The salt formed from a weak acid and a strong base hydrolyzes in water to form

Analysis

The question asks about the nature of the solution formed when a salt derived from a weak acid and a strong base undergoes hydrolysis in water.

Concept Explanation

Hydrolysis is the reaction of an ion (from a salt) with water to produce either an acidic or alkaline solution.

• Strong Acid + Strong Base: The resulting salt does not hydrolyze; the solution remains neutral (pH = 7).
• Weak Acid + Strong Base: The anion of the weak acid reacts with water (hydrolysis) to produce hydroxide ions ($OH^-$). Because the base is strong, it "wins" the character of the solution, making it basic (alkaline).
• Strong Acid + Weak Base: The cation of the weak base reacts with water to produce hydrogen ions ($H^+$), making the solution acidic.

Step-by-Step Solution

1. Identify the components: We have a weak acid (e.g., $CH_3COOH$) and a strong base (e.g., $NaOH$).
2. Form the salt: The reaction is $CH_3COOH + NaOH \rightarrow CH_3COONa + H_2O$. The salt is Sodium Ethanoate ($CH_3COONa$).
3. Hydrolysis reaction: When the salt dissolves in water, it dissociates into $CH_3COO^-$ and $Na^+$. • The $Na^+$ ion comes from a strong base and does not react with water. • The $CH_3COO^-$ ion comes from a weak acid and reacts with water: $CH_3COO^- + H_2O \rightleftharpoons CH_3COOH + OH^-$
4. Conclusion: The production of $OH^-$ ions increases the concentration of hydroxide ions in the solution, which makes the solution alkaline (basic).

Identification of Answer

The correct option is D.

Exam Tip

Think of it as a "tug-of-war." In a salt, the "stronger" parent (acid or base) determines the pH of the solution. If the base is strong, the solution is alkaline. If the acid is strong, the solution is acidic. If both are strong, it is neutral.