Standard Electrode Potential and EMF - NEET Notes, Formula & Common Mistakes
EMF of CellElectrochemistryNEET ChemistryNEET 2025Standard Electrode PotentialCell Potential
Standard Electrode Potential and EMF - NEET Notes, Formula & Common Mistakes
ElectrochemistryĀ·2 min readĀ·NEET 2026
What NEET Asks
Numerical problems calculating standard cell potential (EĀ°cell).
Conceptual questions on Standard Hydrogen Electrode (SHE) and its role.
Identifying anode/cathode based on standard reduction potentials.
Relationship between EĀ°cell and Gibbs free energy (ĪGĀ°).
Key Points
Electrode Potential (E): Tendency of an electrode to gain or lose electrons when in contact with its own ions in solution.
Standard Electrode Potential (EĀ°): Electrode potential measured under standard conditions (1 M ion concentration, 1 atm pressure for gases, 298 K temperature).
Standard Hydrogen Electrode (SHE): A reference electrode assigned EĀ° = 0.00 V. All other electrode potentials are measured relative to SHE.
Standard EMF of a Cell (EĀ°cell): The potential difference between the two electrodes of a galvanic cell under standard conditions.
Convention: Standard reduction potentials are commonly tabulated and used.
Spontaneity: A redox reaction is spontaneous if EĀ°cell > 0, which corresponds to ĪGĀ° < 0.
Must-Know Formula / Reaction
EĀ°cell = EĀ°cathode - EĀ°anode
EĀ°cell: Standard electromotive force of the cell (Volts).
EĀ°cathode: Standard reduction potential of the cathode (Volts).
EĀ°anode: Standard reduction potential of the anode (Volts).
ĪGĀ° = -nFEĀ°cell
ĪGĀ°: Standard Gibbs Free Energy change (Joules).
n: Number of electrons transferred in the balanced reaction.
F: Faraday's constant (96485 C/mol).
Common Mistakes
Students often use oxidation potential for anode when given reduction potentials. Always use reduction potentials and apply EĀ°cell = EĀ°cathode - EĀ°anode.
Don't confuse standard conditions (1 M, 298 K, 1 atm) with non-standard conditions where the Nernst equation is required.
EĀ°cell is the potential difference under standard conditions. SHE is the reference (0 V). Calculate EĀ°cell using EĀ°cathode(red) - EĀ°anode(red). A positive EĀ°cell indicates a spontaneous reaction (ĪGĀ° < 0). Remember Faraday's constant for ĪGĀ° calculations.
Frequently Asked Questions
What is standard electrode potential?ā¾
Standard electrode potential (EĀ°) is the potential developed at an electrode when it is in contact with its own ions at a concentration of 1 M, at 298 K (25Ā°C), and 1 atm pressure for gases. It measures the tendency of a half-cell to gain or lose electrons.
How is the standard EMF of a cell calculated?ā¾
The standard EMF of a cell (EĀ°cell) is calculated as the difference between the standard reduction potential of the cathode and the standard reduction potential of the anode. The formula is EĀ°cell = EĀ°cathode - EĀ°anode.
What is the role of the Standard Hydrogen Electrode (SHE)?ā¾
The Standard Hydrogen Electrode (SHE) serves as a reference electrode, assigned a standard electrode potential of exactly 0.00 Volts. All other standard electrode potentials are measured relative to the SHE, allowing for a consistent comparison of the reducing or oxidizing power of various electrodes.
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