1. Molar Volume

2. Counting Without Counting
If you had to count the number of coffee beans in this bag how would you do it? How long would it take?

3. Counting Atoms in a Sample by Mass
Weigh out 2 moles of Carbon
2 mol C x g C = 24 g C
mol C
Weigh out 2 moles of Helium
2 mol He x g He = 8 g He
mol He

4. Gases
How do we count the number of atoms in objects that are difficult to weigh…. Like gases?
To find out more, we need to explore the properties of gases

5. Properties of Gases
Gases do not have definite volume. They expand to fill the entire container. The volume of the container is the volume of the gas
Gases are compressible.
The volume of a gas changes dramatically with temperature and pressure

6. Molar Volume
Molar volume is the volume of one mole of gas, under a specific set of temperature and pressure conditions
Those conditions are known as
Standard Temperature and Pressure (STP)
0o Celcius (about 32oF)
1 atmosphere of pressure (1 atm).
The molar volume of any gas at STP is 22.4 L
This is true for any gas. It doesn’t matter which gas.