Question

$\textbf{Match List I with List II}$
$\begin{array}{|c|c|c|} \hline \text{List I (Compound)} & \text{List II (p}K_a\text{ value)} \\ \hline \text{A. Ethanol} & \text{I. } 10.0 \\ \text{B. Phenol} & \text{II. } 15.9 \\ \text{C. m-Nitrophenol} & \text{III. } 7.1 \\ \text{D. p-Nitrophenol} & \text{IV. } 8.3 \\ \hline \end{array}$
$\text{Choose the correct answer from the options given below :-}$

• A. A-I, B-II, C-III, D-IV
• B. A-IV, B-I, C-II, D-III
• C. A-III, B-IV, C-I, D-II
• D. A-II, B-I, C-IV, D-III

Answer 1

The Correct Option is D

To solve the question, we need to match the given compounds in List I with their respective \(pK_a\) values in List II. The \(pK_a\) value is a measure of the acidity of a compound; a lower value indicates stronger acidity.

1.  Understanding the Compounds and their Acidity:
   • Ethanol: Ethanol is a simple alcohol and relatively weaker acid compared to phenols. It generally has a higher \(pK_a\) value.
   • Phenol: Phenol is more acidic than ethanol due to the resonance stabilization of the phenoxide ion formed after losing a proton. It typically has a lower \(pK_a\) value compared to ethanol.
   • m-Nitrophenol and p-Nitrophenol: Both of these compounds are nitrophenol derivatives, where the nitro group, an electron-withdrawing group, increases the acidity further. Among nitrophenols, the para derivative typically has a lower \(pK_a\) due to stronger electron-withdrawing effects.
2. Matching the \(pK_a\) Values:
   • Ethanol: The \(pK_a\) value for ethanol is around 15.9.
   • Phenol: Typically, the \(pK_a\) value for phenol is around 10.0.
   • m-Nitrophenol: The \(pK_a\) value for m-nitrophenol is around 8.3.
   • p-Nitrophenol: The \(pK_a\) value for p-nitrophenol is around 7.1.
3. Conclusion: Based on the above analysis, we can match the compounds with their respective \(pK_a\) values:
   • A. Ethanol - II. 15.9
   • B. Phenol - I. 10.0
   • C. m-Nitrophenol - IV. 8.3
   • D. p-Nitrophenol - III. 7.1

Answer 2

The correct matching is as follows:  

- A. Ethanol has a \( pK \) value of 15.9, so \( A - II \).  
- B. Phenol has a \( pK \) value of 10.0, so \( B - I \).  
- C. \( m \)-Nitrophenol has a \( pK \) value of 8.3, so \( C - IV \).  
- D. \( p \)-Nitrophenol has a \( pK \) value of 7.1, so \( D - III \).  

Hence, the correct matching is \( A - II, B - I, C - IV, D - III \).

The Correct Answer is: A-II, B-I, C-IV, D-III