1. S yllabes of 331 chem course Kinetic theory. Forces between atoms, ions and molecules. Colligative properties. Vapor pressure and enthalpy. Boiling and freezing. Solid phase and its structure. Solubility and dissociation Phase equilibrium. Ideal and non-ideal solutions. Solvent and solute activities. Ion hydration. Born and Debye-Hükle models. Activity coefficient. Electrolytic conductance. Ionic mobility. Transport number. Diffusion, transport and Fix’s laws. Formation of colloidal dispersions, Colloid stability, Reference of course Physical chemistry, Gordon Barow, Ch 1,2,9,10,17

2. Objective for gases Revision of Characteristics of Gases, ideal gas law, Dalton’s law of partial pressures. Kinetic Molecular Theory : Kinetic energy of gases, molecular speed Deviations from ideal behaviour Condensation of gases

3. 331 chem course Reference of these Slides : 1. James Brady 2.(Meteorology Today) Prof. Jin-Yi Yu 3.(from The Blue Planet) ESS55 Prof. Jin-Yi Yu 4. (Harcourt school Publishers) 5.Lecture Plus Timberlake 2000

4. Example: The molar mass of oxygen is 32.0 g/mol. What is the density of oxygen at STP? Solution: At STP,P=1atm,T= 273K d = PM = 1 atm x 32g mol -1 = RT 0.0821 Latm K -1 mol -1 x273K d =1.43 g /L

5. Lecture PLUS Timberlake 2000 Learning Check G16 Dinitrogen monoxide (N 2 O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23°C, what is the pressure (mmHg) in the tank in the dentist office?

6. Lecture PLUS Timberlake 20006 Rearrange ideal gas law for unknown P P = nRT V Substitute values of n, R, T and V and solve for P P = (2.86 mol)(62.4L-mmHg)(296 K) (20.0 L) (K-mol) = 2.64 x 10 3 mm Hg

7. Lecture PLUS Timberlake 20007 Molar Mass of a gas What is the molar mass of a gas if 0.250 g of the gas occupy 215 mL at 0.813 atm and 30.0°C? n = PV = (0.813 atm) (0.215 L) = 0.00703 mol RT (0.0821 L-atm/molK) (303K) Molar mass = g = 0.250 g = 35.6 g/mol mol 0.00703 mol

8. Lecture PLUS Timberlake 20008 Learning Check G19 A. If the atmospheric pressure today is 745 mm Hg, what is the partial pressure (mm Hg) of O 2 in the air? 1) 35.6 2) 156 3) 760 B. At an atmospheric pressure of 714, what is the partial pressure (mm Hg) N 2 in the air? 1) 557 2) 9.143) 0.109

9. Example: A sample of oxygen (250mL)is collected over water at 30 o C and a pressure of 738 torr. What is the partial pressure of wet oxygen? What is the volume of dry oxygen at STP ? P (H 2 O=31.8 torr) SOLUTION: Now we use combined gas law P 1 V 1 ( 30 o C ) = P 2 V 2 (STP) ; V 2 = P 1 V 1 ( 30 o C )x T 2 T 1 T 2 T 1 P 2 V 2 = 0.929 atm x 0.25L x 273K = 0.209 L 303 K x 1 atm

10. Lecture PLUS Timberlake 200010 Solution G19 A. If the atmospheric pressure today is 745 mm Hg, what is the partial pressure (mm Hg) of O 2 in the air? 2) 156 B. At an atmospheric pressure of 714, what is the partial pressure (mm Hg) N 2 in the air? 1) 557

11. Lecture PLUS Timberlake 200011 Health Note When a scuba diver is several hundred feet under water, the high pressures cause N 2 from the tank air to dissolve in the blood. If the diver rises too fast, the dissolved N 2 will form bubbles in the blood, a dangerous and painful condition called "the bends". Helium, which is inert, less dense, and does not dissolve in the blood, is mixed with O 2 in scuba tanks used for deep descents.

12. Lecture PLUS Timberlake 200012 Learning Check G20 A 5.00 L scuba tank contains 1.05 mole of O 2 and 0.418 mole He at 25°C. What is the partial pressure of each gas, and what is the total pressure in the tank? P = nRT P T = P O + P He V 2 P T = 1.47 mol x 0.0821 L-atm x 298 K 5.00 L(K mol) =7.19 atm

13. J. D. van der Waals corrected the ideal gas equation into : The constants a and b are called the van der Waals constants a, b are different for each gas

14. At sea level the atmospheric pressure is about 14.7 psi Other common pressure units are the bar: 1.00 atm =14.7 psi =1.0133 bar

15. The Kinetic Molecular Theory and Graham's Law µ 2 = 3RT M Kg/mol µ rms = √3RT/M Question 1: Explain all the variables in this equation. This equation states that the velocity (rate) at which gas molecules move is inversely proportional to the square root of their molar masses. µ rms is the ‘root mean square’ velocity of a collection of gas molecules (the square root of the average squared value) so doubling temperature increases u rms by a factor of 2½ = 1.41

16. Calculating Molecular Speeds : Question : Calculate the average speed of O 2 in air at 20 o C. 1660 km/h! (1.6km=1mile). Question : What is the r.m.s. speed of SO2 atoms at 25°C? u rms = 340.78 ms-1

17. Triple Point of Water This is a unique, and reproducible, state in which water, water vapor and ice can coexist. This occurs at P = 4.58 mmHg t = 0.01 o C