Standard Temperature and Pressure
Definition and meaning of Standard Temperature and Pressure in chemistry.
Standard Temperature and Pressure, very frequently abbreviated as STP, is a standard set of environmental reference conditions used to evaluate and compare the physical properties of different gases.
In more detail
The International Union of Pure and Applied Chemistry (IUPAC) currently defines STP strictly as a temperature of 273.15 K (0 degrees Celsius) and an absolute atmospheric pressure of exactly 100 kPa (1 bar). Before the year 1982, the standard pressure was officially defined as 1 atmosphere (101.325 kPa), and this slightly older definition is still frequently utilized in many modern chemistry textbooks. At the current IUPAC accepted STP, one single mole of an ideal gas occupies a specific volume of approximately 22.71 liters. These standardized conditions consistently allow scientists around the world to report and compare experimental gas data, such as volume and density, on an entirely consistent basis.
Key facts
| Field | Physical Chemistry |
|---|---|
| Standard Temperature | 273.15 K (0 °C) |
| Current Standard Pressure | 100 kPa (1 bar) |
| Abbreviation | STP |
At standard temperature and pressure, scientists confidently know that a sealed balloon containing exactly one mole of helium gas will occupy roughly 22.7 liters of physical volume.
Frequently asked questions
What is the molar volume of an ideal gas at standard temperature and pressure?
Under the current IUPAC definition (100 kPa), it is 22.71 L/mol, though the older 1 atm definition yields the widely taught 22.4 L/mol which remains popular in educational settings.