Buffer A contains nearly equal concentrations of its...

Buffer A contains nearly equal concentrations of its conjugate acid-base pair. Buffer $B$ contains the same total concentration of acidic and basic components as buffer $\mathrm{A}$, but B has twice as much of its weak acid as its conjugate base. Which buffer experiences a smaller change in $\mathrm{pH}$ when: a. the same small quantity of strong base is added to both? b. the same small quantity of strong acid is added to both?

Buffer A contains nearly equal concentrations of its conjugate acid-base pair. Buffer $B$ contains the same total concentration of acidic and basic components as buffer $\mathrm{A}$, but B has twice as much of its weak acid as its conjugate base. Which buffer experiences a smaller change in $\mathrm{pH}$ when:
a. the same small quantity of strong base is added to both?
b. the same small quantity of strong acid is added to both?

Key Concepts

Conjugate Acid-Base Ratio Effects

The effectiveness of a buffer in resisting pH changes is highly sensitive to the ratio of its conjugate base to acid. When the ratio is near one, the buffer is equally capable of neutralizing added acid and base. If the ratio deviates from unity, as in systems with an excess of one component, the capacity to neutralize additions in one direction decreases, leading to larger changes in pH.

Buffer Solution

A buffer solution is a system that consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) that work together to minimize changes in pH when small amounts of strong acid or base are added. The equilibrium between these components allows the solution to absorb added H+ or OH? ions, thereby stabilizing the pH.

Buffer Capacity

Buffer capacity is a measure of the ability of a buffer to resist changes in pH upon addition of strong acids or bases. It depends on the total concentration of the buffering species and their ratio; a buffer has its maximum capacity when the concentrations of the weak acid and its conjugate base are approximately equal.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation (pH = pKa + log([Base]/[Acid])) is used to estimate the pH of a buffer solution based on the ratio of the concentrations of the conjugate base and acid. This equation highlights how small deviations in the ratio away from unity can lead to significant changes in pH upon the addition of external acids or bases.

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