This problem is describing a mixture composed by diethyl ether and actic acid, in which it is desired to extract the latter somehow.
In this case, it turns out relevant to recall the concept of polarity, hydrogen bonds, and, in general, intermolecular forces. Acetic acid is a highly polar compound, able to have both dipole and hydrogen-bonding interactions, which are by far stronger than nonpolar-based London dispersion forces.
In such a way, since diethyl ether and actic acid are able to interact via dipole-dipole interactions, they latter is able to be dissolved in the former; however, when it is desired to extract the acid, it would be necessary to add a substance able to form H-bonds with acetic acid, which are stronger than the dipole interactions.
Therefore, the best solvent for this extraction will be water due to its higher polarity and superior capacity to form H-bonds.
Learn more:
