puskurikyky

Puskurikyky, commonly referred to as buffer capacity, is the ability of a solution to resist changes in pH when small amounts of acid or base are added. It arises from the presence of a conjugate acid–base pair, typically a weak acid and its conjugate base or a weak base and its conjugate acid. The capacity is greatest when the pH is near the pKa of the buffering species and the concentrations of the buffer components are high.

Mechanism and scope: In a typical weak acid–base buffer, added acid is partly neutralized by the conjugate base, forming the weak acid and limiting pH change. When base is added, the weak acid donates protons to form the conjugate base, again moderating pH shifts. Buffer capacity is thus linked to the amount of buffering species present and to how closely the solution’s pH matches the pKa.

Measurement and estimation: Buffer capacity can be assessed by titration with a strong acid or base and observing the change in pH, or by using approximate relations derived from buffer equilibrium concepts. In practice, the capacity is higher for solutions with greater total concentrations of buffering components and near the pKa, and it decreases when pH moves far from the pKa or at higher temperatures.

Applications and examples: Buffers are widely used in chemical analyses, biological experiments, pharmaceutical formulations, and environmental science. Common buffers include acetate, phosphate, and ammonium systems. Biological fluids, such as blood, rely on buffering systems (for example bicarbonate) to maintain near-constant pH for proper cellular function.

Limitations: A buffer has finite capacity and can be overwhelmed by large additions of acid or base or by substantial pH shifts far from the pKa.