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Chapter 5: Gases

Chapter 5: Gases. Pressure The Empirical Gas Laws The Ideal Gas Law & Its Applications Mixtures of Gases The Kinetic Molecular Theory of Gases Effusion & Diffusion Real Gases. Example 1. Find the volume of a gas at a pressure of 1.5 x 10 3 mmHg if it has a volume of

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Chapter 5: Gases

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  1. Chapter 5: Gases • Pressure • The Empirical Gas Laws • The Ideal Gas Law & Its Applications • Mixtures of Gases • The Kinetic Molecular Theory of Gases • Effusion & Diffusion • Real Gases

  2. Example 1 Find the volume of a gas at a pressure of 1.5 x 103 mmHg if it has a volume of 1.0 L at 1.0 atm.  Assume the temperature is unchanged.   Answer: 0.51 L

  3. Example 2 A sample of CO2 has a volume of 533 mL at 23.2ºC and 749 mmHg.  How many moles of CO2 are in this sample? Answer: .0216 moles CO2

  4. Example 3 An experiment calls for 4.00 moles of CO gas at STP.  What volume of gas is this? Answer: 89.7 L

  5. Example 4 For a gas at 25ºC the volume  is 2.0 L.  Find its volume at 100.ºC if its pressure remains constant. Answer: 2.5 L

  6. Example 5 What is the volume of a sample of O2 at 25 ºC and 1.00 atm if it has a mass of 1.50 g? Answer: 1.15 L

  7. Example 6 LiOH is used in spacecraft to absorb the CO2 exhaled by the astronauts: 2 LiOH (s)  +  CO2(g)  Li2CO3(s)  +  H2O (l) What volume of CO2 can be absorbed by 1.00 g of LiOH at 25.0°C and 1.00 atm? Answer: 0.511 L

  8. Example 7 What is the density of neon gas in g/L at 27ºC and 748 mmHg? Answer: 0.806 g/L

  9. Example 8 An unknown gas has a density of 0.164 g/L at 21ºC and 752 mmHg. Find the molecular weight of this gas. Answer: 4.00 g/mole (helium)

  10. Example 9 An experimental undersea habitat had an atmosphere consisting of the following mole percents: 79.0% He17.0% N24.0% O2 What are the partial pressures of each gas at 58.8 m below sea level where the pressure is 6.91 atm? Answer: 5.46 atm He, 1.17 atm N2, 0.28 atm O2

  11. Example 10 The reaction between zinc metal and acid produces hydrogen gas.  Assume the hydrogen produced by this reaction was collected over water at 753 mmHg and at 23ºC.  If 215 mL of hydrogen were collected, what mass of hydrogen was produced? Answer: 1.72 x 10-2 g H2

  12. Example 11 Calculate the average kinetic energy for 1.00 mole of oxygen gas at 21°C. Answer: 3.67 x 103 J

  13. Example 12 Calculate the average velocity of oxygen molecules at 21°C. Answer: 479 m/s

  14. Example 13 It takes 5.28 seconds for 15.0 mL of He gas to effuse through a pinhole in a container.  It takes 14.9 seconds for the same volume of an unknown gas to effuse through the same hole under the same conditions.  What is the molecular weight of the unknown gas? Answer: 31.9 g/mole (oxygen?)

  15. Example 14 Find the pressure of ethanol vapor at 82ºC if 1.00 mole occupies a volume of 35.00 L.  Use both the Ideal Gas Law and Van der Waals equation and compare your answers. a = 12.02 L2atm/mole2 b = .08407 L/mole Answer: 0.832 atm (IGL); 0.825 atm (VDW)

  16. Example 15 Use the Van der Waals equation to find the volume of 1.00 g of CO2 at 0ºC and 10.0 atm.  a = 3.59 L2atm/mole2 b = .0427 L/mole (Hint:  because this problem results in a cubic equation, simplify by using the Ideal gas law to estimate V and use this estimate in the correction factor to P.  You will be making a small error in a small correction term so the final result will be very close to the exact solution.) Answer: 48.5 mL

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