General Chemistry
In Galvanic Cells, also known as Voltaic Cells, oxidation and reduction reactions take place to generate a flow of electrons, creating electricity. These electrochemical cells consist of two compartments called half-cells, each containing an electrolyte and an electrode. The negatively charged electrode, known as the anode, is where oxidation occurs, while the positively charged electrode, called the cathode, is the site of reduction. Electrons travel from the anode to the cathode through a conductive material, generating a positive electromotive force (EMF).
A salt bridge connects the two half-cells, balancing the shifting charges caused by the movement of electrons. Anions are drawn to the anode, while cations are drawn to the cathode. The accumulation of cations on the cathode is called plating. Concentration cells are a type of Galvanic cell that use a concentration gradient between two identical electrodes to drive electron movement. Lastly, cell notation describes the oxidation and reduction reactions occurring in an electrochemical cell, allowing for detailed descriptions without the need for an extensive image.
Lesson Outline
<ul> <li>Introduction to Galvanic Cells</li> <ul> <li>Electrochemical cells: enclosed systems generating electricity</li> <li>Also known as voltaic cells or batteries</li> </ul> <li>Components of Galvanic Cells</li> <ul> <li>Two half-cells: anode and cathode</li> <li>Anode: negatively charged, site of oxidation</li> <li>Cathode: positively charged, site of reduction</li> <li>Electrodes: solid conductors carrying electrons</li> <li>Electrolytes: liquid solutions containing ions</li> <li>Conductive wire connecting the electrodes</li> </ul> <li>Electron Flow and Current</li> <ul> <li>Electrons flow from anode to cathode</li> <li>Current moves opposite the direction of electrons</li> </ul> <li>Salt Bridge</li> <ul> <li>Connects the two half-cells</li> <li>Balance charges by moving anions and cations</li> </ul> <li>Plating</li> <ul> <li>Accumulation of cations on the cathode</li> <li>Increases cathode size over time</li> </ul> <li>Spontaneity and Gibbs Free Energy</li> <ul> <li>Redox reactions in Galvanic cells are spontaneous</li> <li>Negative change in Gibbs free energy</li> </ul> <li>Electromotive Force (EMF)</li> <ul> <li>Difference in electrical potential between half-cells</li> <li>Positive EMF in Galvanic cells</li> </ul> <li>Concentration Cells</li> <ul> <li>Type of galvanic cell</li> <li>Based on concentration gradient between half-cells</li> <li>Identical electrodes</li> </ul> <li>Cell Notation</li> <ul> <li>Describes oxidation and reduction reactions</li> <li>Single lines separate phases</li> <li>Double lines represent salt bridge</li> <li>Concentrations indicated in parentheses</li> </ul> </ul>
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FAQs
Galvanic cells are a type of electrochemical cells. While the term "electrochemical cells" refers to a wide range of devices that convert chemical energy into electrical energy, or vice versa, "galvanic cells" specifically refers to devices that convert chemical energy into electrical energy. Galvanic cells are also commonly known as "voltaic cells". Another type of electrochemical cells is electrolytic cells, which perform an opposite function to galvanic cells, converting electrical energy to chemical energy.
In a galvanic cell, oxidation and reduction are the redox (reduction-oxidation) reactions that occur at the anode and cathode respectively. Oxidation is the process of losing electrons and occurs at the anode where a negative electrode potential is generated. Reduction, on the other hand, is the process of gaining electrons and occurs at the cathode where a positive electrode potential is generated. The flow of electrons from the anode to the cathode through the conductive wire determines the electrical current produced by the galvanic cell.
A salt bridge is an essential component of a galvanic cell, as it is responsible for maintaining electrical neutrality by allowing the flow of ions between the anode and cathode compartments. Without a salt bridge, the buildup of positive charge at the anode and negative charge at the cathode would prevent the flow of electrons through the conductive wire, resulting in the cessation of the redox reaction and current flow. The salt bridge facilitates the movement of ions, counterbalancing the charges and allowing the electrochemical reaction to proceed.
Concentration cells are a special type of galvanic cells where the electrodes are made of the same material, and the generated voltage stems from a difference in ion concentration between the two half-cells. In a typical galvanic cell, the electrodes are different materials with different redox potentials, and the generated voltage is due to the difference in these potentials. Concentration cells ultimately reach equilibrium as the ion concentrations equalize, thus stopping the flow of electrons and current production.
