Question

Buffers are mixtures of a ..............

• A. Weak acid and weak base
• B. Weak acid and their conjugate base
• C. Strong base and their conjugate acid
• D. Strong acid and weak base

Hint:

To make a buffer solution, mix a weak acid with its conjugate base or a weak base with its conjugate acid, which will resist changes in pH.

Answer 1

The Correct Option is B

Buffers are solutions that resist changes in pH when small amounts of acid or base are added. The most common type of buffer is a mixture of a weak acid and its conjugate base. This combination allows the buffer to neutralize both acids and bases.

(1) Weak Acid and Their Conjugate Base:
- In this type of buffer, the weak acid (e.g., acetic acid) partially dissociates, and the conjugate base (e.g., acetate) can neutralize excess H\(^+\) ions. This balance helps stabilize the pH.

(2) Why Other Options Are Incorrect:
- Weak acid and weak base (Option 1) is not a typical buffer system, as weak acids and weak bases do not provide the necessary balance for efficient buffering. - Strong base and their conjugate acid (Option 3) is not effective as a buffer because strong bases dissociate completely and do not maintain the required equilibrium.
- Strong acid and weak base (Option 4) would not function as a buffer because strong acids completely dissociate and thus do not provide the buffering capacity needed.

Conclusion: Buffers are mixtures of a weak acid and its conjugate base, which maintain a stable pH by neutralizing excess acids or bases.