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Chemistry 16.3

Chemistry 16.3. Colligative Properties of Solutions. 16.3.

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Chemistry 16.3

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  1. Chemistry 16.3

  2. Colligative Properties of Solutions 16.3 • The wood frog is a remarkable creature because it can survive being frozen. Scientists believe that a substance in the cells of this frog acts as a natural antifreeze, which prevents the cells from freezing. You will discover how a solute can change the freezing point of a solution.

  3. 16.3 Vapor-Pressure Lowering • Vapor-Pressure Lowering • What are three colligative properties of solutions?

  4. 16.3 Vapor-Pressure Lowering • A property that depends only upon the number of solute particles, and not upon their identity, is called a colligative property.

  5. 16.3 Vapor-Pressure Lowering • Three important colligative properties of solutions are • vapor-pressure lowering • boiling-point elevation • freezing-point depression

  6. 16.3 Vapor-Pressure Lowering • In a pure solvent, equilibrium is established between the liquid and the vapor.

  7. 16.3 Vapor-Pressure Lowering • In a solution, solute particles reduce the number of free solvent particles able to escape the liquid. Equilibrium is established at a lower vapor pressure.

  8. 16.3 Vapor-Pressure Lowering • The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution.

  9. 16.3 Vapor-Pressure Lowering • Three moles of glucose dissolved in water produce 3 mol of particles because glucose does not dissociate.

  10. 16.3 Vapor-Pressure Lowering • Three moles of sodium chloride dissolved in water produce 6 mol of particles because each formula unit of NaCl dissociates into two ions.

  11. 16.3 Vapor-Pressure Lowering • Three moles of calcium chloride dissolved in water produce 9 mol of particles because each formula unit of CaCl2 dissociates into three ions.

  12. 16.3 Freezing-Point Depression • Freezing-Point Depression • What factor determines the amount by which a solution’s vapor pressure, freezing point, and boiling point differ from those properties of the solvent?

  13. 16.3 Freezing-Point Depression • The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent is the freezing-point depression.

  14. 16.3 Freezing-Point Depression • The magnitude of the freezing-point depression is proportional to the number of solute particles dissolved in the solvent and does not depend upon their identity.

  15. 16.3 Freezing-Point Depression • The freezing-point depression of aqueous solutions makes walks and driveways safer when people sprinkle salt on icy surfaces to make ice melt. The melted ice forms a solution with a lower freezing point than that of pure water.

  16. 16.3 Boiling-Point Elevation • Boiling-Point Elevation • The difference in temperature between the boiling point of a solution and the boiling point of the pure solvent is the boiling-point elevation. • The same antifreeze added to automobile engines to prevent freeze-ups in winter, protects the engine from boiling over in summer.

  17. 16.3 Boiling-Point Elevation • The magnitude of the boiling-point elevation is proportional to the number of solute particles dissolved in the solvent. • The boiling point of water increases by 0.512°C for every mole of particles that the solute forms when dissolved in 1000 g of water.

  18. 16.3 Section Quiz. • 16.3.

  19. 16.3 Section Quiz. • 1. Which of the following is NOT a colligative property of • vapor-pressure lowering • freezing-point depression • boiling-point elevation • solubility elevation

  20. 16.3 Section Quiz. • 2. Choose the correct word for the space: The magnitude of each colligative property of solutions is proportional to the __________ solute dissolved in the solution. • type of • number of particles of • molar volume of • particle size of the

  21. 16.3 Section Quiz. • 3. The decrease in vapor pressure when a solute is added to a liquid is due to • attractive forces between solvent particles. • repulsion of the solute particles by the solvent particles. • dissociation of the solvent particles. • attractive forces between solvent and solute particles.

  22. 16.3 Section Quiz. • 4. You have 500 mL of 1M solutions of NaCl, Na2SO4, Na3PO4, and Al2(SO4)3. Which solution will have the highest boiling point? • NaCl(aq) • Na2SO4(aq) • Na3PO4(aq) • Al2(SO4)3(aq)

  23. END OF SHOW

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