Final answer:
The solubility of benzoic acid in water and its partial ionization are relevant in calculating concentration and preparing buffer solutions. With a solubility of 6.80g per 100ml at 25°C, knowing the ratio of dissociated ions to the undissociated form is crucial for accurate pH calculations and buffer preparation in chemistry applications.
Step-by-step explanation:
The question is about the solubility of benzoic acid in water and its dissociation into ions when forming a solution. Benzoic acid has a moderate solubility in water at 25°C, which is essential information when preparing solutions for various chemical processes or for pH calculations in buffer systems. When benzoic acid dissolves in water, it partially ionizes into benzoate anions and hydrated protons, but most of it remains in the form of hydrated neutral molecules.
The degree of dissociation of benzoic acid is relevant in calculating the overall concentration of the acid in solution, which is not just the concentration of dissociated ions. For instance, at a pH of 2.85, the concentration of hydronium ions [H⁺] is given as 1.4 × 10⁻³ M, but the total concentration of benzoic acid is significantly higher at 2.8 × 10⁻² M, due to the presence of the non-ionized acid.
This concept also applies when discussing the formation of buffers using benzoic acid and its conjugate base sodium benzoate. Given a pKa of benzoic acid of 4.2, one can use the Henderson-Hasselbalch equation to calculate the necessary amounts of benzoic acid and sodium benzoate to achieve a desired buffer pH.