1. Molar Mass

2. Let’s Compare 1 bag of beans to 1 mole of carbon 1 “bag” 1 mole carbon
6 x 1023 carbon atoms
Mass
Mass
12 grams
453 grams

3. Let’s Compare Same number of atoms Different masses.
one mole of hydrogen to one mole of gold
1 mol H
1 mol Au
6 x 1023 atoms H
6 x 1023 atoms Au
Mass
Mass
1 gram H
197 grams Au
Same number of atoms
Different masses.

4. Molar Mass Molar Mass – the mass of one mole of any substance
Atoms have different masses, so the molar mass of every element is different
The unit for molar mass is “grams per mole”

5. Mass on the Periodic Table6 C
Carbon
12.01
MICROSCOPIC
Atomic Mass
Mass in amu
6 protons +
6 neutrons
12 amu
Mass of 1 carbon atom
MACROSCOPIC
Molar Mass
Mass in grams
1 mole of Carbon weighs 12 grams
12 g
Mass of 1 mole of carbon atoms

6. Molar Mass Conversion Factors6 C
12.01
Molar mass = 1 mol = ___ g
Carbon: 1 mol C =
Oxygen: 1 mol O =
Sodium: 1 mol Na =
Nitrogen: 1 mol N =
Fluorine: 1 mol F =
Calcium 1 mol Ca =
12 g C
16 g O
23 g Na
14 g N

7. Check for Understanding
Oxygen (O)
How many atoms in one mole of oxygen?
How much does one mole of oxygen weigh?
Silver (Ag)
How many atoms in one mole of silver?
How much does one mole of silver weigh?
Phosphorus (P)
How many atoms in one mole of phosphorus?
How much does one mole of phosphorus weigh?

8. MOLAR MASS OF COMPOUNDS
The molar mass of a compound is the sum of the molar mass of the individual elements
H = 1g
O = 16g
1 mole of H2O
(6.02 x 1023 molecules H2O)
= O + H + H
= 16g + 1g + 1g
= 18 g H2O
H = 1g

9. Molar Mass of Compounds
Add up the molar mass of all the elements in the compound: 1 mole of CO2 = 16g + 16g + 12g = 44g CO2 = 6.02 x 1023 CO2 molecules
O = 16g
O = 16g
C = 12g

10. Compounds with parenthesis: Ca(OH)2
Multiply the subscript across all atoms inside the parenthesis
1 mole of Ca(OH)2 (multiply everything inside the parenthesis by 2)
= 1 calcium atom, 2 oxygens, 2 hydrogens
= = 74 g Ca(OH)2
O = 16g
H = 1g O H Ca H O
H = 1g
O = 16g
Ca = 40g

11. Compounds with parenthesis: (NH4)3P
Multiply the subscript across all atoms inside the parenthesis
1 mole of (NH4)3P (multiply everything inside the parenthesis by 3)
= 3 nitrogens, 12 hydrogens, 1 phosphorus H N
P: 1 x 31g = 31 g
N: 3 x 14g = 42g
H: 12 x 1g = 12g
85g H N P H N