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Clarification Regarding the conditions for STP

  1. Apr 12, 2014 #1
    Hello all,

    I am currently in possession of two chemistry textbooks, Changs and Atkins, which I believe are both fairly new versions. Changs defines STP at 25 degrees Celsius and 1 atm, and Atkins defines STP at 25 degrees Celsius and 1 bar; I understand that numerically it would not make a huge difference (1 atm=101.3 kpa=almost 100 kpa), but which is technically correct?

  2. jcsd
  3. Apr 12, 2014 #2


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    Staff: Mentor

    There is no one, universally accepted definition of STP. Bar is a recommended pressure for a standard state.
  4. Apr 12, 2014 #3
    Atmospheres were used for something like 100 years until "they" decided to switch standard pressure to 1 bar. Numerically they are nearly identical, obviously.

    Ref: http://goldbook.iupac.org/S05921.html
    (Getting a lot of mileage out of IUPAC today :smile:)
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