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As the temperature increases, the solubility of a gas decreases. More gas is present in a solution with a lower temperature compared to a solution with a higher temperature. The reason for such variation is that increased temperature causes an increase in kinetic energy. The higher kinetic energy causes more motion in molecules which break intermolecular bonds andresulting in escape of gas molecules from solution.
The solubility of solids is dependent on the enthalpy of dissolution. When a solid dissolves in a liquid, a change in the physical state of the solid takes place. Heat is required to break the bonds holding the molecules in the solid together. At the same time, heat is given off during the formation of new solute - solvent bonds. Two clear cases may be identified:
CASE I: Decrease in solubility with temperature:
If the heat given off in the dissolving process is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic. The addition of more heat inhibits the dissolving reaction since excess heat is already being produced by the reaction. This situation is not very common, though where an increase in temperature produces a decrease in solubility.
CASE II: Increase in solubility with temperature:
If the heat given off in the dissolving reaction is less than the heat required to break apart the solid, the net dissolving reaction is endothermic. The addition of more heat facilitates the dissolving reaction by providing energy to break bonds in the solid. This is the most common situation where an increase in temperature produces an increase in solubility for solids.
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