Real vs. Ideal Gas• Under what types of pressure do gases behave ideally?

• Under what type of temperatures do gases behave ideally?

• We originally defined ideal gases with as series of requirements. These included, no volume, elastic collisions, and they do not interact. Match these requirements with the conditions above.

• We haven’t learned about how to tell if molecules interact with each other yet (it is in 1B), however, would a molecule that strongly interacts with other molecules be more or less ideal?

Low pressure

High temperatures

No volume: Low pressure means volume of atoms are a lower percent of the total volume.

No interactions: High temperatures mean molecules are moving quickly and lots of kinetic energy, interact less.

Less ideal.

• Calculate the pressure exerted by 1.00 mol of C2H6 behaving as an ideal gas and a Van der Waals gas when it is at 1) 273.15K in 22.414L and also 2) at 1000. K in 0.100L. Think about what these answers tell you.

Ideal Gas Law

Van Der Waals Gas

Rearranged for P

Conditions 1a=4.562b=0.0638

• Calculate the pressure exerted by 1.00 mol of C2H6 behaving as an ideal gas and a Van der Waals gas when it is at 1) 273.15 in 22.414L and also 2) at 1000. K in 0.100L. Think about what these answers tell you.

Rearranged for P

Ideal Gas Law

Van Der Waals Gas

Conditions 2

• Calculate the pressure exerted by 1.00 mol of C2H6 behaving as an ideal gas and a Van der Waals gas when it is at 1) 273.15 in 22.414L and also 2) at 1000. K in 0.100L. Think about what these answers tell you.

Ideal Gas Law

Van Der Waals Gas

Summary

Difference 0.006atm 989atm

Condition 1Atmospheric like

Condition 2High Pressure

At atmospheric pressures gases act ideally. At high pressures they do not. (Note: high temperatures in general actually make a gas act more ideally if still at a low pressure, however if the high temperatures increase the pressure then the change in pressure causes gases to act non-ideally.)