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Gas Laws!

Gas Laws!. AP Chemistry Chapter 10. 10.1 Characteristics of Gases. Gases expand to fill container Gases are highly compressible Gases form homogeneous mixtures Gas molecules are far apart. Kinetic Molecular Theory. Observations:

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Gas Laws!

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  1. Gas Laws! AP Chemistry Chapter 10

  2. 10.1 Characteristics of Gases • Gases expand to fill container • Gases are highly compressible • Gases form homogeneous mixtures • Gas molecules are far apart

  3. Kinetic Molecular Theory • Observations: 1. Small molecules move faster than large molecules (on average). All molecules are moving at different speeds (Graham’s Law). 2. Molecules move in straight lines until: a.) hit one another or b.) hit walls of the container.

  4. Kinetic Molecular Theory • Observations: 3. The distance between molecules is large. 4. There is no pattern to the motion. 5. Molecules are in ceaseless motion.

  5. Mass-volume problems • How many liters of hydrogen will be produced from 0.654 grams of Zn reacting w/ excess hydrochloric acid? • Zn + 2HCl  ZnCl2 + H2 • 0.654g x 1 mol Zn x 1 mol H2 x 22.4 L = • 65.4g Zn 1 mol Zn 1 mol H2 0.224 L H2

  6. Volume-volume problems • 2.) How many liters of oxygen, at STP, are needed to react w/ 1.00 L of methane, CH4? • CH4 + 2O2 CO2 + 2H2O • 1.00 L CH4 x 1 mol CH4 x 2 mol O2 x 22.4 L O2 = 22.4 L CH4 1 mol CH4 1 mol O2 • 2.00 L O2

  7. Volume-mass problems

  8. 10.2 • Pressure = force/area • SI units= Pascals (Pa) = 1N/m 2 !. 100kPa = 1 bar B. STP standard temp & pressure = 1 atm = 760 mm Hg = 760 torr = about 30 in Hg = 29.92 in Hg = 101.325 kPa

  9. Pascal’s Law • pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same.

  10. Pascal’s triangles Blaise Pascal

  11. barometer • Invented by • Evangelista Torricelli

  12. II. Manometer p. 357 Barometer p. 355

  13. 10.3 • P & V are inversely proportional. • P1V1 = P2V2 • T = K Boyle's Law Charles' Law • V & T are directly proportional. • V1/ T1 = V2/T2 P= K • P & T are directly proportional • V =K Gay-Lussac's Law

  14. IV. Combined Gas Law P1V1= P2V2 T1 T2 Amedeo Avogadro Avogadro’s Law V. Volumes of gases at same P, V, and T, will contain = # of molecules. =mol.

  15. 1627-1691 1746-1823 • Boyle Charles Gay-Lussac • 1778-1850

  16. Lismore Castle, Co Waterford, Ireland

  17. 10.4 I. Ideal Gas Law PV=nRT R = ideal gas law constant ( on your pink card.) R = PV/nT = (1atm)(22.4l)/(1mol)(273K) = .0821 atm-l/mol-K = (101.325kPa)(22.4l)/(1mol)(273K) = 8.31 kPa-l/mol-K =(760 torr)(22.4l)/(1mol)(273K) = 62.4 torr-l/mol-K p. 363 Table 10.2

  18. STP • temp. 273 Kelvin = 0degrees C Kelvin= degrees C + 273 ALL GAS LAW PRB MUST BE DONE IN KELVIN!!!!! B. 1 mol of any gas = 22.4 L at STP liters = 22400ml. That number (yes, that one) is an average.

  19. #+ LN #+ LN SAMPLE 10.5 & 10.3 10.5 Other equations D=m/V mw=g/mol PV=nRT Sample 10.7 & 10.8 10.6 • Dalton’s Law of Partial Pressure total pressure of a mixture of gases = sum of the pressure that each would exert if it were present alone. Ptotal= P1 + P2 + P3 …. And into infinity! INFINITY!!! SAMPLE 10.9

  20. 10.6 part 2 II. Collected over water- Subtract out vapor pressure of water Sample 10.11 10.7 • Kinetic Molecular Theory (KMT) • Assumptions 1.) gases are in ceaseless motion. Do you know what ceaseless means? No? How old are you? What grade? 2.) volume of molecules is negligible compared to total volume of container.

  21. 10.7 Con. 3.) attractive and repulsive forces are negligible 4.) collisions are perfectly elastic 5.) Avg KE (fish) absolute temp Temp = KE = 1/2mv2 B. Assumptions lead to the Ideal Gas Law (PV=nRT) 1.) will NOT work at high pressure and low temp. 2.) at high pressure  low volume; #2 will not be true 3.) at low temp #3 will not be true

  22. C. root-mean square speed, u Є = ½ mu2 4, 6, 10, 12 x = 8 m/s u = ¼(42+62+102+122) 74 8.31 8.6 m/s I. U = 3RT/MW A. effusion- diffusion thru a pinhole B. diffusion- high conc.  low conc. Kg/mol

  23. Graham's Law II. - small gas molecules move faster than larger ones. = sec2/sec1 Rate1/rate2 = MW2/MW1 III. Mean free path- average distance traveled by molecule between collisions 10.9 I. Real Gases A. van der Waal’s Equation (P + n2a/V2)(V-nb)=nRT (an2/V2)

  24. 10.9 Con. 1.) n2a/V2 = pressure correction cuz molecules do have attractive forces. 2.) nb = volume correction cuz molecules do take up space 3.) noble gases behave most ideally + - + - POLAR Most ideal- small and non polar

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