Kinetic Reaction Lab

Kinetics

Introduction Nivaldo J. Tro describes kinetics as the study of how changes that occur in chemical reactions take place over time, and because of its vast utilization in a multitude of industries, it may be one of the most significant and fascinating aspects in the entire chemical world. One application of the study of kinetics can be applied to the determination of the rate of a chemical reaction involving a certain selection of chemicals (FD&C Blue #1 and sodium hypochlorite). The purpose of the proceeding experiment is to make such a determination, as well as determining the rate law for the reaction by establishing the rate constant and concentrations and reactions orders of the chemicals.

Discussion/Results The first
A sodium hypochlorite (NaOCl) solution was also prepared by mixing 8.00 mL of a stock solution with DI water to obtain 50 mL. The concentration of the NaOCl solution was also determined using the following equation:
M1V1 = M2V2 (Eq. 2) The second part of the experiment involved mixing different proportions of both the NaOCl solution and blue food coloring solution, and this was performed in order to determine the proportion of each which was necessary to find a combination which would become colorless in approximately fifteen minutes. It was determined that a mixture of 60% blue food coloring solution and 40% NaOCl would satisfy the requirement. The third part of the experiment was performed using the aforementioned proportions of the solutions. 4.8 mL of blue food coloring solution and 3.2 mL of NaOCl were mixed and placed in the Spectronic 20. The transmittance of the mixture was recorded at one minute intervals. By using Eq. 1, these values were converted to obtain the absorbance of the blue food coloring. The absorbance was then used to determine the concentration of the blue food coloring by using the following
3)
The data was then plotted as concentration vs. time (Figure 1), ln concentration vs. time (Figure 2), and 1/concentration vs. time (Figure 3). Since a linear graph was assembled using the data set of ln concentration vs. time, the blue food coloring solution was determined to be first order in this reaction. The slope of the linear graph was determined to be -0.4581, and since its absolute value is equal to the observed rate constant, kobs, the observed rate constant equaled 0.4581. The fourth part of the experiment was performed by preparing a diluted solution of NaOCl by combining equal parts of the original NaOCl solution and DI water. In lieu of the original NaOCl solution, the diluted solution was combined with the blue food coloring solution and the procedure of the third part of the experiment was repeated; however, only a ln concentration vs. time data set was plotted (Figure 4) to determine if the slope would change by the same factor as the ln concentration vs. time graph of the third part of the experiment. Since the slope did change by the same factor, the NaOCl solution was determined to be first order in this reaction, as