Limiting Reactant Lab Report

The purpose of this lab was to determine the molecular formula of the complex ion formed between iron (II) and phenanthroline through the use of spectroscopy and knowledge of limiting reactants. This lab is important as it can be used to discover molecular formulas of compounds as well as provide a representation of how limiting and excess reactants influence chemical reactions. To accomplish the main goal of this lab, we had to find a way to determine what the limiting reactant was and how we could use that knowledge to prove the ratio that allows for the most product to be made. The idea of limiting reactants says that the amount of product made cannot be greater than the amount of limiting reactant used, in terms of moles of each. By holding

Then multiples of the number of moles of Fe+2 were chosen for the moles of phen in each solution. Since the solutions were made in a 50 mL volumetric flask we then used M = mol/volume again to figure out the molarity of each reactant in the solution. Finally, the solutions were also diluted again in a 1:10 using the formula M1V1 = M2V2, where the V2 was 10 mL so the absorbance values would be acceptable. This made sense as the solutions were an initially a deep red color and would thus need greater dilution to reach the appropriate absorbance values. We began testing with the 1:5 solution and that maximum absorbance value seen was beneath one, and because the lesser ratios would have less product, we knew that all of our solutions would fit in the range of .1 to 1

Hypothetically, there should be no absorbance value change as the molarity is same due to the amount of product being the same. This could be explained simply by human error during the experiment, most likely reusing pipets to fill the cuvettes before measuring or not mixing the solutions enough during dilution. This discrepancy in the results does not severely impact the experiment as the rate of increase from equivalence 1 to 3 is much greater than that of from equivalence 3 to 4. While these results are accurate and easily reproduced, one way to ensure consistency would be to retry the experiment starting with a different initial number of mols of