Chapter 5 Gases Flashcards
Kinetic molecular theory
A model that views gases as a collection of particles in constant motion
Pressure
A measure of force exerted per unit area. In chemistry, this is most commonly the force
exerted by gas molecules as they strike the surfaces around them
The ideal gas law
PV = nRT. Relates the pressure, volume, temperature and amount of a gas
The ideal gas constant
When used with the ideal gas law: 0.08206 Latm/molk. When used to calculate the
RMS velocity of gas particles: 8.314 J/mol*k .
Standard temperature and pressure (STP)
273.15 K and 1.00 atm
Molar volume at STP
One mole of any gas occupies 22.4 L at STP. Can be used to convert between
volume and moles of a gas.
Mole fraction
The number of moles of a component in a mixture divided by the total number of moles
in the mixture
Partial pressure
The pressure exerted by an individual gas within a mixture
Dalton’s law of partial pressures
The law stating that the sum of the partial pressures of the
components in a gas mixture must equal the total pressure
Root mean square velocity
A method of describing the speed at which gas particles travel.
Mean free path
The average distance traveled by a gas particle between collisions
Diffusion
The process by which gas particles spread out in response to a concentration gradient.
Effusion
The process by which gas escapes from a container into a vacuum through a small hole
Graham’s law of effusion
A scientific law that states the ratio of effusion rates of two gases is equal to
the square root of the inverse of their molar masses
Elastic collisions
Collisions in which the total kinetic energy of the colliding bodies is the same before
and after the collision
Real gases
Gas that behaves in a non-ideal manner because of intermolecular forces and particle
volume. All gases are technically real gases
Use kinetic molecular theory to describe why gas assumes shape of containers
Gas are free to move past each other
Use kinetic molecular theory to describe why gases are compressible
space between gases; external forces force gas particles closer together
Use kinetic molecular theory to explain why gases exert pressure on their surroundings
colliding creates a small amount of force; gas colliding with surroundings is called pressure
At higher temperatures, do gas particles have a higher or lower average velocity?
higher
Do lighter gas particles, such as He, have a higher or lower average velocity than heavier gas particles, such as Xe?
higher
What two assumptions are made about ideal gases
1.The volume of the gas particles is small relative to
the volume of the container
2.Collisions are perfectly elastic
(energy before = energy after
Why do the volume of gas particles causes gases to behave in a non-ideal manner
The volume of gas particles adds to the total volume of the gas, therefore increasing the molar volume.
Why do intermolecular forces (attractions between gas particles) causes gases to behave in a non-ideal
manner
cause some collisions between gas particles to be inelastic. results in fewer
collisions between the gas particles and their container, causing a decrease in pressure
