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From which gas law does the idea of absolute zero arise?
Charles law because gases condense into liquids before -273.15 C is reached
Boyles law states the volume of gas
Charles law states that the volume of gas is
avogadro's law states that the volume of a gas is
inversely proportional to its pressure
directly proportional to its temp
directly proportional to amount of moles
What two properties of molecules does the van der Waals equation account for?
Excluded volume of gas particles + intermolecular forces
What is the SI unit of pressure
Pascal (Pa)
Pa- KPA- Torr-Atm
101 325 Pa = 101.325 kPa = 760 Torr = 1 atm
1 bar= _______ psi
14.504 psi
100 kpa =
1 bar
Boyles law assumes
constant temperature and constant amount of gas
volume decreases pressure increases
P1V1=P2V2
Charles law calculates
calculate volume of a gas following a temp change or the temperature of a gas
V1/T1= V2/T2
Avogadros law
calculate amount of gas particles per volume of a gas
Boyles, Charles law all assume
constant pressure and constant amount of gas
Avogadros law assumes
increase constant temp and pressure results in direct increase gas particles
The partial pressure of water in a mixture is called
vapor pressure
Vapor pressure increases with increasing temperature because
higher temperatures can cause more water molecules to evaporate.
Kinetic Molecular Theory
1. size of particle is neglible and they do affect volume or partial pressure
2. Average kinetic energy particle is proportional to temp in kelvins
3. Collisons are elastic. Exchange energy during collisions and no loss of energy or deformation of particles
Consider a 1.0 L sample of helium gas and a 1.0 L sample of argon gas, both at room temperature and atmospheric pressure.
1. Do the atoms in the helium sample have the same average kinetic energy as the atoms in the argon sample?
2 Do the atoms in the helium sample have the same average velocity as the atoms in the argon sample?
3 Do the argon atoms, because they are more massive, exert a greater pressure on the walls of the container? Explain.
4 Which gas sample would have the faster rate of effusion?
1. average kinetic energy proportional to temp K = same KE
2. He move faster to have same KE as argon atoms
3. no argon move slower due to size and exert same pressure as He
4. He is lighter = faster effusion
A flask at room temperature contains exactly equal amounts (in moles) of nitrogen and xenon.
a.Which of the two gases exerts the greater partial pressure?
b.The molecules or atoms of which gas have the greater average velocity?
c.The molecules of which gas have the greater average kinetic energy?
d.If a small hole were opened in the flask, which gas would effuse more quickly?
a Same amount of moles = same partial pressure
b Nitrogen because it is lighter
c KE dependent on temp. since both are at room temp = same KE
d Nitrogen because lighter
Charles's law states that, for a constant number of particles at constant pressure, the volume of a gas is
proportional to its temp
Avogadro's law states that
at constant temperature and pressure, the volume of a gas is
proportional to the number of particles.
Dalton's law states that the total pressure of a gas mixture is the
sum of the partial pressures of its components
Mean free path
average distance a molecule travels between collisions
diffusion
process in which gas molecules spread out in response to changes in concentration gradients
Heavier molecules diffuse more slowly than
lighter molecules
Root mean square velocity
measure of velocity of particles in a gas
what is effusion
process that gas escapes from container into a vacuum through a small hole.
Rate of effusion is also related to
root mean square velocity
Heavier molecules effuse more
slowly than lighter ones
Rate of effusion- the amount of gas that effuses in a given time is inversely proportional to the
to the square root of the molar mass of the gas as follows
Particle Volume and Ideal Behaviour
As a gas is compressed, the gas particles themselves begin to occupy a significant portion of the total gas volume, leading to deviations from ideal behavior.
Intermolecular forces
attraction between atoms or molecules in a substance
High temperatures and low pressures, the weak attractions, compared with the relatively large kinetic energy between them, do not significantly affect their collisions. At lower temperatures, however, the collisions occur with less kinetic energy, and weak attractions can affect the ______________and even the direction of their motion
molecular collisions
Non-ideal gas one that does not obey the assumption that define an ideal gas - is called a
real gas. (helium, neon, argon, CO2, Kr
Which postulate of the kinetic molecular theory breaks down under conditions of high pressure? Explain.
That the volume of gas particles is small compared to the space between them breaks down under conditions of high pressure. At high pressure the particles themselves occupy a significant portion of the total gas volume.
Which postulate of the kinetic molecular theory breaks down under conditions of low pressure
low temp molecues have reduced kinetic energy
lower KE reduces collisions + reactivity + # interaction
= lower pressure than ideal gass law predicts.
How do real gases differ from ideal gases?
don't fit assumption of kinetic molecular theory
high pressure= particles take up space
Low temp = low kinetic energy= inelastic collisions
