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Chemistry 16.4

Chemistry 16.4. 16.4. Molality and Mole Fraction. The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution. 16.4. Molality and Mole Fraction.

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Chemistry 16.4

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  1. Chemistry 16.4

  2. 16.4 Molality and Mole Fraction • The unit molality and mole fractions are two additional ways in which chemists express the concentration of a solution.

  3. 16.4 Molality and Mole Fraction • The unit molality (m) is the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent. Molality is also known as molal concentration.

  4. 16.4 Molality and Mole Fraction • To make a 0.500m solution of NaCl, use a balance to measure 1.000 kg of water and add 0.500 mol (29.3 g) of NaCl.

  5. 16.4 Molality and Mole Fraction • Ethlylene Glycol (EG) is added to water as antifreeze.

  6. 16.6

  7. 16.6

  8. 16.6

  9. 16.6

  10. Practice ProblemsFor Sample Problem 16.6 for Sample Problem 16.6 Problem Solving 16.29 Solve Problem 29 with the help of an interactive guided tutorial.

  11. 16.4 Molality and Mole Fraction • The mole fraction of a solute in a solution is the ratio of the moles of that solute to the total number of moles of solvent and solute.

  12. 16.4 Molality and Mole Fraction • In a solution containing nA mol of solute A and nB mol of solvent B (XB), the mole fraction of solute A (XA) and the mole fraction of solvent B (XB) can be expressed as follows.

  13. 16.7

  14. 16.7

  15. 16.7

  16. Sample Problem 16.7 16.7

  17. for Practice Problem 16.7 Problem Solving 16.32 Solve Problem 32 with the help of an interactive guided tutorial.

  18. 16.4 Freezing-Point Depression and Boiling-Point Elevation • Freezing-Point Depression and Boiling-Point Elevation • How are freezing-point depression and boiling-point elevation related to molality?

  19. 16.4 Freezing-Point Depression and Boiling-Point Elevation • The magnitudes of the freezing-point depression and the boiling-point elevation of a solution are directly proportional to the molal concentration (m), when the solute is molecular, not ionic.

  20. 16.4 Freezing-Point Depression and Boiling-Point Elevation • The constant, Kf, is the molal freezing-point depression constant, which is equal to the change in freezing point for a 1-molal solution of a nonvolatile molecular solute.

  21. 16.4 Freezing-Point Depression and Boiling-Point Elevation

  22. 16.4 Freezing-Point Depression and Boiling-Point Elevation • The constant, Kb, is the molal boiling-point elevation constant, which is equal to the change in boiling point for a 1-molal solution of a nonvolatile molecular solute.

  23. 16.4 Freezing-Point Depression and Boiling-Point Elevation

  24. Freezing-Point Depression and Boiling-Point Elevation • Simulation 21 Discover the principle underlying the colligative properties of solutions.

  25. 16.4 Freezing-Point Depression and Boiling-Point Elevation

  26. 16.8

  27. 16.8

  28. 16.8

  29. 16.8

  30. for Sample Problem 16.8 Problem Solving 16.33 Solve Problem 33 with the help of an interactive guided tutorial.

  31. 16.9

  32. 16.9

  33. 16.9

  34. 16.9

  35. for Sample Problem 16.9 Problem Solving 16.36 Solve Problem 36 with the help of an interactive guided tutorial.

  36. 16.4 Section Quiz. • 16.4.

  37. 16.4 Section Quiz. • 1. What is the mole fraction of He in a gaseous solution containing 4.0 g of He, 6.5 g of Ar, and 10.0 g of Ne? • 0.60 • 1.5 • 0.20 • 0.11

  38. 16.4 Section Quiz. • 2. The freezing point depression caused by a given concentration of a nonvolatile molecular solute • depends on the solute. • depends on the solvent. • is always the same. • cannot be determined.

  39. 16.4 Section Quiz. • 3. What are the freezing and boiling points of a 0.1m solution of CaCl2 in water? • -0.2°C, 100.1°C • -0.6°C, 100.1°C • -0.6°C, 100.2°C • -0.6°C, 99.8°C

  40. 16.4 Section Quiz. • 4. Compared to the freezing point depression by ethylene glycol (C2H6O2,) for a given solvent, the freezing point depression caused by the same molal concentration of CaCl2 would be • exactly the same. • twice as large. • three times as large. • four times as large

  41. END OF SHOW

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