Solubility equilibrium

The solubility equilibrium (also: solution equilibrium) describes the thermodynamic equilibrium between sediment and a saturated solution .

In the case of saturated solutions , a few examples can be used to directly show that a constant exchange of substances takes place even in equilibrium, i.e. that particles of the soil body go into solution, but also that particles from the solution pass into the soil body (crystallization). So there is a dynamic equilibrium in which the dissolution rate is equal to the crystallization rate. The sediment and the saturated solution form a heterogeneous system .

With the help of the principle of least constraint, it can be predicted how the solubility equilibrium depends on the temperature :

• If the dissolution process is exothermic , the solubility decreases with increasing temperature.
• If the dissolution process is endothermic , the solubility increases with an increase in temperature.

The solubility equilibrium can be disturbed by substances that react with the dissolved particles (for example: addition of oxonium ions to the solution of a hydroxide ). A new equilibrium is then established.

literature

• Chemistry secondary level II - physical chemistry - chemistry and environment, people and knowledge, Berlin 1995, 1st edition