Hydrolysis of Salts: Explanation and Examples

🧪 Quick Study Guide

• 💧 Hydrolysis is the reaction of a salt with water.
• ⚖️ Salts formed from strong acids and strong bases do NOT undergo hydrolysis (e.g., $NaCl$).
• слабый Salts formed from weak acids and strong bases undergo hydrolysis to produce a basic solution (pH > 7) (e.g., $CH_3COONa$).
• 💪 Salts formed from strong acids and weak bases undergo hydrolysis to produce an acidic solution (pH < 7) (e.g., $NH_4Cl$).
• 📉 Salts formed from weak acids and weak bases undergo hydrolysis, and the pH depends on the relative strengths of the acid and base (e.g., $CH_3COONH_4$).
• 📝 The hydrolysis constant, $K_h$, indicates the extent of hydrolysis.
• ➕ $K_h = \frac{K_w}{K_a}$ (for salts of weak acids) or $K_h = \frac{K_w}{K_b}$ (for salts of weak bases), where $K_w$ is the ion product of water.

Practice Quiz

1. Which of the following salts does NOT undergo hydrolysis?
   1. $NaCl$
   2. $CH_3COONa$
   3. $NH_4Cl$
   4. $AlCl_3$
2. A salt of a weak acid and strong base will produce which type of solution upon hydrolysis?
   1. Acidic
   2. Basic
   3. Neutral
   4. It depends on the concentration of the salt
3. What is the approximate pH of a solution of $NH_4Cl$?
   1. Greater than 7
   2. Equal to 7
   3. Less than 7
   4. Cannot be determined
4. The hydrolysis constant, $K_h$, for a salt of a weak acid is given by:
   1. $\frac{K_a}{K_w}$
   2. $K_a \times K_w$
   3. $\frac{K_w}{K_a}$
   4. $\frac{1}{K_a \times K_w}$
5. Which of the following salts will produce an acidic solution when dissolved in water?
   1. $KCl$
   2. $NaCN$
   3. $CuSO_4$
   4. $K_2CO_3$
6. Which of the following statements about hydrolysis is correct?
   1. Salts of strong acids and strong bases always undergo hydrolysis.
   2. Hydrolysis always results in a neutral solution.
   3. The pH of a solution of a salt of a weak acid and weak base depends on the relative strengths of the acid and base.
   4. Hydrolysis only occurs in salts containing transition metals.
7. Which salt would likely result in a pH closest to 7?
   1. $NaF$
   2. $NH_4NO_3$
   3. $KNO_3$
   4. $Al(NO_3)_3$