Oct_12 - Physical Properties of Solutions The physical...

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Physical Properties of Solutions The physical properties of solvents change when solutes are dissolved in them These include: lowering of equilibrium vapour pressure elevation of b.p. freezing point depression osmotic pressure These are called colligative properties
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Vapour Pressure of Solutions Dissolution of a solute decreases the vapour pressure of the solvent. There are fewer solvent molecules at the surface. Lower rate of solvent evaporation leads to a lower equilibrium pressure of solvent vapour.
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Raoult's Law In ideal solutions the change in vapour pressure is proportional to the mole fraction amount of solvent Raoult's Law: P solvent = P ˚ X solvent Pº is the vapour pressure of pure solvent .
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Molecular Weight Determination Pº of water is 17.54 torr at 20ºC. If 18.0 g of a sugar is dissolved in 100.0 g of water the vapour pressure is 17.23 torr. Determine the molecular weight of the sugar. P = P
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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_12 - Physical Properties of Solutions The physical...

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