DALTON’S LAW GRAHAM’S LAW GAS MIXTURES

THINK ABOUT THIS Two students in the classroom bring a bottle of cologne and a bottle of perfume to the classroom. They accidentally bump into each other and both bottles break in their bags. 1. What will be a result of this crash? 2. What will be some observations you experience during this crash? Keep in mind that perfume has a stronger scent than cologne does.

RECALL—GASES Gas pressure results from the collisions of particles in a gas with the walls of a container If we increase the number of particles in a container, there will be more collisions and more pressure Gas pressure depends on the particles of a gas and their collisions

GAS MIXTURES H 2 He H 2 and He

GAS MIXTURES H 2 He H 2 and He P = 2.9 atm P = 7.2 atm P = ????

GAS MIXTURES H 2 He H 2 and He P = 2.9 atm P = 7.2 atm P = 10.1 atm

DALTON’S LAW The pressure each gas contributes in a mixture is known as its partial pressure In a mixture of gases, the total pressure is the sum of the partial pressures of the gases. P Total = P 1 + P 2 + P 2 + …

DALTON’S LAW Given the partial pressures of the gases in containers A, B and C below, what will the total pressure of the mixture of these gases be in Container T? ????????

DALTON’S LAW EXAMPLE 1: Given the partial pressures of the gases in containers A, B and C below, what will the total pressure of the mixture of these gases be in Container T?

DALTON’S LAW EXAMPLE 2: Air contains mostly oxygen, nitrogen, and carbon dioxide gases. What is the partial pressure of oxygen (P O ) at a total pressure of kPa if the partial pressure of nitrogen is kPa and the partial pressure of carbon dioxide is kPa? P Total = P 1 + P 2 + P 2 + … P Total = P O + P N + P CO2 P Total = kPa P N = kPa P CO2 = kPa P O =???

MOVEMENT OF GASES

DIFFUSION – the mixing of gas molecules by random motion

MOVEMENT OF GASES EFFUSION —the escape of a gas through a pinhole

GRAHAM’S LAW STATES THAT THE RATE OF EFFUSION OF A GAS IS INVERSELY PROPERTIONAL TO THE GAS’S MOLAR MASS IN GENERAL: THE LOWER THE MOLAR MASS, THE FASTER THE RATE OF EFFUSION

GRAHAM’S LAW EXAMPLE 3: IF NITROGEN (MM=28G/MOL) AND HELIUM (MM = 4.0 G/MOL) ARE MIXED INTO A CONTAINER WITH A TINY PINHOLE…WHICH GAS WOULD EFFUSE THROUGH THE PINHOLE FIRST, OR THE FASTEST?