The purpose of the lab was to determine the order of reaction for the dye Red #40. By measuring the reaction rate between bleach and the dye, the order of the reaction was determined to be first order.
The study of kinetics is important for studying the amount of time it takes for a particular reaction to reach completion. By comparing two solutions of dye that have different concentrations, the reaction rate can be experimentally found. At this point, reaction rates can only be determined experimentally and cannot be calculated. The equation Rate=k[Dye]y can be determined for all its variables, but because the second part of the lab was not completed, the entire rate law equation of Rate=k[OCl-]x[Dye]y cannot be determined because changes in the bleach concentration were not measured. The experimental data will be analyzed using Beer’s Law. By plotting the data in an excel graph, the slope will give the concentration of the dye over time in seconds. With this information, the “y” value can be calculated and the rate law equation completed.
OCl- + H2O + 2e-(dye) 2OH- + Cl-
[Red dye #40]=3.989×10-3
Molar Absorptivity of Red dye #40 = 2.7×104 abs*mol-1*cm-1
Trial| Trial 1— [dye]=6×10-5 M| Trial 2 – [dye]= 8×10-5 M| Reaction
Time| 150 seconds| 150 seconds|
Wavelength| 499 nanometers| 499 nanometers|
Absorbance| 1.436| 1.852|
Trial| Trial 1 – [dye]= 6×10-5 M| Trial 2 – [dye]= 8×10-5 M| Slope of Concentration vs. Time| -2.96×10-7| -6.30×10-7|
This kinetics lab studies the reaction rate of a particular dye and NaOCl, also known as bleach. The rate equation for this particular reaction is Rate=k[Dye]y. The concentration of the dye was known, the rate of the reaction was experimentally found, and then the “y” value was calculated. By analyzing the graphs of comparing concentration and time, especially the natural log graph because it had the best R2 value, the reaction was determined to be a first-order reaction. In the end, the lab showed how chemical kinetics in equation form can be applied to real experimental data.