Question

What are the standard temperature (in Kelvin) and pressure (in atm.) conditions for gas measurements?

Answer 1

Hi. STP is 273.15 K and 0.986 92 atm.

STP is defined as 273.15 K and a pressure of exactly 100 kPa (1 bar).

1 atm = 101.325 kPa, so

`"100 kPa" × "1 atm"/"101.325 kPa" = "0.986 92 atm"`

Hope this helps!

Answer 2

Many online sources actually get this one wrong.

STP is set by the IUPAC as 0°C and 100kPa. Many old books and sources online will say that standard pressure is 101.325kPa (the old IUPAC standard which was changed in 1982), but I defer to the current IUPAC of 100kPa. See this link from Wikipedia for further discussion.

0°C is the same as 273.15K.

100kPa converts to 0.986923267 atm

Hope this helps!