posted by casey .
why is the solubility of benzoic acid dependent on pH?
Benzoic acid is C6H5COOH. It ionizes as
C6H5COOH ==> H^+ + C6H5COO^-
At low levels of H^+ the reaction shifts to the right; at high levels of H^+ the reaction shifts to the left. Read up on Le Chatelier's Principle.