Analysis Of Sodium Hydroxide And Crystal Violet

Discussion

Objectives:
This experiment is monitoring the reaction of sodium hydroxide and crystal violet using spectroscopy. Graphical methods will be used to determine the kinetic rate law, rate constant and activation energy for the reaction.

General Discussion: The order of hydroxide was determined by the varying the initial concentration of hydroxide in runs 1 and 2. We used the isolation method, which calls for having much higher concentrations of one reactant then the other, in this case the concentration of NaOH being much higher than the concentration of Crystal Violet. This method allows to be converted to where . kobs was determined by linearizing the data for absorbance with regards to time, with the slope of the linearized graph being kobs. The equation for reaction 1 was then divided by the same equation for reaction 2, allowing for a calculation of n which was approximately 1. The order of crystal violet was calculated by graphing absorbance with regard to time for the first set of data. Since the spectrometer was set to detect crystal violet and according to Beers law concentration is proportional to absorbance, this data is proportional to the concentration of Crystal Violet. In plots

The first possible source of error is the assumption that [OH-] does not change over the course of the experiment, even though it does. However, since the order of magnitude of [OH-] is so large compared to [CV] this error is miniscule. Another possible error is inaccuracies in the spectrometer, and for the calculation of the order of OH-, the measurement of the initial concentrations of the reactants. While these sources of error probably did contribute to slight differences in concentration, they were consistent and small enough to have little impact on the calculation of order, which is demonstrated by the extremely high R2 values (R2 >.999) for the graph of natural log of absorbance versus