The purpose of this lab is to determine the concentration of a colorful solution. Transmittance and absorbance are two important physical quantities when describing the ability of a solution to absorb light. Transmittance is the number of transmitted photons (the intensity) per unit time with the absorbing species present over the number of transmitted photons per unit time with the absorbing species absent. When that is multiplied by 100, it gives the percentage of photons that can pass through a solution. Absorbance is the negative log of transmittance. Absorption is color specific and depends on wavelength.
In this lab five solutions of CuSO4 were prepared with different concentrations. The absorbance of these five solutions were measured to construct a calibration curve. Based on the calibration curve, the absorbance of the solution of CuSO4 with an unknown concentration could be determined. In order to solve for the unknown's concentration Beer's Law can be used. It is Absorbance = the absorbency coefficient time the path length times the concentration. The absorbency coefficient can be found by using the slope of the calibration curve.