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Beer-Lambert Law

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  • April 2013
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Beer-Lambert Law
Gabe Garrison & Paige England
Buffalo High School

Abstract

In this lab, the Beer-Lambert Law is tested by using a spectrophotometer. This is a quick and easier way to determine the concentration of a solution.

Keywords: Beer-Lambert Law, Spectrophotometer, concentration

Beer-Lambert Law

The Beer-Lambert-Law states that there is a direct correlation between the concentration of the absorbing molecule, the distance the light travels, and the degree to which the molecules absorb light. It states that: A=a (lambda) bc (A equals total absorbance), a (lambda) is the absorptive coefficient, b is the distance the light travels through the substance and c is the concentration. It is possible to determine the concentration of a solution using a spectrophotometer. It has two advantages: capable of transmitting monochromatic light through a solution and it allows for a standard paralength (b) for all tested samples. By standardizing the distance light travels (b) and limiting the light exposure to a single wavelength, concentration can be determined experimentally. Method

Participants

The participants in this activity were the students of the Buffalo High School Biochemistry class.

Materials

In this experiment, the materials used were 0.1M ferric Chloride Solution, ascorbic acid, 10 phenanthroline solution, acetate buffer solution, 100mm test tubes, spectrophotometer, cuvettes, 5mL volumetric pipettes, droppers, 1mL volumetric pipettes, safety goggles, rubber gloves, and aprons. Procedure

Label six test tubes (1 through 5 and B for blank). A series of 5 test solutions of Ferric Chloride are made by serial dilution. Dilute 1Ml of the stock Ferric Chloride to 10 mL with de-ionized water to make a 0.01M solution. Place 1mL of the 0.01M Ferric Chloride solution in the first test tube...