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distillation-091015205719-phpapp02 - Distillation...

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Unformatted text preview: Distillation Distillation Macroscale Technique Definitions Definitions Distillation: Separation of compounds based on differences in Distillation Separation their boiling point Evaporation: process in which molecules in a liquid state gain Evaporation: process sufficient energy to enter the gaseous state. Boiling Point: temperature at which the vapor pressure of a Boiling liquid equals to the external pressure applied to the surface of the liquid (usually atmospheric pressure) Vapor Pressure: pressure exerted by a vapor in equilibrium with Vapor pressure its liquid state. Vapor pressure depends on the substance and the temperature. Raoult’s Law Raoult PT = x1P1° + x2P2° Toluene b.p. (For a mixture of compounds 1 and 2) PT is the total vapor pressure of the solution is P1° is the vapor pressure of compound 1 P2° is the vapor pressure of compound 2 x1 is the mole fraction of compound 1 x2 is the mole fraction of compound 2 is Vaporization Cyclohexane b.p. ⇒The vapor contains a larger percent of the more volatile (i.e., lower boiling point) compound Simple Distillation Simple b.p. > 40 ºC apart A (liquid) + B (liquid) Heating (above b.p. of B) A (liquid) B (vapor) Cooling (below b.p. of B) A (liquid) B (liquid) One vaporization step = Simple ditillation Simple vs Fractional Distillation Simple Simple Fractional Condensation Revaporization Fractional distillation = series of subsequent simple distillations Simple vs Fractional Distillation Simple Simple distillation if boiling points more than 40 °C apart Simple Fractional distillation if boiling points less than 40 °C apart Fractional Fractional distillation much more efficient but more costly (slower process) Fractional Distillation Setups Distillation Simple Fractional rubber band * * Use labjack to support Reuse mixture for fractional distillation Plug to controller (not to wall) Experiments Experiments Begin building apparatus from round bottom flask (high enough so you Begin can add or remove the heating device). Grease joints and use a rubber band to secure vacuum adapter to condenser. Support heating device with a labjack. Plug heating device to controller Support (not to the wall outlet). Use a mixture of Water and Ethanol (25 mL of each). Reuse the same Use Water mixture for fractional distillation. Add 2 boiling chips before the mixture is heated. Add Have your TA check your set-up before starting anything. Have Distill at a slow but steady rate: 1 drop/2-3 seconds. Distill Record temperature every 2 mL of distillate. Record Use glass beads to pack the fractionating column. Use Construct graph Temperature vs Volume for each type of distillation in Construct your lab notebook. your At the end of the experiment, discard distillation mixture in the sink. At Simple vs Fractional Distillation Simple ...
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