Why does adding distilled water to a buffer solution not effectively change its pH?

• A. It dilutes both the acid and base simultaneously
• B. It increases the volume without changing concentration
• C. It alters the solubility of ions in solution
• D. It introduces contaminants into the solution

Answer: (A)

Adding distilled water to a buffer solution does not effectively change its pH primarily because it dilutes both the acid and base components of the buffer simultaneously. Buffers are designed to resist changes in pH when small amounts of acid or base are added. They work by maintaining a balance between the weak acid and its conjugate base.

When distilled water is added, the concentrations of both the weak acid and the conjugate base decrease, but the ratio of their concentrations remains unchanged. Since pH is determined by the ratio of the concentrations of the acid and base rather than their absolute concentrations, the pH of the solution stays relatively constant.

Thus, the ability of the buffer to maintain its pH is preserved, and a significant change in pH does not occur under these circumstances. This understanding is critical in practical applications, such as biochemical experiments, where precise pH control is essential.