Intermediate Topic 541 of 1102 Acids, Bases & Electrochemistry
Buffer Solutions
Mixtures of weak acid and conjugate base that resist pH change.
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In-depth explanation of Buffer Solutions
A buffer is a mixture of a weak acid and its conjugate base, or of a weak base and its conjugate acid, that resists changes in pH when small amounts of acid or base are added. Added hydrogen ions are consumed by the base component, and added hydroxide ions are consumed by the acid component, so the pH changes only slightly. Buffers work best when the ratio of base to acid lies between about 0.1 and 10, which corresponds to a pH within one unit of the pKa. Buffers are essential in biological systems, laboratory analysis and industrial processes. Understanding them requires both the weak acid equilibrium and the Henderson-Hasselbalch relation.
Going deeper: Buffer Solutions
Key ideas: A buffer holds pH nearly constant by pairing a weak acid with its conjugate base (or weak base with conjugate acid) in comparable amounts. It works because added H+ is consumed by A- and added OH- by HA. Effective range is pKa plus or minus 1, and ratio of base to acid between 0.1 and 10.
Common mistakes and connections: Mistakes: mixing a strong acid with its conjugate base (not a buffer), or using a weak acid with the wrong pKa. Buffer pH is not changed by dilution much, but capacity is. Prepare by mixing acid with strong base to convert part of it into conjugate base. Foundation of biological buffering.
Visualization of Buffer Solutions
An acetic acid and acetate buffer holds pH near 4.76; the plot shows pH versus the base to acid ratio, flattest around the pKa. The interactive lesson shows this as a live animation or chart.
Worked example and use case
An acetic acid and acetate mixture acts as a buffer near pH 4.76, the pKa of acetic acid.
Frequently asked questions about Buffer Solutions
What is Buffer Solutions?
Mixtures of weak acid and conjugate base that resist pH change.
Is Buffer Solutions a beginner, intermediate or advanced topic?
Buffer Solutions is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Buffer Solutions?
Study these earlier topics in Acids, Bases & Electrochemistry first: Acid-Base Indicators, Universal Indicator, Choosing Indicators.
What comes after Buffer Solutions?
The next topics in Acids, Bases & Electrochemistry are Henderson-Hasselbalch Equation and Buffer Capacity.
Can I practise Buffer Solutions with quizzes?
Yes. The interactive lesson includes a self-check question on Buffer Solutions, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Buffer Solutions fits in Acids, Bases & Electrochemistry
Buffer Solutions is topic 31 of 105 in Acids, Bases & Electrochemistry.