1
CHAPTER 10
CHAPTER 10
GASES
GASES

2
CONTENT
10.1
Characteristics of Gases
10.2 Pressure
10.3
The Gas Laws
10.4
The Ideal-Gas Equation
10.5
Further Applications of The Ideal Gas
Equation
10.6
Gas Mixture and Partial Pressures
10.7
Kinetic-Molecular Theory
10.8
Molecular Effusion and Diffusion
10.9
Real Gases: Deviations from Ideal Behaviour

3
Learning Outcomes
•
Able to apply the
Ideal Gas Law
in
calculations involving gaseous system
•
Able to calculate
partial and total
pressure
in a mixture of gases (with or
without reaction)
•
Able to differentiate
effusion and
diffusion
•
Able to apply
kinetic molecular theory
in problem solving

4
Bonds
HGFGJDF

5
10.1 Characteristics of
10.1 Characteristics of
Gases
Gases
Expand spontaneously to fill its container.
Volume of gas = Volume of the container.
Highly compressible.
Form homogeneous mixtures with other
gases.
Occupy about 0.1% of the volume of their
containers.

6
10.2 Pressure
10.2 Pressure
Measured properties of a gas:
Temperature (T),
Volume (V),
Pressure
(P)
Pressure, P is the force F acting on an object
per unit area, A.
P = F/A
Our atmosphere exerts a downward
force/pressure on Earth’s surface because
of gravity.

7
10.2.1 Atmospheric
10.2.1 Atmospheric
Pressure and The
Pressure and The
Barometer
Barometer
The acceleration produced by earth’s
gravity
is
9.8 ms
-2
.
A column of air
1m
2
in cross section has a
mass of roughly
10,000 kg.
The force exerted by this column is:
F = ma
where,
a = 9.8 m/s
2
= (10,000 kg) (9.8 m/s
2
)
= 1
10
5
kg m/s
2
=
1
10
5
N

8
Con’t: 10.2.1 Atmospheric
Con’t: 10.2.1 Atmospheric
Pressure and The
Pressure and The
Barometer
Barometer
The pressure exerted by the column is the
force divided by its cross-sectional area, A:
P = F/A
= (1
10
5
N)/(
1m
2
)
= 1
10
5
N/m
2
= 1
10
5
Pa
=
1
10
2
kPa
SI unit for P = N/m
2
(also called Pascal, Pa)
1Pa = 1 N/m
2
1 bar = 10
5
Pa

9
Con’t: 10.2.1 Atmospheric
Con’t: 10.2.1 Atmospheric
Pressure and The
Pressure and The
Barometer
Barometer
Therefore, the atmospheric pressure at sea
level is about 100kPa.
The actual atmospheric pressure at any
location depends on weather conditions and
on altitude.
Atmospheric pressure can be measured by
a mercury barometer.

10
Bonds
HGFGJDF

11
Con’t: 10.2.1 Atmospheric
Con’t: 10.2.1 Atmospheric
Pressure and The
Pressure and The
Barometer
Barometer
Standard atmospheric pressure is the pressure
required to support a column of mercury 760
mm in height.
Units:
1 atm
= 760 mmHg
= 760 torr
= 1.01325
10
5
Pa
SI units: 1 atm = 1.01325
10
5
Pa
Other common units
1 atm = 14.70 psi

12
Bonds
HGFGJDF

13
Example 1
Example 1
Convert 0.378 atm to:
a) torr;
b) pascal
(1atm = 760 torrs = 101325 Pa)
torr
atm
torr
atm
271
1
760
357
.
0
Pa
atm
Pa
atm
36173
1
101325
357
.
0

14
10.2.2 Pressure of Enclosed
10.2.2 Pressure of Enclosed
Gases and Manometers
Gases and Manometers
Closed-tube manometer
measures pressure below atmospheric pressure.

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- Spring '09
- RobertKirshner
- Partial Pressure