2. Fractional Distillation Boiling point of mixtures Separation of mixtures by distillation.

3. Ethylene glycol, HOCH 2 CH 2 OH, boils at 198 o C and melts at -13 o C. What happens to the melting point of water if you add antifreeze? Melting point goes down. Boiling Points - Distillations

4. What happens to the boiling point of water if you add antifreeze? The boiling point goes up. Add antifreeze

5. Solids Usually melt low Liquids Usually boil between the two components Mixtures

6. Solution boils when the vapor pressure = applied pressure Vapor pressure of water vs. temperature

7. If you add salt, NaCl, to water what happens to the melting point? Impurities depress the melting point so it goes down. Add Salt – Melting Point

8. If you add salt, NaCl, to water what happens to the boiling point? The boiling point goes up. Add Salt – Boiling Point

9. P = P o *N Observed Pressure Pure Substance Mole Fraction Raoult’s Law

10. Two Volatile Liquids

11. a P a = P o a * N a b P b = P o b * N b Mixture boils when P a + P b = P applied Boiling Point Two Volatile Liquids

12. Mixture of acetone and benzene. Plot of boiling point vs. mole fraction

13. Mole fraction benzene = 0.50 What is the composition of the vapor? Boiling point of an acetone-benzene mixture

14. Vapor richer in the lower boiling component Vapor Composition

15. Fractional Distillation

16. Temperature vs. Volume

17. HETP = 1.5 cm Packed Column

18. HETP = 10 cm Vigreux Column

19. Which column has the greater holdup? Packed because it has the larger surface area.

20. Separate Pentane and Octane. Which column would you use to separate a mixture of pentane, b.p. 36 o and octane, b.p. 99 o ? Vigreux

21. Separate Methanol and Water Which column would you use to separate a mixture of methyl alcohol, b.p. 65 o and water, b.p. 100 o ? Packed

22. Separate mixture of methanol and water. Plot volume distilled vs. temperature. Experiment

23. Equipment

24. CH 3 OH Methyl alcohol is toxic!

25. 14/20 20 mm 14 mm Standard Taper Joints

26. Grease joints to prevent sticking.

27. Thermowell

28. Plug the thermowell into the variable transformer Use Variable Transformer

29. Boiling Chips Put boiling chips in bottom of flask

30. Equipment

31. Thermometer Adapter

32. Water out Water in

33. Joint – Hose Clamps

34. Same interactions between like and unlike molecules NONIDEAL MIXTURES: Strong attractions between like molecules Strong attractions between unlike molecules A. B. IDEAL MIXTURES:

35. Minimum - boiling azeotrope Ethanol - Benzene

36. Azeotrope

37. Maximum-boiling azeotrope Acetone - Chloroform

38. Maximum Azeotrope

39. Simple Distillation

40. Sample Equipment

41. Distillation Equipment

42. Solvent Purification