1. Chemistry 130 Solubility equilibria Dr. John F. C. Turner 409 Buehler Hall jturner@ion.chem.utk.edu

2. Chemistry 130 Solubility and sparingly soluble salts Solubility is an important feature of geology, medicine and biology. Solubility is determined by the equilibrium between a solid and a solution of the solid in a liquid. For calcium oxalate, the equilibrium would be written as And the equilibrium constant is therefore Note that as solids have an invariant concentration

3. Chemistry 130 Solubility and sparingly soluble salts is the solubility product and is used for sparingly soluble salts. We only apply the solubility product for materials that are sparingly soluble because ● we know that there is only one equilibrium between the solute and the solid ● the solution is dilute and therefore we can easily apply thermodynamics to the problem The solubility product is related to the molar solubility by

4. Chemistry 130 Solubility and sparingly soluble salts The solubility product depends only on the ions in solution and is constant for a set of particular ions. Le Chatelier's principle applies and so if the concentration of one of the ions is increased, precipitation of the least soluble phase will occur.

5. Chemistry 130 Solubility and sparingly soluble salts Q. Calculate the molar solubility of calcium oxalate if

6. Chemistry 130 Solubility and sparingly soluble salts Q. Calculate the molar solubility of calcium oxalate if If 10 ml of a 0.1 M solution of sodium oxalate is added to this solution, what is the final of calcium ions in solution?

7. Chemistry 130 Solubility and sparingly soluble salts If the ion concentration product is greater than the solubility product, precipitation will take place. This is simply Le Chatelier's principle in action – we force the solubility equilibrium towards the solid by increasing the concentration of one of the ions in solution – the ions being the products of the equilibrium

8. Chemistry 130