In electrochemical systems, Gibbs energy change (∆G) and cell potential (Ecell) are closely related thermodynamic quantities that describe the feasibility and direction of an electrochemical reaction. Gibbs energy provides a measure of the maximum useful non-expansion work that a system can perform at constant temperature and pressure, whereas cell potential represents the electrical driving force associated with the movement of electrons between the electrodes. The relationship between these quantities provides an important theoretical foundation for understanding spontaneity, equilibrium, and the operation of electrochemical cells. Gibbs free energy is defined as [ G = H - TS ] where G is Gibbs free energy, H is enthalpy, T is absolute temperature, and S is entropy. For a chemical reaction, the Gibbs energy change is expressed as [ \Delta G = \Delta H - T\Delta S ] under constant temperature and pressure. The value of ∆G indicates whether a reaction is thermodynamically favorable. A negative value of ∆G indicates that the reaction can proceed spontaneously in the forward direction, while a positive value indicates that the forward reaction is non-spontaneous under the specified conditions. When ∆G is zero, the system is at thermodynamic equilibrium. In an electrochemical cell, a chemical reaction involves the transfer of electrons from one species to another. The oxidation process occurs at the anode, while reduction occurs at the cathode. The difference in electrical potential between these two electrodes is called the cell potential or electromotive force (Ecell). When the cell operates reversibly, this potential is directly related to the maximum electrical work obtainable from the reaction. The electrical work associated with the transfer of electrons can be expressed as [ W_{\text{electrical}} = -nFE_{\text{cell}} ] where n is the number of moles of electrons transferred in the balanced electrochemical reaction, F is the Faraday constant, approximately 96485 C mol⁻¹, and Ecell is the cell potential in volts. The negative sign is associated with the convention that work done by the system is negative in thermodynamics. For a reversible electrochemical cell operating at constant temperature and pressure, the maximum useful non-expansion work is equal to the decrease in Gibbs energy. Therefore, [ \Delta G = -nFE_{\text{cell}} ] This is the fundamental relationship between Gibbs energy change and cell potential. It shows that Gibbs energy and cell potential contain equivalent information about the thermodynamic driving force of an electrochemical reaction. If the cell potential is positive, ∆G is negative, indicating a spontaneous electrochemical reaction under the specified conditions. Conversely, if Ecell is negative, ∆G is positive and the reaction is non-spontaneous in the direction written. The relationship can be understood by considering the movement of electrons in an electrochemical cell. A spontaneous reaction causes electrons to flow from the electrode where oxidation occurs toward the electrode where reduction occurs through an external circuit. This flow of electrons generates