The expression of the chemical potential of a solute in a solvent is derived exploiting the van der Waals model of liquids using a statistical thermodynamical approach. Then the solvation thermodynamics is determined, and discussed in detail for the case of an infinitely dilute solution. The analysis shows that the definitions introduced by Ben-Naim are exact and need no corrections. Moreover, the results obtained are in line with the theoretical approach devised by Lee to rationalize the experimental thermodynamic data of solvation.