Introduction to Buffer Solutions

Buffer Solutions Overview

• Definition: Buffer solutions resist changes in pH when small amounts of acid or base are added.

Behavior of Buffer Solutions

• Neutral Solution: Initial solution has a pH of ~7 (neutral) with universal indicator.
• Acid Addition: Adding a small amount of acid (H+) does not change the pH.
• Alkali Addition: Adding a small amount of alkali (OH-) also does not change the pH.
• Limitations: Buffers only function within a specific range; excessive acid or alkali will overwhelm the buffer.

Components of a Buffer Solution

• Key Ingredients:
  • Weak Acid (e.g., HA): Partially dissociates, producing H+ and conjugate base (A-).
  • Salt of the Weak Acid (e.g., NaA): Fully dissociates, providing additional A- to mitigate pH changes.

Buffer Mechanism

• Acid Reaction:
  • When acid is added, A- from the buffer reacts with H+, forming the weak acid HA, minimizing pH change.
• Alkali Reaction:
  • When alkali is added, the weak acid HA reacts with OH-, forming water and A-, keeping pH stable.

Conclusion

• Functionality: Buffers maintain pH in a narrow range, relying on the equilibrium between weak acids and their conjugate bases. Excessive amounts of acids or bases lead to buffer failure.