ABSTRACT
Chemical thermodynamics is concerned primarily with the distribution and changes in the energy of the system. The values of enthalpy, entropy, and free energy are expressed in terms of heat units. Enthalpy is usually expressed relative to an arbitrary standard state or zero point. The standard free energy of a reaction is mathematically related to the equilibrium constant for the reaction. This allows the calculation of equilibrium constants from readily obtainable standard free-energy data. In order to be useful, the equilibrium constant must be corrected to the temperature of the water being examined. Solubility product is a special type of equilibrium constant that enables us to predict the concentration of ion released when a substance dissolves in water. The activity coefficient varies with: the ionic strength of the solution, the charge of the ion, the size of the ion, and the temperature.
