1. Chapter 12 Notes, Part II Ideal Gas Law
Dalton’s Law of Partial Pressures
Graham’s Law of Effusion

2. Ideal Gas Law
When a gas behaves ideally (that is, it obeys the assumptions about gases in the kinetic theory) then it is possible to use the ideal gas law to define it.

3. Ideal Gas Law The equation is: PV=nRT
Pressure x vol. = # of moles x ideal gas constant x temp.

4. Ideal Gas Law The letter R is the ideal gas constant.
R’s value is based on the pressure units:
KiloPascals: 8.31 L kPa / mol K
Atm: L atm / mol K
mmHg: 62.3 L mmHg / mol K

5. Ideal Gas Law Two factors make a gas not ideal:
1. particles will interact
2. that they do have volume.
Because of this, the relationship breaks down at very high pressures and very low temperatures.

6. Practice Problem #1
You fill a rigid container that has a volume of 20.0L with nitrogen gas to a pressure of 2150 kPa at 28oC. How many moles of gas are present?

7. Practice Problem #2
What volume will 12 grams of oxygen gas (O2) occupy at 25oC and 52.7 kPa?

8. Dalton’s Law of Partial Pressures
Avogadro's hypothesis-identical volumes of gas at the same temperature and pressure have the same number of particles, regardless of the type of gas!

9. Dalton’s Law of Partial Pressures
Based on this, Dalton could say that the total pressure in a container is equal to the sum of the pressures of a mixture of gases.
Ptotal=P1+P2+P3...

10. Practice Problem #3
Air contains oxygen, nitrogen, carbon dioxide and trace amounts of other gases. What is the partial pressure of oxygen at 101.3kPa if the partial pressures of nitrogen, carbon dioxide and other gases are 79.1kPa, kPa and 0.94kPa, respectively?

11. Practice Problem #4
What is the total pressure in a container where the partial pressures are as follows:
Nitrogen—20.0kPa
Oxygen—37.2kPa
Helium 19.1kPa

12. Avogadro’s Law: Equal volumes of gas contains equal number of moles.
V1 = V2
n n2
Example: A sample of gas occupies 2.00 L with 5.00 moles present. What would happen to the volume if the number of moles is increased to 10.0?