© 2013 Pearson Education, Inc. Chapter 7, Section 2

General, Organic, and Biological Chemistry

Fourth EditionKaren Timberlake

7.2Gas Pressure

Chapter 7Gases

© 2013 Pearson Education, Inc.Lectures

© 2013 Pearson Education, Inc. Chapter 7, Section 2

Gas pressure is the force acting on a specific area.

has units of atm, mmHg, torr, lb/in.2, and kilopascals(kPa).

1 atm = 760 mmHg (exact)

1 atm = 760 torr (exact)

1 atm = 14.7 lb/in.2

1 atm = 101.325 kPa

Gas Pressure

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

1. What is 475 mmHg expressed in atmospheres (atm)?

A. 475 atm B. 0.625 atm

C. 3.61 x 105 atm

2. The pressure in a tire is 2.00 atm. What is this pressure in mmHg?A. 2.00 mmHgB. 1520 mmHgC. 22 300 mmHg

Learning Check

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

1. What is 475 mmHg expressed in atmospheres (atm)?

B. 0.625 atm

2. The pressure of a tire is measured as 2.00 atm. What is this pressure in mmHg?

B. 1520 mmHg

Solution

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

Atmospheric pressure is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth.

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Atmospheric Pressure

© 2013 Pearson Education, Inc. Chapter 7, Section 2

Atmospheric Pressure

Atmospheric pressure is about 1 atmosphere at sea level. depends on the altitude and the weather. is lower at high altitudes where the density of air is

less. is higher on a rainy day than on a sunny day.

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

Altitude and Atmospheric Pressure

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

Barometer

A barometer measures the pressure exerted by the gases in the atmosphere by the height of mercury in the column (mmHg).

A barometer: The pressure exerted by the gases in the atmosphere is equal to the downward pressure of a mercurycolumn in a closed glass tube.

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

1. The downward pressure of the Hg in a barometer is _______ the pressure of the atmosphere.

A. greater than B. less than C. the same as

2. A water barometer is 13.6 times taller than a mercury barometer (DHg = 13.6 g/mL) because

A. H2O is less dense.

B. H2O is heavier.

C. air is more dense than H2O.

Learning Check

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© 2013 Pearson Education, Inc. Chapter 7, Section 2

1. The downward pressure of the Hg in a barometer is

the same as the pressure of the atmosphere.

Answer: C

2. A water barometer is 13.6 times taller than a mercury barometer (DHg = 13.6 g/mL) because

H2O is less dense.

Answer: A

Solution

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