You are asked to prepare a pH = 3.00 buffer solution starting from 1.25 L of a 1.00 M solution of hydrofluoric acid (HF) and any amount you need of sodium fluoride (NaF). (a) What is the pH of the hydrofluoric acid solution prior to adding sodium fluoride?

Key Concepts

pH and Acid-Base Chemistry

pH is a measure of the hydrogen ion concentration in a solution, indicating its acidity or basicity. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic. Understanding pH is crucial for analyzing solutions, especially in buffer systems where the pH remains relatively stable despite the addition of acids or bases.

Weak Acids and Their Dissociation

Hydrofluoric acid (HF) is a weak acid that partially dissociates in water to produce hydrogen ions (H⁺) and fluoride ions (F⁻). The degree of dissociation is characterized by the acid dissociation constant (Ka), which helps determine the concentration of H⁺ ions in the solution and thus the pH. This concept is essential for calculating the pH of the HF solution before any buffer components are added.

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acids or bases. It typically consists of a weak acid and its conjugate base, which in this case is HF and NaF. Understanding how buffers work is important for preparing solutions with specific pH values, as they maintain stability in pH during chemical reactions or external changes.