1. Definite Proportions, Multiple Proportions and Atomic Theory

2. Law of Conservation of Mass
The sum of the masses for the reactants equals the sum of the masses for the products
Lavoisier
Mass is neither created nor destroyed in a chemical reaction
If you start with 10g, you will wind up with 10g

3. Law of Definite Proportions
• Proust
• Atoms are neither lost nor gained in a chemical reaction
• Chemical compounds have the same mass ratio of elements no matter how formed (e.g., water always has an O to H ratio of 8.01:1.00)
• Evidence for this law: Berzelius’ experiments with lead and sulfur
• Constant composition implies constant properties (i.e., water always boils at 100ºC and freezes at 0ºC)

4. Chemical compounds have the same mass ratio of elements no matter how formed
Copper Carbonate

5. Law of Definite Proportions

6. Law of Multiple Proportions
• Compounds of differing mass ratios of the same elements are found, but they will have different properties
• Example: carbon dioxide (CO2) and carbon monoxide (CO)

7. Dalton’s Atomic Theory
• John Dalton- (1803)
Law of Multiple Proportions, Atomic Theory of Matter
Elements of Dalton’s atomic theory:
Matter is composed of atoms
Different elements have different atoms
(e.g, C has a mass=12, O has a mass=16)
Compounds form when different elements combine in fixed proportions

8. Determining the Mass of a Compound
EXAMPLE:
If C has a mass of 12 and O has a mass of 16, what is the mass of:
a) Carbon monoxide (CO)
= 28
b) Carbon dioxide (CO2)
12 + 2(16) = 44

9. Determining the Mass of a Compound
Find the mass of NaCl, NaOH, CaCO3, and H2SO4
The atomic masses for each element are found on the periodic table.
(for now use these amounts)
Na=23 Cl=35 O=16 Ca=40
C=12 H=1 and S=32