Chapter 12 Notes
As students, professors, and chemists, we sometimes need to
understand the concepts before we can apply it, and assuming the
gases are in an ideal state where it is unaffected by real world
conditions will help us better understand the behavior the gases. In
order for a gas to be ideal, its behavior must follow the KineticMolecular Theory whereas the Non-Ideal Gases will deviate from
this theory due to real world conditions.
Kinetic Molecular Theory of gases
1. Gases consist of tiny particles – atoms or molecules
2. They are so small compared to the distance between them,
that the size of the individual particles (their volume) is
negligible.
3. Particles are in constant random motion, colliding with the
walls of the container . These collisions with the walls cause
the pressure exerted by a gas
4. Particles don’t repel or attract one another
5. Average kinetic energy is directly proportional to the Kelvin
temperature.
Implications
1. Temperature is temperature of a gas reflects how fast gas
particles are moving
a. Hi temp – fast
b. Lo -slow
2. As gas moves faster, hits walls harder, so increase pressure
3. Increase temp, particles faster, increase pressure, which will
increase the volume
Put your finger on the constant
Pressure
Temperature
Volume
**Boyle’s Law – at a constant temperature and mass, a gas’s
pressure and volume are inversely proportional to one another
P1V1 = P2V2
**Charles’s Law – at constant pressure and mass, a gas’s
volume and temperature are proportional to another
V1 =
T1
V2
T2
Amonton’s Law - given a constant number of mole of a gas
and an unchanged volume, pressure is directly proportional to
P1 =
T1
temperature
P2
T2
Avagadro’s Law - Volume of a gas is directly proportional to
the amount of gas at a constant temperature and pressure
V1 =
n1
V2
n2
**Gay- Lussac’s Law (Combined Law) -
P 1V 1 =
T1
P 2V 2
T2
**Ideal Gas Law
PV = nRT
OR
P 1V 1 =
n1RT1
P 2V 2
n2RT2
**Dalton’s Law of Partial Pressures
PT = P 1 +
P2 +
P3 + Petc……
Variables
Factor
Pressure
Variable
P
Volume
V
Moles
Temperature
Gas Constant
n
T
R
Units
atm
Torr
Pa
mmHg
L
m³
mol
K
0.0821L •atm
Standard Temperature and Pressure (STP)
Standard condition of temperature and pressure is known as STP.
Two things you should know about this is listed below.
o
 The universal value of STP is 1 atm (pressure) and 0 C.
Note that this form specifically stated 0o C degree, not
273 Kelvin, even thought you will have to convert into
Kelvin when plugging this value into the Ideal Gas
equation or any of the simple gas equations.
 In STP, 1 mole of gas will take up 22.4 L of the volume
of the container (we will use this concept next chapter)
 STP = 273K at 1 atm
Conversions
Pressure: (at sea level)
1 atm = 760.0 mm Hg = 760 torr =101.326 KPa = 101,326 Pa
Volume: 1 cm3 (cubic centimeter) = 1 mL (milliliter)
Temperature:
o
o
F = (1.8oC) + 32
C = (F –32)/1.8
o
o
K = C + 273
C = K - 273