Final answer:
Acetylsalicylic acid in aqueous acid undergoes hydrolysis to form salicylic acid and acetate ions, with the reaction rate being higher in acidic conditions. The concentrations of hydronium and hydroxide ions are inversely proportional. Calculations for equilibrium concentrations can be simplified by assuming minimal dissociation of a weak acid or base and equating changes in concentration to the produced ions.
Step-by-step explanation:
In the presence of aqueous acid, acetylsalicylic acid (aspirin) undergoes hydrolysis to form salicylic acid, which is responsible for the drug's therapeutic effects, such as pain relief, fever reduction, and inflammation reduction. The hydrolysis of aspirin is relatively slow at neutral pH but much faster under the acidic conditions found in the stomach. The reaction produces salicylic acid and acetate ions as it proceeds.
When considering the behavior of weak acids or bases in a solution, two common simplifying assumptions can be made to facilitate the calculation of equilibrium concentrations. First, the concentration of the weak acid/base initially added is assumed to remain virtually unchanged as only a small amount dissociates in water. Second, the change in the concentration of the acid/base is typically assumed to be equal to the concentration of hydronium (H3O+) or hydroxide (OH-) ions produced. Regarding the question of concentration proportions, the concentrations of hydronium ions and hydroxide ions in an acidic or basic solution are inversely proportional to each other, as described by the ion product constant for water (Kw = [H3O+][OH-] ≈ 1.0 x 10-14 at 25°C).
In a 0.001-M aqueous solution of salicylic acid (C6H4OH(CO2H)), which is a weak acid, the likely species present in order of descending concentration would be the salicylic acid molecule itself, its conjugate base (the salicylate ion), hydronium ions, and hydroxide ions.