Colligative Properties of Solutions

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Colligative Properties of Solutions

• A Study of Boiling Point Elevation

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Colligative Properties

• Colligative Property a property that depends
  only on the amount of dissolved solute rather
  than on the chemical identity of the solute.
  Properties include
• Lowering the vapor pressure of a solution
• Increasing the boiling point of a solution
• Lowering the freezing point of a solution
• Osmosis

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Examples

• Vapor pressure a nonvolatile solute lowers the
  vapor pressure of a volatile solvent.
• Freezing point freezing point is lowered when a
  nonvolatile solute is dissolved in a solvent
  (e.g. salt in ice)
• Boiling Point boiling point is increased when a
  nonvolatile solute is dissolved in a solvent
  (e.g. salt in water)

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Molality

• molality, m moles of solute
• kilograms of solvent
• m DT / K
• or DT K m
• where K is a constant
  
• (equation for nonionizing solute)
• DT i K m
• (i is the number of different ions)

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Procedural Notes

• Check your calculation for 1 with me before
  proceeding.
• Add the salt slowly to the water or your solution
  will boil over and you will have to start over.
• Your graphs should take up a whole page. It
  should have a title and both axes should be
  labeled.
• Show all your work and include units!

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Homework

• Bring your completed lab report over colligative
  properties.
• Have your pre-lab for Exp. 10 (Solutions
  Solubility) ready for me to sign.
• Be prepared for a quiz over Exp. 10 and
  colligative properties calculations.