Question

What is the effect of temperature on solubility of solids in water? Give examples.

Answer 1

1. The effect of temperature on solubility of a substance depends on enthalpy of solution.

a. When the substance dissolves in water by an endothermic process, that is, with the absorption of heat, its solubility increases with an increase of temperature.
e.g. KCl dissolve in water by endothermic process.

b. On the other hand, when the substance dissolves in water by an exothermic process, that is, with the release of heat, its solubility decreases with an increase of temperature.
e.g. CaCl₂ and Li₂SO₄.H₂O dissolve in water releasing heat.

2. It is important to understand that there is no direct correlation between solubility and exothermicity or endothermicity. For example, dissolution of CaCl₂ in water is exothermic and that of NH₄NO₃ is endothermic. However, the solubility of these substances increases with the temperature