Inverse Solubility of Solid Solutes

[Misha Kuznetsov]

Why is the solubility of some solids lower when the solution is heated? I read that it is because the process is exothermic (heat from breakdown is greater than the heat needed for breakdown). But why would having extra heat from outside sources inhibit the dissolving process, wouldn't it only help it?

My source: http://www.chem.fsu.edu/chemlab/chm1046course/solubility.html

-Misha

 

[Borek]

Dissolution can be speed up by the increasing temperature, but the solubility doesn't have to grow. Think in terms of Le Chatelier's principle.

 

[Bystander]

The other thing you'll want to examine is the temperature dependence of the equilibrium constant for the solution process.

 

[Quantum Defect]

Why is the solubility of some solids lower when the solution is heated? I read that it is because the process is exothermic (heat from breakdown is greater than the heat needed for breakdown). But why would having extra heat from outside sources inhibit the dissolving process, wouldn't it only help it?

My source: http://www.chem.fsu.edu/chemlab/chm1046course/solubility.html

-Misha

As Borek noted think about this in terms of Le Chatelier:

solid + H2O --> solute + heat (exothermic) ---> Increasing T will reduce solubility

solid + H2O + heat ---> solute (endothermic) --> Increasing heat will increase solubility

Interestingly, gases typically have reduced solubility in water with increasing temperature -- one reason why warm soda tastes bad...