Final answer:
To create a buffer, a specific ratio of conjugate base to conjugate acid is needed, often near 1:1 for optimal buffering capacity.
Step-by-step explanation:
To create a buffer, the ratio of the concentrations of the conjugate base to the conjugate acid is crucial. According to the Henderson-Hasselbalch equation, a good buffer mixture should have about equal concentrations of both components. For a buffer with a specific pH, such as 3.0 in the case of hydrofluoric acid (HF), you must adjust the ratio of fluoride ions (F-) to HF to be within a certain range to maintain the desired pH. When creating an HF buffer at a pH of 3.0, this ratio is generally between 1:1 and 1:10, given that the pKa of HF is 3.75.
For our example with 100 ml of 1 M HF, to prepare a buffer at pH 3.0 using NaF, we need to calculate the amount of sodium fluoride that would create a conjugate base to conjugate acid ratio that corresponds to the pH of 3.0. Using the Henderson-Hasselbalch approximation, we know the ratio would have to be such that the pH is between the pKa of HF and one unit above it. Consequently, the required amount of NaF would be determined to provide this optimal buffering capacity.
Effective buffers like acetic acid/sodium acetate work on the principle that a buffer is most effective when the acid and its conjugate base are in approximately equal amounts in solution. This is beneficial for resisting drastic changes in pH when acids or bases are added to the solution.