Definitions for "Standard state"
State in which all concentrations are 1 M and all partial pressures are 1 MPa.
the state of the substance at 25°C and 1 atm; for solutions, standard state is 1 molar.
A reference state for thermodynamic measurements, defined for a liquid or solid as the pure substance at one atmosphere external pressure, for a gas as an ideal gas at one atmosphere pressure, and for a solution as a 1 M solution, in each case at the specified temperature