key term - Concentration Cell

Definition

A concentration cell is a type of electrochemical cell where the electrodes are made of the same material but are immersed in solutions of different concentrations. The difference in concentration creates a potential difference, driving the flow of electrons from the more concentrated solution to the less concentrated one. This cell operates based on the Nernst Equation, which relates the concentration difference to the electromotive force (EMF) generated, emphasizing its importance in electrochemistry.

5 Must Know Facts For Your Next Test

1. In a concentration cell, the electrode reactions occur due to differences in ion concentration, which establishes a voltage difference.
2. The Nernst Equation for a concentration cell is given by $$E = E^\circ - \frac{RT}{nF} \ln \frac{[Ox]}{[Red]}$$, where E is the cell potential, R is the universal gas constant, T is temperature, n is the number of moles of electrons transferred, and F is Faraday's constant.
3. Concentration cells can be constructed with various ions and can serve as simple models to study electrochemical principles.
4. The overall cell reaction in a concentration cell can be represented as an ion migrating from a region of high concentration to one of low concentration, which exemplifies spontaneous processes.
5. The emf generated by a concentration cell decreases as the concentrations approach equality, leading to a zero potential when both sides reach the same concentration.

Review Questions

• How does the difference in concentration between two solutions in a concentration cell create an electric potential?
  • The difference in concentration generates a gradient that drives the movement of ions from the higher concentration side to the lower concentration side. This movement results in electron flow through an external circuit, producing an electric potential. Essentially, as ions migrate to balance concentrations, they cause oxidation at one electrode and reduction at another, creating a measurable voltage.
• Discuss how the Nernst Equation applies specifically to concentration cells and what it reveals about their behavior as concentrations change.
  • The Nernst Equation provides a quantitative relationship between the concentrations of reactants and products and the electromotive force (EMF) of a concentration cell. As concentrations become more equal, the logarithmic term approaches zero, indicating that the EMF decreases toward zero. This demonstrates how concentration cells operate under non-standard conditions and emphasizes that their voltage output directly correlates with the relative concentrations of solutions.
• Evaluate the practical applications of concentration cells in real-world scenarios, particularly in relation to electrochemistry.
  • Concentration cells have practical applications in various fields such as analytical chemistry and battery technology. They can be used for measuring ion concentrations in solutions through potentiometry, providing insights into chemical processes occurring in biological systems. In battery design, understanding how concentration differences affect voltage can lead to more efficient energy storage systems. Thus, they serve as foundational elements that bridge theoretical concepts with real-life applications in electrochemistry.

Related terms

Electrochemical Cell: A device that generates electrical energy from chemical reactions or facilitates chemical reactions through an electric current.

Nernst Equation:

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

Redox Reaction: A chemical reaction that involves the transfer of electrons between two species, where one species is oxidized and the other is reduced.