The pK_hw for the autodeuterolysis of heavy water, D₂O (the analog of autoprotolysis, but involving the transfer of a deuteron), is 13.83 at 30.°C. Assuming ΔH_r° for this reaction to be independent of temperature and using information from Exercise 6.17, calculate ΔS_r° for the autodeuterolysis reaction. Suggest an interpretation of the sign. Suggest a reason why the autodeuterolysis constant of heavy water differs from the autoprotolysis constant of ordinary water.

Exercise 6.17

The autoprotolysis constant, K_hw, for heavy water, D₂O, at 25°C is 1.35 * 10^–15.