Where t is time (s), [A] is the concentration of species A, and k is the rate constant of the reaction.

The integrated form of this differential equation can be written as

The above is a straight line when ln[A] is plotted against t. Note, any experimental parameter proportional to concentration (e.g., partial pressure (torr), absorbance, fluorescence intensity, etc.) can be substituted for concentration in the analysis of kinetic data. The slope of this line gives the rate constant as -k.

To graph the best fit line enter the (t,p) data pairs (Data tab) and then click the Plot tab. To determine the rate constant click the Least-Squares Analysis tab. To pick off a value on the graph, move your cursor to the desired location then click and hold... the (t, ln(p) ) pair will appear.