See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Acid Strength Order **Step 1: Identify the structures** - **I:** $p$-Nitrobenzoic acid ($NO_2$ group at para position) - **II:** $p$-Methoxybenzoic acid ($OCH_3$ group at para position) - **III:** Benzoic acid (unsubstituted) **Step 2: Apply substituent effects on acid strength** Acid strength depends on the stability of the conjugate base (carboxylate anion, $COO^-$). **Step 3: Analyze each substituent** - **Nitro group ($NO_2$):** Strongly **electron-withdrawing** (via inductive and resonance effects) - Stabilizes $COO^-$ by delocalizing negative charge - **Increases** acid strength significantly - **Methoxy group ($OCH_3$):** **Electron-donating** (via resonance) - Destabilizes $COO^-$ by pushing electron density toward it - **Decreases** acid strength - **Unsubstituted:** Reference baseline **Step 4: Rank acid strength** $$\text{Acid strength: } I > III > II$$ The nitro-substituted acid is strongest, unsubstituted is intermediate, and methoxy-substituted is weakest. **Answer: (C)** $I > III > II$