Experiment 3

Experiment 3 - Experiment #3 Spectrophotometric Analysis of...

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Experiment #3 Spectrophotometric Analysis of Commercial Aspirin In this laboratory we will use visible electromagnetic radiation (sunlight or white light) to analyze the percent composition of commercially grade aspirin. The visible region of the spectrum usually contains wavelengths from 380 nm to 750nm. When light in the visible region is absorbed by a substance, it is usually an electron that is excited from a lower to a higher energy state. When sunlight passes through a sample, our eyes detect the wavelengths of the visible light not absorbed, i.e. the light transmitted; the light absorbed excites the electron. Recitation February 7 1
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Experiment #3 Spectrophotometric Analysis of Commercial Aspirin Therefore the color we see is complementary to the one absorbed. Page 174, Table 1, show the correlation between wavelength, color and complementary color. For example if the color that we see is yellow , the sample absorbed the energy from the violet region. Factors that control the amount of energy that a sample absorbs: -the concentration of the absorbing substance ( c ) -the thickness of the solution containing the absorbing substance ( b ) -the probability of light absorption by the substance (called the molar absorptivity coefficient or extinction coefficient) ( a ) Recitation February 7 2
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This note was uploaded on 05/01/2011 for the course CHEM 112 taught by Professor Hibbard during the Spring '08 term at Spelman.

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Experiment 3 - Experiment #3 Spectrophotometric Analysis of...

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