Rate Law and Activation Energy Methyl Blue Determining the Rate Law using the Time Dependent Rate

The Reaction

Reaction takes about 30 s to a few minutes depending on the initial concentrations Can use a continuous monitoring method Because there is a color change we can use spectroscopy

The Reaction In this experiment, the initial concentration of the hydroxide is at least 1000 times larger than the concentration of the MB This means that And

Figuring out x To figure out the order with respect to the MB + we will observe [MB + ] vs t To do this we use Beer’s Law Plot A t vs t, LN(A t ) vs t and 1/A t vs t to see if the reaction is zeroth order, first order or second order wrt MB+ Absorbance Constants

Figuring out x AtAt LN(A t )1/A t Which one gives a straight line? If straight x = 0If straight x = 1If straight x = 2

The Math Zeroth Order First Order Second Order The slope of the linear curve will get you k’=k[OH-] o y to within a constant Repeating the experiment at a second [OH-] will get you access to how slope depends on [OH-] and get y