Oct_15 - Osmosis Osmosis is a property seen when a semi-permeable membrane separates solutions of different composition Some important membrane

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Osmosis In the example left, the water (permeable) is moving to equilibrate sugar concentration Osmosis is a property seen when a semi-permeable membrane separates solutions of different composition Some important membrane materials are Gore-Tex(water vapour) and Nafion (cations)
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Osmotic Pressure Solvent flow will raise solution level This creates a pressure differential Equilibrium is reached when solvent migration is balanced by the pressure difference
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Osmotic Pressure You can predict osmotic pressure (π) from π ≈ c R T or c = solute concentration (mol/L) R = Ideal Gas Constant c is the concentration of solute particles and doesn't depend on the type of solute Reversible by applying this pressure to the concentrated side → reverse osmosis.
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Example What pressure is needed to desalinate seawater which is approximately 3% w/w NaCl at 15 ° C? c NaCl = (30 g) / (58.5 g/mol) = 0.51 M c Cl = c Na so c tot = 1.02 M π = cRT = 1.02 M * .08206 L atm mol -1 K -1 * 288 K = 25 atm
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This note was uploaded on 01/20/2011 for the course CHEM 154 CHEM 154 taught by Professor Yang during the Spring '10 term at The University of British Columbia.

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Oct_15 - Osmosis Osmosis is a property seen when a semi-permeable membrane separates solutions of different composition Some important membrane

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