Standard Hydrogen Electrode
Definition and meaning of Standard Hydrogen Electrode in chemistry.
The Standard Hydrogen Electrode (SHE) is a reference electrode consisting of a platinum electrode with hydrogen gas bubbling through at 1 atm, immersed in a 1 M H+ solution at 25°C. Its cell potential is defined as exactly 0.00 V by convention.
In more detail
The SHE provides a universal reference point against which all other electrode potentials are measured. This is essential for predicting redox reaction spontaneity and comparing the reducing or oxidizing power of different half-reactions. Without this defined standard, electrode potential measurements would be meaningless and incomparable across experiments.
Key facts
| Field | Physical Chemistry |
|---|---|
| Half-reaction | 2H+ + 2e- → H2 |
| Standard Potential | 0.00 V |
| Standard Conditions | 1 atm H2, 1 M H+, 25°C |
To predict whether copper metal can be oxidized to Cu2+ by dilute nitric acid, you compare the copper half-reaction potential (0.34 V) with the nitric acid reduction potential (approximately 0.96 V, for NO3- + 4H+ + 3e- → NO + 2H2O). The higher potential indicates the reaction is thermodynamically spontaneous.
Frequently asked questions
Why is hydrogen used as the reference electrode?
Hydrogen is easily produced and reduced, its half-reaction is reproducible and well-understood, and hydrogen is one of the most common elements in chemistry, making it a practical and reliable universal standard.
Can the SHE be used in all types of solutions?
No, it only functions in acidic solutions containing H+ ions. Other reference electrodes like silver-silver chloride are used in neutral and basic conditions.