Full Lab Manual
Introduction & Goals
Chemistry & Background
In Your Write-up
This experiment illustrates the molecular basis for color and the complementary relationship between the perceived color of a solution and the color of light absorbed. In the first part of this week's lab, you will measure the absorption spectra of two conjugated dyes and compare the results to the theoretical predictions of a particle-in-a-box model. In the second part of the experiment, you will identify the food dyes present in a sample of Koolaid or Gatorade from the absorption spectrum and paper chromatography. Finally, you will use Beer's Law to determine the concentration of food dyes in your sample of drink mix.
What makes a red solution, like cherry Koolaid, appear red to your eye? What colors of light are absorbed and what colors are transmitted?
How are absorbance and transmission spectra related?
What is the scanning spectrometer doing, when it measures the spectrum of a solution? What steps must it automate from the procedure you used to measure a "point-by-point" spectrum with a Spec 20?
What are the approximations made in applying the particle-in-a-box model to the electron energy levels of conjugated dyes? How well do these approximations work?
Trustees of Dartmouth College, Copyright 19972001