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Properties of Buffers

Buffers are solutions that resist changes in pH when small amounts of acid or base are added. They are essential in chemical and biological systems.

Composition of Buffers​

  • Weak acid + Conjugate base (e.g., CH₃COOH/CH₃COO⁻)
  • Weak base + Conjugate acid (e.g., NH₃/NH₄⁺)
  • The ratio of conjugate base to acid determines buffer capacity.

Buffer Action​

  • Adding Acid (H⁺): Conjugate base reacts with H⁺ to minimize pH change.
  • Adding Base (OH⁻): Weak acid reacts with OH⁻ to minimize pH change.

Key Properties​

  • Resists pH changes within a certain range, usually ±1 pH unit of pKa.
  • Buffer capacity depends on concentration: higher concentrations resist pH change better.
  • Effective buffer range is typically pKa ± 1.

Calculating Buffer pH​

  • Henderson-Hasselbalch Equation:
    pH = pKa + log([A⁻]/[HA])
  • [A⁻] = conjugate base concentration, [HA] = acid concentration

Importance​

  • Maintains pH in biological systems (blood, cells)
  • Controls pH in chemical reactions and industrial processes
  • Essential in titrations and analytical chemistry

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