Questions: A solution is buffered at a pH of 3.5, and a small amount of acid is added. What happens to the pH of the solution? The pH will decrease a small amount. The pH will increase a small amount. The pH will not change at all. IDONT KNOWYET

Solution Steps

Buffers are solutions that resist changes in pH when small amounts of acid or base are added. They typically consist of a weak acid and its conjugate base. The pH of a buffer solution is given by the Henderson-Hasselbalch equation: \[ \mathrm{pH} = \mathrm{pK}_a + \log \left(\frac{[\mathrm{A}^-]}{[\mathrm{HA}]}\right) \]

The solution is buffered at a pH of 3.5. This means that the ratio of the concentrations of the conjugate base \(\mathrm{A}^-\) and the weak acid \(\mathrm{HA}\) is such that the pH is maintained at 3.5.

When a small amount of acid is added to the buffer solution, the added \(\mathrm{H}^+\) ions will react with the conjugate base \(\mathrm{A}^-\) to form more of the weak acid \(\mathrm{HA}\). This reaction will slightly increase the concentration of \(\mathrm{HA}\) and decrease the concentration of \(\mathrm{A}^-\).

Since the buffer system is designed to resist changes in pH, the pH will decrease only a small amount. The buffer will neutralize most of the added acid, but not all, leading to a slight decrease in pH.

Final Answer