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Boiling Points - Distillations

Boiling Points - Distillations. 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. Add Antifreeze. What happens to the boiling point of water if you add antifreeze?.

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Boiling Points - Distillations

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  1. Boiling Points - Distillations Ethylene glycol, HOCH2CH2OH, boils at 198oC and melts at -13o C. What happens to the melting point of water if you add antifreeze? Melting point goes down.

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

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

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

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

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

  7. Raoult’s Law P = Po*N Observed Pressure Mole Fraction Pure Substance

  8. Two Volatile Liquids

  9. Two Volatile Liquids Pa = Poa * Na Pb = Pob * Nb Mixture boils when Pa + Pb = Papplied

  10. Boiling point vs. mole fraction Plot of boiling point vs. mole fraction for a mixture of acetone and benzene.

  11. Boiling point vs. mole fraction Boiling point vs. mole fraction Boiling point of an acetone-benzene mixture with a mole fraction benzene of 0.50 What is the composition of the vapor?

  12. Vapor richer in the lower boiling component

  13. Fractional Distillation

  14. Fractional Distillation

  15. Packed Column HETP = 1.5 cm

  16. Vigreux Column HETP = 10 cm

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

  18. Separations Which column would you use to separate a mixture of pentane, b.p. 36o and octane, b.p. 99o? Vigreux

  19. Separations Which column would you use to separate a mixture of methyl alcohol, b.p. 65o and water, b.p. 100o ? Packed

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

  21. Setup

  22. Methyl alcohol is toxic! CH3OH

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

  24. Grease joints to prevent sticking.

  25. Thermowell

  26. Plug the thermowell into the variable transformer

  27. Put boiling chips in bottom of flask Boiling Chips

  28. Distilling Column

  29. Thermometer Adapter

  30. Digital Thermometer

  31. Probe for digital thermometer

  32. Digital Thermometer

  33. Water out Water in

  34. Clamps

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

  36. Ethanol - Benzene Minimum - boiling azeotrope

  37. Min Azeotrope

  38. Acetone - Chloroform Maximum-boiling azeotrope

  39. Max Azeotrope

  40. Simple Distillation

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