Colligative Properties Of Solutions

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A presentation discussing the main colligative properties of solutions, applicable for high school chemistry or AP Chemistry

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Colligative Properties Of Solutions

  1. 1. Colligative Properties of Solutions<br />
  2. 2. The presence of solutes affects the properties of solutions.<br />Some of these properties are not dependant on what dissolved substance but only on how much.<br />Colligative properties are those that depend on the concentration of solute particles but not on their identity.<br />Colligative Properties? What the…<br />
  3. 3. Vapor pressure is the pressure caused by molecules that have escaped from the liquid phase to the gaseous phase.<br />Experiments show that the vapor pressure of a solvent containing a nonvolatile* solute is lower than the vapor pressure of the pure solvent at the same temp.<br />This lowers the freezing point and raises the boiling point.<br />*a substance with little tendency to become a gas<br />Vapor Pressure<br />
  4. 4. Phase Diagram<br />
  5. 5. Pure Solvent v. Solution<br />
  6. 6. Freezing Point Depression<br />The freezing point of a 1-molal solution of a nonelectrolyte solute in water is found by experiment to be 1.86°C lower than the freezing point of water.<br />When the solution is 2-molal the freezing point is lowered by 3.72°C.<br />In fact, for any concentration of a nonelectrolyte solute in water, the decrease in freezing point can be determined using the value of -1.86°C/m.<br />This value is called the molal freezing-point, Δtf<br />
  7. 7. Freezing-point depression can be calculated by using the following equation.<br />Δtf= Kfm<br />Kfis the freezing-point depression constant.<br />m is the molality.<br />Each solvent has its own characteristic molal freezing-point constant. See Table 14-2 on page 438.<br />
  8. 8. 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 this solution?<br />Sample Problem 14-3<br />
  9. 9. A water solution containing an unknown quantity of a nonelectrolyte solute is found to have a freezing point of -0.23°C. What is the molal concentration of the solution?<br />Sample Problem 14-4<br />
  10. 10. Page 449 Questions 19-24<br />Assignment <br />

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