Chemical Reaction Lab

The purpose of this lab was to provide a more visible representation of reaction kinetics through dye decomposition with differing concentrations of reactants and the addition of ions within the solution. On day one of the lab, a linear relationship between absorbance and concentration of the dye was determined by creating multiple samples of dye with differing concentrations and measuring their absorbance in a spectrophotometer. On lab day two, using a similar method from day one, the absorbance of different reactions was analyzed and the rate order of both the dye and NaOH were determined to be 1 through graphical data analysis. Additional ions were introduced as a part of the experiment and the effect of the addition of KNO3 slowed down

When concentration increased, absorbance increased, and when concentration decreased absorbance decreased as seen in the graph of Concentration vs Absorbance.
Equation 1 〖rate〗_1/〖rate〗_2 =(k〖[Dye]〗^n 〖[NaOH]〗^m)/(k〖[Dye]〗^n 〖[NaOH]〗^m ) For all the solutions, the rate of decay of dye was linear on a ln[A] vs time graph with a slope of -k, thus indicating the rate order for the dye as first order4. However, this can also be determined through use of the general rate law equation: equation 1.The rates, rate constant, and rate order for the dye were all determined experimentally, therefore leaving only the rate order of NaOH to be determined. Using equation 1 and replacing the variables with known values and keeping the concentration of Dye the same, the rate of NaOH was determined to be 1 as well.

The cleanliness of the apparatus used is was a possible source of error. Even after trying to find the cleanest pipets and glassware, there were a distinct hint of purple and blue that covered parts of the apparatuses. Even after cleaning with ethanol, the residue could not be fully removed from the materials, thus possibly affecting the concentration of solutions that passed through the stained apparatuses. Having a more effective cleaning method would resolve this source of error. Since the reaction between the dye and NaOH was instantaneous, it was impossible to mix the solution together and measure the absorbance of the solution from the moment of reaction. The error was ameliorated as much as possible through minimizing the time the solution was not in the spectrophotometer. My lab group found it best to simply mix the solution within the cuvet in the spectrophotometer and start the data recording after the NaOH was mixed in. Another source of error comes from the accuracy of the pipets used. Beral pipets are only accurate to the nearest 1mL, leaving a lot of room for dispensing the incorrect amount of reactant and thus possibly skewing the intended concentration. Being trained in more accurate pipet usage or even have more accurate pipets could ameliorate this source of error. Further applications of reaction kinetics exploration could delve into the effects of environmental factors