Lab 4 - Gaurav Singh Brooke Leslie/Chad Landrie 25 February...

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Gaurav Singh Brooke Leslie/Chad Landrie 25 February 2009 Lab Four: Separation of Liquids by Fractional Distillation. Analysis by Gas Chromatography Introduction In this experiment, two liquids (ethyl and butyl acetate) were separated by fractional distillation and the efficacy of the process was determined using GC machines and Volume vs. Temperature graphs that were created during the distillation. Findings indicate that ethyl acetate distilled first into fraction one. Fraction two contained a mixture of ethyl and butyl acetate, and fraction three was purely butyl acetate. This was confirmed by percent composition calculations from GC results. Fractional distillation is used to isolate individual pure liquid components from a mixture containing two (or more) volatile substances. The difference between fractional and simple distillation is the presence of a fractional distillation column between the stillpot and the stillhead in fractional. The column is similar to the condenser; however, it has a large outside jacket and some indentions at the male end to hold the packing in place. Fractional distillation can be applied to substances with closer boiling points. The vapor pressure is the measure of the ease with which its molecules escape the liquid’s surface. When a liquid has two volatile components, the number of molecules of each is proportional to their respective partial pressures. The partial pressures are determined by the composition of the solution in accordance with Raoult’s law;
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solution boils when the sum of the partial pressures X and Y equals the external pressure. The boiling temperature determined by the solution’s composition is expressed by Dalton’s Law. The fractional column is a path through which vapor must pass from the stillpot to the condenser before it is collected in the receiver. The path is longer than in simple distillation to the addition of the rings, which increases the surface area to which the vapor is exposed. As the vapor from the still pot rises up in the column, some of it condenses in the column and returns to the distilling flask containing the 1:1 mixture. Equilibrium between the liquid and vapor phases must be set up in a fractional distillation column so that the more volatile components can selectively be carried to the top of the column and into the condenser, where the vapor condenses into the distillate. Ethyl acetate (see figure one) has a lower boiling point of 77-78 degrees Celsius, whereas butyl acetate (see figure one) has a higher point of 126 degrees Celsius. Butyl acetate also has a higher molecular mass (116 g/mol) versus ethyl acetate’s 88 g/mol. Since the molecular weight is higher, there are more London dispersion forces, and thus the vapor pressure
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This note was uploaded on 04/14/2010 for the course ENGL 104 taught by Professor Osbourne during the Spring '08 term at A.T. Still University.

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Lab 4 - Gaurav Singh Brooke Leslie/Chad Landrie 25 February...

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