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What are the Factors Affecting Electrochemical Cells?

Published in Electrochemical Cell Factors 3 mins read

The performance and voltage of electrochemical cells are primarily affected by Gibbs free energy, concentration and gas pressure, and temperature. These factors directly influence the chemical reactions occurring within the cell, thereby determining its overall efficiency and output.

Key Factors Influencing Electrochemical Cells

According to Vedantu, the driving force (voltage) of an electrochemical cell is fundamentally determined by the system's Gibbs free energy. This energy measures how far a system is from equilibrium, directly reflecting the spontaneity and potential work that can be extracted from the cell. Consequently, any factor that alters the Gibbs free energy will impact the cell's voltage.

Here's a breakdown of the critical factors:

1. Gibbs Free Energy

  • Core Principle: As highlighted by Vedantu, “The Gibbs free energy measures how far a system is from equilibrium. It therefore determines the voltage (driving force) of an electrochemical cell.” A more negative change in Gibbs free energy (ΔG) indicates a greater driving force and a higher cell voltage.
  • Relationship to Voltage: The relationship between Gibbs free energy change (ΔG) and the cell potential (E) is given by the equation: ΔG = -nFE, where 'n' is the number of moles of electrons transferred, and 'F' is Faraday's constant. This equation explicitly shows that cell voltage is directly proportional to the negative change in Gibbs free energy.

2. Concentration and Gas Pressure

  • Impact on Reactants/Products: The concentrations of dissolved species (ions) and the partial pressures of gases involved in the electrode reactions significantly influence the cell's voltage.
  • Deviation from Standard Conditions: Changes in concentration and pressure alter the reaction quotient (Q) from its standard state value (Q=1). This deviation directly affects the cell's non-standard Gibbs free energy change, and thus its voltage, as described by the Nernst equation (though not explicitly mentioned as Nernst equation in the reference, the concept is implied).
  • Effect: For instance, increasing the concentration of reactants or decreasing the concentration of products generally shifts the equilibrium towards product formation, increasing the cell's voltage. Conversely, diluting reactants or increasing product concentrations can reduce the voltage.

3. Temperature

  • Influence on Reaction Kinetics and Equilibrium: Temperature affects both the rate of electrochemical reactions and the equilibrium constant of the overall cell reaction.
  • Direct Impact on Gibbs Free Energy: Temperature is a critical variable in the Gibbs free energy equation (ΔG = ΔH - TΔS), where ΔH is enthalpy change, T is temperature, and ΔS is entropy change. Therefore, changes in temperature directly modify the Gibbs free energy, and consequently, the voltage of the electrochemical cell.
  • Practical Implications: Higher temperatures typically increase reaction rates and can alter the solubility of species, potentially affecting cell performance. However, extreme temperatures can also lead to degradation of cell components or undesirable side reactions.

These three factors are interconnected, primarily through their influence on the system's Gibbs free energy, which serves as the fundamental thermodynamic basis for the cell's operation and voltage.

Reference: For more details, you can refer to the information on Vedantu's explanation of factors affecting electrochemical cells.