Composition Identification lab

Composition Identification lab - Composition Identification...

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Composition Identification Author: Austin Kelly Instructor: LaKeisha McClary Class: Chem247A-005 Date Executed: 9-03-08 Date Submitted: 9-10-08 Abstract:
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The purpose of this experiment was to identify an unknown compound by using three methods of identification: Infrared Spectroscopy, Thin Layer Chromatography, and Mixed Melting Point. The unknown was compared to 6 known substances all of whose data was known. The melting point of the unknown given was 119 ˚ C, the IR spectrum as well as the TLC suggested that the unknown was Mandelic Acid. Introduction The goal of this particular lab is to identify an unknown substance that is given to us. We will be identifying this unknown substance by comparing a range of properties of the unknown to properties of the known compounds by use of Infrared Spectroscopy, Thin Layer Chromatography, and Mixed Melting Point. Infrared Spectroscopy (IR) uses an infrared laser from a spectrophotometer to determine what exactly the compound consists of. The Spectrometer is able to detect the movement of the molecules of whatever substance that we expose the light to by the use of the extremely sensitive light sensors that are in the device. As this technique is used to determine what the compound consists of from the readings from the spectrophotometer, the results depend on how exactly the molecule reacts to the infrared laser. This laser enables the bonds of the molecules to move in certain directions with certain patterns and, of course, certain intensities. Each molecule has certain characteristics when it is exposed to the IR beam. Once the intensity of the bond movement in the molecules is recorded, it is plotted on what is known as an IR spectrum. From the spectrum, we are able to determine what is in the compound by identifying the different functional groups in different regions of the spectrum. The Thin Layer Chromatography technique is used in order to determine the approximate size of the molecules that are being analyzed by use of a silica gel on a glass plate. The TLC technique works by adding a spot of the dissolved unknown substance to a line one centimeter above the very bottom of the plate using a micropipet. Since the silica gel on the plate is polar, the molecules are “pulled” up the plate
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Composition Identification lab - Composition Identification...

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