Why is benzoic acid well soluble in benzene (and other unpolar solvents, see e.g. wikipedia). What causes the hydrogen bonds in the solid to break? Something (i.e. polar and ionic substances) is soluble in water because of the hydration enthalpy with water, but i can see no similar cause for a solubility in benzene!
Solubility is one of the most complicated phenomena in chemistry. The "why" part of science is extremely difficult to answer in general. As a result one can ask one millions questions as to why iodine is soluble is benzene? What is so unique about benzoic acid? So many organic acids dissolve in benzene including acetic acid. Even a trace of water is soluble in benzene. Everything dissolves everything, to a very very small extent (depends on your limit of detection).
So the point to keep in mind is that although benzoic acid has a carboxylate group, it is a very hydrophobic acid and it literally floats on water. Similarly, you can sublime benzoic acid easily, so the intermolecular bond in benzoic is apparently not that strong.
I would guess that benzoic acid forms dimers or trimers connected by hydrogen bonds in nonpolar solvents. To the outside, these only show the phenyl rings.
The colligative properties of those solutions would clearly show how many individual particles they contain. I´ll leave the literature research for you. ;)