1. THE MOLE

2. MEASURING MATTER 3 ways to measure things: count: 1 dozen = 12 apples
mass: 1 dozen = 2 kg of apples
volume: 1 dozen = 0.20 bushel
(for typical wicker basket)
We need to measure ATOMS!

3. IMPOSSIBLE, IMPRACTICLE!
MASS OF 1 CARBON ATOM
1 amu = one proton or one neutron
= 1.66 x g
carbon has 12 protons & neutrons
mass of one C atom = x g
IMPOSSIBLE, IMPRACTICLE!

4. MASS OF 1 CARBON ATOM One atom cannot be weighed.
Can we weigh many atoms and still compare one atom to another? …

5. Mass ratio ( 2 : 7 ) is always
MASS RATIO: He vs. N
1 atom
He = 4 amu
N = 14 amu
2 atoms
8 amu
28 amu
10 atoms
40 amu
140 amu
100 atoms
400 amu
1400 amu
Mass ratio ( 2 : 7 ) is always
the same!

6. AVOGADRO’S NUMBER 1 carbon atom = 12.01 amu
?? atoms = grams of carbon
ANSWER: x 1023 atoms!
Avogadro’s number: number of atoms whose mass in grams = mass of one atom in amu

7. AVOGADRO’S NUMBER We call this number of “things” one MOLE:
6.02 x 1023 “things” = 1 mole
just like 12 “things” = 1 dozen

8. “THINGS”: REPRESENTATIVE PARTICLES
1 mole = 6.02 x 1023 representative particles
1 mole carbon = 6.02x1023 atoms
1 mole CO2 = 6.02x1023 molecules
1 mole NaCl = 6.02x1023 formula
units

9. THE MOLE AND MOLAR MASS 1 atom of hydrogen = 1.01 amu
6.02x1023 atoms of H = 1.01 grams
1 mole of H = 1.01 grams
usually written as: g/mole
This number is called the
MOLAR MASS of hydrogen.

10. MOLAR MASS In textbook: gram atomic mass gram molecular mass
gram formula mass
ALL mean the same – the mass of one mole of a substance:
MOLAR MASS

11. MOLAR MASS carbon: MM = 12.01 g/mole 12.01 g = 1 mole = 6.02x1023atoms
magnesium: MM = g/mole
24.34 g = 1 mole = 6.02x1023atoms
1 mole = same number of atoms
= different number of grams

12. MOLAR MASS What is the molar mass of sulfur? 32.07 g/mole
What is the molar mass of SO3?
80.07 g/mole
What is the molar mass of NaCl?
58.44 g/mole

13. AMADEO AVOGADRO