1. Chapter 12 Actual NEW information!

2. Kinetic Molecular Theory (Ok… Maybe not new)  The average kinetic energy of the gas molecules is proportional to the gases temperature.  If two gases have the same temp, they have the same average KE  KE= ½ mu 2

3. Other KMT points  The space between gas molecules is SO BIG compared to the sizes of the actual molecules themselves  The molecules are in continuous random motion  When gas molecules collide, it is a perfect elastic collision with no loss of energy

4. Average KE does not paint the complete picture!  Although the temp tells you the average, there are some molecules going faster and slower at any given point. At higher temperatures, the molecules move faster.  Pretty graph!  Furthermore since KE is mass and velocity, heavier gases have a slower speed

5. How do we figure out the speed?  Well Billy, we use the root-mean-square speed a.k.a rms speed… This is also called “Maxwell’s expression” Molar mass TinK!!!

6. So when the move, what happens?  Well… Thanks for asking… When someone does not shower and you can smell them across the room (yes I am talking to you)… That is called diffusion  Diffusion is the mixing of two or more gases due to their molecular motion  Given time, the molecules of two gases will completely mix

7. Well give me the math!  Related to diffusion is effusion  It is the movement of gas through a tiny opening in a container into another container where the pressure is low..  Where is the math… Well if you want to compare effusion rates you can use Graham’s Law (got a cracker and a law named after him… he is special... Like you)

8. Umm.. Where is my math  Rate of effusion is inversely proportional to the square root of its molar mass. Or

9. One more

10. Demo time!  If we use 6M HCl and 6M NH 3 (NH 4 Cl) and put them on opposite side of a tube, simultaneously and at the same time, where will they meet?

11. Applications?  Helium Balloons?

12. Non-Ideal Gases  Gases are attractive and actually have a volume  How could you think it doesn’t?  We need correction factors for intermolecular attractions and molecular volume.  This is the van der Waals equation which comes from the ideal gas law.

13. atm L 2 /mol 2 Correction for intermolecular forces L/mol Correction for molecular volume

14. Vapor Pressure  Liquids will reach a dynamic equilibrium between the liquid and vapor phase as molecules evaporate.  If it is a closed container, there is no net change in molecules once equilibrium is reached.  In an open container, the molecules will escape and leave.  The gas molecules from the liquid will then exert a pressure on the surroundings. This is called the VAPOR PRESSURE

15. How does this effect the gas problems.