1 × 10−14 at 25 °C and 1 × 10−13 at 60 °C.
The CORRECT statement with respect to ΔH and ΔS is:
Thermodynamic Nature of Ionic Product of Water (Kw) with Temperature
The ionic product of water (Kw) represents the extent of auto-ionization of water.
Its variation with temperature provides important information about the
enthalpy change (ΔH) and entropy change (ΔS)
of the reaction.
Correct Answer
Option (C): ΔH is positive and ΔS is negative
Thermodynamic Explanation
Auto-ionization of Water
H2O (l) ⇌ H+ (aq) + OH− (aq)
Enthalpy Change (ΔH)
Since the value of Kw increases with temperature,
the forward reaction is favored at higher temperature.
This indicates that the reaction is endothermic.
Therefore, ΔH > 0.
Entropy Change (ΔS)
The formation of hydrated H+ and OH− ions
causes increased ordering of surrounding water molecules.
This results in a net decrease in randomness.
Therefore, ΔS < 0.
Final Conclusion
The increase in ionic product of water with temperature shows that
the auto-ionization of water is an endothermic process
accompanied by a decrease in entropy.
Final Answer
Correct Option: (C) ΔH is positive and ΔS is negative
