If you decrease the temperature of a solution what will happen to the rate of dissolution?

Answer 1

How temperature affects the rate of dissolution is dependent on whether the reaction is endothermic or exothermic.

Endothermic reactions: These reactions use heat during dissolution. The kinetic energy that is generated from heat is used to help break apart the molecules from the solid. Thus, when temperature is decreased, the dissolution rate decreases. An example would be sugar being dissolved in water. This dissolution reaction requires heat, and occurs much faster in boiling water than in room temperature water.

Exothermic reactions: These reactions give off heat energy during dissolution. When excess heat is already in the system, the reaction rate will adjust to maintain equilibrium (see Le Chatieler's principle). Thus, when temperature is decreased (less heat in the system), the dissolution rate increases. An example would be sodium hydroxide being dissolved in water. This dissolution reaction gives off heat. It dissolves much faster in ice cold water than in room temperature water.

Answer 2

That will depend on whether the dissolution process is endothermic or exothermic. Generally, decreasing the temperature will slow down the rate of dissolution. This is true for dissolutions that are endothermic.