Concentration cell

A galvanic cell whose voltage arises from differences in the activities of the same chemical species in its two half-cells.

Nernst equation: An equation relating electrode potential to chemical activities, temperature, and electron-transfer stoichiometry. It quantifies how unequal activities of the same species generate the cell’s potential.
Chemical activity: An effective concentration that accounts for non-ideal interactions in a chemical system. The cell responds to activity differences, which can diverge from measured concentration differences.
Electrode concentration cell: A concentration cell whose voltage comes from differences in composition or pressure between otherwise matching electrodes. It places the concentration difference in the electrode materials rather than solely in the electrolytes.
Galvanic cell: An electrochemical cell that produces electrical energy from a spontaneous chemical reaction. Concentration cells are galvanic cells whose net driving force is species equalization.
Potentiometry: An electroanalytical method that determines chemical information from voltage measured under negligible current. Concentration-cell principles underpin voltage-based measurements of solution composition.
Chemical potential: A thermodynamic measure of how a system’s Gibbs energy changes when the amount of a substance changes. The activity difference creates a chemical-potential gradient that drives charge separation.
Oxidation-reduction reaction: A chemical reaction involving electron transfer and changes in oxidation states. Electrode oxidation and reduction convert the chemical driving force into electrical current.
Electrolyte concentration cell: A concentration cell whose matching electrodes contact electrolytes with different activities of a shared ion. It is the standard solution-based form of the concentration cell.
Electrolytic cell: An electrochemical cell that uses an external electrical source to drive a nonspontaneous chemical reaction. It consumes electrical work, whereas a galvanic concentration cell can deliver it spontaneously.
Ion-selective electrode: An electrode whose potential responds selectively to the activity of a particular ion in solution. Its response converts an ion-activity difference across a membrane into a measurable potential.

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ElectrochemistryBroader topic: It shows that a concentration gradient alone can generate cell voltage.