Which of the following compounds has a negative enthalpy of solution? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: The enthalpy of solution is given by: delta_H_sol = delta_H_lattice + delta_H_hyd. Step 2: For potassium halides, as we go down the group from F^- to I^-, the size of the halide increases, causing both lattice energy and hydration energy of the salt to decrease. Step 3: For Potassium Fluoride (KF), the small size of the fluoride ion (F^-) leads to highly exothermic hydration. The hydration energy of KF exceeds its lattice energy, resulting in a net negative (exothermic) enthalpy of solution, which corresponds to option (c).