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Gas Laws Overview: Properties, Equations, and Applications

Learn about the properties of gases, gas laws, and their practical applications. Understand kinetic molecular theory, volume relationships, ideal gas law, and solve example problems.

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Gas Laws Overview: Properties, Equations, and Applications

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  1. Properties of Gases • Expand to completely fill their container • Take the shape of their container • Low density • Much less than solid or liquid state • Compressible • Mixtures of gases are always homogeneous • Fluid Chapter 6

  2. Gas Laws – Kinetic Molecular Theory • All matter is composed of tiny discrete particles called molecules • Molecules in a gas are in rapid constant motion and move in straight lines • Molecules of a gas are tiny compared with distances between gas molecules • There is little attraction between molecules of a gas Chapter 6

  3. Molecules collide with each other, with energy being conserved in the collision • Temperature (T) is a measure of the average kinetic energy of the gas molecules Chapter 6

  4. Pressure and Temperature (cont.) Chapter 6

  5. Volume Relationships • Law of combining volumes – when all measurements are made at same temperature and pressure, volumes of gaseous reactants and products are in small whole-number ratio Chapter 6

  6. Avogadro’s hypothesis – equal volumes of gases at constant pressure and temperature have the same number of molecules Chapter 6

  7. UNITS • Pressure • Temperature Chapter 6

  8. Molar Volume • Volume occupied by 1 mol of gas • Standard temperature and pressure (STP) • 1 atm pressure and 0°C • 1 mole of gas has volume of 22.4 L Chapter 6

  9. Talk about Density • This is at STP Chapter 6

  10. Boyle’s Law • PV=PV Chapter 6

  11. Talk about Lungs Chapter 6

  12. EXAMPLE Boyle's Law: Pressure-Volume Relationships Exercise A gas is enclosed in a 10.2-L tank at 1208 mmHg. (The mmHg is a pressure unit; 760 mmHg = 1 atm.) Which of the following is a reasonable value for the pressure when the gas is transferred to a 30.0-L tank? 300 mmHg 400 mmHg 3,600 mmHg 12,000 mmHg A gas is enclosed in a cylinder fitted with a piston. The volume of the gas is 2.00 L at 0.524 atm. The piston is moved to increase the gas pressure to 5.15 atm. Which of the following is a reasonable value for the volume of the gas at the greater pressure? 0.20 L 0.40 L 1.00 L 16.0 L

  13. EXAMPLE Boyle’s Law: Pressure-Volume Relationships A cylinder of oxygen has a volume of 2.25 L. The pressure of the gas is 1470 pounds per square inch (psi) at 20 °C. What volume will the oxygen occupy at standard atmospheric pressure (14.7 psi) assuming no temperature change?

  14. Exercise 2 Exercise 3 A sample of air occupies 73.3 mL at 98.7 atm and 0 ºC. What volume will the air occupy at 4.02 atm and 0 ºC? A sample of helium occupies 535 mL at 988 mmHg and 25 °C. If the sample is transferred to a 1.05-L flask at 25 °C, what will be the gas pressure in the flask? EXAMPLE Boyle’s Law: Pressure-Volume Relationships continued Chapter 6

  15. Charles’s Law Chapter 6

  16. Charles' Law • V/T = V/T Chapter 6

  17. Charles’s Law: Temperature-Volume Relationships EXAMPLE 6.15 A balloon indoors, where the temperature is 27 °C, has a volume of 2.00 L. What would its volume be (a) in a hot room where the temperature is 47 °C, and (b) outdoors, where the temperature is –23 ºC? (Assume no change in pressure in either case.)

  18. Charles’s Law: Temperature-Volume Relationships continued EXAMPLE 6.15 Exercise 6.15A Exercise 6.15B A sample of oxygen gas occupies a volume of 2.10 L at 25 °C. What volume will this sample occupy at 150 °C? (Assume no change in pressure.) b. A sample of hydrogen occupies 692 L at 602 °C. If the pressure is held constant, what volume will the gas occupy after being cooled to 23 °C? At what Celsius temperature will the initial volume of oxygen in Exercise 6.15A occupy 0.750 L? (Assume no change in pressure.) Chapter 6

  19. Ideal Gas Law PV = nRT • P = pressure • V = volume • n = number of moles • R = gas constant = 0.0821 L atm/mol K • T = absolute temperature Chapter 6

  20. EXAMPLE 6.16 Ideal Gas Law Exercise 6.16A Determine (a) the pressure exerted by 0.0330 mol of oxygen in an 18.0-L container at 313 K, and (b) the volume occupied by 0.200 mol of nitrogen gas at 298 K and 0.980 atm. Use the ideal gas law to calculate (a) the volume occupied by 2.00 mol of nitrogen gas at 244 K and .9500 atm pressure, and (b) the pressure exerted by 0.500 mol of oxygen in a 15.0-L container at 303 K.

  21. EXAMPLE 6.16 Ideal Gas Law continued Exercise 6.16B Determine the volume of nitrogen gas produced from the decomposition of 130 g sodium azide (about the amount in a typical automobile airbag) at 25 °C and 1 atm. Chapter 6

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