In electrochemistry, a galvanic cell is a device in which chemical energy is converted to electrical energy. In a galvanic cell, a redox reaction is split into two oxidation/reduction half-reactions split across two containers, connected by a metal wire (where electrons flow) and a salt bridge to allow ion flow and maintain neutral charge.
Both containers contain one redox half-reaction each:
- oxidation at the anode (where electrons flow into)
- reduction at the cathode (where electrons flow out)
To collect energy from the overall reaction, we split the reaction in half by placing the reactants of the half reactions in two separate cells. The oxidizing agent (reduction reactant) pulls electrons through a wire from the reducing agent (oxidation reactant) in another compartment of the galvanic cell, thus causing an potential difference or electromotive force (voltage) and can be harvested as electricity. This pull is called the cell potential of this galvanic cell. If the cell is running in the spontaneous direction, then .
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Labeling galvanic cells
- Put anode left and cathode right (“A comes before C”). This is not required but is easier to remember. Electrons flow from anode to cathode (“ACE”, ends up at the cathode site)
- Draw a salt bridge.
- Label: anode, cathode, solids species of electrodes, redox reactant ions, soluble ions (e.g. ) in salt bridge, salt bridge anion flows to anode and cation to cathode, and the flow of electrons (anode to cathode; make sure this flow produces a positive cell potential)
- If the problem attach phase to species, do the same in the labels.