Chemistry 152, Fall 2013
5 September 2013
For this experiment the main objectives were to determine the best wavelength to use for a Beer’s Law Analysis for the dye assigned which happened to be brilliant blue. The molar absorptivity of Brilliant Blue at 622.0 nm had an absorbency of 0.321. These results were obtained by completing a series of five cuvets filled with stock solution using a parallel dilution. The absorbencies were recorded and placed on a graph with a best of fit line.
Our first task was to determine the lambda max of the assigned food dye, brilliant blue. Our max was 622.0 nm. To get this number we used Absorption Spectroscopy, a device that measures the wavelength of light that can pass through the solution, or is absorbed by the brilliant blue solution. Another objective we had was to measure how much of the substance absorbs light at our max wavelength.
The proportionality constant that relates absorbance to concentration is as follows. (A=εbC) To find ε, we used Absorption spectroscopy to measure the absorbance values. An excel graph was made from the collected values that were taken from the cuvettes.
We measured how strongly a substance may absorb the light at a particular wavelength. Absorption Spectroscopy was then used to measure our absorbance values at the maximum wavelength. We tested 5 different dilutions of the dye and recorded each specific wavelength. We can then say that ε may be determined. Ε is related to molar absorptivity in this equation.
Original 1:5 0.367 8:10 3.792 x 10-6