1 / 15

Solutions

Solutions. Colligative Properties of Solutions. Objectives. Describe the colligative properties of a solution. Calculate freezing point depression and boiling point elevation for solutions. Colligative Properties.

lynne
Download Presentation

Solutions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Solutions Colligative Properties of Solutions

  2. Objectives • Describe the colligative properties of a solution. • Calculate freezing point depression and boiling point elevation for solutions

  3. Colligative Properties A property that depends on the concentration of solute particles but not on the identity of the solute.

  4. Vapor Pressure Lowering • As the concentration of a solute increases, the concentration of the solvent particles at the surface of a liquid decreases. This causes the vapor pressure to be lower. • A 1.0 m solution of glucose (C6H12O6) lowers the vapor pressure to the same extent as a 1.0 m solution of sucrose (C12H22O11)

  5. Freezing Point Depression Freezing Point Depression (Δtf): the difference between the freezing point of a pure solvent and a solution of a solute in the same solvent. Δtf = Kfm Kf = molal freezing point constant in oC/m m = molality

  6. Sample Problem • What is the freezing point depression of water in a solution of 17.1 g of sucrose (C12H22O11) and 200. g of water? What is the actual freezing point of water. Water has a Molal F.P. constant of -1.86 oC/m.

  7. Sample Problem • A water solution containing an unknown quantity of a non-electrolyte solute is found to have a freezing point of -0.23 oC. What is the molal concentration of the solution?

  8. Sample Problems • Determine the freezing point of a water solution of fructose (C6H12O6) made by dissolving 58.0 g of fructose in 185 g of water. -3.24oC • Calculate the molality of a solution of 39.2 g of urea, H2NCONH2, in 485 g of pure acetic acid. Determine the freezing point of this solution. For acetic acid: Normal f.p. = 16.6oC Kf = -3.90 oC/m 1.35 m, 11.3 oC

  9. Sample Problems • What is the expected change in the freezing point of water in a solution of 62.5 g of barium nitrate, Ba(NO3)2, in 1.00 kg of water.

  10. Sample Problems • What is the expected freezing point depression for a solution that contains 2.0 mol of magnesium sulfate dissolved in 1.0 kg of water? -7.4oC • A water solution contains 42.9 g of calcium nitrate dissolved in 500. g of water. Calculate the freezing point of the solution. -2.92oC

  11. Boiling Point Elevation Boiling Point Elevation (Δtb): the difference between the boiling point of a pure solvent and a solution of a solute in the same solvent. Δtb= Kbm Kf = molalboiling point constant in oC/m m = molality

  12. Sample Problem A solution contains 50.0 g of sucrose, C12H22O11, a non-electrolyte, dissolved in 500.0 g of water. What is the boiling point elevation?

  13. Sample Problems • What is the boiling point of a solution of 25.0 g of 2-butoxyethanol, HOCH2CH2OC4H9, in 68.7 g of ether? (For ether, ∆tb= 2.02oC/m) 40.8oC • What mass of glycerol, CH2OHCHOHCH2OH, must be dissolved in 1.00 x 103 g of water in order to have a boiling point of 104.5oC? 810g • What is the expected boiling point of a 1.70 m solution of sodium sulfate in water? 102.6oC

More Related