The standard hydrogen electrode (SHE) is assigned a standard reduction potential of:

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0.00 V. The standard hydrogen electrode (SHE) is assigned a standard reduction potential of exactly 0.00 V by convention. It serves as the reference electrode against which all other standard electrode potentials are measured. The SHE consists of a platinum electrode immersed in a 1 M H⁺ solution with hydrogen gas bubbling over it at 1 atm pressure and 25°C. Since there is no absolute way to measure a single electrode potential, the SHE provides a universal reference point from which all other potentials are determined.

The values -1.00 V, +1.00 V, and +2.71 V are standard reduction potentials of other half-reactions, not the SHE. The SHE was specifically assigned 0.00 V as a convention to create a consistent scale. Electrodes with positive standard reduction potentials are more easily reduced than hydrogen (stronger oxidizing agents), while those with negative standard reduction potentials are less easily reduced than hydrogen (their metals are more active reducing agents).

Standard reduction potentials are used to predict the spontaneity of redox reactions and to calculate cell potentials for galvanic cells. The standard cell potential is calculated as E°cell = E°cathode - E°anode. A positive E°cell indicates a spontaneous reaction. Standard reduction potentials also relate to the thermodynamic quantities ΔG° = -nFE° and to equilibrium constants through the Nernst equation. Understanding how to use standard reduction potential tables is essential for the CLEP Chemistry exam.

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