Examples of Common Buffer Solutions in the Lab

📚 Quick Study Guide

• 🧪 A buffer solution resists changes in pH upon the addition of small amounts of acid or base.
• ⚗️ Buffers are typically composed of a weak acid and its conjugate base, or a weak base and its conjugate acid.
• ➗ The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: $pH = pK_a + log(\frac{[A^-]}{[HA]})$ 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, Ammonium/Ammonia, and Phosphate buffers.
• 🌡️ Temperature affects the equilibrium constant ($K_a$) of the weak acid, thus impacting buffer capacity.

Practice Quiz

1. Which of the following pairs could act as a buffer solution?
   1. HCl and NaCl
   2. $HNO_3$ and $KNO_3$
   3. $CH_3COOH$ and $CH_3COONa$
   4. NaOH and $Na_2SO_4$
2. What is the purpose of a buffer solution in a chemical experiment?
   1. To catalyze the reaction
   2. To maintain a stable pH
   3. To increase the reaction rate
   4. To change the color of the solution
3. Which formula is used to calculate the pH of a buffer solution?
   1. $pH = -log[H^+]$
   2. $pH = pK_a + log(\frac{[A^-]}{[HA]})$
   3. $pH + pOH = 14$
   4. $pH = K_a + [H^+]$
4. What is the conjugate base in a buffer solution of acetic acid ($CH_3COOH$) and sodium acetate ($CH_3COONa$)?
   1. $H_3O^+$
   2. $CH_3COOH$
   3. $CH_3COONa$
   4. $CH_3COO^-$
5. If the $pK_a$ of a weak acid is 4.76, and the concentrations of the acid and its conjugate base are equal, what is the pH of the buffer solution?
   1. 2.38
   2. 9.24
   3. 4.76
   4. 7.00
6. Which of the following factors can affect the capacity of a buffer solution?
   1. The color of the solution
   2. The temperature
   3. The stirring rate
   4. The size of the container
7. Which of the following is NOT a common buffer system?
   1. Acetic acid/Acetate
   2. Ammonium/Ammonia
   3. Hydrochloric acid/Chloride
   4. Phosphate