Unit 10 Notes
Gases
I. Pressure – force a gas exerts on its surroundings due to collisions of gas molecules
with the surroundings.
A. A barometer is –
B. Units of pressure
1. mm Hg or torr
2. atmospheres (atm)
3. pascals (Pa)
1 atm = 760 mm Hg = 760 torr = 101,325 Pa
C. Example Conversions
II. Pressure and Volume: Boyle’s Law
A. When pressure increases, volume will ____________if the temperature and
amount of gas remain constant. Due to this fact we say that pressure and volume
are _____________ proportional.
B. If a change in the pressure of volume of a gas occurs, that gasses new pressure
or volume can be determined using:
*Boyle’s Law: P1V1 = P2V2
*Practice
III. Volume and Temperature: Charles’s Law
A. Temperature is a measure of kinetic energy. For a gas this means –
B. At a temperature of 0 K, all motion stops. This temperature is known as
__________________.
C. As the temperature of a gas increases, the volume of the gas will
_____________ if the pressure and amount of the gas are held constant. Due to
this fact we say that temperature and pressure are _____________proportional.
D. Charles’s Law:
V1 V2

T1 T2
Example
Practice
IV. Volume and Moles: Avagadro’s Law
A. As the number of moles of gas increases, the volume of the gas
_____________ assuming that the temperature and pressure of the gas remain
constant. Due to this fact we say that that the number of moles of gas and the
volume of a gas are _________________ proportional.
This relationship between moles and volume of gas is known as
__________________.
B. Avagadro’s Law:
V1 V2

where n is the number of moles of gas.
n1 n2
Example
Practice
V. Ideal Gas Law
A. PV = nRT , where R is the universal gas constant
*(R = 0.08206 L atm/K mol) Note: the units of pressure, volume, and
Temperature that you plug into the above equation must match the corresponding
units in the R value)
B. The ideal gas law has limitations,
It assumes the following:
C. It is important to note that the ideal gas law is an approximation. Real
gases may deviate from the way this model says that they should behave, but the
model gets better at extremely low pressures and/or high temperatures.
Practice
VI. Dalton’s Law of Partial Pressures
This law applies when there is a mixture of gasses.
A. The ____________________ of a gas is the pressure that the gas would exert
if it were alone in the container.
B. Dalton’s law says that the total pressure of gas in a container is equal to the
sum of the partial pressures of the gasses in the container:
Ptotal = P1 + P2 + P3 + ….. however, many gasses there are.
Example
Practice
VII. Laws and Models: A review
A. It is important to note that the ideal gas law is an approximation. Real
gases may deviate from the way this model says that they should behave, but the
model gets better at extremely low pressures and/or high temperatures.
VIII. Kinetic Molecular Theory of Gasses
*What does the word kinetic mean?
A. This theory is based on speculations about the behavior of individual gas
molecules and attempts to explain the behavior of an ideal gas.
B. Kinetic Molecular Theory –
IX. Implications of Kinetic Molecular Theory
A. The meaning of temperature –
B. The relationship between pressure and temperature –
C. The relationship between volume and temperature –
X. Gas Stoichiometry
A. Remember…Stoichiometry is all about using a mole ratio. Well…how can
you get moles of gas from other information given about the gas?
Answer: often you can use PV = nRT to find moles of the gas given
before doing a mole ratio.
Example
Example
Practice