Question

What is the definition of standard temperature and pressure (STP)?

Answer 1

Standard Temperature and Pressure is defined by IUPAC as:

• `0^@ "C"` and `"1.000 bar"` after 1982
• `0^@ "C"` and `"1.000 atm"` before 1982

The numerical difference is that one obtains a molar volume of ideal gas to be:

• `"22.414 L/mol"` at `0^@ "C"` and `"1.000 atm"`.
• `"22.711 L/mol"` at `0^@ "C"` and `"1.000 bar"`.

and the universal gas constant is:

• `"0.082057 L"cdot"atm/mol"cdot"K"` at `0^@ "C"` and `"1 atm"`.
• `"0.083145 L"cdot"bar/mol"cdot"K"` at `0^@ "C"` and `"1 bar"`.

where

• `"1.000 bar"` `=` `"100000 Pa"`
• `"1.000 atm"` `=` `"101325 Pa"`

As such, you should always specify which pressure your STP uses for your textbook for your course.

Note that `0^@ "C" = "273.15 K"`. You can always choose to use `"273.15 K"` instead of `"273 K"`, and it therefore should not limit the number of significant figures you have in a calculation.