Experiment Two - Experiment Two Simple Distillation of...

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Experiment Two Simple Distillation of Organic Molecules O BJECTIVES 1. Set up a simple distillation apparatus. 2. Carry out a simple distillation of an unknown. 3. Plot a temperature vs. volume curve. 4. Identify the unknown from the boiling point. T HEORY A purification and separation technique of liquids 1. Properties of liquids: Liquids are held together by the same forces mentioned in the recrystallization lecture, only they do not have as tight of an arrangement (less attractions). If these attractions are overcome, the liquid will vaporize. a. Vapor pressure At any temperature a liquid exerts a pressure on the atmosphere above it. When this pressure equals or exceeds the force exerted by the atmosphere on the surface of the liquid, the liquid will begin to boil. b. Boiling point The temperature at which the vapor pressure of the liquid equals the pressure exerted upon the surface of that liquid is the boiling point of that liquid. Atmospheric pressure suppresses the liquid, so energy in the form of heat is required to increase the kinetic energy and to overcome this pressure so the liquid can boil. The boiling point is used in characterization. Determining the boiling point of a liquid is much more complex than recording the melting point. Since distillation requires more material and is affected less by impurities, it is not as good an indicator as the melting point. Impurities will either lower or raise the boiling point of a liquid depending on how the impurities interact with the compound whose boiling point is being measured. A pure liquid has a constant boiling point and if there is a change in boiling point during distillation then this is a very good indication of impurities. Note: A constant boiling point does not always mean that the distillate is one pure liquid. It is very possible that two miscible liquids will have almost the exact same boiling points as a mixture.
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This note was uploaded on 02/08/2012 for the course CHEM 331l taught by Professor Mr.handy during the Fall '11 term at South Carolina.

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Experiment Two - Experiment Two Simple Distillation of...

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