Review: Molar Mass of
Compounds
 Ex. Molar mass of CaCl
2
 Avg. Atomic mass of Calcium = 40.08g
 Avg. Atomic mass of Chlorine = 35.45g
20
Ca
40.08
17
Cl
35.45
 Molar Mass of calcium chloride =
40.08 g/mol Ca + (2 X 35.45) g/mol Cl
 _110.98______ g/mol CaCl
2

Practice
 Calculate the Molar Mass of calcium phosphate
 Formula =
 Ca
3
(PO
4
)
2
Masses elements:

Ca = 40.08g/mole
P = 30.97 g/mole
O = 16.00 g/mole
Molar Mass =
(40.08 g/mole)(3) + (30.97 g/mole)(2) + (16 g/mole)(8)
= 310.18 g/mole

Divide by 6.02 X 10 23
Multiply by 6.02 X 10 23
Divide by atomic/molar mass from periodic table
Multiply by atomic/molar mass from periodic table
Mass
(grams)

Review
 5.7 kg = ?? mg

 3.5 dozen roses = ?? Roses
 2.5 mol roses = ?? Roses (use Avogadro's #)

Practice
 Find the mass of 0.89 mol of CaCl
2.
 Find the molar mass of the compound:
 Make the conversion:

Practice
 A bottle of PbSO
4 contains 158.1 g of compound. How many moles of PbSO
4 in the bottle?
are

Grams molar mass Avogadro’s number
Moles particles/formula units/atoms

Practice
 Determine the number of atoms that are in
0.58 mol of Se.

Practice
 How many moles of barium nitrate (BaNO
3
) contain 6.80 x 10 24 formula units?

Grams molar mass Avogadro’s number
Moles particles/formula units/atoms

 2.5 g Roses = ?? Roses
 Atomic mass of 1 Rose is 3.0 g/mol

Multi-step Practice
 How many molecules are in 5.1g of TiO
2
?

Multi-step Practice
 If you burned 6.10 x 10 24 molecules of ethane
(C
2
H
6
), what mass of ethane did you burn?

Molar Volume
 Definition: The volume of one mole of an ideal gas at standard conditions (STP) equal to 22.4 L.
 STP = standard temperature and pressure which is 0 ºC and 1 atmospheric pressure
 1 mole gas at STP = 22.4 L

Practice
 A container with a volume of 893L contains how many moles of air at STP?

Practice
 A chemical reaction produced 0.37 mol of N
2 gas. What volume will the gas occupy at
STP?