Buffer solutions can effectively maintain pH levels within what range?

Buffer solutions are specifically designed to maintain a relatively stable pH when small amounts of acids or bases are added to them. The effectiveness of a buffer is primarily determined by the pKa of the weak acid and the corresponding conjugate base in the solution, as well as their concentrations.

Typically, a buffer is most effective within one pH unit above and below its pKa. Most buffer systems used in biological and chemical applications have pKa values that fall within the range of approximately 4 to 10. This encompasses a wide array of commonly used buffer solutions, such as those based on acetic acid/sodium acetate or phosphate buffers, which are crucial for maintaining physiological pH levels in biological systems.

The other ranges mentioned do not provide an effective buffering capability for most practical applications. For instance, the ranges of 1 to 3 and 14 to 20 are well outside the common pKa values, and thus would not effectively stabilize pH in the situations where buffers are most needed, such as in biological or environmental contexts. A pH range of 7 to 14 does include neutral to alkaline conditions but does not reflect the most commonly employed buffers.

Therefore, the range of 4 to 10 is optimal for effective buffering