1. The Gas Laws A Tutorial on the Behavior of Gases. Mr. Forte Chemistry
Presented by:
Mr. Forte
Chemistry
Atascadero High School

2. Kinetic Molecular Theory of Gases
Gases consist of small particles in constant motion.
The individual particles occupy a very tiny volume.
Collisions with walls of container are elastic and exert pressure.
Particles do not interact with one another.
Average kinetic energy is directly proportional to the Kelvin temperature.

3. Properties of Gases Gases expand to fill their containers
No definite shape or volume
Gases are fluid – they flow
Gases have low density
1/1000 the density of the equivalent liquid or solid
Gases are compressible
Gases effuse and diffuse

4. Abbreviations P – Pressure V – Volume
n – Number of particles, in moles
R – Universal Gas Constant
T – Temperature, in Kelvin

5. Units of Pressure atm - atmospheres mm Hg - millimeters of mercury
torr – same as mm Hg
Pa – Pascal (SI (metric) standard)
kPa - kiloPascal

6. Units of Temperature K - Kelvin °C - degrees Celsius
°F - degrees Fahrenheit

7. Standard Conditions STP: Standard Temperature and Pressure
273 K = 0.0 °C
Pressure:
1.00 atm = 760 mm Hg (torr)

8. 1 = original; 2 = new Robert Boyle (1627-1691)
Boyle’s Law: the volume of a fixed mass of gas varies inversely with the pressure at constant temperature.
P1V1 = P2V2
1 = original; 2 = new

9. Sample Boyle’s Law Problem
A gas occupies 12.3 liters at a pressure of 400 mm Hg. What is the volume when the pressure is increased to 600 mm Hg and the temperature remains constant?
P1V1/P2 = V2
(400 torr)(12.3 L)/(600 torr) = 8.2 L

10. Jacques Charles ( )
Charles’ Law: The volume of a fixed mass of gas varies directly with the Kelvin temperature at constant pressure.
V1/T1 = V2/T2

11. Sample Charles’ Law Problem
Calculate the new temperature of a gas when 2.50 L at 293 K is compressed to 1.00 L at constant pressure.
V2T1/V1 = T2
(1.0 L)(293 K)/(2.5 L) = 117 K

12. P1/T1 = P2/T2 Joseph Gay-Lussac (1778-1850)
Gay-Lussac’s Law: The pressure of a fixed mass of gas varies directly with the Kelvin temperature at constant volume.
P1/T1 = P2/T2

13. Sample Gay-Lussac’ Law Problem
Calculate the new pressure of a gas when a sample at 1.25 atm and 300 K is cooled to 210 K assuming constant volume.
P1T2/T1 = P2
(1.25 atm)(210 K)/(300 K) = atm

14. Amedeo Avogadro ( )
Avogadro’s Law: for a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas
V1/n1 = V2/n2