3.12: Buffers: Overview

Buffers play a crucial role in stabilizing the pH of a solution by mitigating the effects of small amounts of added acid or base. They consist of a weak acid and its conjugate base or a weak base and its conjugate acid. A solution of acetic acid and sodium acetate is an example of a buffer that consists of a weak acid and its salt: CH₃COOH (aq) + CH₃COONa (aq). An example of a buffer that consists of a weak base and its salt is a solution of ammonia and ammonium chloride: NH₃ (aq) + NH₄Cl (aq).

This combination prevents significant pH changes as long as the buffer's capacity is not exceeded. For example, human blood uses a carbonic acid-bicarbonate buffer system to maintain its pH near 7.4. In a buffer, the weak acid component neutralizes added bases by reacting with hydroxide ions, while the conjugate base neutralizes added acids by reacting with hydronium ions.

Adding a small amount of acid or base to a solution can cause a significant decrease or increase in the pH. However, many chemical and biochemical processes need a stable pH to function. Buffers can prevent a drastic change in the pH of a solution when their buffering capacity is not exceeded.

Buffers contain a weak acid and its conjugate base or a weak base and its conjugate acid. For example, human blood maintains its pH near 7.4 with a buffer composed of carbonic acid, a weak acid, and bicarbonate ions, its conjugate base.

Conjugate acid-base pairs form buffers as they do not neutralize their conjugate acid or base, for example acetic acid and acetate cannot react.  However, if acetic acid, a weak acid, and ammonia, a weak base, are added together, they will react to form a salt-ammonium acetate.

In a buffer, the weak acid neutralizes any added base by reacting with the hydroxide ions produced, whereas its conjugate base neutralizes any added acid by reacting with any hydronium ions. A similar mechanism works in the case of a weak base and its conjugate acid.

• Buffer - A solution that stabilizes pH by neutralizing added acids or bases.
• Conjugate Base - The compound remaining after donation of a proton.
• Weak Acid - Partially ionizing acid in a solution.
• Chemical Titration - A method to determine the concentration of an unknown solution.
• Buffer System - Consists of a weak acid/base and its salt to prevent pH changes.

• Define Buffer – Explain what it is (e.g., A solution that stabilizes pH).
• Contrast Weak acid vs Conjugate base – Explain key differences (e.g., Weak acid donates protons, conjugate base accepts).
• Explore Examples – Describe scenario (e.g., Human blood uses a carbonic acid-bicarbonate buffer system).
• Explain Buffer System – The combination of a weak acid/base and its salt in maintaining pH.
• Apply Buffer in Context – Use of buffers in lab procedures like titration and biochemical processes.

• What is a buffer and how does it stabilize pH?
• What distinguishes a weak acid from a conjugate base?
• How do buffers function in the human body, such as in blood pH regulation?

• Students – Understand How the concept of buffer supports their knowledge in chemistry and biochemistry
• Educators – Provides a clear framework to teach the concept of buffers and their functioning.
• Researchers – Integral in various research methodologies, especially in pH sensitive experiments.
• Science Enthusiasts – Offers insights into the importance of buffers in maintaining homeostasis and their applications in science.