Under standard conditions, what is the standard electrode potential value for the standard hydrogen electrode (SHE)?

• A. 0 V
• B. 1.23 V
• C. -0.44 V
• D. +0.76 V

Answer: (A)

The standard hydrogen electrode is defined as the reference point for all electrode potentials, so its standard potential is set to zero by convention. Under standard conditions (H+ activity = 1, H2 at 1 atm, 25°C) the half-reaction H+ + e− ⇌ 1/2 H2 is assigned E° = 0 V, making all other standard potentials measured relative to this zero. In practice, when you pair the SHE with another electrode, the cell potential you observe is the potential of that other electrode relative to SHE, i.e., E°cell = E°cathode − E°anode.