 g/mol), then ME (Ме) = 35,45 – 8 = 27,45
g/mol.
The problem 3. From 3,85 g nitrate of metal Me (NO3) x were received 1,60 g of its
hydroxide Me (OH) x. Calculate equivalent weight of metal.
The decision.
Using the law of the ratio of equivalent attitudes we can write down expression:
m( M E ( NO3 ) x ) M E (Me( NO3 ) х ) M E ( Mex ) M E ( NO3 )
;
m(M E (OH ) x ) M E (Ме(ОН ) х ) M E ( Mex ) M E (OH )
3,85 M E ( Меx ) 62
x
; M E ( Mex ) 15 g/mol
1,60 M E ( Me ) 17
Problem 4. At interaction 3,24 g trivalent metal with an acid it is allocated 4,03 л Н2
(n.c.) Calculate equivalent’s molar weight of metal and molar weight of metal. Is this
metal called?
The decision.
Using the law of the ratio of equivalent attitudes we can write down expression:
m( M E ) M E ( Ме) m(Me) VE ( H 2) 3,24 11,2
M E (Me) 9 g/mol
V (H 2 ) VE ( H 2 ) V (H 2 ) 4,03
M ( Me)
M E ( Me) Ì ( Ìå ) M E ( Me) Val 9 3 27 g/mol
Val
The metal is called aluminium.
Review Questions
1. What do you know about the law of preservation of a matter?
2. What do you know about the law of Proust?
3. What do you know about the law of Аvоgadro?
4. How many molecules contain into one mol of any substance?
5. What is the volume of one mol any gas under normal conditions?
6. What is the definition of this notion “substance’s chemical equivalent”?
7. What is the definition of this notion “element’s molar weight of an equivalent”?
8. What is the definition of this notion “base’s molar weight of an equivalent”?
9. What is the definition of this notion “acid’s molar weight of an equivalent”?
10. What is the definition of this notion “salt’s molar weight of an equivalent”?
11. What is the definition of this notion “oxide’s molar weight of an equivalent”?
12. What is the definition of this notion “the equivalent volume” (Vэ)?
13. What do you know about the law of the ratio of equivalents?
Further Reading
1. Frolov V.V.Chemistry. Part V, §51-56.
2. Luchinsky G.P,rate of chemistry. Part. V, §8-12,
Part. VI, §13-18
11
QUANTUM-МECHANICAL INTRODUCION ABOUT THE STRUCTURE OF
AN ATOM. RULES AND THE ORDER OF FILLING NUCLEAR ОRBITALS.
Obgectives After studying this chapter, students should
be able to know:
1. Various theories about a structure of an atom.
2. Quantum numbers, their physical sense.
3. Principles of filling nuclear орбиталей.
The works by Russian scientist M.V.Lomonosov, the French chemists Lavoisier
and Prust, English chemist Dalton and others are scientific bases of the аtomic-
molecular doctrine. However till the twentieth century, the atom was considered as
not divisible. Only a series of discoveries 1896 – 1898 of the natural radio-activity by
Anry Becquerel (1896 - the radio-activity of uranium), Maria Skladovska-Kurie and
Pierre Kurie, have allowed to change representations on indivisibility of an atom.
The atom is the electroneutral particle consisting of a nuclear which is charged
positively and the electrons ( e ) rotating around it. Electrons are charged negatively.
1
Nuclears of atoms have a complex structure and consist of nucleons (protons ( 1 р ) and
1
neutrons ( 0n )).
Nucleons
1 1
Atom [the nuclear [∑ 1 р + ∑ 0n] + ∑ē] ← Subatomic particles
mass number (A)
The weight of a nuclear is less than the sum of weights of protons and neutrons.
The name of this difference is colled the defect of the weight. It characterizes stability
1
of the atoms nuclears and energy of connection of nucleons (protons ( 1 р ) and neutrons
1
( 0 n )).
The connection’s energy of nuclons in the nuclear is 7.106 eV. It is more then the
connection’s energy of atoms in a molecule (5eV) in millions times.Therefore in
chemical reactions a nuclear of atoms does not change.
Table 1
International System (SI) System of atomic units
The name Weight, Charge, Weight, Charge,
Subatomic particle Kg Кl а.u.w. а.u.ch.
-31
electron e 9,109•10 1,602•10-19 0,0005486 -1
Nucleons Proton 1,673•10-27 1,602•10-19 1,007277 +1
1
1р
12
Neutron 1,673•10-27 0 1,008695 0
1
0n
(Here you can see the weight of an electron in International System (SI) 9,109•10-31………………
and in System of atomic units……0,0005486……………………………………….
The charge of an electron in International System
-19
is…………………………………………….1,602•10 .it is constant.
In system of atomic units the electron’s charge is minus one(-1).
So about nucleons:
- the weight of a proton in International System is……………………………………………………..
- the weight of a neutron in International System is……………………………………………too
- the charge of a electron in International System is………………………………………it is constant.
- a neutron hasn’t got the charge
In system of atomic units:
- the proton’s charge is plus one(+1)
- the neutron’s charge is zero(0).
Chemical element - is the kind of atoms with an identical charge of a nuclear and with
An identical nuclear number.
Each chemical element has some isotopes.
Isotopes - is the kind of atoms with an identical charge of a nuclear , but
different mass number (A).
Table №2
1
The name of an isotope 1р 1
0n
mass number (A)
1
Isotopes 1H - protium 1 0 1
of
2
1Н Д -deuterium
hydrogen 1 Н Т - tritium
3 1 1 2
1 2 3
12
6 С Carbon-12 6 6 12
13
Isotopes 6 С Carbon-13
14
С Carbon-14 6 7 13
of carbon 6
6 8 14
(Write down, please the isotopes of hydrogen
1
1H - protium - has only one proton and it mass number (A) equals to one.
2
1 Н Д - deuterium - has one proton too and one neutron more, it mass number (A) equals to two.
3
1 Н Т - tritium - has one proton too and two neutron, it mass number (A) equals to three(3).
13
Except for isotopes there are isotones and isobars.
1
isotones - are atoms with identical number of neutrons 0 n , but various
1
quantity of protons 1 р ( with a different charge of a nuclear) ,
for example,
1 230 231 0
88 Ra ( radium, 228( À) 88( 1 ð ) 140( n )), 90Th (thorium), 91 Pa ( protoactinium) ( n=140)
228 1
0
Isobars - are atoms with identical mass number (A), but different nuclear
40 40 40
numbers, for example, 18
Ar; K ; Ca
19 20
1 1
After that as the three fundamental particles (е; 1 р ; 0 n ) have been opened, many
models of atom’s structure has been extended.
1. Tomson's Model, 1903(model « a pudding with raisin ») represents
the positively charged atom’s sphere with an electrons inclusions.
Fig. 1
2. In 1911 as a result of the well-known experiments on dispersion by a gold foile - α
particles have been established by E.Rutherford, the atom:
- Has massive positively charged nuclear having very small size and electrons which is
surround it;
- The atom is electroneutral, a positive charge of a nuclear is equal to the sum of a
negative charge of the electrons;
- The meaning of a nuclear’s charge equals to a serial number of the elements in the
D.I.Mendeleev's periodic system.
Fig.2
However, according to laws of classical mechanics and electrodynamics, rotation of
electrons around a nuclear should be accompanied by electromagnetic radiation with a
continuous spectrum. This theoretical fact contradicted descrepted spectra was received
during the expirements in 1880 by the student of Rutherford, Nils Bor.
14
3. N.Bor has developed theplanetary model of an atom in 1913 which is used now.
Such scientists as Rutherford, N.Bor considered thet the atom has massive positively
charged nuclear having very small sizes and the electrons wich surround it. However
N.Bor said, that the electrons were moving around a nuclear on their stability orbits.
These orbits had various energy. Passing from one orbit on another, electron could get
or loose energy. N.Bor сould explain and calculate theoretically descrepted spectrum
of hydrogen’s atom, and also a series of lines in x-ray spectrs of elements.
рис.3
4.In 1924 Луи де Бройль showed, that an elementary particle, moving with the speed,
could be not only as a particle having the weight of calmness, but also as a wave with
the frequency of fluctuations ():
In the case when the electrons is a particle, having the weight of calmness you can write Einstein’s
equation of Energy : E mc2 ,roughly that energy equals mass times the square of the speed of light.
In the case when the electrons are the wave you can write an equation of
Energy as creation Planck's constant (h) and frequency of fluctuations (), write down E h ,
If a particle on the one hand has the weight of calmness, and on the other hand it is a wave then
Energy’s weight of calmness equals the Energy of a wave: mc2 h
E mc 2
h
E h , mc 2 h ;
mc
c/
Planck's constant =6,626. 10–34 Dj.;
с=3. 10 8 km/s (speed of light);
We can see at this equation λ=h/mc
the length of a wave (λ) is result attitudes of numerator Planck's constant(h) to a denominator, which
is a product of a weight of calmness and speed of light. If the mianing of the weight of calmness or
denominator increases, the length of a wave (λ) will decrease. In this situation, the properties of
macrobodies have been studied by classical mechanics.
And If the meaning of the weight of calmness or denominator are very small as an electron then the
length of a wave (λ) will increase.
The result of де -Brol, Dirak, Gejzenberg, Shrjedinger’s works and others have made
the scientific bases of the new physical theory - QUANTUM MECHANICS. This new
physical theory has declared Corpuscle-wave dualism of microparticles, for example, an
electron has a weight of calmness of 9,109•10-31 kg., showing properties of a particle,
and in experiences on diffraction it shows properties of a wave). In the quantum
mechanics the classical concept "trajectory" is replaced with concept « wave function »
or « atomic orbital (AO) ».
The atomic orbital (AO) is an area about nuclear space where electron can be with
enough high degree of probability. The term orbital is conformable to the term an
orbit, however their sense is the different. The orbit is a trajectory of a movement,
nuclear orbital – wave function. If a wave function (ψ) of the particles are known, it is
possible to calculate probability (ψ2) findings of a particle in various areas of space.
15
In 1925 Эрвин Shrjedinger has offered the Mathematics equation allowing to
describe wave function of particles.
h 2 d 2 d 2 d 2
H E - Where Н – Hamilton H U
8 2 m dx2 dy 2 dz 2
h 2 d 2 d 2 d 2
2 2 2 2 - The operator of kinetic energy,
8 m dx
dy dz
U - the operator of the potential energy.
This differential linear equation of the second order in partial derivatives has many
decisions. From them we are interested in only such meanings, which do not contradict
to physical representations. These are quantum numbers n, l, ml, s.
n - THE MAIN QUANTUM NUMBER
n – characterizes a power condition of an electron in an atom. Accepts positive integer
meanings from 1 up to (infinite) (n=1... 7 …).
n 12345
Power KLNO
Level, cover
The number of the period in periodic system of D.I. Mendeleyev is such as meaning of
the main quantum number.
With the increase of the meanings of the main quantum number (n ) the energy of AO
increases too. If n=1 then energy is minimal, electron is in a stationary condition
,steadiest of all. - orbital QUANTUM NUMBER
(COLLATERAL; AZIMUTHAL)
– characterizes:
-defines energy of an electron to a power sublevel (subshell);
- The form of the nuclears orbital
(l=0, there corresponds a s-sublevel, the spherical form nuclear orbital;
l =1, corresponds р - the sublevel, the form of nuclear orbital reminds a dumbbell;
l = 2, there corresponds a d-sublevel, the form orbital of nuclear represents « four
petal » a figure).
- quantity orbital of nuclear (sublevels) on the level.
-admissible values 0,1,2,3.., n-1,where n - THE MAIN QUANTUM NUMBER .
Let's make the table. This table will contain four lines and five vertical columns.
In the first lines, please, write down the meanings of the n - THE MAIN QUANTUM
NUMBER
In the second lines, please, write down the meanings of the - orbital QUANTUM
NUMBER
In The third lines, please, write down the Subshell
16
In The fourth lines, please write down the maximal number of an electrons at the level.
The maximum quantity of an electrons at a power level you can calculate using this
equation: 2n2
If electrons situate at the first power level it means that this power level is characterized
by the first MAIN QUANTUM NUMBER n=1.
If n=1 then will be equal to zero.
If =0 it means that first power level has only one s - sublevel.
Electron-clouds at this nuclear orbital have a spherical form
The maximum quantity of an electrons at s - sublevel is 2 , then at first power level it is
2 too.
You can use this equation: 2n2 for your calculations: n=1 2.12=2
If electrons situate at the second power level it means that this second power level is
characterized by the n=2.
If n=2 then will be equal to zero and one. It means thet this second power level has
two sublevels: s – sublevel and p- sublevel. Electron-clouds at p- sublevel have the
form of remind a dumbbell.
The maximum quantity of an electrons at s - sublevel is 2, at p- sublevel -6 , then at the
second power level will be 8 electrons .
You can use this equation: 2n2 for your calculations: n=2 2.22=8
If electrons situate at the third power level it means that this third power level is
characterized of the n=3
If n=3 then will be equal zero, one and two. It means thet this third power level has
three sublevels: s – sublevel, p- sublevel and d- sublevel. Electron-clouds at d- sublevel
have the form represents « four petal » a figure.
The maximum quantity of electrons at s - sublevel is 2, at p- sublevel -6, at d- sublevel -
10, then at the third power level will be 18 electrons.
You can use this equation: 2n2 for your calculations: n=2 2.32=18
.
17
If electrons situate at the fourth power level it means that this fourth power level is
characterized by the n=4
If n=4 then will be equal to zero, one, two and three. It means that this fourth power
level has four sublevels: s – sublevel, p- sublevel, d- sublevel and f- sublevel.
The maximum quantity of electrons at s - sublevel is 2, at p- sublevel -6, at d- sublevel -
10, at f- sublevel -14 then at fourth power level will be 32 electrons.
You can use this equation: 2n2 for your calculations: n=2 2.42=32
Table №3
Environment K L M. N
Power level
n 1 2 3 4
l 0 0 1 0 1 2 0 1 2 3
Subshell s s p s p d s p d f
(Sublevel)
Maximal 2 2 6 2 6 1 2 6 1 1
Number the electrons
0 0 4
2
at the level, 2n
2 18 18 32
Alphabetic symbols s -sublevel; p-sublevel; d-sublevel; f-sublevel -were entered in
1890г. At the description of a spectrum of alkaline metals: (sharp-острый) l=0 (s-
sublevel); l=1 (p-sublevel) (main- главный); l=2 (d-sublevel) (diffuse-диффузный);
(fundamental) l=3 (f-sublevel). These letters are not reductions of the words describing
"form" орбитали.
ml – MAGNETIC QUANTUM NUMBER
Defines orientation nuclear orbital in space.
Give by a Klechkovky’s rule we shall calculate the energy of a sublevel
make the table. This table will contain 6 vertical columns.
In the first column, please write down the meanings of the - orbital QUANTUM NUMBER
In the second lines, please write down the alphabetic meanings of the - orbital
QUANTUM NUMBER
-In The third column, please write down the meanings ml – MAGNETIC QUANTUM NUMBER
-In The fourth column, please write down the number of the orbital at Subshell.
18
You can use this equation: ml =2l+1 for your calculations number of the orbital at
Subshell.
-In The fifth column, please write down the number of free orbitals (the number a
section). This is graphic representation of the number of free orbitals.
-In The sixth column, please write down the maximal number an electron on the atomic
orbital.
What does it mean if n=1?
How many meanings has - orbital QUANTUM NUMBER got? =0
What does it mean if =0? (It means that an electron situats at the first power level, s –
sublevel, electron-clouds at this nuclear orbital have spherical form)
If =0 it means that then m will be equal to zero. You can use this equation: ml =2l+1
for your calculations number of the orbital at s – subshell: ml =2.0+1=1 - it means m
has only one meaning. This is zero, and then at s – subshell there is only one free
orbital.
Graphic representation of this frees orbital at s – subshell is the one section.
m =0 - it means that spherical electron-clouds are oriented in the space equal all axis of
coordinates, accordingly: x, y,z.
What does it mean if =1? (It means that an electron situats at the, p – sublevel,
electron-clouds at this nuclear orbital have the form reminds a dumbbell.
spherical form)
If =1 it means that then m will be equal to -1, 0, +1(Minus one, zero and plus one). You
can use this equation: ml =2l+1 for your calculations the number of the orbital at p –
subshell: ml =2.1+1=3 - it means m has three meanings. These are -1, 0, +1, then at p
– subshell there are three free orbitals.
The graphic representation of this free orbital at p – subshell is the three sections.
m =-1,0,+1 - it means that electron-clouds are oriented variously in the space along
axis of coordinates x, y, z.
What does it mean if =2? (It means that electrons situate at the, d – sublevel, electron-
clouds at this nuclear orbital have the form represents «four petals» a figure.)
If =2 it mean that then m will be equal to -2,-1, 0,+1,+2(Minus two, minus one, zero and
plus one, plus two). You can use this equation: ml =2l+1 for your calculations number of
19
the orbital at d – subshell: ml =2.2+1=5 - it means m has five meanings. Thse are -2,-1,
0, +1, +2, then at d – subshell there are five free orbitals.The graphic representation of
these free orbitals at d– subshell are the five sections.
m =-2,-1,0,+1,+2 - it means that electron-clouds are oriented variously in the space
along axis of coordinates x, y, z,xy,yz ,z2.
Table №4
ℓ Subshell ml Number of the
Graphic representation of The maximal number an
number free orbital electrons on atomic orbital
of the
orbital
(AO)
ml =2l+1
s 0 1 2
0
p -1
1 0 3 6
+1
2 d -2
-1
0 5 10
+1
+2
3 f -3
-2
-1
0 7 14
+1
+2
+3
20
In absence of an external magnetic field electrons on orbitals with identical value of
orbital quantum number are energetically equivalent. However in a constant magnetic
field some spectral lines are split. It means, that electrons become energetically not
equivalent. For example, p-sublevel has three values (рх, рy, pz) of conditions in a
magnetic field, d -sublevel has 5 values conditions.
S - SPIN QUANTUM NUMBER
It is not connected with the movement of an electron around a nucleus;
-characterizes only the moment of the rotation of an electron about its axis;
- meanings: +1/2 (the movement of an electron сlocwise direction); -1/2 (the movement
of an electron counter сlocwise direction).
Dutch physicists Ulenbek and Goudsmith opened the spin of an electron in 1925
SPIN of an electron is not a simple rotation electron about its axis; it is a complex of
physical phenomena. Дирак in 1928 showed presence of parallel () and antiparallel
()spins.
The condition electron in an atom is defined by these laws:
1. a principle of a minimum of the energy:
The orbital with smaller value of energy is filled at the first !
(1s2s2p3s4s3-rd4p5s4d5p6s4f5d6p7s);
2. PRINCIPLE Pauli :
- In an atom there cannot be two electrons whith all four identical quantum
numbers (1925).
Let's consider an example, using Pauli's principle.
Hydridgen is situated in Mendeleev’s periodic system in the first period. The number of
the period is the same as a value of the main quantum number. Therefore for elements
of the first period of hydrogen and helium n=1. It means thet their electrons situated at
the first power level, s – sublevel.
It mean that Hydridgen’s only one electron is characterized by such quantum numbers:
n=1, =0, ml=0 ,S=+1/2 or n=1, =0, ml=0 ,S=-1/2
its electronic formula 1s1 , its electrono- graphic formula
1s ↑
Helium has two electrons situated at the first power level, s – sublevel.
One helium’s electron is characterized by such quantum numbers as n=1, =0, ml=0,
S=+1/2
if second helium’s electron will be characterized by such quantum numbers: n=1, =0,
ml=0 ,S=+1/2 then helium’s electrons will have all four identical quantum numbers .
Such situation contradicts Pauli's principle. The second helium’s electron must be
characterized only by such quantum numbers as: n=1, =0, ml=0, S=-1/2
Two electrons with any value opposite spins can be on this s-orbital
21
Helium’s electronic formula 1s2, its electrono- graphic formula 1s ↓↑
Thus, at the first power level there are no more than two electrons!
3.RULE ХУНДА - The steady condition of an atom is a condition with the
maximum number not coupled electron.
An electron must fill the power sublevel that their absolute value of the sum of a their
spins |S | is maximum
For example: the electronic structure of the last power sublevel of carbon’s atom is 6С
2s22p2 It can be described various by variants of electron-graphic formulas and-in.
It is forbidden
а) 2р ↓↑ |S|=0 б)2р ↑ ↓ | S|=0
It is authorized:
в) 2р ↑ ↑ |S|=1
The condition в) is more steady, because their absolute value of the sum of a their spins
|S | is maximal.
5. The first Klechkovsky’s rule:
Electrons are filling the energy levels from orbital with smaller value of the sum
(n+l) to оrbital with great value of this sum.
For example, the atom of potassium(K) is in Mendeleev’s periodic system in the four
the period. The number of the period is such as the value of the main quantum number.
Therefore for elements of the fourth period n=4. It means that their electrons are at the
power level 1, s – sublevel: 1s
power level 2, s,p – sublevels: 2s 2p electronic formula is 1s2 2s2 p6 3s2 p6 d0 4s1
power level 3, s,p,d – sublevels: 3s 3p 3d
power level 4, s,p,d,f – sublevels: 4s 4p 4d 4f
Serial number калия is 19. It means nuclear’s charge equal to19 too. The atom is
electroneutral therefore an electrons in the atom of potassium(калий) must be 19 too.
How does an electrons fill in the energy levels? To answer this question,
Let’s calculate energy of a sublevel by Klechkovsky’s rule:
for ls – sublevel: the sum (n+ )=1+0=1
for 2s– sublevel: the sum (n+ )=2+0=2
for 2p– sublevel: the sum (n+ )=2+1=3
for 3s– sublevel: the sum (n+ )=3+0=3
for 3p– sublevel: the sum (n+ )=3+1=4
for 3d– sublevel: the sum (n+ )=3+2=5
for 4s– sublevel: the sum (n+ )=4+0=4
for 4p– sublevel: the sum (n+ )=4+1=5
for 4d– sublevel: the sum (n+ )=4+2=6
22
for 4f– sublevel: the sum (n+ )=4+3=7
REMEMBER!
For s – sublevel according to =0
For p – sublevel according to =1
For d – sublevel according to =2
For f – sublevel according to =3
1s – sublevel will be filled at first because it has the smallest value of energy, then
will be filled 2s, then 2p, then 3s, then 3p, then 4s
electron fills 4s- sublevel, instead of 3d – sublevel, because the sum (n+l) for4s -
sublevel(4+0=4) smallest of energy then the sum (n+l) for Зd (3+2=5), according to first
rule Клечковского.
6. The second Klechkovsky’s rule: If the sum of the main quantum number
and orbital quantum number (n+l) of the оrbitals is identical, the orbital with
smaller value of the main quantum number (n) is filled before.
At filling electron orbital at atom of scandium which electronic formula
1s22s2p63s2p6d14s2, электрон fills 3-d (3+2=5), instead of 4р-sublevel (4+1=5), in
conformity with second rule Клечковского.
At some atoms the phenomenon « electronic jump », as, for example, at atom
of chrome is observed: Cr 3d44s2→3d54s1 or at atom of copper: Cu 3d94s2→3d104s1.
It is said that the raised power stability of electronic configurations with completely
(atom Сu) or half filled sublevel (Cr).
Review Questions
1. What do you know about a structure of an atom.?
2. What do you know about various theories about a structure of an atom?
3. What do you know about the main quantum number, it physical sense?
4. What do you know about the orbital quantum number, it physical sense?
5. What do you know about the magnetic quantum number, it physical sense?
6. What do you know about the spin quantum number, it physical sense?
7. What do you know about the principle of a minimum of the energy?
8. What do you know about the principle of Pauli?
9. What do you know about the rule Hunda?
10. What do you know about the first rule of Klechkovsky?
11. What do you know about the second rule of Klechkovsky?
Further Reading:
1. Frolov V.V.chemistry. Ch. V, §51-56.
2. Luchinsky G.P.rate of chemistry. Ch. V, §8-12, ch. VI, §13-18
3. Ahmetov N.S.general and inorganic chemistry. Section V, ch.3,4.
4. The general chemistry under ред. Sokolovskoj E.M., etc. Ch.6, §1-11.
23
PERIODIC D.I.MENDELEEV’S LAW.
LAW OF the PERIODIC SYSTEM.
Obgectives
After studying this chapter, students should
be able to know:
1. D.I.Mendeleyev's periodic law.
2. A structure of periodic system of D.I.Mendeleyev.
3. Physical sense of periodic system value.
4. Laws of periodic system. Radius of the atom. Valency of an element.
5. Energy of ionization, energy of electron affinity, electronegativity.
6. The plan of the characteristic of elements’s properties by their position in periodic
system.
The periodic law has been formulated on March, 1 first, 1869 by great Russian
scientist Dmitry Ivanovich Mendeleyev. D.I.Mendeleyev, the outstanding Russian
scientist, was born in Tobolsk in 1834. In 1850 at the age of 16 he entered the
Pedagogical Institute in Petersburg to study chemistry. Five years later he graduated
from it with a gold medal and was invited to lecture on theoretical and organic
chemistry at Petersburg University.To continue his studies and research Mendeleyev
was sent to Germany in 1859. While living abroad he made a number of important
investigations.
The year 1868 was the beginning of his highly important work “Fundamentals of
Chemistry”. When working at the subject D.I.Mendeleyev analysed an enormous
amount of literature, made thousands of experiments and calculations. This tremendous
work resulted in the Table of Elements consisting of vertical groups and horizontal
periods. Mendeleyev was the first to suggest a system of classification in which the
elements are arranged in the order of increasing atomic weights. The main idea of the
periodic System is the idea of periodic repetition of properties with the increase of the
atomic weights.
The periodic law in D.I.Mendeleyev's interpretation:
properties of simple bodies, and forms and properties of their chemical compounds
also are in periodic dependence of the value of its atomic weights.
Arranging all the existing elements in the Table Mendeleyev had to overcome great
difficulties, as a considerable number of elements were unknown at that time and the
atomic weights of 9 elements (out of 63) were wrongly determined.
Thanksn to his investigations Mendeleyev was able to predict not only the
extence of a few unknown elements but their properties as well. Later these elements
were discovered.h
Mendeleyev was engaged not only in the study of chemistry. His more than
350 works deal with many subjects. Combining theory with practical activity he carried
24
out enormous reserch in coal, petroleum, iron and steel industries. He died in 1907 at
the age of 73.
The modern formulation of the periodic law:
properties of simple bodies, and also forms and properties of their connections are
in periodic dependence on value of charges of their atomic nuclears.
The periodic system of elements is a graphic representation of the periodic law.
Some hundreds forms of periodic system are known, however, the short variant of
periodic system is used in Ukraine. The periodic system consists of the periods and
groups.
The period is a horizontal row of the elements, where the elements are located in
order of the increasing serial number from the first s-element (ns1) to a p-element
(ns2np6). Each period (except the first one) begins active alkaline metal and ends the
inert gas before which there is a nonmetal (halogen). The last (n) level, and also
before last (n-1) and (n-2) levels of atoms in the periods are filled by electrons. There is
: small (1,2,3) and greater (4,5,6,7) periods. In the period from left to right metal
properties of elements decrease, and nonmetallic – increase.
Number of the period and number of power levels in atom and value of the main
quantum number (n) an external power level are equel.
Groups is a vertical row of the elements, where the the elements have same
electronic structure. Elements of periodic system are subdivided into eight groups.
There are main (A) and collateral (B) subgroups in the group. The main (A)
subgroup there are s-, р - elements of the small and greater periods.Collateral (B)
subgroup have the elements only greater periods.
The number of group corresponds to the maximum valency of an element.
Valency of a chemical element is its ability to formate the chemical communications. In
representation of a method of valent communications value of valency is the quantity
of unpaired electrons. In periodic system each element has strictly certain serial
number and takes strictly a certain place.
The serial number of an element corresponds to a positive charge of a nuclear of
atom (to quantity of protons- 1 р ) and to sum of the electrons ( e ) on it orbitals.
1
Valency electrons have the greatest reserve of energy; they define the chemical
properties of atoms. Atoms, entering into chemical reactions, can to give off valent
electrons or accept them or form the general electronic pairs.
The radius of atom (Rаt) defines the ability of atoms to give off or accept electrons. The
more Rаt, the easier the atom loses the valency electrons and it is more difficult accepts
them.
In period Rат decreases from left to right. The serial number of an element
increases, then the quantity electrons of an element increases too, but the quantity of
25
power layers does not vary.As resalt: a positive charge of a nuclear in atom (to quantity
of protons- 1 р ) increases and a sum of negative charge of the electrons ( e ) on all
1
orbitals increases too. Electrostatic interaction increases. It leads to compression of
electronic density and as consequence, to reduction Rаt.
In the group Rat increases from top to down (as with increase in a serial number
of an element, the quantity of power layers increases too and the electrostatic interaction
decreases.) The atoms easier loses valent electrons and more difficultly them accepts.
The atoms lose valent electrons, show regenerative properties.
The quantitative characteristic of regenerative properties of elements is energy of
ionization (I, кDj/mol, eV/atom).
Energy of ionization (I) is the quantity of the energy which is necessary for
valent electrons detachment from еlectroneutral atom with transformation of last in
positively charged ion (кation). The first energy of ionization characterizes the
ability of atom to give of one electron:
Э0(еlectroneutral atom) + I(energy of ionization) Э+( positively charged ion
(кation))+ one electron.
For multielectronic atoms of energy of ionization I1; I2; I3... characterizes the first
valent electron detachment, the second electron detachment … Thus I1 I2 I3...,
becouse the increase the quantityof the loseing valent electrons leads to increase of a
positive charge of an ion.
Potential of ionization -is the attitude energy of ionization to a electron’s charge
(is measured in electron-volt, (eV)). The potential of ionization is numerically equal to
energy of ionization.
In the period value of energy of ionization from alkaline metals to inert gases
increases, because the Rаt in the period decreases, and the charge of a nuclear of atom
increases, therefore there is a compression of electronic density, and it is necessary to
spend a lot of energy for tearing off electron from neutral atom.
The value of energy of ionization decreases from top to down in groups, because the
radius of atom (Rаt) increases in groups from top to down, therefore it isn’t necessary
to spend a lot of energy to tear off electron from neutral atom.
Francium 223Fr has the smallest energy of ionization.
87
The atoms accepting valent electrons, show oxidizing properties. The quantitative
characteristic of oxidizing properties of an element is energy of affinity to electron (Е;
eV/atom).
Energy of affinity to electron is the energy allocated at connection electron to
neutral atom; it characterizes the ability of atom to formation of negatively
charged ions:
Э0 (not raised atom) + one electron Э- (negatively charged ions) +E(Energy
of affinity to electron).
Fluorine atom (F) has the greatest Energy of electron affinity. Energy of electron
affinity is much less than ionization energy of the same atoms.
Both these valuas (I and E) are depended on a charge of a nuclear and the atom’s
size: they should grow with increase in a nuclear’s charge, and with increase in radius of
atom – to decrease.
26
American scientist Poling entered the the special characteristic – electronegativity
(ЭN) 1932. It is characterizes the ability of atoms in molecule to attract the electronic
density.
ЭN = 1/2 (I +E).
The more valua of the ЭN, the nonmetallic properties of an element are expressed
more strongly. There are more strongly expressed metal properties of an elements if the
valua of the ЭN to less. Electronegativity (ЭN) has no strictly physical sense, but it is
used for the estimation of a real condition of chemical communication in molecules.
Lithium’s electronegativity is accepted for unit of the ЭN . The most electronegative
element is fluorine.
The elements of D.I.Mendeleev’s periodic system can be divided into four types
according to the atom structure.
s - elements (the s-sublevel of the last level is filled at the end):... ns1, ns2
p - elements (the p-sublevel of the last level is filled at the end)... np1-np6.
d - elements (the d-sublevel of the before last level is filled at the end)... (N-1) d1ns2 –
(n-1) d10ns1.
f - elements (the f-sublevel – the second of the before last level is filled at the end)...
(N-2) f1 ns2 - (n-2) f14 ns2.
s - elements settle down in IА and IIА groups, the main subgroups. The maximum
quantity of an electron at s - sublevel is 2.
These are typical metals, have similar chemical properties as are electronic analogues.
Electronic analogues are elements having the electronic formula of the last level
general for all, described by s – elements of the IА group:
Li (Lithium) Na(sodium) K(potassium) Pb, Cs, Fr
2s1 3s1 4s1 5s1 6s1 7s1
ns1 – electronic analogues (these elements have only one electron at s – sublevel)
Table №5
Reducer оxide The basis asid Salt
At atom 11Na
11 эlectrons, from them one
is valent, therefore Na is Na0 Na+
e
Na2O NaOH - --- NaCl
metal ( (is oxidized)
I valent basic= 1
s – elements of the IIА group:
Be(beryllium) Mg(magnesium) Ca(calcium) Sr Ba
2 2 2 2
2s 3s 4s 5s 6s2
ns2 – electronic analogues(these elements have two electrons at s – sublevel)
Table №6
Окси The basis Acid Salt
Reducer
д
56Ba – metal
Ba0 Ba2+
е
2
valentbasic =0 - - ---
V* (возб.сост). = 2 BaO Barium BaSO4
(OH) 2
27
p - elements arrages from IIIА to VIIIА groups, the main subgroups. At p –
subshell there is three free orbitals, wich of them can consist of two electrons
The maximum quantity of an electrons at p - sublevel is 6.
Thus, the main subgroups has only s-, p – elements. Among p-elements there are
metals, but they can be amphoteric often:
Table №7
Reducer оxide The basis Acid Salt
13Al
AlCl3
valent basic=0 HAlO2
Al0 3e
Al 3+
Al2O3 Al(OH)3 NaAlO2
V* (возб.сост). H3AlO3
Na3[Al(OH)6]
=3
p-elements are nonmetals if there are 4-8 electrons at last power level.
Table №8
Oxidizer оxide The basis Acid Salt
0 e
-
F F
9F F2O – HF NaF
()
The element 17Cl has vacant 3d – a sublevel, to which can pass valent electrons from 3s
and 3p- sublevels. As resalt - the element 17Cl shows variable valency:
Table №9
оxide Acid Salt
0 e -
Cl Cl HClchlorohydric CaCl2-chloride of calcium
Cl0 Cl+1
e NaClO–
Cl2O HClO hypochlorite of sodium
hypochlorous
17Cl
valent basic=1 Cl2O3 HClO2 Chlorous NaClO2–sodium chlorite
V*(возб.сост).= Cl0 Cl3+
3e
3,5,7 Cl0 Cl+5
5e
HClO3chloric NaClO3-
Cl2O5 хлорноватая chlorate of sodium
Cl0 Cl+7
7e
Cl2O7 HСlO4 perchloric NaClO4–perchlorate of
sodium
The inert gases (He, a neon) have the p-sublevel is filled completely by its
electrons. The valency of these inert gases (He, a neon) is equal to zero, there is no
place for any electrons.
The inert gas 18Ar has vacant 3d – a sublevel. valencies are possible:
28
valent норм=0; V * = 2,4,6,8.
The inert gas 54Xe burns in fluorine with formation: XeF2, XeF4, XeF6, XeF8.
d – elements are metals. Its have two (2) eletctrons at the last electronic level ns2. A
vacant оrbitals of the preexternal layer is filled by valency of electrons. d – elements
are named transitive, because it is in periodic system between s- and thet the p-
elements, they form collateral groups.
Table №10
оxide The basis Salt
21Sс
(3d14s2) Sc0 2 е Sc+2
ScO Sc (OH) 2 ScCl2
valent Sc0 Sc+3
3e
basic=1 Sc2O3 Sc (OH) 3 ScCl3
V*(возб.
сост).=
2,3
The plan of the characteristic of properties of elements by position in periodic
system (PS).
1. Position of an element in PS (a serial number, the period, group, and a subgroup).
2. A structure of atom (a charge of a nuclear and its structure) – number of protons,
neutrons, number of electrons in atom, structure of an electronic level of atom, the
electronic formula of valent levels, valency basically and the raised conditions.
3. Type of an element (s-, p-, d-, a f-element), (metal, nonmetal), possible degrees of
oxidation, the oxide’s formula and gidroxide for each valent condition.
Example: to give the characteristic of sodium. Its serial number is 11, a charge of a
nuclear of atom is equal to +11, around of a nuclear to rotate 11 electrons. Sodium is
located in the third period, therefore it electrons settle down at three power levels.
Sodium is located in the first group, the main subgroup; atom Na has one valent
electron at an external level. Na – metal ( the atom is metal if it has at an external power
level 1,2,3 electrons), oxside of sodium Na2O has the basic character. To it there
corresponds basis NaOH.
Opening of the periodic law by D.I.Mendeleyev and creation of periodic system of
chemical elements by it was triumph in the development of chemistry of theXIX
century.
The knowledge of properties 63 chemical elements which has been collected has
been resulted by D.I.Mendeleyev in the strict order. With opening the periodic law there
was an opportunity to predict property of new elements and their connections.
D.I.Mendeleev on the basis of the periodic law has predicted properties then still
unknown elements: Sc, Ga, Germany, Tc, Rе,Po, At, Fr, Rа, Аc, Pa. D.I.Mendeleev
could correct nuclear weights of elements already known at that time: Be, Ti, Y, In, La.
The achievements in chemistry and physics at the end of the 19th and the
beginning of the 20th century made it necessary to reconstruct the Periodic Table taking
into account new descoveries. This progress resulted in the discovery of the inert gases
of the so- called zero group, and the study of 14 rare earth elements. In the last few
29
decades 11 new radio- active elements were obtained. Two of them were named in
honour of Russian scientists: the 101st was called mendelevium and the 104th –
kurchatovium (in memory of Igor Kurchatov)
Time is the severest judge in science. After the 100 years of its existence, the
Periodic Law has preserved its full value and is being constantly developed with each
new discovery.
Review Questions
1. Definition of notion “group” of periodic system of D.I.Mendeleev.
2. Definition of notion “period” of periodic system of D.I.Mendeleev.
3. Definition of notion “radius” of atom. How is it chang in the group, period?
4. Definition of notion “energy of ionization” of atom. How is it chang in the group,
period?
5.Definition of notion “energy of affinity” of atom. How is it chang in the group,
period?
6. Definition of notion “electronegativity” of atom. How is it chang in the group,
period?
7. Definition of notion “Electronic analogues”
8. What do you know about s – elements?
9. What do you know about p – elements?
10. What do you know about d – elements
11. What do you know about f – elements
12 Fluorine and chlorine are electronic analogues. Why chlorine has more valence than
fluorine?
13 Why Ar or Xe has more compounds than He or Ne?
Further Reading:
1. Frolov V.V.Chemistry. v. V, §51-56.
2. Luchinsky G.P.rate of chemistry. v. V, §8-12, Ch. VI, §13-18
3. Ahmetov N.S.general and inorganic chemistry. Section V, ch.3,4.
4. The general chemistry under ред. Sokolovskoj E.M., etc. Ch.6, §1-11.
30
CHEMICAL THERMODYNAMICS.
Obgectives After studying this chapter, students should
be able to know:
1. Definition of this notion « chemical thermodynamic ».
2. The basic notions of section « chemical thermodynamic »:
Thermodynamic system, kinds of systems;
Thermodynamic parameters;
Process, classification of processes;
Cycle;
Thermodynamic functions.
3. The first law of thermodynamics:
izohorny process, internal energy of system
Izobarny process, definition of notion «entalpiy».
4. Thermochemistry:
Definition of notion "thermochemistry";
Thermal effect of chemical reaction;
Gess's law is important laws of thermochemistry.
The thermodynamics – as a science has arisen in the beginning of XIX century (in
connection with problems of perfection of thermal machines). In translation with Greek
"thermos" means heat, and «dynamic» – force and power. The classical thermodynamic
is researching of energy and work in macroscopical systems. It has value for such
sciences, as physics, chemistry, biology, geology, for numerous branches of technics as
any nature’s processes, wich are accompanied by changes of energy.
The chemical thermodynamics is a section of chemistry, which
studies 1) transitions of energy from one form in another at chemical processes and
2) establishes a direction and limits of their spontaneous course under the given
conditions.
Thermodynamic chemical system – the complex of substances cooperating
among themselves mentally isolated from an environment. For example, system can be
the chemical glass containing certain quantity of water, or heat- exchanger, used at the
chemical enterprise, etc.
There are three types of thermodynamic systems (Table.11).
The isolated systems – cannot change with environment energy, weight. For
example, isolated termostat, the Universe as a whole.
The closed systems – can change with an environment with energy only, but not
with weight. For example, molecules of the dissolved substance can be considered as
the closed system, and as an environment there can be all rest (probably solvent if it
31
does not participate in reaction). Therefore in chemical thermodynamics the closed
systems are more often used.
The open systems are systems which can change with an environment and
energy, and weight. For example, alive objects of an animal or flora.
Table №11
The isolated The closed The open
systems systems systems
E E E
m m m
All systems can be in various conditions. The thermodynamic characteristics are
used to describe their conditions. (рис.4). A condition of systems can be considered by
thermodynamic parameters of a condition. It is temperature (T), pressure (P) and
quantity of substance (n).
Other thermodynamic characteristics depend on these three parameters (Т, Р, n), and
from a condition of system at whole. Therefore them name are functions of a
condition. They are: U- internal energy, S-entropy, H-entalpy, Energy of
Гельмгольца,Energy of Гиббса.
Термодинамические характеристики
параметры состояния состояние я
функции состоя иия
Рис.4
A condition of any systems can be considered by U- internal energy.
Internal energy of system (U) is the sum of energy of thermal movement of molecules,
intramolecular energy and energy of intermolecular interaction. Whether is it possible to
calculate absolute value of internal energy? Whether is it possible to calculate kinetic or
potential energy of atoms and molecules from which any system consists of? No.
32
Absolute value of the Internal energy of system (U) is not known. So, what can we
calculate?
Let’s consider ourselves as open system. Imagine that you got up in the morning, had
breakfast, were full of forces and energy. It means thet you possess a stock of internal
energy U1. Then you went to university, attended lectures, someone can be also a sports
hall, and someone had visit to the girl. It depends on morning condition, from a
reference value of internal energy. In the evening you already feel weariness. The stock
of your internal energy has been spent for cares of day. Therefore your evening
condition will be characterized by a smaller quantity
of internal energy U2. Thus, internal energy characterizes a condition of system during
the certain moment of time, for example in the morning or in the evening as has been
shown in our example. And so we cannot calculate morning absolute value of internal
energy or evening absolute value of internal energy. But what can we calculate? We can
calculate changes of internal energy in processes–U. U does not depend on the a way
of transition of system from one condition in to another. Internal energy is a function of
a condition of system. Internal energy is defined by kinetic energy it mean, that it
depends on temperature. Internal energy is defined by potential energy, it mean, that it
depends on volume. Internal energy is a function of a condition of system, and depends
on the temperature and the volume. Therefore there is a sense to write down equation of
full differential for internal energy.
U U
dU= ( )V dT ( ) T dV
T V
Tell, please: What was between a morning condition, full of forces and energy and an
evening condition of weariness? You have worked! Thus during the transition of system
from one condition in another there is a sense to speak about work(A) or heat (Q)
which is allocated or absorbed as a result of performance of this or that process.
Work and heat are not functions of a condition of system. These notions have sense only
when processes are. Therefore is possible to speak only about infinitesimal quantity of
heat and work and isn’t possible to speak of it full differential.
As to heat (Q) and works (A) it is two unique forms of transfer of energy from
system to an environment and back. Signs on heat and work are defined by the scheme
5.
Q0
Q0
System
A0 A0
scheme.5
1. Q0; A0 if the system receives heat or above it work is made.
2. Q 0; A0 if the system gives heat or itself makes work.
33
The corresponding sign (plus or a minus) isn’t wrote before letters Q and A, and it has
been written before digital value of the corresponding size, for example, Q =-300 кДж
or A= + 50 кДж.
All three concepts heat, work and internal energy are interconnected among themselves.
It is at the first law of thermodynamics.
Heat is transferred to system (Q) goes on change of its internal energy (U) and to
work
Q =U+A
The first law of thermodynamics has been formulated by Joule in the middle of the
XIX century. Inherently it is the law of conservation of energy
Thermodynamic processes are changing of any condition’s parameters ( transition
of a system from one condition in to another). Processes are:
- Isohorniy (V=const);
- Izobarniy (P=const);
- Isothermal (T=const);
- Adiabatic (there is no exchange of energy of system with an environment);
- Izobarniy - isothermal (P; Т=const);
- Isohorny - isothermal (V; T=const).
Let’s write down the differential equation of the first law of thermodynamics for
isohorny processes (V=const). QV=dU+ A, where A is the work of expansion:
A=P dV
.
QV=dU+ P dV, but there isn’t the changes of volume for isohorny
.
Then
processes (V=const). P.dV=0
the differential equation of the first law of thermodynamics for isohorny processes
(V=const) is QV=dU
the integrated kind equation of the first law of thermodynamics for isohorny processes
(V=const) is QV = U.
For example, heating of gas under the fixed piston, the work is not made (А=0),
therefore QV = U.
Conclusions:
1. the heat of isohorny processes (QV) is function of a condition of system such
asU.
2. QV = U.This first mathematical equation of tht Gess’s law (see further).
Izobarniy processes (P=const).
For example, heating gas makes work of expansion against constant external
pressure. The work of expansion (А) is defined as sum of pressure(P) and changes of
34
volume (V). Therefore the differential equation of the first law of thermodynamics
QP =dU+ P dV
.
for izobarniy processes (P=const) is
The pressure(P) is constant, then you can write down: QP =dU+ d P.V. The sum
of the differential’s U and P.V is the differential of their sum: QP =d(U+ P.V)
If the sum U+ P.V to designates as one letter H (H= U+ P.V) you can write down
QP =dH it is
the differential equation of the first law of thermodynamics for Izobarniy processes
(P=const).
the integrated kind equation of the first law of thermodynamics for isohorny processes
(V=const) is QP = H.
Conclusions:
1. The sum H= U+ P.V is system’s heat or system’s energy at whole.
2. This letter H means ENTALPIY
3. Entalpiy is function of a system’s condition such as the heat of isobarny
processes QP.( as work against constant external pressure does not depend on a
way of fulfilment of the process, it is defined only by an initial and
final condition of the system V. The work is function of a
condition during izobarniy process only the done.
4. QP = H this second mathematical Equation of the Gess’s law
(see further).
5. For exothermal reactions QP 0, the system gives of heat to the
Environment and its internal energy decreases Н 0. (entalpiy is belong
ziro)
For endоthermal reactions QP 0, the heat is given to a system and its
internal energy increases H 0(entalpiy is above ziro).
The thermochemistry- is the section of thermodynamics studying thermal effects of
chemical reactions.
Gess's law is the law of thermochemistry (1840):
The thermal effect of chemical reaction does not depend on the mechanism of a
reaction, and depends only on nature and a physical condition of initial substances
and products of reaction( or of finel(конечные) substances) (under condition of
V=const; P=const).
QV = U - this first mathematical equation of the Gess’s law
QP = H - this second mathematical Equation of the Gess’s law
Let's illustrate the meaning of this law in an example.
Димер оксида nitrogen’s(IV) di oxid can be received in several ways.
The first, 1) N2 + O2 = (is) 2NO, H1 = 180900 Djoul/mol ;( Djoul per mol)
35
2) 2NO + O2 = 2NO2, H2 =-77100 Djoul/mol ;( if we add one molecula O2
to two NO molecula then we receve NO2)
3) 2NO2 = N2O4, H3 =-10800 Djoul/mol.
Or, the second,
4) N2 + 2O2 = N2O4, H4=93000 Djoul/mol.
H1 + H2 + H3 = H4.
If illustrate it to Graphic:
Рис.6
The entalpy’s definition includes internal energy, so absolute value of entalpy of a
system (or any substance) is not known. Substances’s enthalpy is characterized by
entalpy of substance’s formations.
Н0298 (form) (standard enthalpy of substance’s formations) is a heat of a reaction of
formation complex substance (X) from simple substances (or elements) under standard
conditions: simple substances X complex substance.
For simple substances Н0form equals zero (in steady modular conditions).
Values Н0form there are in tables.
Reaction’s enthalpiy of any substances can’t be defined at the laboratory. For
example, it is impossible to define ethanol’s enthalpy in the laboratory, becouse ethanol
cannot be synthesized from atoms C, Н, O. Entalpy can be calculated in such case by
law of Gess.
Consequences from Gess's law:
The thermal effect (or hte enthalpiy) of chemical reaction can be found, as a
difference between the sum of heats of formation of ( finel(конечные) substances)
products and the sum of heats of formation of initial substances, accounting chemical
reaction’s coefficients.
Нc.r. = Н0 (products) – Н0(initial substances),
accounting chemical reaction’s stehiometric coefficients!
- The Greek letter “sigma”, shows operation of summation.
Problem: To define standard enthalpy of formations Н0 (РН3), from the equation.
2РН3 (g) + 4О2 (g) = Р2О5 (с) + 3Н2О (l), Нc.r =-2360 кlJoul.
(с) - a сrystal condition, (l) a-liquid condition, (g) - a gaseous condition.
The decision:
0 0 0
Нc. r. = [Н (Р2О5 (c) +3Н (Н2О (l)] - 2Н (РН3);
2Н0 (РН3) = [Н0 (Р2О5 (c) +3Н0(Н2О (l)]- Н0c. r.,
Н (Р2О5 (c) =-1492 кDj/mol, Н (Н2О (l) =-285,8 кDj/mol.
0 0
36
2Н0 (РН3) = [(-1492 + 3 (-285,8))] – (-2360) = 10.6 кDj/mol
Н0 (РН3) = 10,6/2=5,3 кDj/mol.
Standard enthalpy of the reaction of neutralization.
The heat is identical for reaction of neutralization.
Let's calculate it:
the reaction of neutralization is the reaction between strong acids and the strong alkali.
for example the reaction between a hydrochloric acid and sodium alkali is
HCl + NaOH NaCl + H2O
The full ionic reaction of neutralization: Н + +Cl- +Na+ + ОН- Н2О + Cl- +Na+
The reduced ionic reaction of neutralization: Н + + ОН- Н2О
for example the reaction between a hydrochloric acid and spotasum alkali is
HCl + KOH KCl + H2O
The full ionic reaction of neutralization: Н + +Cl- +K+ + ОН- Н2О + Cl- +K+
The reduced ionic reaction of neutralization: Н + + ОН- Н2О
for example the reaction between a Nitric acid and calcium alkali is
2HNO3 + Ca (OH) 2 Ca (NO3)2+ 2H2O
The full ionic reaction of neutralization: 2Н + + 2NO3- +Ca2+ +2 ОН- 2Н2О + 2NO3-
+Ca2+
The reduced ionic reaction of neutralization: Н + + ОН- Н2О
What is identical in these chemical reactions of neutralization?
The chemical meaning of these chemical reactions of neutralization is identical. It is the
reaction to receive a molecule of water.
Let's calculate it: Н + + ОН- Н2О Н0neutral. = - 55.8 кDj/mol. It is the constant.
standard enthalpy of phase transformations.
Heat of phase transition is equal to a difference standard enthalpy of substances (Н0)
in one and in the other condition. For evaporation of water (250С) it has:
Н2O(l) Н2O(g)
Н (Н2O(l))= -241.8 кDj/mol, Н (Н2O(g))= -285.8 кDj/mol
0 0
Н evaporation. =-241.8 + 285.8 = +44 кDj/mol (endothermal process).
Review Questions
1. What is the definition of this notion « chemical thermodynamic »
2. What do you know about thermodynamic system, kinds of systems?
3. What is the definition of this notion “thermodynamic process” What do you know
about classification of processes?
37
4. What do you know about thermodynamic parameters?
5. What is the definition of this notion “thermodynamic cycle”?
6. What are thermodynamic functions? Named them,please.
7. What do you know about the first law of thermodynamics?
8. What do you know about izohorny process?
9. What is internal energy of a system?
10. What do you know about izobarny process, the definition of notion «entalpiy».?
11. Define the notion of "thermochemistry".
12. What do you know about Gess's law?
13. Can you name the consequence from Gess's law?
14. Can you name two mathematical equations of the Gess’s law
15. Define the notion Н0298 (form) “standard enthalpy of formations of substance”
16. Define the notion “standard enthalpy of reaction of neutralization”.
17. Define the notion “standard enthalpy of phase transformations”.
Further Reading:
1. Frolov V.V.chemistry. ChaterV, §51-56.
2. Luchinsky G.P.rate of chemistry. Ch. V, §8-12, гл. VI, §13-18
3. Ahmetov N.S.general and inorganic chemistry. Section V, ch.3,4.
4. The general chemistry under ред. Sokolovskoj E.M., etc. Ch.6, §1-11.
38
THE SECOND LAW OF CHEMICAL THERMODYNAMICS.
Obgectives After studying this chapter, students should
be able to know:
1. Conception of thermodynamic probability.
2. Entropy.
3. Formulations of the second law of thermodynamics.
4. Energy of Helmholts.
5. Energy of Gibbs.
Essence the first law of thermodynamic, which you have studied at the last lecture,
is such as essence of the law of preservation.
Dear friends, let me tell you some examples which could happen in our life.
Have you ever met such phenomenon in your life: All the gases composing the air we
breathe (such as oxygen, nitrogen) without any external influence have been divided. If
there were the molecules of oxygen in one part of our audience, and the molecules of
nitrogen in another, which one would we breathe in such a situation? What do you
think?
For example you stroked your clothes, and switched off an iron. Instead of cooling
down, its temperature was increased. The iron took energy from an environment.
Tell me please do these phenomena contradict to the first law of thermodynamics?
The first law only allows counting the power of the process.
However it does not solve the problem of direction of the process and its possibility. For
example, the direction of such processes as spontaneous division of gases and the
transition of heat from a cold body to the hot one is impossible in nature. However,
such phenomena don’t contradict the first law of thermodynamics.
So, these problems are solved by second law of thermodynamics.
There are f lot of processes have to spontaneous go only one direction. For example,
time. Ray Bradbury in “A sound of thunder” wos riten:
- A touch of the hand, and this time on the instant, beautifully reverse itself. The old
years, the green years,might leap;roses sweeten the air, white hair turn black, wrinkles
vanish; all, everything fly back to seed, flee deas, rush down to their beginninggs, suns
rise in western skies end set in glorious easts. Can be such things in our life? It is
impossible as the certain processes have the certain direction. And time is going only
one direction from birth to death, unfortunately.
There are formulations, of the second law of thermodynamics in the textbooks for
example:
39
1. Klauzius’s formulation Клаузиус
« Heat cannot spontaneously be transferred from colder body to the hotter one».
2. Thomson’s formulation
« Heat of the coldest body cannot be a source of work ».
3. « The efficiency of the steam machine always is less than the unit », etc.
But these formulations are important for physical processes. And for chemical
processes it is important that the the second law of thermodynamics gives criteria
which helps us to solve the problem of possibility of the process and its direction.
The first criteria: The thermodynamic probability, W
And now there are some examples.
We use notion of probability in our life, to characterize a lot of processes. For example,
the low bird’s flying means the possible rain.
If you do well during the semester, you will possible pass the examination successfully.
So imagine, there are two rooms in a house, they were divided by a door. In the first
room there are the molecules of ‘He’, in the other one there are the molecules of ‘H2’. If
you opened the door, what would it be?
a) Probably these gases will mix. Let's put the letter W1 as a probability of this process
b) Probably these gases will not mix. Let's put the letter W2 as a probability of this
process.This is possible, if there are only a few molecules in a room. But our
experience, and practice have proved that the mixture is more possible. The
thermodynamic probability, W1> W2
He He W1
H2 H2 HHe
2
H2 HeHe He
H 2
He H2 H2
He H2 He H2
He He H2
He H2 W2
He H2
The thermodynamic probability, W -is a quantity of microconditions of the
system.
Let’s defermine the notion “microconditions of the system”
The microconditions of the system are a concrete position in space of separate
particles (molecules) at present time which corresponds to the steadiest condition
of system.
40
It is the function of a condition and it is maximal at the chemical equilibrium.
However W is connected with mechanical characteristics of the system: kinetic rate of
molecules, their position in space and so on. And for chemical thermodynamics it is
important to find out the criterion of a direction of the process, defined in
thermodynamic parameters: Т, Р, V (temperature, pressure, and volume).
The second criteria: Entropy S
Entropy S is a measure of the power disorder in the system.
Entropy S is connected with thermodynamic probability a parity: S = klnW, where
k -is Boltsman constant =R/NA 1,381.10-23 Dj/ degree
Dj * K
R- Gas constant = 8,31
mol
NA- number of the Аvоgadro = 6, 02 .10 23 моль–1.
k- Больцмана constant helps to transite the system from the simple "disorder" to « the
power disorder ». Counting upon 1 mol particles: S = R lnW.
Change Entropy is defined by the change of the number system’s microconditions
S = S2 – S1 = R ln W2/W1.
The mathematical equation of the second law of thermodynamics: S Q/T
For reversible S = Q reversible/Т.
For irreversible processes: S Q irreversible /Т (the algebraic sum of the resulted heats
for irreversible processes: Q irreversible proc. Q irreversible pros.
Experience shows, that many spontaneously continuing processes go with
allocation of heat (Н0). Among spontaneous processes there are also absorption’s
processes (Н0). For example, there is dissolution nitrate of ammonium in water:
NH4NO3 (c) NH4NO3 (l); Н0c.r. = + 27 кDj/mol.
So, allocation of heat (Н0) is not the solving criterion of an opportunity of
spontaneous course of processes.
There are a lot of spontaneously continuing processes whiсh are characterized by
increase Entropy. But there are spontaneously continuing processes whiсh are
characterized to reduce Entropy(S0): C + О2 СО2.
Chemical communication has formated between molecules of carbon and oxygen О2.
As result the degree of the power disorder decreases.
What is criterion of spontaneity – Entalpy (heat) or Entropy?
Balance between Entalpy (heat) and Entropy (S) is the criterion to define an
opportunity of course of process. Spontaneous processes with absorption of
Entalpy (heat) can be, if growth of power "disorder" is incrising Entropy(S>0), and
processes with S0 are possible too, if it is accompanied by stronger allocation of heat.
41
For the isolated systems where the exchange of energy with an environment is
excluded Q=0, the inequality of the second law of thermodynamics is: S 0.
Thus, for the isolated systems there is only one criterion of spontaneous course
of processes – increase Entropy. The processes lead to increase Entropy is only
spontaneous.
So:
1. Entropy is a function of a system condition; therefore you can calculate
Entropy’s change using consequence from Gess's law. Entropy’s change of chemical
reaction is equal to a difference between the sums Entropy’s products of reaction
and Entropy’s initial substances, accounting chemical reaction’s coefficients.
Sc.r. = S0 (products) – S0 (initial substances),
accounting chemical reaction’s stehiometric coefficients!
- The Greek letter “sigma”, shows operation of summation.
Problem: To calculate Entropy’s change this chemical reactions (Sх.р.):
3С2Н2 (g) С6Н6 (l).
The decision: Sх.р. = S0 (C6H6 (l)) – 3 S0 (С2Н2 (g)).
Sх.р. = 269,2 – 3.200,8 = - 333,2 Dg/mol.
2. Entropy is measured by the attitude Q (heat) /T or H/T.
Problem: What is Entropy’s change of transition from crystal in a liquid condition one
mol iron (Fe) if Тfusion =15360С (1809K) at, if Entalpy Нfusion = 13765 Dj/mol.
At the temperature of fusion for equilibrium condition this system Fe(с) Fe(l)
T=const = Тfusion =15360С (1809K)
Sfusion = S (Fe (l))-S (Fe (c)) =Нfusion/Тfusion = 13765/1809 = 7,61 Dg/K mol.
S0 Process of transition from crystal in to a liquid condition at Тfusion=15360С
(1809K) is spontaneously.
3. Entropy is criterion of spontaneous course of processes only for the isolated
systems. Processes go spontaneously in the isolated systems with only increase
Entropy.
Состояние равновесия
S
S0 S0
изолированные системы
42
4. S is connected with the number of possible microconditions in the system (with
thermodynamic probability, W), characterizes a measure of the power disorder in the
system. S = klnW.
5. S is a thermodynamic function which unlike from thermodynamic probability
W is connected with thermodynamic values Q; T, it is more comprehensible to chemical
thermodynamics.
However, more often there are no systems isolated in natural, in technics. Entropy can
not be used for the closed systems.
For izothorno -isothermal conditions (T, V=const.) the first law of thermodynamics
has mathematical form possible to write down so:
QV = U (= РV; V = a constant A=0)
For the second law of thermodynamics, write down so: S QV/T QV ТS.
Uniting two expressions, we shall receive: TS U; U - TS 0.
Let’s name a difference U - TS to name a new value F. It is the thermodynamic
function of a condition – free Helmholts’s energy, U - TS =F.
For izothorno -isothermal conditions (T, V=const.) the second law of
thermodynamics has mathematical form possible to write down so: F 0.
We can use only one criterion of a direction of the process for izothorno -isothermal
conditions (T, V=const.) (Such as Entropy (S) for the isolated systems). However this
criterion F of a direction of the process is only balance same criterias: U and S.
So:
1. For izothorno -isothermal conditions F is criterion of spontaneous course of
processes. If the Helmholts’s energy decreases (F 0), such processes are
spontaneous.
F
F 0 F 0
F = 0
Закрытые системы при постоя нном V и T
Состоя ние равновесия
рис10
F0, processes can go spontaneously;
F = 0, equilibrium condition of thisprocess;
F 0, processes cannot pass.
43
2. F =U - TS this is incorporated first and second laws of thermodynamics (T,
V=const.)
3. Helmholts’s energy is a function of a system condition; therefore you can
calculate the change of the Helmholts’s energy using consequence from Gess's law.
change of the Helmholts’s energy of the chemical reaction is equal to a difference
between the sums of Helmholts’s energy of the products of reaction and
Helmholts’s energy of the initial substances, accounting chemical reaction’s
coefficients.
Fc.r. = F0 (products) – F0(initial substances),
accounting chemical reaction’s stehiometric coefficients!
- The Greek letter “sigma”, shows operation of summation.
For izobarno -isothermal conditions (P, T =const.) the first law of thermodynamics
has mathematical form possible to write down so:
QP = U + РV =H
For second law of thermodynamics to write down so: S QP/T QP ТS.
H ТS
Uniting two expressions, we shall receive: TS H; H - TS 0.
Let’s name a difference H - TS to name a new value G. It is the thermodynamic
function of a condition – free Gibbs’s energy, H - TS =G.
For izobarno-isothermal conditions (P, T=const.) the second law of
thermodynamics has mathematical form possible to write down so: G 0.
We can to use only one criterion G of a direction of the process for izobarno -
isothermal conditions (P, T=const.) (Such as Entropy(S) for the isolated systems, such
as criterion F for the closed systems (V, T=const.)). However this criterion G, such
as criterion F for the closed systems (V, T=const.) is only are determined by the
balance of the same criteria: Н and S.
So,
1. For izobarno -isothermal conditions G is criterion of spontaneous course of
processes. If the Gibbs’s energy decreases (G 0), such processes are
spontaneous.
G
G 0 G 0
G = 0
Состояние равновесия
н
Закрытые системы при постоя ных Т и Р
44
рис.11
G0, processes can go spontaneously;
G = 0, equilibrium condition of thisprocess;
G 0, processes cannot pass.
2. G =Н - TS this is incorporated first and second laws of thermodynamics (T,
P=const.)
3. Gibbs’s energy is a function of a system condition; therefore you can to calculate
change of the Gibbs’s energy using consequence from Gess's law. Change of the
Gibbs’s energy of chemical reaction is equal to a difference between the sums
Gibbs’s energy of the products of reaction and Gibbs’s energy of the initial
substances, accounting chemical reaction’s coefficients.
Gc.r. = G0 (products) – G0 (initial substances),
accounting chemical reaction’s stehiometric coefficients!
- The Greek letter “sigma”, shows operation of summation.
G0 (X) – standard of Gibbs’s energy of substance X under standard conditions
and in the certain condition.
G0 (X) standard of Gibbs’s energy of simple substances and elements (such as
Н0 (X)) is equal to zero.
Problem: Can these processes go spontaneously?
С6Н12О6 (l) ( Glucose) 2С2Н5 (OH) (l)( spirit) + 2СО2 (g)( сarbonic gas)
G0(С6Н12О6) =-915кDg/mol; G0(С2Н5 (OH)) =-174кDg/mol ; G0(СО2) =
-394кDg/mol
The decision: using consequence from Gess's law let’s write down:
G0c.r.=[2G0(С2Н5 (OH)) +2G0(СО2)] - G0(С6Н12О6)
G0c.r.=[ 2 (-174) + 2 (-394)] – (-915) =-221 кDg/mol
Н0c.r. this process is -79 кDg/mol. Hence, due to энтропийного the
Ability of fermentation process of spirit to make useful work increases in three times,
due to
Entropy’s contribution.
Fermentation process of spirit is source of the energy. It is very important for anaerobic
organisms, and on animals and the people in during intensive physical work.
4. G equal to useful maximal work which could be during isobarno-isothermal
process.
Review Questions
1. What is the definition of this notion « chemical thermodynamic »?
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2. What do you know about the first law of thermodynamics?
3. What do you know about the second law of thermodynamics??
4. What are thermodynamics functions? Named them, please?
5. What do you know about izobarny process?
6. What do you know about «entropy»?
7. Whan the entropy is criterion of spontaneous course of processes only?
8. Whan Gibbs’s energy is criterion of spontaneous course of processes only?
9. Whan Gelmgolce’s energy is criterion of spontaneous course of processes only?
10. What the thermodynamic function is used for definition of an opportunity of
spontaneous course of process for the isolated systems?
11. What the thermodynamic function is used for definition of an opportunity of
Spontaneous course of process under condition Р, Т=const?
12. Shall the process are, if G0?
13. Can you name incorporated first and second laws of thermodynamics (T,
P=const.)?
14. Can you to name incorporated first and second laws of thermodynamics (T,
V=const.)?
15. The definition of this notion G0298 (form) “standard Gibbs’s energy” of substance.
16. What is the definition of this notion “Gibbs’s energy” of reaction.
17. Define the notion “entropy” of reaction.
Further Reading:
1. Frolov V.V.chemistry. Ch. VI, §6.1 – 6.11.
2. Luchinsky G.P.rate of chemistry. Ch. IV, §1-7.
3. Ahmetov N.S.general and inorganic chemistry. Section V, ch. 1,2.
4. The general chemistry under ред. Sokolovskoj E.M., etc. Ch. 5, 1-6.
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CHEMICAL KINETICS.
Obgectives After studying this chapter, students should
be able to know:
1. Homogeneous and heterogeneous chemical processes.
2. The factors influencing on the rate of chemical reactions.
2.1 natures of reacting substances;
2.2 concentrations (pressure). The law of action of weights.
2.3 temperature. Rule of the Vant-Goph. Equation of the Аrrenius.
Energy of activation.
2.4 catalyst.
3. Chemical balance. A constant of balance.
4. Displacement of balance. Principle of the Le-Shatelye.
The chemical thermodynamics studies an opportunity, a direction and limits of
spontaneous course of chemical processes. However, the mechanism and rate of
processes in chemical thermodynamics are not considered. At the same time
representation of a rate of chemical reactions and the factors influencing on it, is
exclusively important for management of chemical processes.
Chemical kinetic is the area of chemistry studying the mechanism and rate of
chemical reactions.
Rate of the chemical reactions are various. One can be instantly: 2H2 + O2
2H2O, or several seconds, minutes: CuSO4 + 2NaOH Na2SO4+Cu (OH)2, FeCl3 +
3NaOH 3NaCl+Fe (OH)3.
Rate of the biological reactions can procced for years, decades, for example, the
transformation of wood into coal occurs during centuries, millenia. When you are
studying rate of chemical reactions it is necessary to know the definition of notions:
“homogeneous” and “heterogeneous” reactions.
Homogeneous reactions are such reactions in which initial substances and
products have identical phase’s conditions: solids(s) or liquids (l) or gases (g), and also
there isn’t not an interface among them.
Heterogeneous reactions are such reactions in which initial substances and
products of the reaction have an interface among them and they have various phases’
conditions.
Chemical kinetic has two main notions an instant rate and an average rate.
What is the rate of the chemical reactions?
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The Instant rate of the chemical reaction is defined as the first derivative of
concentration to time.