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AP Chemistry Unit 5 – States of Matter. Lesson 3 – Partial Pressures Book Section: 10.6. Dalton’s Law of Partial Pressures. If you have a gas mixture, the total pressure equals the sum of the pressures that each individual gas would exert if it were present alone. In other words..
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AP ChemistryUnit 5 – States of Matter Lesson 3 – Partial Pressures Book Section: 10.6
Dalton’s Law of Partial Pressures • If you have a gas mixture, the total pressure equals the sum of the pressures that each individual gas would exert if it were present alone. • In other words.. Ptotal = P1 + P2 + P3 + …
Dalton’s Law of Partial Pressures • If you have a gas mixture, the total pressure equals the sum of the pressures that each individual gas would exert if it were present alone. • In other words.. Ptotal = P1 + P2 + P3 + …
Gas Collection • If you collect gas over water, there is some water vapor mixed in with the gas due to evaporation. • The find only the desired gas, you must subtract the vapor pressure of water from the total pressure.
1984 MC #39 • Equal masses of three different gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct? • It is equal to 1/3 the total pressure • It depends on the intermolecular forces of attraction between molecules of X, Y, and Z • It depends on the relative molecular masses of X, Y, and Z • It depends on the average distance traveled between molecular collisions • It can be calculated with knowledge only of the volume of the container.
1984 MC #39 • Equal masses of three different gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct? • It is equal to 1/3 the total pressure • It depends on the intermolecular forces of attraction between molecules of X, Y, and Z • It depends on the relative molecular masses of X, Y, and Z – 54% correct - medium • It depends on the average distance traveled between molecular collisions • It can be calculated with knowledge only of the volume of the container.
1984 MC #72 • A compound is heated to produce a gas whose molecular weight is to be determined. The gas is collected by displacing water in a water-filled flask inverted in a trough of water. Which of the following is necessary to calculate the molecular weight of the gas, but does NOT need to be measured during the experiment? • Mass of the compound used in the experiment • Temperature of the water in the trough • Vapor pressure of the water • Barometric pressure • Volume of water displaced from the flask
1984 MC #72 • A compound is heated to produce a gas whose molecular weight is to be determined. The gas is collected by displacing water in a water-filled flask inverted in a trough of water. Which of the following is necessary to calculate the molecular weight of the gas, but does NOT need to be measured during the experiment? • Mass of the compound used in the experiment • Temperature of the water in the trough • Vapor pressure of the water – 50% correct, medium • Barometric pressure • Volume of water displaced from the flask
1989 MC #16 • A gaseous mixture containing 7.0 moles of nitrogen, 2.5 moles of oxygen, and 0.50 moles of helium exerts a total pressure of 0.90 atmosphere. What is the partial pressure of the nitrogen? • 0.13 atm • 0.27 atm • 0.63 atm • 0.90 atm • 6.3 atm
1989 MC #16 • A gaseous mixture containing 7.0 moles of nitrogen, 2.5 moles of oxygen, and 0.50 moles of helium exerts a total pressure of 0.90 atmosphere. What is the partial pressure of the nitrogen? • 0.13 atm • 0.27 atm • 0.63 atm – 81% correct, very easy • 0.90 atm • 6.3 atm
1989 MC #30 • Hydrogen gas is collected over water at 24 ºC. The total pressure of the sample is 755 millimeters of mercury. At 24 ºC, the vapor pressure of water is 22 millimeters of mercury. What is the partial pressure of the hydrogen gas? • 22 mm Hg • 733 mm Hg • 755 mm Hg • 760 mm Hg • 777 mm Hg
1989 MC #30 • Hydrogen gas is collected over water at 24 ºC. The total pressure of the sample is 755 millimeters of mercury. At 24 ºC, the vapor pressure of water is 22 millimeters of mercury. What is the partial pressure of the hydrogen gas? • 22 mm Hg • 733 mm Hg – 82% correct, very easy • 755 mm Hg • 760 mm Hg • 777 mm Hg
1994 MC #40 • The system shown above is at equilibrium at 28 ºC. At this temperature, the vapor pressure of water is 28 millimeters of mercury. The partial pressure of O2(g) in the system is • 28 mm Hg • 56 mm Hg • 133 mm Hg • 161 mm Hg • 189 mm Hg
1994 MC #40 • The system shown above is at equilibrium at 28 ºC. At this temperature, the vapor pressure of water is 28 millimeters of mercury. The partial pressure of O2(g) in the system is • 28 mm Hg • 56 mm Hg • 133 mm Hg – 67% correct, easy • 161 mm Hg • 189 mm Hg
Homework: 10.60, 10.62, 10.66, 10.68, 10.70 • This week: • Friday: Kinetic-Molecular Theory (10.7) • Due Dates: • Volume-Temperature Behavior of Gases: 11/30 • States of Matter Exam: Monday, 12/6 • Molar Mass of Condensable Vapor: 12/8 • Problem Set 4: 12/10