Determining Dye Using Beer-Lambert’s Law and Spectroscopic Methods

by Iman Abu-Khdair

Submitted : Fall 2019

The first step of this project is gathering data through an experiment  of spectroscopy, which had been done previously from a General Chemistry I Lab. After collecting the data, the next step was to plot the points of absorbance at each value of concentration on a graph. Once the graph was created, the regression line was added along with its equation and R-squared value. This graph serves as the calibration curve, in which the dilution values lied along the x-axis and the absorbance values lied along the y-axis.

            The calculus in this application for chemistry is simplified from a combination of basic concepts of the topic into the equation known as Beer’s Law, or sometimes called Beer-Lambert’s Law, written as  or . The main calculus involved in this problem is the derivation of Beer’s Law, which requires the understanding of each factor involved of the current equation as well as the understanding of integration. A represents the absorbance of light of a solution (no units),  represents the molar absorptivity coefficient (Lmol^-1cm^-1) which is dependent on the on the solute, solvent, wavelength the solution is measured at, L (or b) represents the path length of light (cm), and C represents the concentration of the solution (mol/L). The result shows that the dye used in the experiment was Red #40 based on the measurement of a maximum wavelength of 500 nm for the stock (original) solution, the dilutions used, and the linear relationship shown in the regression line of the graph.

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