1. Kinetic Molecular Theory

2. Energy Kinetic Potential Energy of motion Energy due to position
SI unit: joules ( J ) 1J = 1kgm2/s2 = 1Nm
Equation: KE = ½ mu2

3. KMT Assumptions
Gas molecules are separated from each other by distances far greater than their own dimensions
Gas molecules are in constant motion in random directions, & frequently collide with one another in perfectly elastic collisions
Gas molecules exert neither attractive nor repulsive forces on one another
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

5. Gas Behavior Ideal Real Hypothetical
P-V-T behavior can be completely accounted for by ideal gas equation
No attraction or repulsion
Volume is negligible
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

6. Gas Behavior Diffusion Effusion
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
molecular path

7. r1 r2 M2 M1  =

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?