Final answer:
The correct option is A). Solutions of a strong acid and a weak acid can have the same pH if they are part of a buffer system containing equal concentrations of a weak acid and its conjugate base. The ratio of acid to base is crucial, as effective buffers resist changes in pH despite the presence of additional strong acids or bases.
Step-by-step explanation:
Solutions of a strong acid and a weak acid can have the same pH in a situation where both solutions are part of a buffer system. This is because buffer solutions are designed to resist changes in pH when small amounts of strong acids or bases are added. The most effective buffers contain equal concentrations of an acid and its conjugate base, maintaining the pH despite the addition of external acids or bases. For example, a solution of acetic acid and sodium acetate can act as a buffer, effectively maintaining a consistent pH value when exposed to other acid or base substances.
A key point is that the pH does not depend on volume. This means that buffers can maintain their pH regardless of the total amount of solution, as long as the ratio of the acid to its conjugate base remains constant and the solution is not so dilute that the autoionization of water significantly alters the concentration of H+ or OH-. Thus, for two acid solutions to have the same pH, they must be buffered, and the buffer must be formulated so that the pH matches the target pH, typically close to the pKa of the weak acid used in the buffer.