SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P1
Gaseous State of matter
Properties of Gases:
Compressibility, Expandability, low density, exerting uniform
pressure on the walls of its container.
To explain observable macroscopic phenomena in terms pf
particulate behavior:
ƒ Particles of gases moving in straight lines (filling their
container, exert pressure)
F
P=
S
ƒ Molecules collide without loss of total kinetic energy.
ƒ Gas molecules are widely spaced.
The volume of 1g of water is 1.04 cm3
The volume of 1g of steam is 1670 cm3
1.04
× 100 = 0.0623 %
1670
It means the actual volume of
molecules is negligible compared to the their occupied
space.
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P2
ƒ Attractive forces between molecules are negligible.
Pressure of Gases:
Mercury Barometer (Torricelli design)
A inverted tube with mercury in a dish of mercury.
h
A mercury barometer at sea level.
h
A mercury barometer on the top of a high mountain.
F
pound
=
= psi
S square inche
F
newton
P= =
= pascal = Pa
S square meter
P=
Pressure Units:
1 bar = 100 Kpa
1 atm = 760 mm Hg = 760 torr =101.3 Kpa = 14.69 psi
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P3
V∝T
Name:
Charles’s Law
Or
V-T Law
Condition:
Relationships
Constant Pressure V
V2
1
=
&
T2
T1
Constant mole
P ∝ 1/V
Name:
Boyle’s Law
Or
V-P Law
Condition:
Constant
Temperature
&
Constant mole
Relationships
P1 V1 = P2V2
If V∝ T and V∝1/P than V∝ (T)(1/P)
Name:
Combined gas Law
Or
P-T-V Law
Condition:
Constant mole
Relationships
P1 V1 P2 V2
=
T1
T2
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P4
Example:
A sample of carbon dioxide occupies 300 mL at 10°C and 750
torr. What volume will the gas have at 30°C and 750 torr?
Pressure is constant!
Charles’s Law
TK = °C + 273
V1 V2
300 mL
V2
=
=
T1 T2 ; 10 + 273 30 + 273 ; V2= 321 mL
**************************************************
Example:
A sample of Freon (CCl2F2) gas used in an air conditioner has
a volume of 325 L and a pressure of 96.3 Kpa at 20°C. What
will the pressure of the gas be when its volume is 975 L at
20°C?
Temperature is constant!
P1V1 = P2V2
(96.3)(325) = P2 (975)
P2 =
(96.3 KPa )(325 L)
975 L
P2 = 32.1 KPa
Boyle’s Law
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P5
Example:
What would be the volume at STP of 3.62 liters of nitrogen
gas, measured at 649 torr and 16°C?
Given: V=3.62 L, P=649 torr, t= 16°C
Wanted: Volume at STP?
At STP condition:
P=1 atm or 760 mm Hg or 760 torr, and T=273 K
The Combined Gas Low:
Wanted part = Given part
P1 V1
T1
P2 V2
=
T2
(760 torr ) V1 (649 torr ) (3.62 L)
=
273 K
(16 + 273) K
(273 K )(649 torr ) (3.62 L)
V1 =
(760 torr )(289 K )
V1=2.92 L
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
Experiment:
Ruler, Capillary tube, Thermometer
Water bath
V-T Law
Height (mm)
100
80
60
40
20
0
-300
-200
-100
0
Temperature (C)
100
P6
SCC-CH110/UCD-CH41C
Chapter: 4
Instructor: J.T.
P7