Announcements To join clicker to class today: – Turn on the Clicker (the red LED comes on). – Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). ● Exam 4 on Chapters 7 & 8 Wednesday. ● Discussion—quiz on & Review. ● Wear appropriate clothes to Lab! ● Do not forget about the Lewis Tutorial, the VSEPR examples on Web site and the text site, as well, for more examples and pictures. ● Will start Chapter 9 after exam. ● Celebration of Scholarship this Thursday in Reeve.

Review PV = nRT –Solved for solve for any variable. –Partial pressures P tot = P 1 + P 2 + … = (n 1 + n 2 + …)RT/V P i = X i P tot ∑  X i = 1 or X 1 + X 2 + X = 1 C gas = k H P gas Kinetic Molecular Theory of Gases.

Kinetic Molecular Theory of Gases Molecules assumed to be very small (essentially points with no volume) They are constantly moving and exchanging kinetic energy through elastic collisions => they are changing direction and speed randomly, but total kinetic energy constant. Pressure = sum of the force of many collisions with the walls of the container. Based on KE = (1/2)mu 2 (u = speed). – Each sample has a distribution of speeds. – lighter particles move faster. Key result: u rms = (3RT/ M ) 1/2 – Higher temperature => higher speeds.

Diffusion and Effusion u rms = (3RT/ M ) 1/2 Diffusion = spread of one substance through another. Effusion = process of a gas escaping through a small hole. Rate for both depends on u rms – Higher T => faster diffusion or effusion. – relative rates r 1 /r 2 =u rms (1)/u rms (2) = ( M 2 / M 1 ) 1/2

Van der Waals gas equation P = nRT/(V-nb) -a(n/V) 2 P, V, n, R, T same as ideal gas law b = volume taken up by 1 mole of molecules (increases P) a = attraction factor (decreases P) Implications If V is small (≈ nb) P will be much higher than expected. If a is larger P will be lower than expected. Ex: O 2 at 10 atm of pressure in 1.00 L at 298 K (25 ˚C): Ideal gas law => moles of gas. Using the van der Waals get moles of gas.

Using Van der Waals gas equation P = nRT/(V-nb) -a(n/V) 2 You must be able to: use equation to calculate the actual pressure observed given all other values. look at a and b to compare molecules and determine which is more affected by attraction or volume of the molecules. Example: For x mol H 2 O in mL at K ideal gas law gives a pressure of x atm. Use VDW calculate P. a(H 2 O) = L 2 atm/mol 2 b(H 2 O) = L/mol

Chapter 7-Greenhouse effect, molecular vibrations and shape A. Greenhouse Effect B. Infrared Spectroscopy C. Lewis structures again D. Unpaired e- (MO diagram review) E. VSEPR model (3-D molecular shapes) F. Valence Bond Theory and 3-D shapes G. Dipole moments and shapes of molecules

Chapter 8 – Gases Pressure Ideal Gas Law (PV = nRT, solutions for P, V, n, T, density and molar mass) Dalton’s Law of Partial Pressures Henry’s Law of gas solubility Kinetic Molecular Theory of Gases (molecular speeds, diffusion and effusion) Real Gases/Non-Ideal behavior (van der Waals equation)