1. States of Matter Podcast 1 Chapter 12.1 Gases

2. Chapter Vocabulary Kinetic molecular theory Elastic collision Temperature Diffusion Effusion Pressure Barometer Pascal Atmosphere Dalton’s Law of Partial Pressures Intermolecular forces (review) Viscosity Surface tension Surfactant Cohesion Adhesion Melting point/boiling point Vaporization Evaporation Vapor pressure

3. Kinetic Molecular Theory

4. Kinetic Energy KE = ½ m v 2 Temperature:

5. Pressure P = F/A Gas pressure results from gas particles colliding with the container The more collisions and the more energy for each collision, the higher the pressure

6. Barometer

7. Manometer

8. Units of Pressure

9. Movement of Gas Molecules Diffusion Effusion

10. Graham’s Law of Effusion =

11. Balloons are made of rubber, which is porous enough for some gas particles to escape over time. Q: Which balloon would go flat the fastest; a balloon filled with helium or a balloon filled with air?

12. Practice Problem 1 In an experiment, nitrogen gas effuses at a rate of 25 mol/s and an unknown gas effuses at 50 mol/s. What is the molar mass of the unknown gas?

13. Practice Problem 2 It takes 3.5 minutes for a sample of Xe to effuse. A different unknown gas takes only 1.2 minutes to effuse. What is the molar mass of the unknown gas?

14. Dalton’s Law of Partial Pressures

15. Sample Problem 3 In a mixture of O 2, CO 2, and N 2, the total pressure is found to be 205 kPa. If CO 2 has a partial pressure of 55 kPa and N 2 has a partial pressure of 125 kPa in the mixture, what is the partial pressure of the oxygen gas?

16. Sample Problem 4 Air is a mixture of 78% N 2, 21% O 2, 1% Ar, and trace amounts of other gases. If the total pressure is 760 mmHg, find the partial pressure of each gas.

17. Mole Fraction For a mixture of gases: X A = n A / n T

18. Derived from Daltons’ Law of Partial Pressures P A = X A * P T number of mol A total number of mol The partial pressure of one gas in a mixture is equal to the ratio of gas molecules in the mixture x the total pressure X P T P A =

19. Sample Problem 5 56 g of N 2 gas are mixed with 128 g of O 2 g at a total pressure of 1.5 atm. a)What is the mole fraction of N 2 ? b)What is the partial pressure of N 2 ?