The solubility of a given solute in a given solvent is given by the total amount of the solute that can be dissolved in the solvent at equilibrium. On the other hand, the solubility product constant is an expression, an equilibrium constant that provides the information at the equilibrium between the solute and the constituent ions that it dissociated into inside the solution. It is important to determine the concentration of the solute in the solvent when a substance has been dissolved to determine how much more can be dissolved in the solvent.