Describe how visible spectroscopy could be used to determine the order of a reac
ID: 565640 • Letter: D
Question
Describe how visible spectroscopy could be used to determine the order of a reaction in which a single colorless reactant produces a colored product. The balanced, chemical equation for the reaction of crystal violet (CV) with hydroxide ion (OH) is CV'(aq) + OH (aq) CVOH(aq). Based on your experimentally determined rte law for this reaction, explain whether or not it is possible that the reaction mechanism consists of one elementary step Explain what experimental condition allowed you to determine the order of the reaction with respect to CV even though both [CV] and [OH ] are included in the rate law. Suppose you added a catalyst to the reaction of CV and OH . Describe how the change in [CV] versus time would be affected (i.e., compared to the uncatalyzed reaction). Also, describe how the rate constant, and the activation energy, would be affected, if at all, in the presence of a catalyst. The structure of crystal violet and "arrow-pushing" for the reaction with OH are shown below :OH OH Ignoring any effects of solvation of the ions, explain whether the reaction is likely to be exothermic or endothermic. Consider the reaction of hydroxide ion with dimethylether shown below, which has an activation energy of 82 kJ/mol. Compare this value with the activation energy you obtained in the crystal violet experiment and provide an explanation for why the values are, or are not, different a. b. Ea82 kJ/mol OH H3CO CH3 CH3 H3C-OHExplanation / Answer
Solution:
In a reaction, where, one of the reactant produces a colored product, visible spectroscopy can be used to determined the order of a reaction, the change in concentration of the reactant which forms the colored product is determined by absorbance measurement over time. The data for the concentration and time are plotted on the y and x axis and If we get a straight line it is a zero-order reaction. If instead, a plot of ln[concentration] versus time gives a straight line, it is a first order reaction. However, If 1/concentration versus time gives a straight line, it is a second order reaction kinetics. The other reactants may be changed while keeping this reactant as constant and change on rate of the reaction is observed to see If the other reactant affects the reaction or not.