1. STP (Standard Temperature and Pressure)
a. standard reference of temperature and pressure commonly used in chemistry and phyiscs
b. Defined by IUPAC (International Union of Pure and Applied Chemistry)
- Standard Temperature and pressure as air at $0^oC$ (273.15 K, 32$^oF$) and $10^5$ pascals (1bar)*
* The old IUPAC standard was 101.325 kPa, which was changed in 1932.
c. For ideal gas law
- STP is used as a reference point for the number of gas present (n) and the gas constant (R).
- Under STP condition: 22.4L/1 mole of any gas
- Molar volume**: $V_m = \frac{V}{n} = \frac{RT}{P} = \frac{8.3145J/(mole K) 273.15 K}{10^5 Pa} = 22.4 L/mol$
** The molar volume of gas around STP can be calculated with sufficient accuracy using the ideal gas law.
2. NTP (Normal Temperature and Pressure)
a. NTP condition: 293.15 K at 1 atm
c. For ideal gas law
- Under NTP condition: 22.4L/1 mole of any gas
- Molar volume**: $V_m = \frac{V}{n} = \frac{RT}{P} = \frac{8.3145J/(mole K) 293.15 K}{101.325 kPa} = 24.04 L/mol$
3. Summary
| NTP | STP | |
| Temperature | 293.15 K | 273.15 K |
| Pressure | 1 atm (101.325 kPa) | 0.987 atm (100 kPa = 1 bar) |
| Molar volume of the ideal gas | 22.4 L/mol | 24.04 ~ 24 L/mol |
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