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solutions3

# solutions3 - Colligative Properties(Continued Properties of...

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Colligative Properties (Continued): Properties of a solution that differ from the pure solvent due to the number of particles, not type, that are dissolved. 11.4 Boiling Point Elevation / Freezing Point Depression Normal boiling point occurs when the vapor pressure equals normal air pressure, 760 torr. A non-volatile solute will lower the freezing point and raise the boiling point of a solution. Boling Point Elevation: T = i K b m K b = molal boiling point elevation constant, Ex. H 2 O = 0.51ºC/ m (See table 11.5) m = solution concentration expressed in molality, moles solute/kg solvent i= number of ions produced from dissociation Freezing Point Depression: T = i K f m K f = molal freezing point depression constant, Ex. H 2 O = 1.86ºC/ m (See table 11.5) m = solution concentration expressed in molality, moles solute/kg solvent i= number of ions produced from dissociation In Class Ex. 1: Determine the boiling point and freezing point of a solution that contains 25.0 g of CaCl 2 (111 g/mol) in 200.g of H 2 O? (CaCl 2 → Ca 2+ + 2Cl - ) m= m ions x g molCaCl O kgH gCaCl 38 . 3 3 111 1 200 . 0 0 . 25 2 2 2 = Boling point of solution: T = 0.51ºC/m . 3.38m = 1.73ºC, 100ºC = 1.73ºC = 101.73ºC Freezing point of solution: T = 1.86ºC/m . 3.38 = 6.29ºC, 0-6.29ºC = - 6.29ºC In Class Ex. 2: What mass of ethylene glycol (non-volatile, non-ionizing, 62.1g/mol) is needed to prepare 10.0L water

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