The solubilities of ionic compounds are affected by solute-solvent interactions, the common ion effect, temperature and molecular size.
1. Solute-solvent attractions : Strong solute -solvent attractions increase solubility of ionic compounds. Ionic compounds are most soluble in polar solvents like water, because the ions of the solid are strongly attracted to the polar solvent molecules.
2. Common ion Effect : Ionic compounds are less soluble in solvents that contain a common ion. For example, CaSO4 is slightly soluble in water.
If the water already Contains calcium ions or sulphate ions, the position of equilibrium moves to the left and the solubility decreases.
3. Temperature : Increasing the temperature usually increases the solubility of an ionic compound because the reaction is usually endothermic.
4. Molecular size : The larger the molecules of the solute, the larger is their molecular weight and their size. It is more difficult for solvent molecules to surround “bigger molecules. If all of the above mentioned factors are excluded, a general rule can be found that larger particles are generally less soluble. If the pressure and temperature are the same then out of two solutes of the same polarity, the one with smaller particles is usually more soluble.
