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Chapter 5

Chapter 5. The Gaseous State. Properties of Gases. can be compressed exert pressure on whatever surrounds them expand into whatever volume is available easily diffuse into one another

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Chapter 5

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  1. Chapter 5 The Gaseous State Dr. S. M. Condren

  2. Properties of Gases • can be compressed • exert pressure on whatever surrounds them • expand into whatever volume is available • easily diffuse into one another • can be described in terms of their temperatures and pressure,the volume occupied, and the amount (number of molecules or moles) present Dr. S. M. Condren

  3. Mercury Barometer Dr. S. M. Condren

  4. Composition of Air at Sea Level Dr. S. M. Condren

  5. Important Units of Pressure Conversion factor to learn Dr. S. M. Condren

  6. Boyle’s Law At constant temperature and mass of gas: Va1/P V = a * 1/P where a is a proportionality constant thus VP = a V1P1 = a = V2P2 V1P1 = V2P2 Dr. S. M. Condren

  7. Boyle’s Law Dr. S. M. Condren

  8. Boyle’s Law Dr. S. M. Condren

  9. Effect of Pressure Differential Dr. S. M. Condren

  10. Charles’ Law At constant pressure and mass of gas: VaT V = b * T where b is a proportionality constant V/T = b V1/T1 = b = V2/T2 V1/T1 = V2/T2 Dr. S. M. Condren

  11. Charles’ Law Dr. S. M. Condren

  12. Combined Gas Law At constant mass of gas VaT/P V = d * (T/P) where d is a proportionality constant (VP)/T = d V1P1 = d = V2P2 T1 T2 V1P1 = V2P2 T1 T2 Dr. S. M. Condren

  13. Avogadro’s Law At constant pressure and temperature Van V = c * n where c is a proportionality constant V/n = c V1/n1 = c = V2 /n2 V1/n1 = V2 /n2 Dr. S. M. Condren

  14. Ideal Gas Law Va(n * T)/P V = R * (n * T)/P where R is proportionality constant P * V = n * R * T (P*V)/(n*T) =R Thus, (P1*V1)/(n1*T1) = (P2*V2)/(n2*T2) Dr. S. M. Condren

  15. What will be volume of an ideal gas at absolute zero? - 10 mL/mole 0 mL/mole 10 mL/mole Dr. S. M. Condren

  16. Ideal Gas Constant R = 0.08205 L*atm/mol*K R has other values for other sets of units. R = 82.05 mL*atm/mol*K = 8.314 J/mol*K = 1.987 cal/mol*K Dr. S. M. Condren

  17. Molar Massfrom Gas Density gas density = #g/V = d PV = nRT where n = #g/MM PV = (#g/MM)*RT MM = (#g*R*T)/(P*V) MM = (#g/V)*((R*T)/P) = (d*R*T)/P Dr. S. M. Condren

  18. Dalton’s Lawof Partial Pressures The total pressure of a mixture of gases is equal to the sum of the pressures of the individual gases (partial pressures). PT = P1 + P2 + P3 + P4 + . . . . where PT => total pressure P1 => partial pressure of gas 1 P2 => partial pressure of gas 2 P3 => partial pressure of gas 3 P4 => partial pressure of gas 4 Dr. S. M. Condren

  19. Dalton’s Law of Partial Pressure Dr. S. M. Condren

  20. Collecting Gases over Water Dr. S. M. Condren

  21. Example: What volume will 25.0 g O2 occupy at 20oC and a pressure of 0.880 atm? (25.0 g)(1 mol) n = ---------------------- = 0.781 mol (32.0 g) V =?; P = 0.880 atm; T = (20 + 273)K = 293K R = 0.08205 L*atm/mol*K V = nRT/P = (0.781 mol)(0.08205L*atm/mol*K)(293K) 0.880atm = 21.3 L Dr. S. M. Condren

  22. ExampleA student generates oxygen gas and collects it over water. If the volume of the gas is 245 mL and the barometric pressure is 758 torr at 25oC, what is the volume of the “dry” oxygen gas at STP? Pwater = 23.8 torr at 25oC; PO2 = Pbar - Pwater = (758 - 23.8) torr = 734 torr P1= PO2 = 734 torr; P2= SP = 760. torr V1= 245mL; T1= 298K; T2= 273K; V2= ? (V1P1/T1) = (V2P2/T2) V2= (V1P1T2)/(T1P2) = (245mL)(734torr)(273K) (298K)(760.torr) = 217mL Dr. S. M. Condren

  23. Kinetic Molecular Theory Matter consists of particles (atoms or molecules) in continuous, random motion. Dr. S. M. Condren

  24. Kinetic Molecular Theory: Gases • particles in continuous, random, rapid motion • collisions between particles are elastic • volume occupied by the particles is negligibly small effect on their behavior • attractive forces between particles have a negligible effect on their behavior • gases have no fixed volume or shape, take the volume and shape of the container Dr. S. M. Condren

  25. Maxwell’s Distribution of Speeds Dr. S. M. Condren

  26. Real Gases • have a finite volume at absolute zero • have attractive forces between gas particles Dr. S. M. Condren

  27. Van der Waals Equation (P + a/V2)(V - b) = nRT where a => attractive forces b => residual volume Dr. S. M. Condren

  28. Dr. S. M. Condren

  29. Dr. S. M. Condren

  30. Carbon Dioxide and Greenhouse Effect Dr. S. M. Condren

  31. Some Oxides of Nitrogen • N2O • NO • NO2 • N2O4 2 NO2 = N2O4 brown colorless • NOx Dr. S. M. Condren

  32. Air Pollution in Los Angles Dr. S. M. Condren

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