14.4 Gases: Mixtures and Movements > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A sample of gas that contains 8.0 moles at 300K and 3 atms. takes up how much space?

14.4 Gases: Mixtures and Movements > 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Thursday DAY 4 = study hall Monday DAY 6 = TEST Wednesday DAY 2 = double period chem for Turkey Olympics

14.4 Gases: Mixtures and Movements > 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Homework # 1 Unit 4 - Due Wed

14.4 Gases: Mixtures and Movements > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 14 The Behavior of Gases 14.1 Properties of Gases 14.2 The Gas Laws 14.3 Ideal Gases 14.4 Gases: Mixtures and Movements

14.4 Gases: Mixtures and Movements > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Dalton’s Law How is the total pressure of a mixture of gases related to the partial pressures of the component gases?

14.4 Gases: Mixtures and Movements > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Dalton’s Law Gas pressure results from __________ of particles in a gas with an object. If the number of particles increases in a given volume, ______ collisions occur. If the average kinetic energy of the particles increases, ______ collisions occur. In both cases, the pressure ___________. collisions more increases

14.4 Gases: Mixtures and Movements > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The total pressure of dry air is the sum of the partial pressures of the component gases. Interpret Data Composition of Dry Air ComponentVolume (%)Partial pressure (kPa) Nitrogen Oxygen Carbon dioxide 0.04 Argon and others Total

14.4 Gases: Mixtures and Movements > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Dalton’s Law The pressure in the container of heliox (500 kPa) is the same as the sum of the pressures in the containers of helium and oxygen (400 kPa kPa).

14.4 Gases: Mixtures and Movements > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law How does the molar mass of a gas affect the rate at which the gas diffuses or effuses?

14.4 Gases: Mixtures and Movements > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughout.

14.4 Gases: Mixtures and Movements > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law A cylinder of air and a cylinder of bromine vapor are sealed together. Bromine vapor diffuses upward through the air. After several hours, bromine vapors reach the top of the column.

14.4 Gases: Mixtures and Movements > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law During effusion, a gas escapes through a tiny hole in its container. With effusion and diffusion, the type of particle is important.

14.4 Gases: Mixtures and Movements > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law Gases of lower molar mass diffuse and effuse faster than gases of higher molar mass.

14.4 Gases: Mixtures and Movements > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law This law can also be applied to the diffusion of gases. If two objects with different masses have the same kinetic energy, the lighter object must move faster. Thomas Graham’s Contribution Graham’s law of effusion states that the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass.

14.4 Gases: Mixtures and Movements > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules of helium have a lower mass than the average mass of air molecules, so helium molecules effuse through the tiny pores in a balloon faster than air molecules do. CHEMISTRY & YOU Why do balloons filled with helium deflate faster than balloons filled with air?

14.4 Gases: Mixtures and Movements > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Graham’s Law Rate A Rate B = molar mass B molar mass A Because the rate of effusion is related only to a particle’s speed, Graham’s law can be written as follows for two gases, A and B.

14.4 Gases: Mixtures and Movements > 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. How much faster does helium (He) effuse than nitrogen (N 2 ) at the same temperature? Sample Problem 14.8 Comparing Effusion Rates

14.4 Gases: Mixtures and Movements > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Calculate Solve for the unknown. Start with the equation for Graham’s law of effusion. Rate He Rate N 2 = molar mass N 2 molar mass He Sample Problem 14.8

14.4 Gases: Mixtures and Movements > 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Calculate Solve for the unknown. 2 Substitute the molar masses of nitrogen and helium into the equation. Rate He Rate N 2 = 28.0 g 4.0 g =7.0= 2.7 Sample Problem 14.8

14.4 Gases: Mixtures and Movements > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Helium atoms are less massive than nitrogen molecules, so it makes sense that helium effuses faster than nitrogen. Evaluate Does this result make sense? 3 Sample Problem 14.8

14.4 Gases: Mixtures and Movements > 21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Which of the following gas particles will diffuse fastest if all of these gases are at the same temperature and pressure? A.SO 2 C.N 2 O B.Cl 2 D.Hg

14.4 Gases: Mixtures and Movements > 22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A.SO 2 C.N 2 O B.Cl 2 D.Hg Which of the following gas particles will diffuse fastest if all of these gases are at the same temperature and pressure?

14.4 Gases: Mixtures and Movements > 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Key Concepts In a mixture of gases, the total pressure is the _____ of the partial pressures of the gases. Gases of lower molar mass diffuse and effuse ________ than gases of higher molar mass. sum faster

14.4 Gases: Mixtures and Movements > 24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. page 474 #s 40-41, 43, 45

14.4 Gases: Mixtures and Movements > 25 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Key Equations Dalton’s Law: Graham’s Law: Rate A Rate B = molar mass B molar mass A P total = P 1 + P 2 + P 3 + …

14.4 Gases: Mixtures and Movements > 26 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A tank used by scuba divers has a P total of 2.21  10 4 kPa. If P N 2 is 1.72  10 4 kPa and P O 2 is  10 3 kPa, what is the partial pressure of any other gases in the scuba tank (P other )? P total = P O 2 + P N 2 + P others P others = P total – (P N 2 + P O 2 ) P others = 2.21  10 4 kPa – (1.72  10 4 kPa  10 3 kPa) P others = 2.59  10 2 kPa

14.4 Gases: Mixtures and Movements > 27 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

14.4 Gases: Mixtures and Movements > 28 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.