Advanced Topic 543 of 1102 Acids, Bases & Electrochemistry
Buffer Capacity
The amount of acid or base a buffer can neutralize before pH changes significantly.
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In-depth explanation of Buffer Capacity
Buffer capacity is the amount of strong acid or base a buffer can neutralize before its pH changes by a significant amount, usually one unit. It depends on the total concentration of the buffer components, since more material can absorb more added acid or base. Capacity is greatest when the ratio of conjugate base to weak acid is close to one, which corresponds to pH equal to pKa. It falls sharply as either component is used up, and at that point the buffer no longer resists pH change effectively. Designing a buffer for a given application therefore requires attention to both concentration and pH.
Going deeper: Buffer Capacity
Key ideas: Capacity is the moles of strong acid or base a buffer absorbs per unit pH change. It is highest when [HA] equals [A-] (pH = pKa) and rises with total buffer concentration. A buffer is effectively exhausted when one component is nearly gone. A 0.5 M buffer resists roughly ten times more addition than 0.05 M at the same ratio.
Common mistakes and connections: Mistake: believing that the pH ratio alone sets capacity; absolute concentration matters too. Another is confusing buffer range with capacity. Dilution leaves pH almost unchanged but reduces capacity. Compare with titration curves, where the flat region is where capacity peaks.
Visualization of Buffer Capacity
Buffer capacity peaks when acid and base are equal, as for the H2PO4-/HPO4(2-) pair at pH 7.2, and drops once either component is used up. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A 1 M buffer resists pH change far better than a 0.01 M buffer of the same pH.
Frequently asked questions about Buffer Capacity
What is Buffer Capacity?
The amount of acid or base a buffer can neutralize before pH changes significantly.
Is Buffer Capacity a beginner, intermediate or advanced topic?
Buffer Capacity is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Buffer Capacity?
Study these earlier topics in Acids, Bases & Electrochemistry first: Choosing Indicators, Buffer Solutions, Henderson-Hasselbalch Equation.
What comes after Buffer Capacity?
The next topics in Acids, Bases & Electrochemistry are Blood Buffer System and Oxidation Number.
Can I practise Buffer Capacity with quizzes?
Yes. The interactive lesson includes a self-check question on Buffer Capacity, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Buffer Capacity fits in Acids, Bases & Electrochemistry
Buffer Capacity is topic 33 of 105 in Acids, Bases & Electrochemistry.