1. (Kinetic Molecular Theory)
KMT
(Kinetic Molecular Theory)
Particle Size
1. Gases consist of tiny (submicroscopic) particles.
The distance between particles is large compared with the size
of the particles themselves. The volume occupied by a gas
consists mostly of empty space.
Particle Motion
3. Gas particles have no attraction for one another.
Gas particles move in a straight line in all directions, colliding
frequently with one another and with the walls of the container.
Particle Energy
No energy is lost by the collision of a gas particle with another
gas particle or with the walls of the container. All collisions are
perfectly elastic.
6. The average kinetic energy for particles is the same for all gases
at the same temperature, and its value is directly proportional to
the Kelvin temperature.

2. Pressure = Force Area 1 atm Units of Pressure: 760 mm Hg
# of collisions & speed of collisions
1 atm
Units of Pressure:
760 mm Hg
(Table 12.1 pg 407)
760 torr
101.3 kPa
1013 mbar
14.7 psi
29.9 in Hg

3. Practice Problem Given unit New unit = New unit Given unit 1.12 atm
A barometer reads 1.12 atm. Calculate the
corresponding pressure in (a) mm Hg and (b) kPa.
Given unit
New unit
= New unit
Given unit
1.12 atm
760 mm Hg
= mm Hg
851
1 atm
1.12 atm
101.3 kPa
= kPa
113
1 atm

4. Dalton’s Law of Partial Pressures
The total pressure of a mixture of gases is the
sum of the partial pressures exerted by each of
the gases in the mixture.
PTotal = P1 + P2 + P3 …
= Σ Pn
Each gas exerts a pressure that is independent
of the others.

5. An application of Dalton’s law is seen in the
collection of gas by water displacement.
PTotal = P1 + P2 + P3 …
Patm = Pgas(es) + PH2O

6. Vapor Pressure of Water @ various Temperatures

7. What would be the partial pressure of N2 gas
collected over water at 20oC and 720. torr?
Patm = PN2 + PH2O
@ 20oC PH2O = 17.5 torr
720. torr = PN torr
720. torr torr = PN2
= torr
= 703 torr