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Learn about colligative properties, including vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure in sugar-water and salt-water solutions. Understand how solute particles affect vapor pressure and apply Raoult’s Law calculations. Homework assignments included.
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Chapter 21 Colligative Properties: Vapor Pressure
Colligative Properties • Properties determined by the number of solute particles in solution rather than the type of particles. • Vapor pressure lowering • Boiling point elevation • Freezing point depression • Osmotic pressure
sugar and water salt and water What are the different properties of these solutions?
sugar and water salt and water How do the colligative properties of these solutions compare?
How Vapor Pressure Lowering Occurs • Solute particles take up space in a solution. • Solute particles on the surface decrease the number of solvent particles on the surface. • Less solvent particles can evaporate from the surface which lowers the vapor pressure of the liquid.
Raoult’s Law Vapor Pressure of solution= (mole fractionsolvent)(Vapor Pressuresolvent)
What is the vapor pressure of an aqueous solution at 70oC if 2.00 x 102g of sucrose (C12H22O11) are dissolved in 1.00 x 102g of water. Answer: 28.2 kPa
What is the vapor pressure of an aqueous solution at 70oC if 3.15 x 102g of C15H9NO4 are dissolved in 5.00 x 102g of water. Answer: 29.9 kPa
What is the vapor pressure of an aqueous solution at 70oC if 3.15 x 102g of C15H9NO4 are dissolved in 5.00 x 102g of water. Answer: 29.9 kPa
Homework • Worksheet: Vapor Pressure, Boiling Point and Freezing Point. (Due Tuesday or Wednesday) • Remember the “Review and Reinforcement” Worksheet. (Due Wednesday) • P and P for Lab Formula Mass from Boiling Point Elevation (Due Wednesday)