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Homework Help: Vacume technology at pressure;molecules in amount of volume

  1. Nov 10, 2008 #1
    1. The problem statement, all variables and given/known data
    Current vacuum technology can achieve a pressure of 1.0 x10-10mm of Hg. At this pressure, and at a temperature of 40.0 degrees C, how many molecules are in 4.00cm3?


    2. Relevant equations
    p=nRT/V


    3. The attempt at a solution
    I would attempt this but I don't see how mm of hg would be considered a pressure... Doesn't that mean millimeters of Mercury?? How is that considered a pressure? My book doesn't explain this. Shouldn't it be in pascal?
     
  2. jcsd
  3. Nov 11, 2008 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi Mugen112! :smile:

    Pascal is an SI unit, but not everyone uses SI for everything. :rolleyes:

    See http://en.wikipedia.org/wiki/Inch_of_mercury: :smile:
    (and you can convert from inHg to mmHg! :wink:)
     
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