All interfaces between component phases are represented by vertical parallel lines if two or more components are present in the same phase, their formulas are separated by commas.The relevant components of each half-cell are represented by their chemical formulas or element symbols.These symbolic representations are called cell notations or cell schematics, and they are written following a few guidelines: Cell NotationĪbbreviated symbolism is commonly used to represent a galvanic cell by providing essential information on its composition and structure. Increasing concentrations of Cu 2+ in the anode half-cell are balanced by an influx of NO 3 − from the salt bridge, while a flow of Na + into the cathode half-cell compensates for the decreasing Ag + concentration.įigure 17.3 A galvanic cell based on the spontaneous reaction between copper and silver(I) ions. The spontaneous reaction in this cell produces Cu 2+ cations in the anode half-cell and consumes Ag + ions in the cathode half-cell, resulting in a compensatory flow of inert ions from the salt bridge that maintains charge balance. To keep the reactants separate while maintaining charge-balance, the two half-cell solutions are connected by a tube filled with inert electrolyte solution called a salt bridge. The redox reactions in a galvanic cell occur only at the interface between each half-cell’s reaction mixture and its electrode. By definition, the anode of an electrochemical cell is the electrode at which oxidation occurs (in this case, the Cu foil) and the cathode is the electrode where reduction occurs (the Ag foil). An external circuit is connected to each half-cell at its solid foil, meaning the Cu and Ag foil each function as an electrode. The right half-cell contains the Ag(I)/Ag(0) couple as solid silver foil and an aqueous silver nitrate solution. The half-cell shown at the left contains the Cu(0)/Cu(II) couple in the form of a solid copper foil and an aqueous solution of copper nitrate. The cell is comprised of two half-cells, each containing the redox conjugate pair (“couple”) of a single reactant. Devices of this sort are generally referred to as electrochemical cells, and those in which a spontaneous redox reaction takes place are called galvanic cells (or voltaic cells).Ī galvanic cell based on the spontaneous reaction between copper and silver(I) is depicted in Figure 17.3. Direct transfer of electrons is, therefore, prevented transfer, instead, takes place indirectly through an external circuit that contacts the separated reactants.

Overall reaction: Cu ( s ) + 2 Ag + ( a q ) ⟶ Cu 2 + ( a q ) + 2 Ag ( s ) oxidation half-reaction: Cu ( s ) ⟶ Cu 2+ ( a q ) + 2 e − reduction half-reaction: 2 Ag + ( a q ) + 2 e − ⟶ 2 Ag ( s ) overall reaction: Cu ( s ) + 2 Ag + ( a q ) ⟶ Cu 2 + ( a q ) + 2 Ag ( s ) oxidation half-reaction: Cu ( s ) ⟶ Cu 2+ ( a q ) + 2 e − reduction half-reaction: 2 Ag + ( a q ) + 2 e − ⟶ 2 Ag ( s )Ĭonsider the construction of a device that contains all the reactants and products of a redox system like the one here, but prevents physical contact between the reactants.

Copper cathode redox