Unit 5: The Mole and
Stoichiometry
Mole as a Bridge
Moles and Gases
At standard temperature and pressure (STP) . . .
1 mole of any gas will occupy the same volume
as any other gas at the same temperature
and pressure.
 At STP (which is 0oC and 1 atm):
 1 mole of any gas occupies a volume of 22.4
liters.



Therefore,
1 mole = 22.4 liters
(of any gas at STP)
Examples:

What is the volume of 0.0035 moles of
CH4 at STP?
0.0035 moles
22.4 Liters
1 mole
= 0.078 Liters CH4

What is the number of moles of oxygen in
an 85 Liter sample at STP?
85 Liters 1 mole
22.4 L

= 3.8 moles
What is the mass of 18 liters of carbon
dioxide gas at STP?
18 Liters 1 mole 44.01 g CO2
22.4 L
1 mole
= 35 grams
One Mole can equal 3 different things
1. 6.02 X 1023 atoms or molecules
2. The mass of any element or
molecule in grams
3. 22.4 Liters of any gas at Standard
Temperature and Pressure (STP)

Since the mole can equal any one of
these, it can also serve as a bridge to
convert from one to another of them.
Mole as a Bridge
Mass
(Molar Mass)
“÷”
“x”
Mole
“x”
Volume
(22.4L)
“÷”
“÷”
“x”
• Going out of the Mole, MULTIPLY (top of T-chart)
•Going into the Mole, DIVIDE (bottom of T-chart)
Particles
(6.02 x 1023)
Using the Mole as a Bridge Examples:

How many grams are there in 7.4 x 1023
molecules of AgNO3?
7.4 x 1023
molecules 1 mole AgNO3
6.02 x 1023
molecules
169.87 g
1 mole
AgNO3
= 209 grams = 210 grams (sig figs!)
Using the Mole as a Bridge Examples

How many molecules are there in 230
grams of CoCl2?
230 g CoCl2
1 mole
6.02 x 1023
molecules
129.83 g CoCl2 1 mole
= 1.07 x 1024 molecules
Using the Mole as a Bridge Examples

What is the volume of 150 grams of N2O
gas at STP?
150 g N2O
1 mole
22.4 L
44.02 grams 1 mole
= 76.3 Liters