9.8 Galvanic (Voltaic) and Electrolytic Cells

Explain the relationship between the physical components of an electrochemical cell and the overall operational principles of the cell.

• Each component of an electrochemical cell (electrodes, solutions in the half-cells, salt bridge, voltage/current measuring device) plays a specific role in the overall functioning of the cell. The operational characteristics of the cell (galvanic vs. electrolytic, direction of electron flow, reactions occurring in each half-cell, change in electrode mass, evolution of a gas at an electrode, ion flow through the salt bridge) can be described at both the macroscopic and particulate levels.
• Galvanic, sometimes called voltaic, cells involve a thermodynamically favored reaction, whereas electrolytic cells involve a thermodynamically unfavored reaction. Visual representations of galvanic and electrolytic cells are tools of analysis to identify where half-reactions occur and in what direction current flows.
• For all electrochemical cells, oxidation occurs at the anode and reduction occurs at the cathode.
  • Exclusion: Labeling an electrode as positive or negative will not be assessed on the AP Exam.