1. Lecture 1810/14/05

2. Quiz 6 1. H 2 (g) and N 2 (g) react completely to form NH 3 (g). If the final pressure in the flask is 4 atm, what was the total pressure in the flask before the reaction? 2. Describe one of the parts of the Kinetic Molecular Theory.

3. Calculate RMS for O 2 (g) at 25 ˚C. R = 8.3145 J/mol-K 1 J = 1 kg-m 2 /s 2 Need to use molecular mass in kg/mol

4. Average Kinetic Energy For all gases, average kinetic energy only dependent on temperature At the same T, all gases have the same average KE. As T goes up, KE also increases — and so does speed. R= 8.314 J/mol-K

5. Consider a sample of N 2 (g) at 25˚C. Explain your answer using the KMT. a) How would raising the temperature to 30˚C affect the pressure of the gas? b) How would adding more N 2 molecules to the sample at constant temperature and volume affect the pressure?

6. Escape of a gas molecules through a tiny hole into a vacuum Molecules effuse at a rate (moles/time): proportional to T inversely proportional to M EFFUSION

7. Graham’s Law of Effusion

8. Application of effusion 235 UF 6 separated from 238 UF 6 by effusion for the atomic bomb in WW II

9. Tetrafluoroethylene (C 2 F 2 ) effuses through a barrier at a rate of 4.6 x 10 -6 mol/h. An unknown gas effuses at a rate of 5.8 x 10 -6 mol/h under the same conditions. What is the molar mass of the unknown?

10. DIFFUSION: Gradual mixing of molecules of different gases

11. KMT and increase in Temperature Increases number of collisions AND Increases average KE so increases force of collision

12. Real Gases Take another look at two of the basic KMT assumptions: Gas molecules occupy no space Gas molecules don’t interact with each other

13. Assumption: Gas molecules occupy no space Volume actually occupied by O 2 molecules: Volume ~ 4.63 x 10 -27 L/molecule Volume ~ 2.79 x 10 -3 L/mol Total volume occupied by O 2 molecules at STP (use PV=nRT): 22.4 L/mol

14. Assumption: Gas molecules occupy no space Volume actually occupied by O 2 molecules: Volume ~ 2.79 x 10 -3 L/mol Total volume occupied by O 2 molecules at 273 K and 100 atm: 0.224 L/mol Total volume occupied by O 2 molecules at 273 K and 1000 atm: 0.0224 L/mol