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Chapter 13

Chapter 13. The Gas Laws. Rates of Effusion Graham’s Law of Effusion:. Rates of diffusion Depends mainly on mass of particles involved Grahams law allows us to compare rates of diffusion of two gasses.

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Chapter 13

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  1. Chapter 13 The Gas Laws

  2. Rates of Effusion • Graham’s Law of Effusion:

  3. Rates of diffusion • Depends mainly on mass of particles involved • Grahams law allows us to compare rates of diffusion of two gasses

  4. Ammonia has a molar mass of 17.0 g/mol, hydrogen chloride has a molar mass of 36.5 g/mol. What is the ratio of their diffusion rates?

  5. What is the molar mass of a gas that takes four times as long to effuse as hydrogen?

  6. Gas Pressure • Pressure = force per unit area • Smaller area = more pressure • Air pressure – pressure of the atmosphere • 1 atm • 760 mm Hg • 101.3 kPa

  7. Dalton’s law of partial pressures: • Total pressure of a mixture of gasses is equal to the sum of the pressures of all of the gasses in the mixture • P1 + P2 + P3…=Ptotal

  8. A mixture of oxygen, carbon dioxide, and nitrogen has a total pressure of 0.97 atm. What is the partial pressure of O2 if the partial pressure of CO2 is 0.70 atm and the partial pressure of N2 is 0.12 atm?

  9. 3 factors affecting gases • Temperature • Kelvin = Celsius + 273 • Volume • L • mL • Pressure • kPa • atm • mmHg

  10. Ping pong ball in hot water video

  11. Boyles Law • TEMPERATURE CONSTANT • Pressure and volume are inversely related • P1 x V1 = P2 x V2

  12. A diver blows a 0.75 L air bubble 10 m under water. As it rises to the surface, the pressure goes from 2.25 atm to 1.03 atm. What ill be the volume of the air in the bubble at the surface?

  13. The volume of a gas at 99.0 kPa is 300.0 mL. if the pressure is increased to 188 kPa, what will be the new volume?

  14. Charles’s Law • PRESSURE CONSTANT • Flexible container • Volume and temperature are directly related • Temperature must be in K!

  15. A helium balloon in a closed car occupies a volume of 2.32 L at 40.0 oC. If the car is parked on a hot day and the temperature inside rises to 75.0 oC what is the new volume of the balloon?

  16. A gas at 89 oC occupies a volume of 0.67 L. At what Celsius temperature will the volume increase to 1.12 L?

  17. Gay-Lussac’s Law • VOLUME CONSTANT • Pressure and Temperature are directly related • Temperature must be in K!

  18. The pressure of the oxygen gas inside a canister is 5.00 atm at 25.0 oC. The canister is located at a camp high on Mount Everest. If the temperature there falls to -10.0 oC, what is the new pressure inside the canister?

  19. Helium gas in a 2.00 L cylinder is under 1.12 atm pressure. At 36.5 oC that same gas sample has a pressure of 2.56 atm. What was the initial temperature of the gas in the cylinder?

  20. The Combined Gas Law • The three gas laws discussed can be combined into a single gas law.

  21. A gas at 110 kPa and 30.0oC fills a flexible container with an initial volume of 2.00 L. If the temperature is raised to 80.0 oC and the pressure increases to 440 kPa, what is the new volume?

  22. A sample of air in a syringe exerts a pressure of 1.02 atm at 22.0 oC. The syringe is placed in a boiling water bath at 100.0 oC. The pressure is increased to 1.23 atm by pushing the plunger in, which reduces the volume to 0.224 mL. What was the initial volume?

  23. The Ideal Gas Law • Relates number of particles, pressure, temperature, and volume • Avogadro’s principle – equal volumes of gases at the same temperature and pressure contain equal numbers of particles

  24. 1 mol of gas = particles • Molar volume of a gas is the volume that 1 mol occupies at STP • STP = • 1 mol = 22.4 L of gas

  25. How many moles of carbon dioxide gas are in a 1.0 L balloon? • What volume will 9.22 g of H2 gas occupy at STP?

  26. The Ideal Gas Law • PV = nRT • R = 8.31 L*kPa/mol*K • R = 0.0821 L*atm/mol*K

  27. Calculate the number of moles of ammonia gas contained in a 2.0L vessel at 300.0 K with a pressure of 1.50 atm

  28. What is the volume of a 0.323 mol sample of a gas at 265 K and 0.900 atm?

  29. How many moles of a gas are in 2.50 L of gas at STP?

  30. Real vs. Ideal Gas • Ideal gases follow the assumptions of the kinetic-molecular theory • Particles take up no space • Experience no intermolecular forces • Not attracted to or repelled by the walls of their container • Follow the gas laws under all temperatures and pressures

  31. Extreme temperature and pressure • Gases deviate most from ideal behavior at high pressures and low temperatures • Polarity and size of particles • Also affect how a gas behaves

  32. Gas Stoichiometry • When gases react, the coefficients in the balanced chemical equation represents both molar amounts and relative volumes 2H2(g) + 2O2(g)  2H2O(g)

  33. Volume – Volume problems • What volume of oxygen gas is needed for the complete combustion of 4.00 L of methane gas? • CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

  34. What volume of carbon dioxide gas can be made from 2.36 L of methane?

  35. Volume – Mass problems • If 5.00 L of nitrogen reacts completely with hydrogen at a pressure of 3.00 atm and a temperature of 298 K, how much ammonia, in grams, is produced? N2(g) + 3H2(g)  2NH3(g)

  36. NH4NO3(s)  N2O(g) + 2H2O(g) • What mass of solid ammonium nitrate must be used to obtain 0.100 L of dinitrogen oxide gas at STP?

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