Final answer:
The Nernst equation is used to calculate the theoretical equilibrium potential of an ion, relating cell potential to reactant and product concentrations in redox reactions.
Step-by-step explanation:
The Nernst equation is used to calculate the theoretical equilibrium potential of an ion. This important equation relates the cell potential to the concentrations of the reactants and products in a redox reaction. By knowing the standard electrode potential, the temperature, the number of electrons transferred, and the concentrations of the ionic species involved in the redox reaction, the Nernst equation allows you to determine the actual cell potential under non-standard conditions.
While it can also be utilized to calculate the concentration of a species given a measured potential (and knowing the concentrations of all other species), its primary function is to ascertain the equilibrium potential. The equation is not directly used for calculating membrane permeability to an ion, nor for determining the osmolality of a solution.