Oxygen is more electronegative than sulphur, yet is acidic in nature while is neutral because: — p Block Elements Chemistry Question

💡 Solution & Explanation

I need to explain why $H_2S$ is acidic while $H_2O$ is neutral, despite oxygen being more electronegative than sulfur. **Step 1: Understand acidity in terms of ionization** For a compound $H_2X$ to be acidic, it must ionize: $H_2X \rightarrow H^+ + HX^-$ The ease of this ionization depends on: - Bond strength (H-X bond) - Stability of the conjugate base ($HX^-$) **Step 2: Compare H-O vs H-S bond strength** - H-O bond: Very strong (~467 kJ/mol) - H-S bond: Much weaker (~366 kJ/mol) Weaker bonds are easier to break, so $H_2S$ more readily releases $H^+$ than $H_2O$. **Step 3: Consider conjugate base stability** - $OH^-$ (conjugate base of $H_2O$): Extremely stable due to high electronegativity of O - $HS^-$ (conjugate base of $H_2S$): Less stable than $OH^-$, but S is larger and can better accommodate negative charge through its larger electron cloud **Step 4: The key factor—Bond strength dominates** Although oxygen's higher electronegativity makes $OH^-$ more stable than $HS^-$, the **much weaker H-S bond** compensates. The ease of H-S bond breaking outweighs the stability difference of conjugate bases. **Conclusion:** $H_2S$ is acidic because the weak H-S bond readily breaks to release $H^+$, while the very strong H-O bond in $H_2O$ resists ionization, keeping it neutral. *The correct answer (C) likely states: "Because H-S bond is weaker than H-O bond" or similar*