See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Each Reaction **(A) Phenol + Sodium phenoxide** Phenol is weakly acidic ($K_a \approx 10^{-10}$), while phenoxide ion is a strong conjugate base. No acid-base reaction occurs between them—they cannot protonate each other. **Not possible.** **(B) Pyruvic acid + Sodium formate** Pyruvic acid ($pK_a \approx 2.5$) is much stronger than formic acid ($pK_a \approx 3.75$). The stronger acid (pyruvic acid) cannot be deprotonated by the conjugate base of a weaker acid (formate). The equilibrium lies left. **Not possible.** **(C) Benzenesulfonic acid sodium salt + Benzoic acid** Benzenesulfonic acid ($pK_a \approx -2$) is a strong sulfonic acid, much stronger than benzoic acid ($pK_a \approx 4.2$). The weaker benzoic acid cannot protonate the sulfonate anion. **Not possible.** **(D) Sodium acetylide + Water** $$\ce{H-C≡C-Na + H2O \rightarrow H-C≡C-H + NaOH}$$ Acetylide ion ($\ce{HC≡C^-}$) is an extremely strong conjugate base (conjugate acid has $pK_a \approx 25$). Water is a weak acid ($pK_a = 15.7$). The stronger base (acetylide) readily deprotonates water to form acetylene and hydroxide. **Reaction is highly favorable.** ✓ **The answer is (D).**