The Laws of Chemistry
Dalton's Atomic Theory
A. Elements are composed of extremely small particles
called atoms. All atoms of the same element are
alike, and atoms of different elements are different
B. The separation of atoms and the union of atoms occur in
chemical reactions. In these reactions, no atom is created or
distroyed, and no atom of one element is converted into an
atom of another element
C. A chemical compound is the result of the combination of
atoms of two or more elements in a simple numerical
ratio
1. Law of conservation of mass
states that there is no detectable change in mass
during the course of a chemical reaction
e.g.
AgNO3 + KI
AgI + KNO3
170 g 166 g
235 g
336 g
101 g
336 g
2. Law of definite proportions
states that a pure compound always contains
the same elements in a fixed ratio
e.g.
Copper (II) oxide
1 g copper
0.252 g oxygen
3. Law of multiple proportions
states that when two elements form more than one
compound the amounts of one element that are
combined with a fixed amount of the other element are
in a small whole - number ratio
Name
oxygen g
%
Ratio
nitrogen
oxygen
1g nitrogen
Dinitrogen oxide
63.7
36.3
0.57
1
Nitrogen oxide
46.7
53.3
1.14
2
Dinitrogen trioxide
36.8
63.2
1.71
3
Nitrogen dioxide
30.4
69.6
2.28
4
Dinitrogen pentoxide
25.9
74.1
2.85
5
4. Gay - Lussac's law of combining volums
states that the volums of gases the are used or
produced in a chemical reaction can be expressed
in ratios of small whole numbers (const. temp. and p.)
e.g.
1 volume hydrogen + 1 volume chlorine
2 volumes hydrogen chloride
H2 (g) + Cl2 (g)
2HCl (g)
The law is applicable only to gases!
5. Avogadro's principle (law)
equal volumes of all gases at the same temperature
and pressure contain the same number of molecules