1. Chapter 6 Gases
6.2
Gas Pressure

2. Gas Pressure Gas pressure is a force acting on a specific area
Pressure (P) = force
area
has units of atm, mmHg, torr, lb/in.2, or kilopascals (kPa)
1 atm = mmHg (exact)
1 atm = 760 torr
1 atm = lb/in.2
1 atm = Pa
1 atm = kPa

3. Altitude and Atmospheric Pressure

4. Learning Check 1. What is 475 mmHg expressed in atm? A. 475 atm
B atm
C  105 atm
2. The pressure in a tire is 2.00 atm. What is this pressure in mmHg?
A mmHg
B mmHg
C mmHg

5. Solution 1. What is 475 mmHg expressed in atm?
The answer is B, atm.
475 mmHg  atm = atm
760 mmHg
2. The pressure in a tire is 2.00 atm. What is this pressure in mmHg?
The answer is B, 1520 mmHg.
2.00 atm  760 mmHg = mmHg
1 atm

6. Barometer Measures Pressure
A barometer
measures the pressure exerted by the gases in the atmosphere
indicates atmospheric pressure as the height in mm of the mercury column
760 mmHg = 1 atm

7. Atmospheric Pressure Atmospheric pressure
is the pressure exerted by a column of air from the top of the atmosphere to the surface of Earth
decreases as altitude increases
is 1 atm at sea level
is higher on rainy day

8. Learning Check
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 Hg barometer (dHg = 13.6 g/mL) because
A. H2O is less dense than mercury
B. H2O is heavier than mercury
C. air is more dense than H2O

9. Solution
1. The downward pressure of the Hg in a barometer is _____ the pressure of the atmosphere.
The answer is C, the same as.
2. A water barometer is 13.6 times taller than a Hg barometer (dHg = 13.6 g/mL) because
The answer is A, H2O is less dense than mercury.