📚 Topic Summary
Preparing buffer solutions with a specific pH is a crucial skill in chemistry and biology. Buffer solutions resist changes in pH upon the addition of small amounts of acid or base. To prepare a buffer, you typically mix a weak acid and its conjugate base, or a weak base and its conjugate acid. The Henderson-Hasselbalch equation helps calculate the required ratio of acid and base to achieve the desired pH. 🧐 The key is selecting the appropriate weak acid/base pair with a pKa close to the desired pH. Once you've chosen your pair, you'll calculate the necessary molar ratios and then convert those ratios into masses or volumes for the lab!
🧪 Part A: Vocabulary
Match the term with its correct definition:
| Term |
Definition |
| 1. Buffer Solution |
A. The negative logarithm of the acid dissociation constant, $K_a$. |
| 2. pH |
B. A solution that resists changes in pH upon addition of small amounts of acid or base. |
| 3. pKa |
C. A measure of the acidity or basicity of a solution. |
| 4. Weak Acid |
D. An acid that only partially dissociates in solution. |
| 5. Conjugate Base |
E. The species formed when an acid loses a proton. |
🧮 Part B: Fill in the Blanks
Complete the following paragraph using the words: Henderson-Hasselbalch, conjugate, pH, buffer, weak.
A good ______ solution contains a ______ acid and its _______ base. The _______ equation is commonly used to calculate the ______ of a buffer solution. This equation relates the pH, pKa, and the ratio of the concentrations of the acid and base components.
🤔 Part C: Critical Thinking
You need to prepare a buffer solution with a pH of 4.75. Acetic acid (pKa = 4.75) and sodium acetate are available. Explain how you would determine the ratio of acetic acid to sodium acetate needed to achieve the desired pH, and then describe the steps for preparing this buffer in the lab.