Buffer Solution Examples: Common Acid-Base Buffer Systems

🧪 Quick Study Guide

• ⚖️ A buffer solution resists changes in pH when small amounts of acid or base are added.
• ⚗️ Buffers typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid.
• ➗ The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution: $pH = pK_a + log(\frac{[A^-]}{[HA]})$ where $[A^-]$ is the concentration of the conjugate base and $[HA]$ is the concentration of the weak acid.
• 💧 Common buffer systems include acetic acid/acetate buffers and ammonia/ammonium buffers.
• 🌡️ The buffer capacity is the amount of acid or base a buffer can neutralize before its pH changes significantly.
• 📝 Buffers are essential in many biological and chemical processes to maintain a stable pH.

Practice Quiz

1. Which of the following mixtures would create a buffer solution when dissolved in water?

   1. HCl and NaCl
   2. NaOH and NaCl
   3. CH₃COOH and CH₃COONa
   4. HNO₃ and KNO₃

2. What is the primary function of a buffer solution?

   1. To neutralize a solution completely.
   2. To maintain a stable pH upon addition of small amounts of acid or base.
   3. To increase the pH of a solution.
   4. To decrease the pH of a solution.

3. Which equation is used to calculate the pH of a buffer solution?

   1. $pH = -log[H^+]$
   2. $pH + pOH = 14$
   3. $pH = pK_a + log(\frac{[A^-]}{[HA]})$
   4. $pH = pK_w + log[H^+]$

4. A buffer solution is prepared using ammonia (NH₃) and ammonium chloride (NH₄Cl). Which component acts as the weak base?

   1. NH₄Cl
   2. NH₃
   3. H₂O
   4. Cl^-

5. What does the term 'buffer capacity' refer to?

   1. The initial pH of the buffer.
   2. The amount of acid or base the buffer can neutralize before its pH changes significantly.
   3. The volume of the buffer solution.
   4. The temperature at which the buffer is most effective.

6. Which of the following is an example of a common buffer system?

   1. Hydrochloric acid and sodium chloride
   2. Acetic acid and sodium acetate
   3. Nitric acid and potassium nitrate
   4. Sodium hydroxide and potassium hydroxide

7. If the $pK_a$ of a weak acid is 4.76, and the concentrations of the weak acid and its conjugate base are equal, what is the pH of the buffer solution?

   1. 0
   2. 7
   3. 4.76
   4. 14