Place the following cations in order from the most negative to the least negative hydration enthalpy: Cs⁺,Na⁺,and Rb⁺. A) Cs⁺

Question

Place the following cations in order from the most negative to the least negative hydration enthalpy: Cs⁺,Na⁺,and Rb⁺. A) Cs⁺ < Rb⁺ < Na⁺ B) Cs⁺ < Na⁺ < Rb⁺ C) Na⁺ < Rb⁺ < Cs⁺ D) Na⁺ < Cs⁺ < Rb⁺ E) Rb⁺ < Na⁺ < Cs⁺

Quizplus · Accepted Answer

The hydration enthalpy increases with decreasing size of the cation. Among the given cations, Cs+ is the largest and therefore has the weakest bond with the water molecules, resulting in the least negative hydration enthalpy. On the other hand, Na+ is the smallest cation and has the strongest bond with the water molecules, resulting in the most negative hydration enthalpy. Therefore, the order of hydration enthalpies is Na+ > Rb+ > Cs+. Hence, the correct order is Na⁺ < Rb⁺ < Cs⁺.

Place the Following Cations in Order from the Most Negative