Final answer:
The Nernst equation predicts the cell potential under non-standard conditions based on reactant and product concentrations, playing a fundamental role in determining the equilibrium potential of specific ions and understanding various electrochemical systems.
Step-by-step explanation:
The Nernst Equation and Equilibrium Potential
The Nernst equation is a fundamental relationship in electrochemistry that predicts the cell potential (or electromotive force) of an electrochemical cell under non-standard conditions. It defines how the potential of a redox system deviates from its standard state value based on the concentrations of reactants and products involved in the redox reaction—denoted by the reaction quotient (Q). This equation is integral for understanding the equilibrium potential of a specific ion across a membrane or within an electrochemical cell.
At equilibrium, the free-energy change for the reaction (ΔG) is zero because there is no net transfer of electrons, meaning the cell potential (Ecell) is also zero. The reaction quotient (Q) at equilibrium becomes the equilibrium constant (K), reflecting equal concentrations of the reactants and products. When applied to a galvanic cell, the Nernst equation can also aid in measuring the solubility product of a sparingly soluble substance or calculating the concentration of a species given a measured potential.
Concentration cells are a particular application of the Nernst equation in which the anode and cathode compartments are identical except for their reactant concentrations. At equilibrium, the concentrations are equal, resulting in a measured potential of zero. This illustrates the 'equilibrium' condition as referenced in the equation, where no net reaction is occurring, and the system is stable.