Question

A best buffer has about equal quantities of weak acid and conjugate base present as well as having a large concentration of each species present. Explain.

Short answer

A best buffer solution maintains a stable pH by having about equal quantities of a weak acid and its conjugate base, which work together to neutralize added acidic or basic substances. Additionally, having large concentrations of each species present increases the buffer capacity, allowing it to neutralize more added substances without significantly changing its pH. This ensures a stable pH environment for various applications, such as biochemical reactions and industrial processes.

Step-by-step solution

1. Buffer Solution: Definition and Purpose

A buffer solution is a solution that can resist changes in pH when small amounts of acidic or basic substances are added. The main purpose of a buffer solution is to maintain a relatively constant pH level, despite the addition of acidic or basic substances. This property is essential in various applications, such as biochemical reactions and industrial processes, where maintaining a stable pH environment is crucial.

2. Weak Acid and Conjugate Base: Maintaining pH Balance

A buffer solution usually consists of a weak acid and its conjugate base. A weak acid is an acid that does not fully dissociate in water, releasing only a small portion of its hydrogen ions into the solution. The conjugate base is the species formed when the weak acid loses a proton (H+). In a buffer solution, the presence of both the weak acid and its conjugate base allows it to neutralize added acidic or basic substances, thus maintaining a stable pH. When an acidic substance is added, the pH of the solution decreases, and the conjugate base reacts with the added hydrogen ions (protons) to form the weak acid. Conversely, when a basic substance is added, the pH increases, and the weak acid donates protons to neutralize the added hydroxide ions (OH-), forming the conjugate base. Therefore, having about equal quantities of weak acid and conjugate base in a buffer solution is crucial to effectively neutralize both acidic and basic substances.

3. Large Concentrations of Weak Acid and Conjugate Base: Buffer Capacity

The buffer capacity refers to the ability of a buffer solution to resist changes in pH. A buffer with a high capacity can neutralize more added acidic or basic substances without significantly changing its pH. A best buffer should have a large concentration of both the weak acid and its conjugate base, as this increases its capacity to neutralize added substances without exhausting the supply of either species. In other words, having large concentrations of both species ensures that the buffer can maintain a stable pH even when significant amounts of acidic or basic substances are added. In summary, a best buffer solution is one with about equal quantities of a weak acid and its conjugate base, and with a large concentration of each species present. These characteristics ensure that the buffer can effectively neutralize added acidic or basic substances, thus maintaining a stable pH environment.