Electrode Potentials

Electrode Potentials

Definition and Basics:

  • Electrode potential, also known as redox potential, refers to the measure of tendency of a chemical substance to acquire electrons and thereby be reduced.
  • The standard electrode potential is measured under standard conditions: 298K, 1atm pressure and 1mol dm^-3 solution concentration.
  • The standard hydrogen electrode (SHE) is the universal reference for all half-cell potentials, set at 0 volts.

Understanding the Sign of Electrode Potentials:

  • A positive electrode potential indicates a strong tendency to be reduced (gain electrons).
  • A negative electrode potential means the species has a tendency to lose electrons and get oxidised.

Electrochemical Series and Predicting Reactions:

  • The electrochemical series, a list of electrode potentials, allows us to predict the direction of a redox reaction.
  • A substance with a higher (more positive) electrode potential will reduce a substance with a lower electrode potential. Therefore, it acts as the oxidising agent.

Voltaic (Galvanic) Cells:

  • The difference in electrode potentials in a voltaic cell provides the driving force for an electrical current.
  • This works through one half-cell undergoing oxidation (anode), and the other undergoing reduction (cathode).
  • The anode is the electrode where oxidation occurs, and the cathode is the electrode where reduction occurs.

Electrolytic Cells and Electroplating:

  • Electrolytic cells use electrical energy to drive a non-spontaneous redox reaction. Here, the electrode at which oxidation takes place is the anode and is positive, while the cathode is negative.
  • Electrode potentials play a vital role in electroplating — the use of electrolysis to deposit a thin layer of metal onto an object.

Factors Influencing Electrode Potentials:

  • Electrode potentials are affected by factors such as temperature, pressure, and concentration of the ions in solution.
  • The Nernst equation can be used to calculate electrode potentials when these conditions deviate from their standard values.

Real-World Applications:

  • Understanding electrode potentials is fundamental in designing batteries, fuel cells, and understanding corrosion of metals.
  • The strong oxidising nature (high electrode potential) of elements like fluorine is widely exploited in chemical industry.