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How does surface pressure increase with a leak in vacuum distillation apparatus?

Discussion in 'MCAT Study Question Q&A' started by libraryismyhome, Apr 30, 2011.

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  1. libraryismyhome

    libraryismyhome Banned Banned Account on Hold 5+ Year Member

    Mar 6, 2010
    This is AAMC 3 BS #114 question.

    If there is a leak in vacuum distillation apparatus, I thought some of the gases would escape which would decrease the pressure in the apparatus, so that the boiling point would decrease.

    But the answer said that if there is a leak, the surface pressure increases which increases the boiling point.
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  3. loveoforganic

    loveoforganic -Account Deactivated- 2+ Year Member

    Jan 30, 2009
    Vacuum distillation apparatus doesn't build up significant pressure relative to the atmosphere. With a leak, you actually have a leak in (i.e., you now have atmospheric pressure pushing on the liquid in your system).
  4. libraryismyhome

    libraryismyhome Banned Banned Account on Hold 5+ Year Member

    Mar 6, 2010

    a trenchant answer! thank you. :thumbup:
  5. xlcooplx

    xlcooplx 2+ Year Member

    Jan 11, 2011
    First Neck Road, SC
    Exactly. Remember the purpose of using vacuum filtration. Vacuum filtration reduces the pressure inside of the apparatus to be below that of atmospheric pressure. In doing so, we are able to distill liquids with otherwise high boiling points at a significantly lower temperature because the internal pressure of the system has decreased. If there is a leak in the vacuum apparatus, then you are allowing atmospheric pressure to act on the gas vapors in the system. In doing so, the boiling point will rise.

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