Puskurivahvuus

Puskurivahvuus, or buffer capacity, is the ability of a solution or system to resist changes in pH when small amounts of acid or base are added. It quantifies how much strong acid or base must be added per liter to change the pH by one unit. In chemical terms, it is often expressed as the derivative β = dB/d(pH), where B is the amount of strong agent added.

For a common buffer consisting of a weak acid HA and its conjugate base A−, an approximate expression for the buffer capacity is β ≈ 2.303 × C_T × Ka × [H+]/(Ka + [H+])^2, where C_T is the total buffer concentration ( [HA] + [A−] ), Ka is the acid dissociation constant, and [H+] is the hydrogen ion concentration. This function reaches a maximum near pH = pKa and is proportional to the total amount of buffering species; thus higher C_T generally yields greater capacity.

Buffer capacity depends on several factors. It increases with total buffer concentration and is highest near the pH corresponding to the buffer’s pKa. Temperature, ionic strength, and the presence of multiple buffering systems can modify β. Outside the effective buffering range (where [A−]/[HA] ratios skew far from equilibrium), the capacity diminishes and pH changes more readily.

Applications of puskurivahvuus include chemical analysis, biochemistry and physiology (for example, blood and cellular fluids rely on buffering systems to maintain stable pH), environmental science (soil and water buffers against acidification), and pharmaceutical formulations. Measurement is commonly done via titration or by analyzing pH responses to added acid or base.