Buffers: Keeping pH in Check

What makes a buffer effective?

Choose the correct option:

a. When 0.1< base: acid < 10.

b. When 0.1 > base: acid > 10.

c. When 0.1 < base: acid = 10.

d. When 0.1 = base: acid < 10.

Final answer:

A buffer is effective when the ratio of base to acid is between 0.1 and 10, with the most effective buffers having equal molar amounts of a weak acid and its conjugate base. Buffer capacity is reliant on the concentrations of these components, and a higher concentration results in greater pH stability.

Explanation:

A buffer is effective when the ratio of base to acid in a solution falls within a specific range. Specifically, a buffer system works optimally when the concentration ratio of the conjugate base ([base]) to the weak acid ([acid]) is between 0.1 and 10. When 0.1 < base: acid < 10, the buffer is able to resist changes in pH effectively upon the addition of small amounts of acid or base. The most effective buffers typically contain equal molar concentrations of a weak acid and its conjugate base, which equips them to neutralize both added acids and bases relatively well.

Following the Henderson-Hasselbalch equation, when [base] = [acid], the pH of the solution equals the pKa of the acid. As the buffer effective ratio is adjusted away from this equilibrium by factors of ten, the pH will shift approximately ±1 pH unit per tenfold change. Buffer solutions are especially important in biological and chemical systems where maintaining a stable pH is crucial for proper functioning.

Buffer Capacity and Range

The buffer capacity is another important aspect of buffer systems. It depends on the concentrations of the acid and conjugate base in the solution. The higher the concentration, the greater the buffer capacity, meaning it can absorb more added acid or base before a significant pH change occurs.