Acid Dissociation Constants and Buffer Solutions

This page delves into the concept of acid dissociation constants and their application in understanding acid-base reactions and buffer solutions. It introduces the constante d'acidité (Ka) and its logarithmic form, pKa.

The acid dissociation reaction is presented:

Example: AH + H₂O ⇌ A⁻ + H₃O⁺

The constante d'acidité formule is given as:

Formula: Ka = ([A⁻][H₃O⁺]) / [AH]

The relationship between pH and pKa is explained, highlighting the importance of these values in determining the predominant species in solution:

Highlight: When pH = pKa, [AH] = [A⁻]

The page introduces buffer solutions, explaining their ability to resist pH changes upon addition of small amounts of acids or bases. The Henderson-Hasselbalch equation is presented for calculating the pH of buffer solutions:

Formula: pH = pKa + log([A⁻] / [AH])

This equation is crucial for understanding the behavior of buffer solutions and their applications in various chemical and biological systems.

Vocabulary: A buffer solution is a mixture of a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists changes in pH when small amounts of acids or bases are added.

The page concludes by emphasizing the importance of buffer solutions in maintaining relatively constant pH in various systems, including biological organisms.