Main Desktop Lessons Desktop Review Desktop Lab Desktop Calculators Search Charts Desktop

4. a. From the standpoint of the kinetic molecular theory, discuss briefly the properties of gas molecules that cause deviations from ideal behavior.   Kinetic Molecular Theory

There are only two properties of gas molecules that cause deviations from ideal behavior.

 1 Ideal gases do not have any attraction between molecules.  Real gases have an attraction that is dependent on the distance between the molecules. 2 Ideal gases are infinitely small points.  Real gas molecules occupy a small volume.  As long as the molecules are far apart, the volume of the molecules is small enough to be ignored.

b. At 25oC and 1 atm, which of the following gases shows the greatest deviation from ideal behavior? Give two reasons for your choice.  CH4   SO2   O2   H2    Periodic Chart

SO2 is the largest molecule.  This creates the largest deviation due to the size of the molecules.

SO2 is the only polar molecule in the group.  Thus it has the greatest attractive forces between the molecules.

Although these two factors tend to counteract each other, SO2 should have the greatest deviation due to the greatest variation due to the two factors that cause deviatons.

c. Real gases approach ideality at low pressure, high temperature, or both. Explain these observations.

The combination of low pressure and high temperature has real gases approach ideality.

The combination has molecules very far apart.  This makes the percentage of the volume occupied by the molecules approach zero.

If the molecules are very far apart the attraction between the molecules is decreased significantly.  Also, since the molecules are at high temperature, they have a high average energy per molecule and they can easily overcome the very slight attraction.