Lecture 14.4- Diffusion (PREP)

16
Chemistry 14.4 Bellwork- Ideal Gas Law How many moles of oxygen gas are in a balloon at 25C with an internal pressure of 1.1 atm and a volume of 1500ml? P 1 V 1 P 2 V 2 PV = nRT T 1 T 2 R= 8.31 LkPa/Kmol =

description

Section 14.4 Lecture for Prep chemistry

Transcript of Lecture 14.4- Diffusion (PREP)

Page 1: Lecture 14.4- Diffusion (PREP)

Chemistry 14.4

Bellwork- Ideal Gas Law

How many moles of oxygen gas are in a balloon at 25C with an internal pressure of 1.1 atm and a volume of 1500ml?

P1V1 P2V2 PV = nRT

T1 T2 R= 8.31 LkPa/Kmol

R= 0.0821 Latm/Kmol

=

Page 2: Lecture 14.4- Diffusion (PREP)

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.

Page 3: Lecture 14.4- Diffusion (PREP)

The contribution each gas in a mixture makes to the total pressure is called the partial pressure exerted by that gas.

Page 4: Lecture 14.4- Diffusion (PREP)

Dalton’s law of partial pressures- In a mixture of gases, the total pressure is the sum of the partial pressures of the gases.

Page 5: Lecture 14.4- Diffusion (PREP)

Three gases are combined in container T.

100 kPa + 250kPa + 200kPa = 550kPa

Page 6: Lecture 14.4- Diffusion (PREP)

The partial pressure of oxygen must be 10.67 kPa or higher to support respiration in humans. The climber below needs an oxygen mask and a cylinder of compressed oxygen to survive.

Atmospheric pressure at the top of the world (29,000ft above sea level)

= 30kPa

Page 7: Lecture 14.4- Diffusion (PREP)

14.6

Page 8: Lecture 14.4- Diffusion (PREP)

14.6

Page 9: Lecture 14.4- Diffusion (PREP)

14.6

Page 10: Lecture 14.4- Diffusion (PREP)

14.6

Page 11: Lecture 14.4- Diffusion (PREP)

for Sample Problem 14.6

Page 12: Lecture 14.4- Diffusion (PREP)

Diffusion is the tendency of molecules to move toward areas of lower concentration until the concentration is uniform throughout.

Page 13: Lecture 14.4- Diffusion (PREP)

Graham’s Law

Bromine vapor is diffusing upward through the air in a graduated cylinder.

Page 14: Lecture 14.4- Diffusion (PREP)

Graham’s Law

After several hours, the bromine has diffused almost to the top of the cylinder.

Page 15: Lecture 14.4- Diffusion (PREP)

Gases of lower molar mass diffuse faster than gases of higher molar mass.

AT THE SAME TEMPERATURE!

HEAVIER = SLOWER

Page 16: Lecture 14.4- Diffusion (PREP)

A helium filled balloon will deflate sooner than an air-filled balloon.

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.