Purpose and applications of standard temperature and pressure
Standard temperature and pressure conditions as well as normal temperature and pressure conditions are used as reference points in thermodynamics of gases. Normally standard and normal temperature pressure conditions are used for specifying vapor volume.
This is because, volume of a given number of vapor moles is a function of temperature and pressure conditions. Hence it becomes imperative to specify the corresponding temperature and pressure conditions for volume measurement, whenever gas quantity is specified in terms of gas volume.
Hence universally recognized reference temperature and pressure conditions can be easily used to specify gas volume measured at those conditions. This gas volume can be readily converted to number of moles or gas mass, as temperature and pressure of this standard reference point is easily known.
Values of standard temperature and pressure depend on the organization which defines them. Usually the standard pressure is close to atmospheric pressure and standard temperature is close to room temperature value.
|Defining Organization||Temperature in 0C||Pressure in kPa|
|NIST, ISO 10780||0||101.325|
|ISA, ISO 13443||15||101.325|
|Defining Organization||Temperature in 0F||Pressure in psi|
|OPEC, U.S. EIA||60||14.73|
|U.S. Army Standard Metro||59||14.503|
|ISO 2314, ISO 3977-2||59||14.696|