How do you remove benzene from water?

1 Answer
Jan 23, 2016

No major effort required. Pipet water out and leave benzene behind. ;)

Benzene is highly symmetrical (#D_(6h)# symmetry, by the way), so there is no way it can perform any of the significantly strong intermolecular forces to the extent that water can perform them (dipole-dipole and H-"bonding").

Although both benzene and water can perform London dispersion, benzene is again, highly symmetrical, which makes it very hard to polarize to generate even an induced dipole.

Since one of the requirements for solvation is similar intermolecular forces, benzene does not fare well. Thus, there is good reason to believe that benzene is poorly soluble in water.

In fact, the solubility of benzene is #~"1.84 g/L"# at #30^@ "C"#, which is on the order of "slightly soluble". "Soluble" would be more like #~"100 g/L"# (the solubility of #"NaCl"# is #~"359 g/L"#).

The density of benzene is #~"0.876 g/mL"#, so it will float upon water. Then you can use a Pasteur pipet, let's say, to transfer benzene out of solution; since benzene will be on top, simply focus your eyes on the bottom of the container.

Squeeze the pipet bulb before immersing it, then immerse it until you reach the bottom, and grab the water until you have a very thin layer of water left (go slowly).