NaCl (Sodium Chloride):
* Endothermic Dissolution: When NaCl dissolves in water, the process is slightly endothermic, meaning it absorbs a small amount of heat from the surroundings.
* Le Chatelier's Principle: According to Le Chatelier's Principle, if you increase the temperature of a system in equilibrium, the system will shift in the direction that absorbs heat. So, increasing the temperature of a NaCl solution favors the dissolution of more NaCl to absorb the added heat.
* Negligible Change: The enthalpy change for dissolving NaCl is small, so the effect of temperature on its solubility is also small. This is why NaCl's solubility changes only slightly with temperature.
Na₂SO₄ (Sodium Sulfate):
* Exothermic Dissolution: When Na₂SO₄ dissolves in water, the process is exothermic, meaning it releases heat to the surroundings.
* Le Chatelier's Principle: Increasing the temperature of a Na₂SO₄ solution favors the reverse reaction (precipitation of Na₂SO₄) to release heat and counteract the temperature increase.
* Decreasing Solubility: This means that as the temperature increases, the solubility of Na₂SO₄ actually decreases.
In summary:
* The solubility of a salt is influenced by the enthalpy change of its dissolution.
* Endothermic dissolutions are favored by higher temperatures, leading to increased solubility.
* Exothermic dissolutions are favored by lower temperatures, leading to decreased solubility.
Note: There are other factors that can affect solubility, such as the presence of other ions in the solution, pressure, and the specific crystalline form of the salt.
