Electrode potential and standard electrode potential

Electrode Potential and Standard Electrode Potential

Definition of Electrode Potential

Electrode potential refers to the tendency of an electrode to either gain or lose electrons when it is in contact with a solution of its own ions. It refers to the voltage generated at the boundary between a metal and its ion solution as a result of redox (oxidation-reduction) processes.

Explanation

When a metal rod is placed in a solution containing its own ions, metal atoms may release electrons and dissolve into the solution as positive ions. At the same time, metal ions from the solution might accept electrons and get deposited onto the metal surface. This bidirectional exchange of electrons establishes a potential difference called the electrode potential.

Types of Electrode Potential

• Oxidation Potential: Tendency of the electrode to lose electrons (acts as anode).
• Reduction Potential: Indicates how readily an electrode accepts electrons, functioning as the cathode in a redox reaction.

Standard Electrode Potential (E⁰)

The standard electrode potential refers to the potential of an electrode measured under specific standard conditions:

• Ion concentration = 1 M
• Temperature = 25°C (298 K)
• Gas pressure = 1 atm (for gaseous systems)

It is denoted as E⁰ and is always measured relative to the Standard Hydrogen Electrode (SHE), which is arbitrarily assigned a potential of 0.00 V.

Standard Hydrogen Electrode (SHE)

The SHE is a reference electrode consisting of a platinum electrode dipped in 1 M H⁺ ion solution with hydrogen gas at 1 atm bubbling over it. It acts as a benchmark for determining the electrode potentials of various other electrodes.

Electrochemical Series

The electrochemical series ranks elements based on their standard electrode (reduction) potentials. It helps predict which element can displace another in a redox reaction.

EMF of a Cell

The EMF (Electromotive Force) of an electrochemical cell is the potential difference between the two electrodes under standard conditions.

EMF = E⁰_cathode – E⁰_anode

Applications

• Helps in determining the electromotive force (EMF) of galvanic cells.
• Assists in assessing whether a redox reaction is likely to occur.
• Essential in designing electrochemical cells and batteries.
• Used in calculating equilibrium constants for redox reactions.