1. II. Graham’s Law of Diffusion & Effusion

2. A. Kinetic Energy
The average kinetic energy of molecules is directly proportional to the absolute temperature

3. A. Kinetic Energy KE = ½ mv2
KE = kinetic energy
m = mass
v = velocity
**At any given temperature, the molecules of ALL gases have the same average kinetic energy

4. B. Diffusion vs. Effusion
Diffusion – tendency of molecules to move towards area of lower concentration until the concentration is uniform throughout

5. B. Diffusion vs. Effusion
Effusion – the movement of gas particles through a small hole

6. B. Diffusion vs. Effusion

7. C. Comparison of Molecules

8. C. Comparison of Molecules
Image two gas samples, one of He (4 g/mol) and one of Ne (20 g/mol). If both have a kinetic energy of 2 J, what speed are both moving at?
Use KE = ½ mv2
He: 2 J = ½ (4 g) x v2 Ne: 2 J = ½ (20 g) x v2

9. HEAVIER GAS PARTICLES MOVE (DIFFUSE & EFFUSE) SLOWER

10. D. Graham’s Law
Recall: If 2 gases (A and B) are at the same temperature, the molecules have the same average kinetic energy. KEA = KEB ½ mAvA2 = ½ mBvB

11. D. Graham’s Law of Diffusion
Example: Mixture of He (4 g/mol) and Ne (20.2 g/mol)

12. Find the ratio of diffusion rates of O2 and N2
Graham’s Law Example
Find the ratio of diffusion rates of O2 and N2