Slide 1 of 30 Chemistry 14.4

© Copyright Pearson Prentice Hall Slide 2 of Gases: Mixtures and Movements A list of gear for an expedition to Mount Everest includes climbing equipment, ski goggles, a down parka with a hood, and most importantly compressed-gas cylinders of oxygen. You will find out why a supply of oxygen is essential at higher altitudes.

© Copyright Pearson Prentice Hall Gases: Mixtures and Movements > Slide 3 of Dalton’s Law How is the total pressure of a mixture of gases related to the partial pressures of the component gases?

Slide 4 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Dalton’s Law The contribution each gas in a mixture makes to the total pressure is called the partial pressure exerted by that gas.

© Copyright Pearson Prentice Hall Slide 5 of Gases: Mixtures and Movements > Dalton’s Law In a mixture of gases, the total pressure is the sum of the partial pressures of the gases.

Slide 6 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Dalton’s Law Dalton’s law of partial pressures states that, at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases.

© Copyright Pearson Prentice Hall Slide 7 of 30 Gases: Mixtures and Movements > Dalton’s Law Animation 17 Observe the behavior of a mixture of nonreacting gases.

Slide 8 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Dalton’s Law Three gases are combined in container T.

Slide 9 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Dalton’s Law The partial pressure of oxygen must be kPa or higher to support respiration in humans. The climber below needs an oxygen mask and a cylinder of compressed oxygen to survive.

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© Copyright Pearson Prentice Hall Slide 14 of 30 Practice Problems for Sample Problem 14.6 Problem Solving Solve Problem 32 with the help of an interactive guided tutorial.

© Copyright Pearson Prentice Hall Gases: Mixtures and Movements > Slide 15 of Graham’s Law How does the molar mass of a gas affect the rate at which the gas effuses or diffuses?

Slide 16 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Graham’s Law Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughout.

Slide 17 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Graham’s Law Bromine vapor is diffusing upward through the air in a graduated cylinder.

Slide 18 of 30 © Copyright Pearson Prentice Hall Gases: Mixtures and Movements > 14.4 Graham’s Law After several hours, the bromine has diffused almost to the top of the cylinder.

Slide 19 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law During effusion, a gas escapes through a tiny hole in its container. Gases of lower molar mass diffuse and effuse faster than gases of higher molar mass.

Slide 20 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law 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. This law can also be applied to the diffusion of gases.

Slide 21 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law Comparing Effusion Rates A helium filled balloon will deflate sooner than an air-filled balloon.

Slide 22 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law Helium atoms are less massive than oxygen or nitrogen molecules. So the molecules in air move more slowly than helium atoms with the same kinetic energy.

Slide 23 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law 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.

Slide 24 of 30 © Copyright Pearson Prentice Hall 14.4 Gases: Mixtures and Movements > Graham’s Law Helium effuses (and diffuses) nearly three times faster than nitrogen at the same temperature.

© Copyright Pearson Prentice Hall Slide 25 of 30 Gases: Mixtures and Movements > Graham’s Law Animation 18 Observe the processes of gas effusion and diffusion.

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