distillation lab.pdf - DISTILLA TION Sketch of apparatus...

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DISTILLA TION Sketch of apparatus: Fig. 5.5 and Fig. 5.7 Make sure the figures are labeled with proper names of glassware from pg. 12 Also, with names on the figures themselves Must also read the section on boiling points, steam distillation and vacuum distillation(assigned reading) Use for distillation - a way to purify liquids (separated based on boiling points) For simple and fractional distillations -liquids must form a homogeneous layer (miscible liquids) When do Liquids Boil? When vapor pressure of liquids = atmospheric pressure as the liquids are heated. The lower the pressure, the lower the boiling point. Note: Higher altitude, lower pressure, lower boiling point Why doesn’t all liquid evaporate once boiling point is reached? - Need to add heat of vaporization - why are bp not as good indicators of purity as mp? Vapor pressure - measures how easily molecules escape the surface of a liquid Liquids with higher vapor pressure have lower bp when compared with liquids with lower vapor pressures. Distillation of a Pure Liquid - Boiling point of liquid = temperature of vapor - Temperature remains constant throughout distillation Distillation of Mixtures Temperature does not remain constant Increases throughout distillation - because composition of vapor that is distilling varies throughout - some lower boiling point component comes of first - then vapor is enriched with higher boiling point component Boiling points are affected by both volatile and nonvolatile impurities (ex. Sugar solution) Boiling Points of Miscible Liquid Mixtures - in between the boiling points of pure compounds - Apparatus -Thermometer bulb must be below sidearm so it accurately records the temperature of the vapor distilling through the sidearm the bulb must not touch glass of apparatus. why ?
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