Dissolution is a process in chemistry where a solute in gaseous, liquid, or solid phase dissolves in a solvent to form a solution/09%3A_Solutions/9.03%3A_The_Dissolution_Process). Solubility is the maximum concentration of a solute that can dissolve in a solvent at a given temperature. The units of solubility can be provided in mol/L or g/L. Factors that affect solubility include the concentration of the solute, the temperature of the system, pressure (for gases in solution), and the polarity of the solute and the solvent.
The rate of dissolution is represented by the Noyes-Whitney equation: dm/dt = DA(Cs - C)/h, where dm/dt represents the rate of dissolution, D represents the diffusion coefficient for the compound, A represents the surface area available for dissolution, Cs represents the solubility of the compound, C represents the solute concentration in bulk solution at time t, and h represents the thickness of the dissolution layer.
When a solute dissolves, its individual particles are surrounded by solvent molecules and are separated from each other/09%3A_Solutions/9.03%3A_The_Dissolution_Process). The interactions between the solute particles and the solvent particles are so strong that the individual solute particles separate from each other and, surrounded by solvent molecules, enter the solution/09%3A_Solutions/9.03%3A_The_Dissolution_Process). This process is called solvation, and it is illustrated in Figure 1 of/09%3A_Solutions/9.03%3A_The_Dissolution_Process). When the solvent is water, the word hydration, rather than solvation, is used/09%3A_Solutions/9.03%3A_The_Dissolution_Process).
Three types of intermolecular attractive forces are relevant to the dissolution process: solute-solute, solvent-solvent, and solute-solvent. The formation of a solution may be viewed as a stepwise process in which energy is consumed to overcome solute-solute and solvent-solvent attractions (endothermic processes) and released when solute-solvent attractions are established (an exothermic process referred to as solvation) . The relative magnitudes of the energy changes associated with these stepwise processes determine whether a solution will form or not.
