Standard Hydrogen Electrode (SHE) as Reference Electrode - NEET Notes, Formula & Common Mistakes
Standard Hydrogen ElectrodeElectrochemistryNEET ChemistryNEET 2025Reference ElectrodeElectrode Potential
Standard Hydrogen Electrode (SHE) as Reference Electrode - NEET Notes, Formula & Common Mistakes
ElectrochemistryĀ·2 min readĀ·NEET 2026
What NEET Asks
Questions on calculating standard electrode potentials using SHE as a reference.
Conceptual understanding of SHE's definition, construction, and its role in the electrochemical series.
Problems involving the Nernst equation where SHE is one of the half-cells under non-standard conditions.
Key Points
The Standard Hydrogen Electrode (SHE) is the primary reference electrode, assigned an arbitrary standard electrode potential of exactly 0.00 V.
Standard conditions for SHE are: 1 M H$^+$ solution, 1 atm H$_2$ gas pressure, and 298 K (25Ā°C).
It consists of a platinum electrode (inert) immersed in an acidic solution, with hydrogen gas bubbled over it.
SHE can act as both an anode (oxidation: H$_2$ ā 2H$^+$ + 2e$^-$) or a cathode (reduction: 2H$^+$ + 2e$^-$ ā H$_2$), depending on the other half-cell.
It enables the determination of unknown standard electrode potentials of other electrodes by forming a galvanic cell.
Must-Know Formula / Reaction
SHE Half-Reaction (Reduction): 2H$^+$(aq, 1 M) + 2e$^-$ ā H$_2$(g, 1 atm); EĀ° = 0.00 V
SHE Half-Reaction (Oxidation): H$_2$(g, 1 atm) ā 2H$^+$(aq, 1 M) + 2e$^-$ ; EĀ° = 0.00 V
EĀ°cell = EĀ°cathode - EĀ°anode: Used to calculate the standard potential of another electrode by connecting it with SHE.
Common Mistakes
Students often forget the specific standard conditions (1 M H$^+$, 1 atm H$_2$, 298 K) for SHE's 0.00 V potential.
Don't confuse the defined standard potential of SHE (0.00 V) with its potential under non-standard conditions (which is calculated using the Nernst equation).
Misidentifying SHE's role (anode or cathode) in a galvanic cell, which depends on the relative reactivity of the other electrode.
Rapid Revision
SHE is the electrochemical reference point, defined as 0.00 V under standard conditions (1 M H$^+$, 1 atm H$_2$, 298 K). It uses an inert platinum electrode for the H$_2$/H$^+$ equilibrium. Critical for measuring other standard electrode potentials by forming a cell where SHE's role (anode/cathode) depends on the partner electrode.
Frequently Asked Questions
What is the primary purpose of the Standard Hydrogen Electrode (SHE)?ā¾
The primary purpose of SHE is to serve as a reference electrode for measuring the standard electrode potentials of other half-cells. Its potential is arbitrarily set to exactly 0.00 V under standard conditions, providing a benchmark for the entire electrochemical series.
What are the standard conditions for a Standard Hydrogen Electrode (SHE)?ā¾
The standard conditions for SHE include a 1 M concentration of H$^+$ ions in the solution, a partial pressure of 1 atm for hydrogen gas, and a temperature of 298 K (25Ā°C). The electrode itself is an inert platinum foil.
Why is platinum used in the construction of a SHE?ā¾
Platinum is used in SHE because it is an inert metal, meaning it does not participate in the redox reaction itself. Instead, it provides a stable surface for the adsorption of hydrogen gas and catalyzes the reversible equilibrium between H$_2$ gas and H$^+$ ions, facilitating electron transfer.
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