Chapter 18 Dalton’s Law of Partial Pressures

We all live in the ocean of air, called the atmosphere.

Teacher Demonstration The syringe demo

Barometers and Standard Atmospheric Pressure

Blizzard of 1978 The rapidly intensifying storm pulled bitter cold air from the west across Ohio on winds of fifty to seventy miles an hour. These conditions combined with heavy snow and blowing of deep snow already on the ground to cause full blizzard conditions all across Ohio. Atmospheric pressure of inches at Cleveland was the lowest pressure ever recorded in Ohio. This was also the second lowest pressure not associated with a hurricane recorded this century in the lower forty-eight states. The arrival of the cold front and blizzard were unmistakable. Temperatures fell thirty degrees in two hours, winds increased to more than 70 miles an hour, and blinding wind-blown snow filled the air. This blizzard caused the most complete disruption of transportation ever known to Ohio. Maj. Gen. James C. Clem of the Ohio National Guard reported the immobilization of Ohio was comparable to the results of a statewide nuclear attack.

A house in Wood County Ohio is nearly buried.

Blizzard of 1978

Barometers and Standard Atmospheric Pressure Standard atmospheric pressure defined as the pressure sufficient to support a mercury column of 760mm high. (units of mmHg, or torr). Another unit was introduced to simplify things, the atmosphere (1 atm = 760 mmHg). 1 atm = 760 mmHg = 760 torr = kPa.

STP standard temperature and pressure Standard temperature 0°C or 273 K Standard pressure 1 atm (or equivalent)

Dalton’s Law of Partial Pressure The total pressure of a mixture of gases is the sum of the partial pressures of all the gases in the container. The contribution each gas makes to the total pressure of a mixture of gases is known as the partial pressure of that gas. P total = P A + P B + P C P total = 100 kPa kPa kPa = 550 kPa A 550 kPa

Dalton’s Law of Partial Pressure What is the partial pressure of all the gas A in the container with a total pressure of 900 kPa? Gas A has a partial pressure of 164 kPa at a total pressure of 900 kPa. A 900 kPa

Turn to the “Dalton’s Law of Partial Pressures” sheet in your notebook.

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure of oxygen at standard atmospheric pressure? torr torr torr = torr ≈ torr 760 torr – torr = torr ≈ 159 torr

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What percent of air is nitrogen? torr 760 torr x 100 = 78.1%

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure in kPa of argon gas at standard atmospheric pressure? torr

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure in kPa of argon gas at standard atmospheric pressure? torr torr

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure in kPa of argon gas at standard atmospheric pressure? torr torr kPa

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure in kPa of argon gas at standard atmospheric pressure? torr 760 torr kPa

Air is composed primarily of four gases: nitrogen (593.4 torr), argon (7.098 torr), carbon dioxide ( torr), and oxygen. What is the partial pressure in kPa of argon gas at standard atmospheric pressure? torr 760 torr kPa = kPa

What would be the partial pressure of oxygen on top of a high mountain where the air pressure is only 534 mm Hg? 159 torr 760 torr = X 534 torr x = 112 torr Remember from the first problem that the partial pressure of oxygen in air is 159 torr

What percent less oxygen is dissolved into the blood on top of the mountain as compared to sea level? 112 torr 159 torr x 100= 70.4% 100 – 70.4 = 29.6% less

Mount Everest

Endurance Training

Homework  Dalton’s Law of Partial Pressures and Ideal Gases Worksheet