Chemistry / Unit 7 Chem 1251 short lesson, about 20 seconds
Standard Temperature and Pressure: the Current IUPAC Convention
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The idea
IUPAC redefined standard pressure from 1 atmosphere to exactly 1 bar in 1982; standard temperature stayed 273.15 kelvin.
In practice
Under this convention, one mole of an ideal gas occupies about 22.7 liters at STP, slightly more than the 22.4-liter figure under the older 1-atm convention.
Where people slip
Reading STP without checking the source's pressure convention silently swaps in the wrong standard molar volume.
Your place on the trail
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