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)013 57911 1315
A1.2000.9050.5260.3170.2000.1330.0940.0710.058

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

t (min) A
01.200
10.905
30.526
50.317
70.200
90.133
110.094
130.071
150.058

or a fit to the transformed data:

t (min) AA - Aoo ln(A - Aoo)1/(A - Aoo)
01.2001.1600.1480.862
10.9050.865-0.1461.157
30.5260.486-0.7222.059
50.3170.277-1.2823.604
70.2000.160-1.8336.250
90.1330.093-2.37610.760
110.0940.054-2.92618.649
130.0710.031-3.48432.593
150.0580.018-4.04156.876