Spectrophotometry Lab Report

The purpose of the lab was to determine the stability constant of the complex ion Thiocyanatoiron[1], Fe(SCN)+2. This was done through the lab technique, spectrophotometry. The main chemical equation focused on for the experiment was [Fe(H2O)6]+3(aq) + SCN-(aq)  [Fe(H2O)5(SCN)]+2(aq) + H2O[2]. However, because the concentration of water in the dilute aqueous solution is constant it can be written in the simple form of Fe+3(aq) + SCN-(aq)  Fe(SCN)+2(aq)[2]. In the experiment the stability constant was achieved by first creating a calibration curve. From the calibration curve data was taken and used in order to find the equilibrium concentrations, once that was found the stability constants were calculated with the following formula k=[Fe(SCN)+2eq]/[Fe+3eq][SCN-eq] and the average taken. The Beer-Lambert Law, states that there are 3 different factors that affect the absorption, and those are the intensity of the light, the pathway and the concentration of the solution. In this experiment the most important one is concentration. This is shown throughout the experiment where the concentration of Fe+3 ions are decreased from solution six to ten meaning that more of it has reacted …show more content…
Where absorbance = epsilon (wavelength dependent constant)*path length * concentration[4]. With the definition alone it is clear that the Beer-Lambert Law is evident in the use of the calibration curve where the axis are the same. However, with the law there comes some limitations. One main limitation is the scattering of light due to particles or their being bubbles within the cuvette, what the particles cause is the light to not go directly through the sample. The initial intensity would be much higher than the intensity of the light through the sample. It would be similar for air bubbles, the light would go through the bubbles and possibly reflect causing the readings to be