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. 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

3. 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

4. GASES (Harcourt school Publishers) A windy day or a still day is a result of the difference in pressure of gases in two different locations.

6. What are the important Characteristics of Gases ?? Gases have a number of Properties such as: 1)Gases are compressible 2)Gases exert pressure 3)Gas pressure depends on the amount of confined gas 4)Gases fill their container 5)Gases mix freely with each other (infinitely miscible) 6)Gas pressure increases with temperature 7)Gases have low viscosity (Gases flow much easier than liquids or solids)

7. Boyle’s Law Hyperbolic Relation Between Pressure and Volume p V p – V Diagram isotherms T1T1 T2T2 T3T3 T 3 >T 2 >T 1 (courtesy F. Remer)

8. Charles’ Law Linear Relation Between Temperature and Pressure P T (K) 0100200300 P – T Diagram isochors V1V1 V2V2 V3V3 V 1 <V 2 <V 3 (courtesy F. Remer)

9. What is the ideal gas law ?? How can we calculate Gas density & Molecular mass?? PV= nRT = m RT M PM =m RT = d RT V PM= dRT

10. (from Meteorology Today) Prof. Jin-Yi Yu Question 1: Explain the following graph. The atmospheric pressure decreases exponentially With height. Question 2: If a helium balloon 1 m in diameter is released at sea level will it expand or shrink why?

11. (from The Blue Planet) ESS55 Prof. Jin-Yi Yu Example If a helium balloon 1 m in diameter is released at sea level, it expands as it floats upward because of the pressure decrease. The balloon would be 6.7 m in diameter as a height of 40 km.

12. What is Mole fraction? ?: For a mixture of A, B, … substances, mole fraction of substance i (X i ) What is Dalton’s law of partial pressures ??

13. from James Bradey Gases are often collected over water, they are saturated with water vapor. The pressure this vapor exerts is called the vapor pressure As gas bubbles through water, water vapor gets into the gas so the total pressure inside the bottle includes the partial pressure of the water vapor.

14. The total pressure is the pressure of the gas plus the vapor pressure of water vapor Vapor pressure of water at various temperatures.

15. Ideal Gas Model Kinetic Molecular Theory (KMT) for an ideal gas states that all gas particles: 1.Gas consists of large number of particles (atoms or molecules) hard spheres of insignificant volume 2.are in random, constant, straight-line motion. 3.are separated by great distances relative to their size. 4.have no attractive forces between them. 5.have collisions that may result in the transfer of energy between gas particles, but the total energy of the system remains constant. Newtonian Mechanics is used.

16. What is the Kinetic Energy &Avg speed of a molecule ?? Compare KE avg of two different gases at the same temp. KE (one mole) = 3/2 RT KE (one molecule ) = 3 RT = 3 k B T 2N A 2 R= gas constant, N A = Avogadro's Number, k B is Boltzmann’s constant KE (one molecule) = (1/2)mµ 2 KE (one mole) = N A (1/2)mµ 2 = (1/2)Mµ 2 Avg velocity of one mole gas µ 2 = 3RT M m is the mass of a gas particle, M is the molecular mass.

17. Maxwell distribution : In 1859, James Clerk Maxwell (1831 – 1879) worked out a formula for the most probable distribution of speeds in a gas. Molecules in a gas sample move at a variety of speeds. speed of each molecule constantly changing due to countless collisions(about 1 billion per second for each molecule). At low temperature most molecules move close to the average speed, at higher temperature there is greater distribution of speeds.

18. Maxwell distribution of speeds : Just for your knowledge do not memorize

19. Brownian motion. Chaotic motion of minute particle suspended in a gas or liquid GASES (Harcourt school Publishers)

20. Ideal vs. Non-Ideal Gases Kinetic Theory Assumptions –Point Mass –No Forces Between Molecules –Molecules Exert Pressure Via Elastic Collisions With Walls xx (courtesy F. Remer)

21. Ideal vs. Non-Ideal Gases Non-Ideal Gas –Violates Assumptions Volume of molecules Attractive forces of molecules (courtesy F. Remer)

22. Deviations from ideal behaviour Question : At what condition a real gas behaves like an ideal gas ?? A real gas behaves like an ideal gas when the real gas is at low pressure and high temperature. At high pressures gas particles are close therefore the volume of the gas particles is considered. At low temperatures gas particles have low kinetic energy therefore particles have some attractive force Example Dry ice, liquid oxygen and nitrogen

23. State Differences between ideal gases & real gases Real gases behave as described by the ideal gas equation; no real gas is actually ideal. Within a few %, ideal gas equation describes most real gases at room temperature and pressures of 1 atm or less. In real gases, particles attract each other reducing the pressure. Real gases behave more like ideal gases as pressure approaches zero.

24. What is wrong in this graph??? James Bradey Deviation from ideal gas law. A plot of PV/T versus P for an ideal gas is a straight line. The same plot for oxygen is not a straight line.

25. Results for Real Gases

26. (a)In an ideal gas, molecules would travel in straight lines. (b) In a real gas, the paths would curve due to the attractions between molecules. Deviations from ideal behavior occur because: 1)Gas molecules interact and 2)Gas molecules occupy a finite volume

27. 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

28. At sea level the atmospheric pressure is about 14.7 psi Other common pressure units are the bar: 1.00 atm =760mmHg =14.7 psi =1.0133 bar

29. Temperature Scale