AP Chemistry: Salt Hydrolysis Multiple Choice Questions

📚 Quick Study Guide

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• Salt Hydrolysis: The reaction of a salt with water, where the cation or anion of the salt acts as an acid or base.
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• Ions that do NOT hydrolyze: Group 1 cations ($Li^+$, $Na^+$, $K^+$ etc.) and anions that are conjugate bases of strong acids ($Cl^-$, $Br^-$, $I^-$, $NO_3^-$, $ClO_4^-$, $HSO_4^-$).
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• Cations that hydrolyze: Small, highly charged metal ions such as $Al^{3+}$ and $Fe^{3+}$ act as weak acids. Ammonium ion ($NH_4^+$) also hydrolyzes.
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• Anions that hydrolyze: Conjugate bases of weak acids such as $F^-$, $CH_3COO^-$, $CN^-$, $S^{2-}$.
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• Salts of Weak Acids and Strong Bases: Produce basic solutions (pH > 7). Example: $NaCN$.
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• Salts of Strong Acids and Weak Bases: Produce acidic solutions (pH < 7). Example: $NH_4Cl$.
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• Salts of Weak Acids and Weak Bases: The pH depends on the relative strengths of the weak acid and weak base. Use $K_a$ and $K_b$ values to determine if the solution will be acidic, basic, or neutral.

🧪 Practice Quiz

1. Which of the following salts will produce a basic solution when dissolved in water?
   1. $NH_4Cl$
   2. $NaNO_3$
   3. $KCl$
   4. $NaCH_3COO$
2. Which of the following salts will NOT undergo hydrolysis?
   1. $KF$
   2. $NH_4NO_3$
   3. $NaCl$
   4. $AlCl_3$
3. What is the approximate pH of a solution of $NH_4Br$? ($K_b$ for $NH_3 = 1.8 \times 10^{-5}$)
   1. pH > 7
   2. pH = 7
   3. pH < 7
   4. Impossible to determine without more information
4. Which ion is responsible for the acidic properties of $AlCl_3$ solution?
   1. $Cl^-$
   2. $Al^{3+}$
   3. $H_3O^+$
   4. $OH^-$
5. A solution of which of the following salts will have the highest pH?
   1. $NH_4Cl$
   2. $NaCN$
   3. $KCl$
   4. $FeCl_3$
6. Which of the following statements is true regarding the hydrolysis of $Na_2CO_3$?
   1. The $Na^+$ ion hydrolyzes to produce $H_3O^+$
   2. The $CO_3^{2-}$ ion hydrolyzes to produce $OH^-$
   3. The solution will be neutral
   4. Neither ion undergoes hydrolysis
7. What is the conjugate acid of the $CN^-$ ion?
   1. $HCN$
   2. $OH^-$
   3. $CN^-$
   4. $H_2O$