key term - Ecell

Definition

The term 'ecell' refers to the cell potential or electromotive force (EMF) of an electrochemical cell, measured in volts. It indicates the ability of the cell to do electrical work and is influenced by factors such as temperature, concentration of reactants and products, and the nature of the electrodes. The value of ecell helps determine whether a redox reaction can occur spontaneously and is crucial for understanding how concentration differences can drive electrochemical processes.

5 Must Know Facts For Your Next Test

1. The value of ecell is positive when the reaction is spontaneous and negative when it is non-spontaneous.
2. At standard conditions, ecell can be calculated using standard electrode potentials from a reference table.
3. The Nernst equation shows how ecell changes with variations in concentration and allows prediction of cell behavior under non-standard conditions.
4. In concentration cells, ecell is determined solely by the difference in concentrations of reactants at each electrode.
5. Temperature can also affect ecell; increasing temperature generally increases the kinetic energy of particles, which can impact reaction rates and cell potential.

Review Questions

• How does the Nernst equation relate to calculating ecell under different conditions?
  • The Nernst equation provides a way to calculate the cell potential (ecell) when conditions deviate from standard state. It takes into account the concentration of reactants and products along with temperature. This allows us to determine how much ecell will change as these concentrations shift, indicating whether a reaction will become more or less favorable.
• What role does ecell play in distinguishing between spontaneous and non-spontaneous reactions in electrochemical cells?
  • In electrochemical cells, ecell serves as an indicator of spontaneity. A positive ecell means that the reaction can occur spontaneously, releasing energy. In contrast, a negative ecell indicates that the reaction is not spontaneous without external energy input. Understanding this concept helps predict whether reactions will proceed under given conditions.
• Evaluate how changes in concentration affect the ecell in a concentration cell and provide an example.
  • Changes in concentration significantly impact ecell in a concentration cell, as it relies on the difference in concentrations between two identical electrolytes. For instance, if one side has a higher concentration than the other, the ecell will be positive, driving the reaction forward. Conversely, if concentrations equalize, ecell approaches zero, indicating that no electrical work can be done. This illustrates how concentration gradients are essential for maintaining cell potential.

Related terms

Nernst Equation:

A mathematical equation used to calculate the cell potential of an electrochemical cell under non-standard conditions, factoring in temperature and concentrations of reactants and products.

Standard Electrode Potential:

The measure of the individual potential of a reversible electrode at standard conditions, typically defined as 25°C, 1 M concentration, and 1 atm pressure.

Concentration Cell:

A type of electrochemical cell that generates electrical energy from a difference in concentration between two solutions of the same electrolyte.