Suppose we put benzoic acid in a buffered solution at pH=2. In this condition, it will be almost completely unionized and therefore not very soluble. Conversely, if it is placed in a basic environment, the solubility will be high. But why does this happen? Is there a shift in the acid equilibrium of benzoic acid? But shouldn't this move only if more H+ or more OH- are added to the benzoic acid already present in solution?