Cell potential

Definition

Cell potential is the measure of the electrical energy difference between two electrodes in an electrochemical cell, typically expressed in volts. It indicates the tendency of a chemical reaction to occur and determines the direction of electron flow in the cell. A higher cell potential means a greater driving force for the reaction, making it more spontaneous.

5 Must Know Facts For Your Next Test

1. Cell potential can be calculated using standard reduction potentials found in tables; the overall cell potential is the difference between the reduction potential of the cathode and the anode.
2. If the cell potential is positive, the reaction is spontaneous; if it's negative, the reaction is non-spontaneous.
3. Standard cell potential is measured under standard conditions: 1 M concentration for solutions, 1 atm pressure for gases, and at a temperature of 25°C (298 K).
4. In galvanic cells, oxidation occurs at the anode, while reduction happens at the cathode; this flow of electrons from anode to cathode generates electrical energy.
5. The Nernst Equation allows you to calculate how changes in concentration affect cell potential, showing that cell potential decreases as reactant concentration diminishes or product concentration increases.

Review Questions

• How do you calculate cell potential using standard reduction potentials?
  • To calculate cell potential, you first need to identify the half-reactions for both oxidation and reduction processes. You then look up their standard reduction potentials (E°) from a table. The overall cell potential is determined by subtracting the standard reduction potential of the anode from that of the cathode: E°cell = E°cathode - E°anode. This value indicates whether the overall reaction is spontaneous or not.
• Discuss the significance of a positive cell potential in an electrochemical cell.
  • A positive cell potential signifies that the reaction occurring within the electrochemical cell is spontaneous, meaning it can proceed without external energy input. This is crucial because it implies that electrical energy can be generated from chemical reactions. In practical applications, batteries are designed to have positive cell potentials so they can efficiently provide power for various devices.
• Evaluate how changes in concentration affect cell potential based on the Nernst Equation.
  • The Nernst Equation illustrates that as the concentrations of reactants and products change, so does the cell potential. Specifically, if the concentration of reactants decreases or products increases, the spontaneity of a reaction may diminish, resulting in a lower cell potential. By using this equation, one can quantitatively predict how shifting conditions influence the electrochemical behavior, which has important implications for optimizing battery performance and other electrochemical applications.

Related terms

Electrochemical Cell: A device that converts chemical energy into electrical energy through redox reactions, consisting of two electrodes immersed in an electrolyte.

Standard Reduction Potential:

The measure of the tendency of a chemical species to be reduced, measured under standard conditions, usually denoted as E°.

Nernst Equation:

An equation that relates the cell potential to the concentrations of reactants and products, allowing for the calculation of cell potential under non-standard conditions.