основные понятия и законы

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lesson plan
1. Basic concept of chemistry:
• matter, elements;
• atom, molecules;
• chemical Reactions;
• equivalent mass.
2. Basic laws of chemistry:
• Law of conservation of mass;
• Law of maltiple proportions;
• Law of constant composition;
• Avagadro’s Law.
Basic consepts of chemistry
Matter
Solid, Liquid, Gas
Elements
Atom and Molecules
Mole
Chemical reactions
Matter
Matter - any material substance with
Mass and Volume. Matter comes in 3
phases.
Solid
Liquid
Gas
Solid
Solids are usually hard, because
their molecules have been packed
together. Solids can be hard, soft,
big or small
Definite Shape
Definite Volume
Liquid
Indefinite Shape – takes the
shape of the container
Definite
Volume
Gas
Indefinite Shape – takes the shape
of the container
Indefinite
Volume – can
expand and be
compressed
What is an ELEMENT?
o
o
A substance
composed of a
single kind of atom.
Cannot be broken
down into another
substance by
chemical or physical
means.
Elements
Elements - pure substances, that make up
everything in the universe
Elements and Symbols
What is a COMPOUND?
oA
substance in
which two or
more different
elements are
CHEMICALLY
bonded together.
What is a MIXTURE?
o Two
or more
substances that
are mixed
together but are
NOT chemically
bonded.
Element, Compound or Mixture?
Element, Compound or Mixture?
Element, Compound or Mixture?
An atom is the smallest particle of an element.
Atoms of elements are measured by their atomic
mass.
A molecule is the smallest particle of a substance
that can have an independent existence. It is
formed when two or more atoms join together
chemically.
Molecules of substances are also measured by
relative mass: the unit of comparison being the
same – one twelfth of the mass of a carbon atom.
It is defined as the average relative mass of a
molecule of a substance.
Glucose Sugar
H
H
C
C
C6H12O6
H
C
OH
Chemical formula
H
OH
C
H
OH
O
H
C
OH
H
C
OH
Structural formula
Mole - measure of concentration in
chemistry. The Mol unit is based on the
number of atoms in exacty 12 grams of pure
carbon.
Mole:
• In terms of particles 6.23·10-23 particles.
In terms of particles such as atoms,
molecules, ions or electrons, this has a
value of 6.23·10-23 of the concerned unit that
can be either an atom or a molecule or
electrons and ions. This is called Avadadro's
number.
• In terms of volume at NTR 22.4 L of a
gas. In terms of volume at normal
temperature pressure this value is 22.4
litres of a given gas.
• In terms of mass 1 gram molecular
mass of a substance. In terms of mass,
this is equivalent to 1 gram molecular
mass of a substance.
Chemical Reactions
A chemical
reaction is a
process that
leads to the
transformation
of one set of
chemical
substances to
another.
Basic laws of chemistry
Law of conservation of mass
Law of maltiple proportions
Law of constant composition
Gay Lussac‘s law
Avagadro’s Law
Law of equivalent proportions - law stating that the
proportions in which two elements separately combine
with a third element are also the proportions in which
they combine together.
Equivalent Weight of an Element (E): It is defined as
the number of parts by weight of the element which
combine with or displace from a compund 1 part by
weight of Hydrogen, 8 parts by weight of Oxygen or 35.5
parts by weight of Chlorine.
In this method you need not balance the chemical
equation. The basic principle is that the equivalents of
each reactant Number
E(oxide)  Мr(oxide)/ nO2·2;
E(acid)  Мr(acid)/n(H+);
E(basis)  Мr(basis)/ n(OH-);
E(salt)Мr(salt)/n(Me) · V(Ме);
solution:
E Fe2(SO4)3=399.7 g/mol /2·3=66.6 g/mol
LAW OF MASS CONVERSATION
(M.V. Lomonosov, 1748, A. Lavoisier 1789)
The elements combine in the same
proportion by mass.
The mass of the substances entering into a
reaction equal the mass of the substances
formed as a result of the reaction.
2Na + 2H2O  2NaOH + H2
28 g
36 g
62 g
64=64
2g
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.
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.
Example
CuS- copper sulphide. m (Cu) : m (S) =
Ar (Cu) : Ar (S) = 64 : 32 = 2 : 1
To get copper sulphide (CuS) it is
necessary to mix up the powders of
copper and sulphur in mass relations 2:1.
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
N2O5
A number of oxygen atoms in molecules of such
compounds corresponding to the two nitrogen
atoms are in a proportion 1:3:5.
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 = 273°K, 1 atm = 101.3 kPa) occupies a
volume of 22.4 litres.
example
 What 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 = = 4.48 l of hydrogen
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/T1=P2V2/ T2
Conversely, from general gas law under P= const.
(P1=P2), possible to get:
V1/T1=V2/T2 (Gay-Lussac’s law)
On the T=const. (T1=T2):
P1V1= P2V2 (Boyl’s-Mariott’s law).
On the V=const.
P1/T1=P2/T2 (Charle’s law).
tests
1. Balancing of chemical reactions is based upon law of
conservation of ...
a. Volume
b. Density
c. Mass
d. Moles
2. The law of multiple proportion is illustrated by …
•CO and CO2
•H2O and D2O
•KBr and KCl
•Ca(OH)2 and Ba(OH)2
3. Matter can neither be created not destroyed ..
а. True
в. False
4. All individual chemical substances have constant
quality and quantity composition and definite chemical
structure and does not depend on how this substance
was prepared. What is law it?
a. Law of mass conversation
b. Law of combining volumes
c. Avogadro law
d. General gas law
5. Equal volumes of gases at the same temperature and
pressure contain unequal number of molecules.
a. True
b. False
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