1. + Kinetic Molecular Theory

2. + Energy Energy of motion Energy due to position KineticPotential SI unit: joules ( J ) 1J = 1kgm 2 /s 2 = 1Nm Equation: KE = ½ mu 2

3. + KMT Assumptions 1.Gas molecules are separated from each other by distances far greater than their own dimensions 2.Gas molecules are in constant motion in random directions, & frequently collide with one another in perfectly elastic collisions 3.Gas molecules exert neither attractive nor repulsive forces on one another 4.Average kinetic energy of the molecules is proportional to temperature of the gas in kelvin; any two gases at the same temp will have the same KE

4. + Distribution of Molecular Speeds The lighter gas molecule moves faster on average than the heavier ones when comparing Cl 2, N 2 and He. The peak on the curve is the most probable speed at that temperature for nitrogen gas.

5. + Gas Behavior Hypothetical P-V-T behavior can be completely accounted for by ideal gas equation No attraction or repulsion Volume of the gas is negligible compared to the container Behave like an ideal gas, but not under all conditions Do attract one another and have a finite volume conditions under which a gas will deviate: High pressure Low temperature IdealReal

6. + Gas Behavior Gradual mixing of the molecules of one gas with the molecules of another by virtue of their kinetic properties High to low Gradual not instant Lighter gases diffuse through a certain space more quickly Process by which a gas under pressure escapes from one compartment of a container to another by passing through a small opening DiffusionEffusion molecular path

7. r1r1 r2r2 M2M2 M1M1  =

8. + Example 1 Under the same conditions of temperature and pressure, how many times faster will helium diffuse compared to nitrogen?

9. + Example 2 What is the relative rate of diffusion of carbon dioxide compared to hydrogen? Does carbon dioxide effuse faster or slower than hydrogen?

10. + Example 3 An unknown gas diffuses 0.25 times faster than helium. What is the molar mass of the unknown gas?