Gases are the state of matter with
the greatest amount of energy.
Pressure
Pressure is created by gas particles running into the wall of the
container. Pressure is measured in many units: 1 atm = 101300 Pa =
101.3 kPa = 760 mm Hg = 14.7 psi. Atmospheric pressure is the
pressure due to the layers of atmosphere above us.
Kinetic Molecular Theory
The Kinetic Molecular Theory has several assumptions for ideal
gases.
- Gases are made of atoms or molecules
- Gas particles are in rapid, random, constant motion
- The temperature is proportional to the average kinetic
energy
- Gas particles are not attracted nor repelled from each
other
- All gas particle collisions are perfectly elastic (they
leave with the same energy they collided with)
- The volume of gas particles is so small compared to the
space between them that the volume of the particle is
insignificant
Real gases do have a volume (that takes up space
which other particles cannot occupy) and they do have
attractions/repulsions from one another as well as in-elastic
collisions.
The KMT is used to understand gas behavior.
Pressure and volume are inversely proportional. Pressure and
temperature are directly proportional. Pressure and number of
particles are directly proportional.
An expandable container will expand or contract
so that the internal and external pressures are the same.
Non-expandable containers will explode or implode if the difference
in the pressures is too great for the container to withstand.
Gas Laws
Symbols for all gas Laws:
P = Pressure; V = Volume; n = moles; T = Temperature (in Kelvin);
R = Gas constant
or
�a� and �b� = correction factors for real gases
Combined Gas Law:
When
something is held constant, it cancels out.
Dalton�s Law of Partial Pressure:
Mole fraction:
Partial
Pressure and mole fraction:
Ideal Gas Law:
Ideal
Gas Law with Molar Mass:
Ideal Gas Law with Density:
Real Gas Law:
Gas Stoichiometry
Use the molar volume of a gas at STP (1 mole of any gas at STP =
22.4 L) to convert between moles and liters of a gas in
stoichiometry. Then use the appropriate gas law to find the volume
at non-STP conditions.
