What Is Standard Temperature and Pressure?
Standard temperature and pressure English name is standard temperature and pressure, abbreviated as STP, also known as standard condition (standard state), referred to as "standard condition". Because the temperature and pressure of the ground surface are different, even the temperature and pressure at the same place will vary with the measurement time. Therefore, for the convenience of research, the standard conditions describing the characteristics of the substance are developed, including temperature and pressure. Standard temperature and pressure generally refer to 273.15K (0 ° C), 100kPa. It is widely used in many disciplines.
- Standard temperature and pressure are two important physical quantities and are specified for scientific research. What we call
- 1. The standard state of the agreement of the 10th International Conference on Metrology (CGPM) in 1954 was: temperature 273.15K (0 ° C), pressure 101.325KPa. This standard is widely used in the scientific and technological fields of countries around the world.
- 2. The International Organization for Standardization and American National Standards stipulate that the temperature is 288.15K (15 ° C) and the pressure is 101.325KPa as the standard state for measuring the volume flow of gas.
- 3. China's "Standard Orifice Calculation Method for Natural Gas Flow" stipulates that the standard state for measuring gas volume flow is temperature 293.15K (20 ° C) and pressure 101.325KPa.
- 4. Pure gas state showing ideal gas properties at any temperature T and standard pressure P = 100 kPa. Note: Before 1993, China stipulated the standard pressure P = 101.325 kPa, and then adopted the provisions of P = 100 kPa according to GB 3102.8-93.
- 5. In chemistry, standard temperature and pressure (STP) were once defined as 0 ° C (273.15K) and 101.325kPa (1atm), but since 1982 IUPAC has redefined "standard pressure" as 100 kPa.
ISO 1 Standard temperature and pressure ISO 1
- ISO 1 is an international standard on standard temperatures defined by the International Organization for Standardization. It sets the standard temperature at 20 degrees Celsius, which is equal to 68 degrees Fahrenheit or 293.15 Kelvin.
- Due to thermal expansion and contraction, accurate length measurement needs to be performed at a certain temperature. The comparison measurement can also use the standard temperature defined by ISO 1 as a reference. The International Committee of Weights and Measures adopted 20 ° C as the standard temperature on April 15, 1931. It became the ISO No. 1 standard in 1951, and then quickly replaced the world s 0 ° C, 62 ° F, 25 ° C. Including other temperature standards. ISO sets the standard temperature to 20 degrees Celsius because it is the temperature of most workshops and its corresponding Fahrenheit is also an integer. [1]
Standard temperature and pressure
- Standard atmospheric pressure is a non-SI unit of pressure, with the unit symbol atm. The specific values have different definitions. Standard atmospheric pressure is generally defined as 101.325kPa. Organizations such as ICAO, International Organization for Standardization use this value.
- The general use of standard atmospheric pressure was recognized at the Tenth International Conference of Weights and Measures in 1954 and determined to be equivalent to 1,013,250 dyne / cm2 (101 325Pa). This unit represents the average atmospheric pressure of the average sea level in Paris, France, and it can represent the average atmospheric pressure of most industrial countries at that time.
- IUPAC once defined standard temperature and pressure (STP) as 0 ° C (273.15K) and 101.325kPa (1atm), but since 1982 IUPAC has redefined "standard pressure" as 100kPa.
- Standard molar enthalpy of combustion
- It refers to the change of the enthalpy of reaction when one mole of substance is completely burned at a standard pressure of 100kPa and a specified temperature (generally 298.15K), which is referred to as the enthalpy of combustion. It is represented by the symbol c H m , the subscript c represents combustion, and the unit of combustion enthalpy is kJ · mol -1 . The enthalpy change of any chemical reaction is equal to the difference between the total enthalpy of formation of the product and the enthalpy of formation of the reactant: the total enthalpy of formation is equal to the standard molar enthalpy of product multiplied by the above formula. The formula shown below: