What is the hydrogen ion concentration and hydrogen gas pressure when the potential of the hydrogen electrode is 0.00 V at 298 K?

In the context of the hydrogen electrode, which serves as a reference for measuring electrode potentials, the standard condition for the hydrogen ion concentration and hydrogen gas pressure is well-defined. When the potential of the hydrogen electrode is set to 0.00 V at 298 K (25 °C), it indicates a standard state of the electrode where typical conditions govern the relationship between the hydrogen ion concentration and hydrogen gas pressure.

For a hydrogen electrode, the Nernst equation is used to relate the potential to the concentrations of hydrogen ions and the pressure of hydrogen gas. When the standard potential is 0.00 V, it implies that the activity (or effective concentration) of hydrogen ions [H⁺] must be defined such that it adjusts to the standard conditions (usually set at 1.0 M for concentration and 1.0 atm for pressure). However, in this case, we are considering concentrations and pressures that yield a stable environment where the potentials align at this reference point.

The accepted standard condition generally describes hydrogen ion concentrations of 1.00 mol/dm³ and hydrogen gas pressure at 100 kPa for the hydrogen electrode potential at 0.00 V. Thus, in this context, a hydrogen ion concentration of 1.