Question:
Which of the following is the weakest acid?
Which of the following is the weakest acid?
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Acidity order: p-Nitrophenol $>$ Phenol $>$ p-Cresol $>$ m-Cresol $>$ Ethanol.
Updated On: Apr 24, 2026
- Phenol
- p-Nitrophenol
- p-Cresol
- Ethanol
- m-Cresol
Show Solution
Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Acidity depends on the stability of the conjugate base. Phenols are more acidic than alcohols due to resonance stabilization of the phenoxide ion.
Step 2: Detailed Explanation:
Alcohols (like ethanol) are neutral or very weakly acidic (pKa ≈ 16). Phenols are more acidic (pKa ≈ 10). The presence of electron-withdrawing groups (like -NO2 at p-position) increases the acidity of phenol. Electron-donating groups (like -CH3 at p- or m-position) decrease the acidity of phenol. However, all phenols are still much stronger acids than ethanol. Therefore, ethanol is the weakest acid among the given options.
Step 3: Final Answer:
Ethanol is the weakest acid.
Acidity depends on the stability of the conjugate base. Phenols are more acidic than alcohols due to resonance stabilization of the phenoxide ion.
Step 2: Detailed Explanation:
Alcohols (like ethanol) are neutral or very weakly acidic (pKa ≈ 16). Phenols are more acidic (pKa ≈ 10). The presence of electron-withdrawing groups (like -NO2 at p-position) increases the acidity of phenol. Electron-donating groups (like -CH3 at p- or m-position) decrease the acidity of phenol. However, all phenols are still much stronger acids than ethanol. Therefore, ethanol is the weakest acid among the given options.
Step 3: Final Answer:
Ethanol is the weakest acid.
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