How do intermolecular forces affect the solubility of cyclopentane in water?

1 Answer
Aug 29, 2015

Cyclopentane has only weak London dispersion forces of attraction, while water has strong hydrogen bonding attractions.


If we add cyclopentane to aqueous salt solution, the cyclopentane will float on the top of the solution with no apparent mixing.

The only attractive forces among the cyclopentane and water molecules are London forces.

Thus, a few cyclopentane molecules will enter the aqueous layer, but the strong attractive forces among the water molecules keeps most of the cyclopentane molecules out.

Similarly, a few water molecules will enter the cyclopentane layer because of the aqueous salt solution-cyclopentane London forces.

Also, the strong attractive forces among the aqueous salt solution molecules holds the aqueous salt solution molecules close together in a compact volume.

The aqueous salt solution is denser than the cyclopentane, so the cyclopentane floats on top.

The easiest way to separate the layers is to use a separatory funnel.