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What is osmotic pressure?

  1. Oct 7, 2009 #1
    I researched on the internet but I can't understand. Please in simple words can someone explain. Is it the same as osmolarity. What is the difference?
  2. jcsd
  3. Oct 8, 2009 #2

    Andy Resnick

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    'osmotic pressure' is a pressure difference the is caused by differences in concentration of a solute. Imagine an open container with a semipermeable membrane, one side has pure water and the other has (for example) saline. The osmotic pressure jump across the membrane will drive water through the membrane, until the change in hydrostatic pressure (the movement of water will change the volume of both sides) compensates.

    'osmolarity' is a quantitative measure of the concentration of solute. Blood, for example, is about 330 mOsm.

    Look up "Donnan equilibrium" for more information.
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