1. Ideal gases and molar volume
Avogadro’s law
Ideal gases and molar volume

2. Elements that exist as gases at 25 °C and 1 atmosphere

3. Physical Characteristics of Gases
Gases assume the volume and shape of their containers.
Gases are the most compressible state of matter.
Gases will mix evenly and completely when confined to the same container.
Gases have much lower densities than liquids and solids.

4. STP stands for standard temperature & pressure
Avogadro’s Law
STP stands for standard temperature & pressure
(0°C and 1 atm)
1 mol H2 at STP = 22.4 L
1 mol O2 at STP = 22.4 L

5. Avogadro’s Law
Constant temperature
Constant pressure
equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

6. Molar Volume of Gases
The volume occupied by one mole of a gas at STP is known as the standard molar volume of a gas. It has been found to be 22.4 L.
1 mol = 22.4 L will be the conversion factor used in Avogadro’s law.

7. Sample Problem 1
A chemical reaction produces mol of oxygen gas. What volume in liters is occupied by this gas sample at STP?
Using our conversion factor of 1 mol = 22.4 L to solve for volume
1 mol
mol x 22.4 L = 1.52 L O2

8. Sample Problem 2
A chemical reaction produced L of sulfur dioxide gas, SO2, at STP. What was the mass (in grams) of the gas produced?

9. Sample Problem 2 First find molar mass of SO2: 1 x S = 32.07 g/mol
2 x O = 16 x 2 = 32 g/mol
64.07 g/mol
1 mol SO2
22.4 L
0.098 L x 1 mol SO2 x g = 0.28 g