Standardtemperatur

Standardtemperatur is a defined reference temperature used in scientific data reporting and calibrations, particularly in chemistry and thermodynamics. It serves to standardize comparisons of properties that vary with temperature, such as enthalpy, entropy, Gibbs free energy, and equilibrium constants. The term is often paired with a standard pressure to form a standard state for substances.

In chemical thermodynamics and physical chemistry, the most widely used standard temperature is 298.15 kelvin (25 degrees Celsius). Under this convention, properties of pure substances and solutions are tabulated at 1 bar of pressure. The standard enthalpy of formation, standard Gibbs energy of formation, and standard molar entropy are defined at 298 K. Historically, some data sets used 0 °C (273.15 K) as the reference temperature, but 298 K is the common modern convention.

Relation to ambient contexts: Standard temperature is not the same as ambient or room temperature, which commonly range around 20–25 °C. In practice, researchers may report data at multiple temperatures and use thermodynamic equations to extrapolate. Temperature must be given in Kelvin in scientific contexts; Celsius can be used for convenience but must be offset by 273.15 to convert to Kelvin.

Notes: When converting or comparing data, the reference temperature and pressure must be stated explicitly; standard temperature may differ in different databases or disciplines. Standard temperature is a convention, not a physical constant, and its exact value depends on the conventions used in a given field.