In case of a standard hydrogen electrode

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absolute electrode potential is not zero

absolute electrode potential is zero

both absolute and standard electrode potential values are zero

electrode potential is zero only at 25°C

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2016

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The absolute electrode potential of a standard hydrogen electrode (SHE) is not zero.

By international convention, the *standard electrode potential* of the SHE is *defined* as zero volts (0 V) at standard conditions (typically 25°C, 1 bar/atm H₂ pressure, and 1 M H⁺ concentration). This defines a relative scale for measuring the standard potentials of other half-cells. However, the absolute potential of the SHE, which represents the potential difference between the electrode and a point infinitely far away in vacuum, is not zero and is estimated to be around +4.44 V at 25°C.

The ability to measure absolute electrode potentials is limited; therefore, a reference electrode with a defined potential, like the SHE, is used to create a relative potential series. Option D is misleading as the zero potential is defined at standard conditions including 25°C, but the phrasing “only at 25°C” is inaccurate and incomplete regarding the conditions.

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