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Chapter 10

Chapter 10. Gases. Barometers and Standard Atmospheric Pressure. Barometers and Standard Atmospheric Pressure. Standard atmospheric pressure defined as the pressure sufficient to support a mercury column of 760mm (units of mmHg , or torr ). Barometers and Standard Atmospheric Pressure.

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Chapter 10

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  1. Chapter 10 Gases

  2. Barometers and Standard Atmospheric Pressure

  3. Barometers and Standard Atmospheric Pressure • Standard atmospheric pressuredefined as the pressure sufficient to support a mercury column of 760mm (units of mmHg, or torr).

  4. Barometers and Standard Atmospheric Pressure • Standard atmospheric pressuredefined as the pressure sufficient to support a mercury column of 760mm (units of mmHg, or torr). • Another unit was introduced to simplify things, the atmosphere (1 atm= 760 mmHg).

  5. Barometers and Standard Atmospheric Pressure • Standard atmospheric pressuredefined as the pressure sufficient to support a mercury column of 760mm (units of mmHg, or torr). • Another unit was introduced to simplify things, the atmosphere (1 atm= 760 mmHg). • 1 atm = 760 mmHg = 760 torr = 101.325 kPa (page 262).

  6. STP standard temperature and pressure Standard temperature0°C or 273 K Standard pressure1 atm (or equivalent)

  7. Boyle's Law • Pressure varies inversely with volume • Volume varies inversely with pressure “The volume of a sample of gas is inversely proportional to its pressure, if temperature remains constant.”

  8. Boyle’s Law

  9. Boyle’s Law: Pressure & Volume (Figure 10.6 (a) page 263)

  10. 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? Boyle’s Law: Pressure-Volume Relationships 1800 mL

  11. 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? Boyle’s Law: Pressure-Volume Relationships 503 mm Hg

  12. Charles' Law • Effects of temperature on a gas • Volume varies directly with Temperature “The volume of a quantity of gas, held at constant pressure, varies directly with the Kelvin temperature.”

  13. Charles’s Law a

  14. Charles Law: Volume and Temperature (Figure 10.8 Page 266)

  15. Charles’ Law and Absolute Zero • Extrapolation to zero volume gives a temperature of • -273°C or 0 K

  16. Charles’s Law: Temperature-Volume Relationships 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.) 2.98 L

  17. Charles’s Law: Temperature-Volume Relationships A sample of oxygen gas occupies a volume of 2.10 L at 25 °C.At what Celsius temperature will the volume of oxygen occupy 0.750 L? (Assume no change in pressure.) -167°C

  18. Pressure varies directly with Temperature If the temperature of a fixed volume of gas doubles its pressure doubles. Pressure vs. Temperature

  19. Pressure vs. Temperature • The pressure exerted by a gas is directly related to the Kelvin temperature. • V is constant.

  20. Pressure vs. Temperature

  21. Example A gas has a pressure of 645 torr at 128°C. What is the temperature in Celsius if the pressure increases to 1.50 atm? Pi = 645 torr Pf = 1.50 atm 760 torr = 1140 torr 1 atm Ti = 128°C + 273 = 401 K Tf = ?K

  22. Solution T2 = 401 K x 1140 torr = 709K 645 torr 709K - 273 = 436°C

  23. Combined Gas Law Problem A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm?

  24. Combined Gas Law Problem A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm? x3.20 atmx 90.0 mL 0.800 atm 180.0 mL 604 K - 273 = 331 °C 302 K = 604 K

  25. Combined Gas Law • A 10.0 cm3 volume of gas measured 75.6 kPa and 60.0C is to be corrected to correspond to the volume it would occupy at STP. 6.12 cm3

  26. Gay-Lussac’s Law Gay-Lussac’s Law of combining volumes: at a given temperature and pressure, the volumes of gases which react are ratios of small whole numbers.

  27. How many liters of steam can be formed from 8.60L of oxygen gas? 17.2 L

  28. How many liters of hydrogen gas will react with 1L of nitrogen gas to form ammonia gas? 3L H2

  29. A

  30. A How many mL of hydrogen are needed to produce 13.98 mL of ammonia? 20.97 ml NH3

  31. Avogadro’s Law: Equal volumes of gases at the same temperature and pressure contain the same number of particles.

  32. The molar volume of a gas at STP = 22.4L 22.4 L

  33. Ideal Gas • An ideal gas is defined as one for which both the volume of molecules and forces of attraction between the molecules are so small that they have no effect on the behavior of the gas.

  34. Ideal Gas Equation PV=nRT

  35. R values • A a • I • R values for atm and kPa on Page 272 in book.

  36. Calculate the volume occupied by 0.845 mol of nitrogen gas at a pressure of 1.37 atm and a temperature of 315 K. 15.9 L

  37. Find the pressure in millimeters of mercury of a 0.154 g sample of helium gas at 32°C and contained in a 648 mL container. 1130 mm Hg

  38. An experiment shows that a 113 mL gas sample has a mass of 0.171 g at a pressure of 721 mm Hg and a temperature of 32°C. What is the molar mass (molecular weight) of the gas? 40.0 g/mol

  39. Can the ideal “gas” equation be used to determine the molar mass of a liquid?

  40. Homework • Do the lab summary for “The Molecular Mass of a Volatile Liquid”. It is due ____. • Attempt the pre-lab for “The Molecular Mass of a Volatile Liquid”. It is due ____.

  41. Problem: A volatile liquid is placed in a flask whose volume is 590.0 ml and allowed to boil until all of the liquid is gone, and only vapor fills the flask at a temperature of 100.0 oC and 736 mm Hg pressure. If the mass of the flask before and after the experiment was 148.375g and 149.457 g, what is the molar mass of the liquid? 57.9 g/mol

  42. What is the density of methane gas (natural gas), CH4, at 125oC and 3.50 atm? 1.71 g/L

  43. Calculate the density in g/L of O2 gas at STP. 1.43 g/L

  44. Dalton’s Law of Partial Pressure • The total pressure in a container is the sum of the partial pressures of all the gases in the container. • In a gaseous mixture, a gas’s partial pressure is the one the gas would exert if it were by itself in the container. • Ptotal = P1 + P2 + P3 • Ptotal = 100 KPa + 250 KPa + 200 KPa = 550 KPa

  45. A B Two 1.0 L containers, A and B, contain gases with 2.0 atm and 4.0 atm, respectively. Both gases are forced into Container B. Find the total pressure of the gas mixture in B. 1.0 L Total = 6.0 atm

  46. Dalton’s Law Problem • Air contains oxygen, nitrogen, carbon dioxide, and trace amounts of other gases. What is the partial pressure of oxygen at standard conditions if the partial pressure of nitrogen, carbon dioxide, and other gases are 79.1 KPa, 0.04 KPa, and 0.94 KPa respectively? • Ptotal = PO2 + PN2 + PCO2 + POther gases • 101.3 KPa = PO2 + 79.1 KPa + 0.04 KPa + 0.94KPa • PO2 = 101.3 KPa – (79.1 KPa + 0.04 KPa + 0.94KPa) • PO2 = 21.2 KPa

  47. A B Z Two 1.0 L containers, A and B, contain gases with 2.0 atm and 4.0 atm, respectively. Both gases are forced into Container Z (vol. 2.0 L). Find the total pressure of mixture in Z.

  48. Two 1.0 L containers, A and B, contain gases with 2.0 atm and 4.0 atm, respectively. Both gases are forced into Container Z (vol. 2.0 L). Find the total pressure of mixture in Z. A B Z Total = 3.0 atm

  49. Find total pressure of the gas mixture in Container Z. A B C Z 1.3 L 2.6 L 3.8 L 2.3 L 3.2 atm 1.4 atm 2.7 atm X atm

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