Example 3.2.1:
Crystal violet reacts with hydroxide to convert the dye to a colorless form:

CV+ + OH- -> CVOH
purple               colorless

The time course, measured as the absorbance of the solution at 590 nm, is given below for an initial crystal violet concentration of 1.2x10-5 M and a hydroxide concentration of 0.0300 M. The long-time absorbance is 0.040. Determine the order of the reaction and the rate constant.

 t (min) 0 1 3 5 7 9 11 13 15 A 1.2 0.905 0.526 0.317 0.2 0.133 0.094 0.071 0.058

Method: Do a fit based on the absorbance directly using non-linear curve fitting:

 t (min) A 0 1.200 1 0.905 3 0.526 5 0.317 7 0.200 9 0.133 11 0.094 13 0.071 15 0.058

or a fit to the transformed data:

 t (min) A A - Aoo ln(A - Aoo) 1/(A - Aoo) 0 1.200 1.160 0.148 0.862 1 0.905 0.865 -0.146 1.157 3 0.526 0.486 -0.722 2.059 5 0.317 0.277 -1.282 3.604 7 0.200 0.160 -1.833 6.250 9 0.133 0.093 -2.376 10.760 11 0.094 0.054 -2.926 18.649 13 0.071 0.031 -3.484 32.593 15 0.058 0.018 -4.041 56.876