E^°_{cell}

Definition

E^°_{cell}, also known as the standard cell potential or standard reduction potential, is a fundamental concept in electrochemistry that quantifies the ability of a redox reaction to produce an electric potential or voltage. It represents the potential difference between the standard reduction potentials of the cathode and anode half-reactions in an electrochemical cell under standard conditions.

5 Must Know Facts For Your Next Test

1. The standard cell potential, E^°_{cell}, is the difference between the standard reduction potentials of the cathode and anode half-reactions.
2. E^°_{cell} is used to determine the spontaneity and feasibility of a redox reaction, as well as the maximum potential energy that can be extracted from the reaction.
3. The sign of E^°_{cell} indicates whether the reaction is spontaneous (positive) or non-spontaneous (negative).
4. The magnitude of E^°_{cell} is related to the free energy change (ΔG^°) and equilibrium constant (K) of the reaction.
5. E^°_{cell} values are tabulated for many half-reactions and can be used to construct electrochemical series, which rank the reducing and oxidizing strengths of species.

Review Questions

• Explain how the standard cell potential, E^°_{cell}, is calculated and its relationship to the standard reduction potentials of the half-reactions.
  • The standard cell potential, E^°_{cell}, is calculated as the difference between the standard reduction potentials of the cathode and anode half-reactions under standard conditions (25°C, 1 atm pressure, and 1 M concentrations of all species). Specifically, E^°_{cell} = E^°_cathode - E^°_anode. This difference in reduction potentials represents the driving force for the overall redox reaction and determines the spontaneity and maximum potential energy that can be extracted from the cell.
• Describe how the sign and magnitude of E^°_{cell} can be used to predict the feasibility and spontaneity of a redox reaction.
  • The sign of E^°_{cell} indicates the spontaneity of the redox reaction. If E^°_{cell} is positive, the reaction is spontaneous and will occur naturally. If E^°_{cell} is negative, the reaction is non-spontaneous and will not occur naturally. The magnitude of E^°_{cell} is related to the free energy change (ΔG^°) and equilibrium constant (K) of the reaction through the equations: ΔG^° = -nFE^°_{cell} and K = e^{nFE^°_{cell}/RT}, where n is the number of electrons transferred, F is Faraday's constant, R is the universal gas constant, and T is the absolute temperature. The larger the magnitude of E^°_{cell}, the more favorable and spontaneous the reaction will be.
• Explain how E^°_{cell} values can be used to construct electrochemical series and discuss the significance of these series in predicting the relative strengths of oxidizing and reducing agents.
  • E^°_{cell} values can be tabulated for various half-reactions and used to construct electrochemical series, also known as activity series or reactivity series. These series rank the reducing and oxidizing strengths of different species based on their standard reduction potentials. The more positive the reduction potential, the stronger the oxidizing agent. Conversely, the more negative the reduction potential, the stronger the reducing agent. Electrochemical series are crucial in predicting the spontaneity and feasibility of redox reactions, as well as the relative tendencies of species to undergo oxidation or reduction. They provide a framework for understanding and predicting the behavior of chemical species in electrochemical processes.

Related terms

Reduction Potential:

The tendency of a species to gain electrons and be reduced, measured relative to a standard reference electrode.

Oxidation Potential:

The tendency of a species to lose electrons and be oxidized, measured relative to a standard reference electrode.

Nernst Equation:

An equation that relates the reduction potential of a half-reaction to the concentrations of the reactants and products.