In: Chemistry
a. Write out in your own words what the van der
Waals a and b parameters represent.
b. Rank in increasing order the van der Waals a and b
parameters for the following four gases: Hydrogen, Benzene,
Ethanol, and Ethane. Check your intuition by looking up these
values and explaining the observed trends in a and b.
1. The value of a is direct measure of magnitude of attractive forces between the molecules
A gas with higher a value gas can be easily liquified
2. Greater the value of b gives an idea about the effective size of gas molecules
Greater the value of b larger is the size of molecule and smaller is compressable volume
For most of the easily liquifible gases the value of a/b is high
Gases | a value | b value |
Hydrogen | 0.2476 | 0.02661 |
benzene | 18.24 | 0.1154 |
ethanol | 12.18 | 0.08407 |
ethane | 5.562 | 0.0638 |
a values Hydrogen<ethane<ethanol<benzene
b values Hydrogen<ethane<ethanol<benzene