December 1st, 2010

Purpose: The purpose of this experiment is to figure out how to determine the concentration of a colorful solution.

Background: The photons that are transmitted and absorbed determine the color of a solution. A solutions ability to absorb the light depends on the wavelength of the photons. Intensity is equal to the number of transmitted photons and transmittance is calculated by dividing the intensity per unit time with the absorbing species present by when its absent. Absorbance is calculated by multiplying the transmittance by negative log. Beer's law states absorbance is equal to the absorptivity coefficient times the path length that the light travels through the solution times the molar concentration of the absorbing species. In this lab, five solutions with varying amount of copper(II) sulfate and distilled water will each have a different concentration. The absorbance will be determined for each solution and then a graph will be made. Based on the graph and the absorbance, the concentration of the unknown solution can also be calculated.