Chapter 5

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