gen-define-buffer-solutions-and-give-one-short-worked-example-22da

Define buffer solutions and give one short worked example.

# Buffer Solutions ## Definition A **buffer solution** is an aqueous solution that resists changes in pH when small amounts of acid or base are added. It consists of: - A weak acid and its conjugate base (acidic buffer), OR - A weak base and its conjugate acid (basic buffer) Buffers work by neutralizing added H⁺ or OH⁻ ions through equilibrium shifts. ## Worked Example **Problem:** Calculate the pH of a buffer containing 0.10 M CH₃COOH (acetic acid) and 0.15 M CH₃COONa (sodium acetate). Ka for acetic acid = 1.8 × 10⁻⁵ **Solution:** Using the Henderson-Hasselbalch equation: $$\text{pH} = \text{p}K_a + \log\frac{[\text{conjugate base}]}{[\text{weak acid}]}$$ First, find pKa: $$\text{p}K_a = -\log(1.8 \times 10^{-5}) = 4.74$$ Then substitute: $$\text{pH} = 4.74 + \log\frac{[0.15]}{[0.10]}$$ $$\text{pH} = 4.74 + \log(1.5) = 4.74 + 0.18$$ $$\text{pH} = 4.92$$ **Answer:** The buffer has a pH of 4.92, which will remain relatively stable even with small additions of acid or base.