Gas Laws
Fundmentals
KINETIC MOLECULAR THEORY
 KMT is a model to explain the
behavior of gaseous particles and
is based on extensive
observations
 If a gas follows all the ideas of the
KMT, it is said to be an ideal gas
THE KINETIC THEORY
1. All matter is composed of very
small particles
2. These particles are in constant
motion
3. Collisions between particles are
perfectly elastic
PRESSURE
 Pressure is defined as force per
unit area
 Units: kPa, atm, mmHg, torr
VOLUME
 Volume is defined as the amount
of space an object occupies
 Units: cm3, mL, L
DALTON’S LAW
Dalton’s Law

The physical properties of
gases are affected by
temperature and pressure

John Dalton found that each
gas in a mixture exerts
pressure independently of the
other gases present
Dalton’s Law

The total pressure of a mixture
of gases equals the sum of the
partial pressures of the
individual gases
Ptotal = P1 + P2 + ...
When a H2 gas is
collected by water
displacement, the gas in
the collection bottle is
actually a mixture of H2
and water vapor
Ex. Problem 1: Dalton’s Law

What is the total pressure in a container if gas A
has a pressure of 13.7 KPa, gas B has a
pressure of 5.3 KPa and gas C exerts a pressure
of 4.5 KPa?
The total pressure in the container is Ptotal
GIVEN:
Pgas A = 13.7 KPa
Pgas B = 5.3 KPa
Pgas C = 4.5 KPa
Ptotal = PA + PB + PC
WORK:
Ptotal = PA + PB + PC
Ptotal =
Ptotal =
Ex. Problem 2: Dalton’s Law
 A mixture of O2, CO2, and N2 has a total
pressure of .97 atm. What is the partial
pressure of O2, if the partial pressure of CO2 is
.70 atm and the partial pressure of N2 is .12 atm.
The total pressure is given, you need to find Poxygen.
GIVEN:
PO = ?
2
PCO = .7 atm
2
PN = .12 atm
2
Ptotal = .97 atm
WORK:
Ptotal = PO + PCO + PN
2
2
2
BOYLE’S LAW
Boyle’s Law

Irish chemist
(1627-1691)

Performed the first
quantitative
experiments on gases

Used j-shaped tube to
study the relationship
between pressure of
trapped gas and its
volume
Boyle’s Law

Boyle’s Law states that at constant
temperature the volume of a fixed amount of
gas is inversely related to pressure
• When the volume INCREASES, pressure
DECREASES
• When the volume DECREASES, pressure
INCREASES
Final conditions
Boyle’s Law:
P1V1 = P2V2
Initial conditions
Ex. Problem #1: Boyle’s Law
 The
volume of a gas is 200 mL at a
pressure of 100 KPa. What is its
volume at a pressure of 200 KPa?
P1V1 = P2V2
GIVEN:
V1 =
P1 =
V2 =
P2 =
WORK:
P1V1 = P2V2
Ex. Problem #2: Boyle’s Law
 If
the pressure of the gas in the 4.0 L
volume is 200 KPa what will the
pressure be at 2.5 L?
GIVEN:
V1 =
P1 =
V2 =
P2 =
WORK:
P1V1 = P2V2