What happens to the solubility product (Ks) if the temperature decreases?

When considering the solubility product (Ksp) and its relationship with temperature, it is important to recognize that Ksp is equilibrium constant specific to solubility equilibria, and its value can change with temperature. For most salts, especially those that dissolve endothermically (where the dissolution process absorbs heat), a decrease in temperature results in a decrease in solubility. Consequently, this reduction in solubility leads to a decrease in the Ksp value.

In contrast, salts that dissolve exothermically typically exhibit an increase in solubility with an increase in temperature, which corresponds to an increase in Ksp. Therefore, for most salts that dissociate in the presence of water and absorb heat, cooling the system reduces their solubility and thereby causes their Ksp value to decrease.

Thus, the correct choice conveys the expected behavior of the solubility product as the temperature changes, reflecting how endothermic dissolution processes are impacted by temperature adjustments in the system.