3.6 Deviations from Ideal Gas Law

When do gases behave ideally?

Under ordinary conditions (high temperatures and low pressure)

Kinetic Molecular Theory, KMT, assumes that under high temperature and low pressure conditions, what happens?

Volumes of gas molecules themselves are insignificant and gases do not experience any intermolecular attractions.

Why can it be assumed that volumes of gas molecules themselves are insignificant and gases do not experience any intermolecular attractions when the gas is at high temperature and low pressure?

Under high temperatures they are moving quickly, and under low pressure they are distant from each other so the gas particles cannot experience forces of attraction to one another

Do real gases behave ideally at high pressures and low temperatures?

No

What is considered high pressure?

Larger than 5 atm

Why do gases not behave ideally at high pressures?

As pressure is increased the particles are pushed closer together which results in the volume of the gas molecules becoming significant

Why do gases not behave ideally at low temperatures?

As the temperature decreases the particles are moving slower and the intermolecular attractions become significant

The volume term in the Ideal Gas Law (IGL) equation is:

The volume of the container

The volume term of the ideal gas law assumes that:

Volume of particles in container is negligible

What does the ideal gas law assume about the volume of gas particles?

They have no volume of their own

The ideal gas law views gas particles as:

Point masses

Why does the ideal gas law assume that gas molecules have no volume of their own?

Molecules are so small compared to empty space that they are insignificant

When at low pressures, do volumes of molecules have to be subtracted from total volume?

No

Why don’t volume of molecules have to be subtracted from total volume at low pressures?

Volume of molecules are so small compared to volume of container that it can be ignored

At high pressures, do molecules occupy significant part of volume of container?

Yes

The fact that molecules occupy significant part of volume of container leads to:

Significantly decreased space in which the molecules can move

Is the volume of the individual molecules significant at high pressures?

Yea

What must be done to calculate volume of molecules at high pressures?

Adjustment made to ideal gas law

Do volumes of molecules have the be subtracted from volume of container at high pressure?

Yes

If the volume of a container is decreased, this causes the pressure to increase/decrease

Increase

If volume of container decreases, gas particles are forced much closer / much farther apart

Much closer

What happens to intermolecular forces when gas particles are forced closer?

Becomes significant

What do we assume about intermolecular forces of particles in ideal gas law and kinetic molecular theory?

There are no intermolecular forces

At high pressures and low temperatures, what happens to intermolecular forces of particles?

There will be intermolecular forces

Can we ignore intermolecular forces when distance between particles is decreased and kinetic energy of particles is decreased?

No

Why can’t we ignore intermolecular forces when distance between particles is decreased and kinetic energy of particles is decreased?

Particles are closer together so they feel attractive forces to one another

A measure of particle collisions to the walls of the container

Pressure

Why is pressure of gas decreased when particles feel attractive forces?

Clump together more so collide with walls of containers less