Calculating volumes of HF and NaF for preparing a buffered solution

Understanding Buffer Solutions

A buffer solution is a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid) that helps maintain a stable pH when small amounts of acids or bases are added. The key to buffer effectiveness lies in the equilibrium between the weak acid and its conjugate base, which enables the solution to resist large changes in pH.

Equilibrium Calculation:

In this scenario, the equilibrium of the weak acid HF (hydrofluoric acid) can be represented as follows:

HF ⇄ H⁺ + F⁻

Since we are dealing with a buffer containing HF and its conjugate base F⁻, derived from the salt NaF, the concentrations of F⁻ and HF are vital in determining the pH of the buffer solution.

Determination of Volumes:

The Henderson-Hasselbalch equation pH = pKa + log [A⁻]/[HA] can be utilized to calculate the ratio of [F⁻] to [HF] in the buffer. By substituting the given concentrations and solving for the volumes of NaF and HF, we arrive at the solution that requires 304 mL of NaF and 696 mL of HF to create a buffered solution with a pH of 2.79.

Understanding the principles of buffer solutions and their ability to maintain pH levels is crucial in various chemical applications, including biological systems where maintaining stable pH conditions is essential for proper function.