Chemistry · MU Sofia

4.4 Buffer solutions

Covers the definition and key properties of buffer solutions, then the Henderson-Hasselbalch equation and its implications for pH and buffering range. Next it explains buffer capacity, its formula and the factors that affect it, with a graph of an acetate buffer. It closes with a practical guide to preparing a buffer of a target pH, listing popular acid-base pairings, and a section on the bicarbonate, protein and phosphate buffers that keep blood pH stable.

Inside: 6 sections · 4 labelled pictures · 22 flashcards · 6 min

Topic 15 of 42 in the MU Sofia syllabus for Chemistry (Medicine, Year 1). The free AceMed note covers it in 6 sections, about 911 words (6 min of reading), with 22 flashcards.

In this note

  1. Introduction
  2. Buffer solutions – definition, properties.
  3. Henderson - Hasselbalch equation.
  4. Buffer capacity (β)
  5. Preparing a buffer solution with a specific pH.
  6. Buffers: The Key to Life-Sustaining Blood pH

Buffer solutions – definition, properties.

  • Buffer Solution (Buffer): A buffer solution, commonly referred to as a buffer, is a solution comprising a conjugate acid-base pair. Buffers resist significant changes in pH when moderate amounts of strong acids or bases are added, or when the solution undergoes dilution. One crucial aspect of a buffer is the presence of at least one component that is a weak electrolyte.

Key Properties of Buffer Solutions:

  • pH Stability:
  • Buffers exhibit property of maintaining a relatively constant pH despite the addition of acids or bases. This ability arises from the equilibrium between the weak acid and its conjugate base, or between the weak base and its conjugate acid, which counteracts pH changes caused by external factors.
  • Conjugate Acid-Base Pair:
  • Buffers consist of a pair of compounds: one acting as a weak acid and the other as its conjugate base, or vice versa. This pair maintains the buffer's pH stability through reversible proton transfer reactions.
  • Capacity to Resist pH Changes:
  • Buffers can withstand the addition of limited amounts of strong acids or bases without experiencing drastic changes in pH.
  • Preparation and Composition:
  • Buffers can be prepared by mixing a weak acid with a salt of its conjugate base or by combining a weak base with a salt of its conjugate acid.
  • Buffer Range:
  • Buffers have an optimal pH range over which they exhibit maximum buffering capacity. This range depends on the pKa (acid dissociation constant) of the weak acid or base present in the buffer system.

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